Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34122 Publications

Synthesis and characterization of tetravalent actinide complexes with amidinates and guanidinates

Schöne, S.; März, J.; Kaden, P.

Recent results of ongoing research of tetravalent actinde complexes with amidinates and guadinates is presented. Thereby the presentation fucuses on solid state characterisations with SC-XRD and paramagnetic NMR studies in organic solvents.

  • Lecture (others)
    FENABIUM Projekttreffen, 04.12.2017, Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26814
Publ.-Id: 26814


Site-controlled Si quantum dots in buried SiO2 layer formed by ion-beam implantation and phase separation

Xu, X.; Wolf, D.; Hlawacek, G.; Engler, M.; Hübner, R.; Bischoff, L.; Pruefer, T.; Heinig, K.-H.; von Borany, J.

The increased use of personal computing devices and the Internet of Things (IoT) is accompanied by a demand for a computation unit with extra low energy dissipation. The single electron transistor (SET), which uses a Coulomb island to manipulate the movement of single electrons, is a candidate device for future low power electronics. However, so far its success is hindered by low temperature requirements and the missing CMOS-compatible fabrication route. By combining standard top-down lithography with bottom-up self-assembly of Si nanodots we will overcome this barrier.
In this work, Si nanodots--suitable for RT operation of SETs--are formed in a CMOS compatible way inside a buried SiO2 layer, providing the basic structure of an SET. This is achieved via phase separation induced by ion beam mixing in a geometrical restricted volume, followed by a thermal treatment. Guided by 3DkMC and TRI3DYN simulations, we utilize Helium Ion Microscopy (HIM) to irradiate continuous layers with Ne+, and Si+ broad beam irradiation of pillars. Both attempts lead to a restriction of the size of the collision cascade and hence the mixed volume. The size and position of the formed Si nanodots are studied with transmission electron microscopy, SIMS, and various electrical characterization techniques.

  • Lecture (Conference)
    Ionenstrahltreffen 2017, 13.02.2017, Göttingen, Germany

Permalink: https://www.hzdr.de/publications/Publ-26813
Publ.-Id: 26813


Site-controlled formation of Si nanodots in a buried SiO2 layer via ion-beam implantation and phase separation

Xu, X.; Wolf, D.; Hlawacek, G.; Hübner, R.; Gharbi, A.; Prüfer, T.; Bischof, L.; Heinig, K.-H.; Facsko, S.; von Borany, J.

The increased use of personal computing devices and the Internet of Things (IoT) is accompanied by a demand for a computation unit with extra low energy dissipation. The single electron transistor (SET), which uses a Coulomb island to manipulate the movement of single electrons, is a candidate device for future low power electronics. However, so far its success is hindered by low temperature requirements and the missing CMOS compatible fabrication route. By combining standard top-down lithography with bottom-up self-assembly of Si nanodots we will overcome this barrier.
In this work, Si nanodots--suitable for RT operation of SETs--are formed in a CMOS compatible way inside a buried SiO2 layer, providing the basic structure of an SET. This is achieved via phase separation induced by ion beam mixing in a geometrical restricted volume, followed by a thermal treatment. Guided by 3DkMC and TRI3DYN simulations, we utilize Helium Ion Microscopy (HIM) to irradiate continuous layers with Ne+, and Si+ broad beam irradiation of pillars. Both attempts lead to a restriction of the size of the collision cascade and hence the mixed volume. The size and position of the formed Si nanodots are studied with transmission electron microscopy, SIMS, and various electrical characterization techniques.

  • Lecture (Conference)
    81. DPG-Jahrestagung und DPG-Frühjahrstagung der Sektion Kondensierte Materie, 22.03.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-26812
Publ.-Id: 26812


Site-controlled Si Nanodot Formation for a RT-SET via Ion Beam Mixing and Phase Separation

Xu, X.; Wolf, D.; Prüfer, T.; Hlawacek, G.; Hübner, R.; Bischoff, L.; Perego, M.; Gharbi, A.; Heinig, K.-H.; von Borany, J.

The increased use of personal computing devices and the Internet of Things (IoT) is accompanied by a demand for a computation unit with extra low energy dissipation. The Single Electron Transistor (SET), which uses a Coulomb island to manipulate the movement of single electrons, is a candidate device for future low-power electronics. However, so far its development is hindered by low-temperature requirements and the absence of CMOS compatibility. By combining advanced top-down lithography with bottom-up self-assembly of Si nano dots (NDs) we will overcome this barrier.
In this work, Si NDs – suitable as RT Coulomb islands – are formed via ion beam mixing followed by thermally stimulated phase separation. Broad-beam Si+ and Ne+ beams followed by a rapid thermal annealing (RTA) treatment were utilized to create a layer of NDs, which are subsequently visualized by Energy-Filtered Transmission Electron Microscopy (EFTEM). The conditions for ND formation, namely the dependence on ion type, primary energy, irradiation fluence, layer thickness and thermal budget during RTA, are optimized based on an extensive survey of this multidimensional parameter space. The presented work is guided by TRIDYN simulations of the Si excess in a SiO2 layer due to ion beam mixing and 3D Kinetic Monte-Carlo (3DkMC) simulation for the phase separation during the thermal treatment. To tailor towards a single Si ND, the focused Ne+ beam from the Helium Ion Microscope (HIM) is utilized to create user defined patterns of NDs in planar layer stacks. This allows achieving a mixing volume small enough for restricted Ostwald ripening and successful single ND formation. The existence of the formation of spatially controlled single NDs with a diameter of only 2.2 nm is confirmed by comparing the EFTEM Si plasmon-loss intensity with simulated plasmon loss images.
In the future – by combining conventional lithography, direct self-assembly (DSA) and ion beam mixing – nanopillars with a single embedded ND will be integrated in a CMOS-compatible way. EFTEM and electrical characterization techniques will be used for realizing this novel pathway towards a room-temperature SET device.

This work has been funded by the European Union’s Horizon2020 research program ‘IONS4SET’ under Grant Agreement No. 688072.

  • Lecture (Conference)
    FOR3NANO: Formation of 3D Nanostructures by Ion Beams, 29.06.2017, Helsinki, Finnland

Permalink: https://www.hzdr.de/publications/Publ-26811
Publ.-Id: 26811


Site-controlled Si Nanodot Formation for a RT-SET via Ion Beam Mixing and Phase Separation

Xu, X.; Hlawacek, G.; Wolf, D.; Prüfer, T.; Hübner, R.; Bischoff, L.; Perego, M.; Gharbi, A.; Engelmann, H.-J.; Facsko, S.; Heinig, K.-H.; von Borany, J.

The increased use of personal computing devices and the Internet of Things (IoT) is accompanied by a demand for a computation unit with extra low energy dissipation. The Single Electron Transistor (SET), which uses a Coulomb island to manipulate the movement of single electrons, is a candidate device for future low-power electronics. However, so far its development is hindered by low-temperature requirements and the absence of CMOS compatibility. By combining advanced top-down lithography with bottom-up self-assembly of Si nano dots (NDs) we will overcome this barrier.
In this work, Si NDs – suitable as RT Coulomb islands – are formed via ion beam mixing followed by thermally stimulated phase separation. Broad-beam Si+ and Ne+ beams followed by a rapid thermal annealing (RTA) treatment were utilized to create a layer of NDs, which are subsequently visualized by Energy-Filtered Transmission Electron Microscopy (EFTEM). The conditions for ND formation, namely the dependence on ion type, primary energy, irradiation fluence, layer thickness and thermal budget during RTA, are optimized based on an extensive survey of this multidimensional parameter space. The presented work is guided by TRIDYN simulations of the Si excess in a SiO2 layer due to ion beam mixing and 3D Kinetic Monte-Carlo (3DkMC) simulation for the phase separation during the thermal treatment. To tailor towards a single Si ND, the focused Ne+ beam from the Helium Ion Microscope (HIM) is utilized to create user defined patterns of NDs in planar layer stacks. This allows to achieve a mixing volume small enough for restricted Ostwald ripening and successful single ND formation. The existence of the formation of spatially controlled single NDs with a diameter of only 2.2 nm is confirmed by comparing the EFTEM Si plasmon-loss intensity with simulated plasmon loss images.
In the future – by combining conventional lithography, direct self-assembly (DSA) and ion beam mixing – nanopillars with a single embedded ND will be integrated in a CMOS-compatible way. EFTEM and electrical characterization techniques will be used for realizing this novel pathway towards a room-temperature SET device.

  • Lecture (Conference)
    AVS 64th International Symposium & Exhibition, 01.11.2017, Tampa, FL, USA

Permalink: https://www.hzdr.de/publications/Publ-26810
Publ.-Id: 26810


Junctionless Nanowire Transistors: Promising Devices for Biosensor Applications

Georgiev, Y. M.

Junctionless nanowire transistors (JNTs) are gated resistors where the source, channel and drain have the same type of doping without any dopant concentration gradient. The JNT is the simplest transistor structure possible and probably the most scalable of all field effect transistor (FET) structures. It is easier to fabricate than standard metal-oxide-semiconductor FETs (MOSFETs) and has also a number of performance advantages over them. , , Two of the advantages are especially important for the JNT application as sensors:

1. The current flow in JNTs is not controlled by a reverse biased p-n junction as in standard MOSFETs but entirely by the gate potential. Therefore, they are more sensitive to any change in the electrostatic potential on the channel surface acting as a gate potential.

2. JNTs demonstrate bulk conductance near the centre of the channel, in contrast to the conductance in a thin surface inversion or accumulation layer near the gate in the inversion mode or accumulation mode MOSFETs, which leads to higher drive currents. Moreover, this fact makes the conduction in JNTs less affected by the noise-inducing parasitic surface states than in the case of conventional MOSFETs, which is very important for achieving high signal-to-noise ratio and low detection limit.

In the presentation, these advantages will be discussed in detail followed by results of implementation of silicon (Si) JNTs as chemical and biological sensors. A series of experiments for sensing the ionic strength and the pH value of buffer solutions have proven the excellent sensitivity of these sensors. , Moreover, sensing of the protein streptavidin at a concentration as low as 580 zM has been observed, which is by far the lowest concentration of this protein ever detected and corresponds to detection in the range of only few molecules.

The high sensitivity of JNT sensors, combined with their very simple structure and relaxed fabrication process, makes them promising candidates for cheap mass production by the conventional microelectronic technology. This can enable their numerous applications in various fields where fast, low-cost, label-free, low-volume and real-time detection of chemical and biological species at low detection levels is required.


REFERENCES:

1. J.P. Colinge, C.-W. Lee, A. Afzalian, N. D. Akhavan, R. Yan, I. Ferain, P. Razavi, B. O'Neill, A. Blake, M. White, A.-M. Kelleher, B. McCarthy, R. Murphy. Nanowire transistors without junctions. Nature Nanotech. 5, 225 (2010).
2. J. P. Colinge, C. W. Lee, N. D. Akhavan, R. Yan, I. Ferain, P. Razavi, A. Kranti, R. Yu. Junctionless Transistors: Physics and Properties, in Semiconductor-On-Insulator Materials for Nanoelectronics Applications. (Eds: A. Nazarov, J. P. Colinge, F. Balestra, J.-P. Raskin, F. Gamiz, V. S. Lysenko), Springer-Verlag Berlin, Heidelberg, Germany, pp.187-200, Ch. 10 (2011).
3. J. P. Colinge, A. Kranti, R. Yan, C. W. Lee, I. Ferain, R. Yu, N. D. Akhavan, P. Razavi. Junctionless Nanowire Transistor (JNT): Properties and design guidelines. Solid State Electron. 65-66, 33 (2011).
4. Y.M. Georgiev, N. Petkov, B. McCarthy, R. Yu, V. Djara, D. O'Connell, O. Lotty, A. M. Nightingale, N. Thamsumet, J. C. deMello, A. Blake, S. Das, J. D. Holmes. Fully CMOS-compatible top-down fabrication of sub-50 nm silicon nanowire sensing devices. Microelectron. Eng. 118, 47 (2014).
5. Y. M. Georgiev, R. Yu, N. Petkov, O. Lotty, A. M. Nightingale, J. C. deMello, R. Duffy, J. D. Holmes. Silicon and Germanium Junctionless Nanowire Transistors for Sensing and Digital Electronics Applications, In "Functional Nanomaterials and Devices for Electronics, Sensors and Energy Harvesting", (Eds: A. Nazarov, F. Balestra, V. Kilchytska, D. Flandre), Springer International Publishing AG, Cham, Switzerland, pp. 367-388, Ch. 17 (2014).

  • Lecture (Conference)
    NanoBioSensors Conference, 04.-05.09.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-26809
Publ.-Id: 26809


High Resolution Nanofabrication

Georgiev, Y. M.

Nanofabrication aims at creating structures and devices having minimum dimensions below 100 nm. This is possible to achieve in two main ways: bottom-up and top-down. In the former, the structures and devices are created from small to large in an additive fashion, which relies to a great extent on self-organisation processes. In the latter, the fabrication goes from large to small where nano-structures and devices are carved from a larger piece of material in a subtractive fashion. The top-down approach is much more mature than the bottom-up one and is based on two long-established processes: (i) nanolithography, where a stencil with the required pattern is created in a sacrificial layer called “resist”, deposited on the main working material (substrate), and (ii) pattern transfer through the resist stencil into the base material.
In this paper we will present results on high-resolution nanofabrication of structures and devices with critical dimensions (CD) below 10 nm on silicon (Si), silicon-on-insulator (SOI), germanium (Ge) and germanium-on-insulator (GeOI) substrates. The fabrication was mainly within the frames of the top-down approach and was based on electron beam lithography (EBL) with positive or negative resists followed by a pattern transfer with both additive (metal deposition and lift-off) and subtractive (dry etching) methods.[1-4] Moreover, high-end results on combination of bottom-up and top-down approaches will also be presented such as (i) contacting of bottom-up grown and randomly distributed nanostructures for their integration into functional devices [5] as well as (ii) pattern density multiplication by directed self assembly (DSA) of block-copolymers (BCP).[6,7] We believe that these results are showing some of the promising trends for future development of high-resolution nanofabrication.
References:
[1] Küpper, D., Küpper, D., Wahlbrink, T., Bolten, J., Lemme, M. C., Georgiev, Y. M., & Kurz, H. (2006). Megasonic-assisted development of nanostructures. Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 24(4), 1827.
[2] Georgiev, Y. M., Petkov, N., McCarthy, B., Yu, R., Djara, V., O’Connell, D., … Holmes, J. D. (2014). Fully CMOS-compatible top-down fabrication of sub-50nm silicon nanowire sensing devices. Microelectronic Engineering, 118, 47-53.
[3] Gangnaik, A., Georgiev, Y. M., McCarthy, B., Petkov, N., Djara, V., & Holmes, J. D. (2014). Characterisation of a novel electron beam lithography resist, SML and its comparison to PMMA and ZEP resists. Microelectronic Engineering, 123, 126-130.
[4] Gangnaik, A. S., Georgiev, Y. M., Collins, G., & Holmes, J. D. (2016). Novel germanium surface modification for sub-10 nm patterning with electron beam lithography and hydrogen silsesquioxane resist. Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 34(4), 041603.
[5] Teschome, B., Facsko, S., Schönherr, T., Kerbusch, J., Keller, A., & Erbe, A. (2016). Temperature-Dependent Charge Transport through Individually Contacted DNA Origami-Based Au Nanowires. Langmuir, 32(40), 10159-10165.
[6] Cummins, C., Gangnaik, A., Kelly, R. A., Borah, D., O'Connell, J., Petkov, N., … Morris, M. A. (2015). Aligned silicon nanofins via the directed self-assembly of PS-b-P4VP block copolymer and metal oxide enhanced pattern transfer. Nanoscale, 7(15), 6712-6721.
[7] Cummins, C., Gangnaik, A., Kelly, R. A., Hydes, A. J., O’Connell, J., Petkov, N., … Morris, M. A. (2015). Parallel Arrays of Sub-10 nm Aligned Germanium Nanofins from an In Situ Metal Oxide Hardmask using Directed Self-Assembly of Block Copolymers. Chemistry of Materials, 27(17), 6091-6096.

  • Invited lecture (Conferences)
    5th International workshop “Nano-Fabrication, Devices & Metrology”, 19.-20.06.2017, Eindhoven, The Netherlands

Permalink: https://www.hzdr.de/publications/Publ-26808
Publ.-Id: 26808


Dopant Induced Single Electron Tunneling within the Sub-bands of Single Silicon NW Tri-gate Junctionless n-MOSFET

Uddin, W.; Georgiev, Y. M.; Maity, S.; Das, S.

We report 1D electron transport of silicon functionless tri-gate n-type transistor at 4.2 K. The step like curve observed in the current voltage characteristic suggests 1D transport. Besides the current steps for 1D transport, we found multiple spikes within individual steps, which we relate to inter-band single electron tunnelling, mediated by the charged dopants available in the channel region. Clear Coulomb diamonds were observed in the stability diagram of the device. It is shown that a uniformly doped silicon nanowire can provide us the window for the single electron tunnelling. Back-gate versus front-gate color plot, where current is in a color scale, shows a crossover of the increased conduction region. This is a clear indication of the dopant–dopant interaction. It has been shown that back-gate biasing can be used to tune the coupling strength between the dopants.

Keywords: functionless transistor; 1D transport; single electron tunnelling; Coulomb blocked; dopant–dopant interaction

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-26807
Publ.-Id: 26807


Doping top-down e-beam fabricated germanium nanowires using molecular monolayers

Long, B.; Alessio Verni, G.; O’Connell, J.; Shayesteh, M.; Gangnaik, A.; Georgiev, Y. M.; Carolan, P.; O’Connell, D.; Kuhn, K. J.; Clendenning, S. B.; Nagle, R.; Duffy, R.; Holmes, J. D.

This paper describes molecular layer doping of Ge nanowires. Molecules containing dopant atoms are chemically bound to a germanium surface. Subsequent annealing enables the dopant atoms from the surface bound molecules to diffuse into the underlying substrate. Electrical and material characterisation was carried out, including an assessment of the Ge surface, carrier concentrations and crystal quality. Significantly, the intrinsic resistance of Ge nanowires with widths down to 30 nm, doped using MLD, was found to decrease by several orders of magnitude.

Keywords: Molecular layer doping; Nanowires; Semiconductors; Germanium; Conformal; Non-destructive

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-26806
Publ.-Id: 26806


Frequency modulation of backward volume spin wave by electric current

Nishida, N.; Lee, S. W.; Lee, S. J.; Lee, K. J.; Schultheiss, H.; Sekiguchi, K.

In the field of magnonics, spin waves are envisioned as a new candidate for information transport and processing. Since spin waves propagate without any charge displacement and are free from Joule heating, they offer significant reduction of energy consumption in devices. The spin transfer torque (STT) effect originating from conduction electrons is a powerful method for modulating spin waves. Here, we investigated the current induced Doppler shift of backward volume spin waves.
We fabricated a NiFe stripe with a width of 2 µm, which was magnetized in backward volume configuration. The antennas fabricated on top of the NiFe stripe were connected to a vector network analyzer for measuring the spin-wave spectra. We applied a dc current to the NiFe stripe. For a current density of 5 × 10^10 A/m^2 the spin-wave frequencies shifted +170 MHz compared to the spin-wave spectra without dc current. This frequency shift is 60 times larger than previous works reported for forward volume spin waves. Hence, we demonstrated giant frequency modulation of backward volume spin waves by a dc current.

  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-26805
Publ.-Id: 26805


Magnetotransport in Half-Metallic Manganese Ruthenium Gallium

Fowley, C.; Rode, K.; Borisov, K.; Atcheson, G.; Lau, Y.-C.; Thiyagarajah, N.; Coey, M.; Stamenov, P.; Gallardo, R.; Kampert, E.; Wang, Z.; Lindner, J.; Deac, A. M.

The recently discovered fully-compensated half-metal, manganese ruthenium gallium (MRG), is a very promising material for spintronics. It possesses tunable magnetic moment, high magnetic anisotropy field and high spin polarisation. Here, we use the extraordinary Hall effect and longitudinal magnetoresistance to characterise the properties of MRG. Experiments are carried out in pulsed magnetic fields up to 60 T at the Dresden High Magnetic Field Laboratory (HLD). The spin-flop transition, as well as a large spontaneous Hall angle are observed. The spontaneous Hall angle is over 2% and is seen to be independent of temperature. The magneto-transport in MRG is shown to be dominated by one sublattice only, even at the magnetic compensation temperature (i.e. when the total magnetic moment is zero). MRG behaves magnetically an antiferromagnet and electrically as a normal ferromagnet with a sizeable spin-polarisation.

Keywords: anomalous Hall effect; half-metals; Heusler alloys; ferrimagnetism; high magnetic fields

  • Lecture (Conference)
    81. DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Germany
  • Lecture (Conference)
    Intermag 2017, 24.-28.04.2017, Dublin (Baile Átha Cliath), Ireland (Éire)

Permalink: https://www.hzdr.de/publications/Publ-26804
Publ.-Id: 26804


Phase stability of magnonic logic operation in the microfabricated ferromagnetic stripe

Nishida, N.; Lee, S. J.; Lee, S. W.; Lee, K. J.; Sekiguchi, K.; Schultheiss, H.

Magnons, which are the quasi-particles of spin waves, have a great potential to realization of low-energy-dissipation devices, because the magnons deliver an angular momentum and the propagation of magnons is free from Joule heating. Magnons are expected as non-charged new information carriers[1], and logic operation of magnons is demonstrated in ferromagnetic thin film[2]. In order to apply to actual devices, miniaturization of logic circuits is essential for integration of circuits. However, in the micrometer-sized magnon waveguides a confinement of magnon emerges[3] and make magnon propagation complex.
In order to make clear the logic operation of magnon in the micro waveguides, we measured magnon densities of spin-wave interference in 2.5-µm-wide ferromagnetic stripe using microfocused Brillouin light scattering spectroscopy. Spatial mapping of the magnon density revealed that the interference pattern of spin wave is confined within a limited area because of contributions of transverse quantized modes. In the limited area the phase of interference pattern is able to be controlled by the spin-wave phase. A micromagnetic simulation revealed transverse 100 nm interference patterns, which affect a signal-to-noise ratio of logic operation. These results will be important to decide the design of integrated magnonic devices.

References
[1] A. V. Chumak et al., Nat. Commun. 5, 4700 (2014).
[2] N. Sato et al., Appl. Phys. Express 6, 063001 (2013).
[3] P. Pirro et al., Phys. Status Solidi B 248, 1404 (2011).

  • Poster
    633. WE-Heraeus-Seminar on `Spin Orbit Dynamics – Connecting timescales from nanoseconds to femtoseconds', 04.-06.01.2017, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-26803
Publ.-Id: 26803


Incorporation of Europium(III) into Scheelite-Related Host Matrices ABO4 (A = Ca2+, Sr2+, Ba2+; B = W6+, Mo6+): Role of A- and B- Sites on the Dopant Site-Distribution and Photoluminescence

Xiao, B.; Schmidt, M.

Calcium orthotungstates and -molybdates are naturally occurring minerals that have been studied extensively. The minerals are named scheelite (CaWO4) and powellite (CaMoO4), respectively. Scheelite is the most important economic W mineral. Powellite is actively studied in the nuclear waste management field. Powellite is one of the primary Mo crystalline phases expected to form in high-level nuclear waste (HLW) borosilicate glasses during waste processing.
Both scheelite and powellite have a large number of synthetic derivatives that are based on a general formula ABO4 (A = Ca2+, Sr2+, Ba2+; B = W6+, Mo6+). Recently, much of the interest in study of scheelite-type materials arises from their exceptional compositional variability. In the context of nuclear waste disposal, this compositional variability offers a potential pathway for the effective retention of highly radiotoxic actinides like Pu and Am in a powellite secondary phase. However, the thermodynamic stability of these solid solutions will depend on their structural deviation from the stoichiometric phases.
Investigations have shown that the presence of excess positive charge in scheelite-typed ABO4 materials upon incorporation of each trivalent ion is compensated via coupled substitution with a monovalent alkali cation. Single-crystal X-ray measurements demonstrate that the crystal structure of the resulting solid solutions is disordered, that is, the trivalent dopant and monovalent charge-compensating cation statistically occupy the same divalent A2+ site in ABO4 structure. However, the structural details behind such disordered substitution, such as specific ionic environment around dopants, number of non-equivalent doping species as well as spatial accommodation of doping centers, are difficult parameters to characterize from the crystallographic data, especially when the dopant is present at trace concentration levels.
Polarization-dependent site-selective time resolved laser-induced fluorescence spectroscopy (p-TRLFS) is unique in its capability to characterize the local environment of a fluorescent probe, here Eu3+, in a multi-species system with point-group accuracy at trace concentration levels. This work aims to clarify the impact of site effect on the local symmetry distortion from the bulk crystallographic site symmetry in scheelite-type ABO4 single crystals. This will improve our understanding of the formation of solid solutions on the molecular scale.

Keywords: TRLFS

  • Lecture (Conference)
    GeoBremen, 24.-29.09.2017, Bremen, Germany

Permalink: https://www.hzdr.de/publications/Publ-26801
Publ.-Id: 26801


Lattice location and electrical activation of tellurium in hyperdoped silicon

Wang, M.; Berencén, Y.; Prucnal, S.; Hübner, R.; Yuan, Y.; Xu, C.; Rebohle, L.; Böttger, R.; Heller, R.; Skorupa, W.; Helm, M.; Zhou, S.

Silicon hyperdoped with chalcogens beyond the equilibrium solubility limit exhibits sub-band gap optical absorption, presenting a potential material for silicon-based optoelectronic applications [1-3]. In our work, tellurium hyperdoped silicon was obtained by ion implantation combined with pulsed laser melting. The crystallization of implanted layers and the lattice location of impurities in silicon matrix were determined by the Rutherford backscattering spectrometry / channeling (RBS/C). The chemical states of tellurium dopants in tellurium-hyperdoped silicon were probed by the tellurium K-edge X-ray absorption fine structure spectroscopy. The electrical transport reveals the insulator-to-metal transition (IMT) in tellurium-hyperdoped silicon, which is confirmed and understood by using calculations based on the density functional theory. However, the critical tellurium concentration for IMT is much higher than the calculated value. The lattice location results suggest that a significant fraction of the tellurium atoms form dimers, which are electrically deactivated. After considering this fraction, the critical concentration claimed from the DFT calculation is consistent with the number of electrically activated tellurium atoms.

[1] T. G. Kim, J.M. Warrender, M. J. Aziz, Applied Physics Letters 88(24), 2006, 1850.
[2] M. Tabbal, T. G. Kim, D. N. Woolf, et al. Applied Physics A 98(3), 2010, 589-594.
[3] Y. Berencén, S. Prucnal, L. Fang, et al. Scientific Reports 7, 2017, 43688.

Keywords: hyperdoped Si; Rutherford backscattering spectrometry; channeling (RBS/C); insulator-to-metal transition (IMT)

  • Lecture (Conference)
    The 23rd International Conference on Ion Beam Analysis, 08.-13.10.2017, Shanghai, China

Permalink: https://www.hzdr.de/publications/Publ-26800
Publ.-Id: 26800


GaAs-based core/shell nanowires with extremely large lattice mismatch grown on Si substrates

Balaghi, L.; Hübner, R.; Bussone, G.; Grifone, R.; Grenzer, J.; Ghorbani Asl, M.; Krasheninnikov, A.; Hlawacek, G.; Schneider, H.; Helm, M.; Dimakis, E.

The geometry and high surface-to-volume ratio of nanowires offer unique possibilities for strain engineering in epitaxial semiconductor heterostructures with large lattice mismatch. In addition, the possibility to grow nanowires of high crystal quality epitaxially on Si substrates adds to their technological significance. In this work, we have investigated the growth of free-standing GaAs/InxGa1-xAs and GaAs/InxAl1-xAs core/shell nanowires on Si(111) substrates by molecular beam epitaxy, the accommodation of the lattice mismatch therein, and its effect on the nanowire properties.
Very thin GaAs core nanowires (20-25 nm in diameter) were grown in the self-catalyzed mode with a sufficiently low number density (to avoid beam shadowing effects) on SiOx/Si(111) substrates, after an in situ treatment of the latter with Ga droplets. This resulted in zinc blende nanowires with their axis along the [111] crystallographic direction and six {1-10} sidewalls. Subsequently, conformal overgrowth of the InxGa1-xAs or InxAl1-xAs shell was obtained only under kinetically limited growth conditions that suppressed mismatch-induced bending phenomena.
The strain in the core and the shell was studied systematically as a function of the shell composition and thickness. To that end, we used Raman scattering spectroscopy, transmission electron microscopy and synchrotron X-ray diffraction, and compared the results with theoretical predictions based on continuum elasticity and density functional theories. Our results demonstrate that highly mismatched core/shell nanowires with defect-free interface can be obtained beyond what is possible in thin film heterostructures.
More interestingly, nanowires with strain-free shell and fully strained core can be grown under certain conditions. The large strain in the GaAs core is expected to have a strong effect on its fundamental properties. Here, we demonstrate a large shrinkage of the band gap, which can be as high as 35 % depending on the composition of the shell.

  • Lecture (Conference)
    Austrian MBE Workshop 2017, 28.-29.09.2017, Wien, Austria

Permalink: https://www.hzdr.de/publications/Publ-26799
Publ.-Id: 26799


Sub-band-gap optical response in Au-implanted silicon

Wang, M.; Berencén, Y.; Prucnal, S.; Hübner, R.; Yuan, Y.; Xu, C.; Rebohle, L.; Böttger, R.; Heller, R.; Skorupa, W.; Helm, M.; Zhou, S.

Recently it was suggested that Au doping in Si can be realized by ion implantation and pulsed laser melting. The sub-band-gap optoelectronic response is observed and increases with the implanted Au concentration [1]. In our work, Au implanted Si was fabricated by ion-implantation with three different fluences of 7×1014 cm-2, 1.4×1015 cm-2 and 2.1×1015 cm-2, followed by pulsed laser melting. The Raman spectrum results confirm the high-quality recrystallization of the Au implanted layer. And the Rutherford backscattering spectrometry / Channeling reveal that Au atoms diffused to the near surface region. In addition the detailed angular scans along Si [001] reveal that Au atoms are mostly in the interstitial lattice sites. From the transport measurements, a p-type conductivity and an increasing carrier concentration are observed in the implanted layer. Moreover, the transmission and reflection were measured using near infrared spectroscopy (NIR) to quantify the sub-band-gap absorptance in the hyperdoped silicon. In the Au implanted layer the spectral response extends to wavelengths as long as 3.2 μm. However, the sub-band-gap absorptance has no dependence on the Au fluence or the carrier concentration.

[1] Mailoa, Jonathan P., et al., Nat. Commun. 5, 3011 (2014)

Keywords: Sub-band-gap optical response; Si; Au-implanted

  • Poster
    19th International Conference on Radiation Effects in Insulators, 02.-07.07.2017, Versailles, France

Permalink: https://www.hzdr.de/publications/Publ-26797
Publ.-Id: 26797


Compositional and strain analysis of In(Ga)N/GaN short period superlattices

Dimitrakopulos, G. P.; Vasileiadis, I. G.; Bazioti, C.; Smalc-Koziorowska, J.; Kret, S.; Dimakis, E.; Florini, N.; Kehagias, T.; Suski, T.; Karakostas, T.; Moustakas, T. D.; Komninou, P.

Extensive high resolution transmission and scanning transmission electron microscopy observations were performed in In(Ga)N/GaN multi-quantum well short period superlattices comprising twodimensional quantum wells (QWs) of nominal thicknesses 1, 2, and 4 monolayers (MLs) in order to obtain a correlation between their average composition, geometry, and strain. The high angle annular dark field Z-contrast observations were quantified for such layers, regarding the indium content of the QWs, and were correlated to their strain state using peak finding and geometrical phase analysis. Image simulations taking into thorough account the experimental imaging conditions were employed in order to associate the observed Z-contrast to the indium content. Energetically relaxed supercells calculated with a Tersoff empirical interatomic potential were used as the input for such simulations. We found a deviation from the tetragonal distortion prescribed by continuum elasticity for thin films, i.e., the strain in the relaxed cells was lower than expected for the case of 1 ML QWs. In all samples, the QW thickness and strain were confined in up to 2 ML with possible indium enrichment of the immediately abutting MLs. The average composition of the QWs was quantified in the form of alloy content.

Permalink: https://www.hzdr.de/publications/Publ-26796
Publ.-Id: 26796


Hyperdoping silicon with tellurium for optoelectronics

Wang, M.; Berencén, Y.; Prucnal, S.; Hübner, R.; Yuan, Y.; Xu, C.; Rebohle, L.; Böttger, R.; Heller, R.; Schneider, H.; Skorupa, W.; Helm, M.; Zhou, S.

Chalcogen-hyperdoped silicon has been a topic of great interest due to its potential optoelectronic applications owing to the sub-band gap absorption [1-3]. In our work, tellurium hyperdoped Si was fabricated by ion-implantation with different fluences ranging from 1.09×1015 to 1.25×1016 cm-2 followed by pulsed laser melting (PLM). The Rutherford backscattering spectrometry / Channeling (RBS/C) results reveal the high-quality recrystallization of tellurium implanted silicon by PLM. From the transport measurements, an insulator-to-metal transition is observed with increasing tellurium concentration. Moreover, the ellipsometry measurements show that the band gap narrows with increasing tellurium doping concentration. And the Fourier transform infrared (FTIR) spectroscopy show that tellurium hyperdoped Si has strong infrared absorption. This gives us a signal that hyperdoped silicon with tellurium could enable silicon-based optoelectronics in the infrared band.

Keywords: Hyperdoping; pulsed laser melting (PLM); silicon; optoelectronics

  • Poster
    19th International Conference on Radiation Effects in Insulators, 02.-07.07.2017, Versailles, France

Permalink: https://www.hzdr.de/publications/Publ-26795
Publ.-Id: 26795


Asymmetric strip line electrodes for photoconductive terahertz emission

Singh, A.; Winnerl, S.; König-Otto, J. C.; Stephan, D. R.; Helm, M.; Schneider, H.

Here we studied various combinations (two symmetric and two asymmetric designs) of stripline widths for stripline photoconductive emitters fabricated on semi-insulating GaAs. We found out that the THz emission efficiency depends strongly on the anode width. The wider the anode, the higher is the THz amplitude. Cathode width does not play a significant role in THz emission performance.

Keywords: Terahertz emitter; stripline; antenna; GaAs

  • Poster
    Optical Terahertz Science and Technology (OTST 2017), 02.-07.04.2017, London, UK

Permalink: https://www.hzdr.de/publications/Publ-26794
Publ.-Id: 26794


Short-time annealing for nanomaterials

Neubert, M.; Rebohle, L.; Berencen, Y.; Prucnal, S.; Hübner, R.; Böttger, R.; Georgiev, Y.; Erbe, A.; Helm, M.; Skorupa, W.

Semiconductor structures with dimensions in the nanometer range become more and more important in microelectronics and other new emerging technologies. Thereby, the transition from bulk to nanomaterials often requires significant changes in the process technology, including the change from equilibrium to non-equilibrium processes. In this work, we investigate the modification of nanomaterials by flash lamp annealing with pulse lengths in the millisecond range [1]. In detail, we focus on two specific materials: (i) the annealing of thin ZnO layers and the impact of different process conditions on the materials properties, and (ii) the high-level doping of Si and Ge nanowires for sensor applications by ion implantation and flash lamp annealing.

Keywords: Semiconductor; hyperdoping; flash lamp annealing; nanomaterials

  • Lecture (Conference)
    NanoApp 2017, 14.-18.06.2017, Bled, Slovenia

Permalink: https://www.hzdr.de/publications/Publ-26793
Publ.-Id: 26793


How indium nitride senses water

Jovic, V.; Moser, S.; Ulstrup, S.; Goodacre, D.; Dimakis, E.; Koch, R.; Katsoukis, G.; Moreschini, L.; Mo, S.-K.; Jozwiak, C.; Bostwick, A.; Rotenberg, E.; Moustakas, T. D.; Smith, K. E.

The unique electronic band structure of indium nitride InN, part of the industrially significant III−N class of semiconductors, offers charge transport properties with great application potential due to its robust n-type conductivity. Here, we explore the water sensing mechanism of InN thin films. Using angle-resolved photoemission spectroscopy, core level spectroscopy, and theory, we derive the charge carrier density and electrical potential of a two-dimensional electron gas, 2DEG, at the InN surface and monitor its electronic properties upon in situ modulation of adsorbed water. An electric dipole layer formed by water molecules raises the surface potential and accumulates charge in the 2DEG, enhancing surface conductivity. Our intuitive model provides a novel route toward understanding the water sensing mechanism in InN and, more generally, for understanding sensing material systems beyond InN.

Keywords: Sensor; two-dimensional electron gas (2DEG); ARPES; surface electronic potential; quantum well

Permalink: https://www.hzdr.de/publications/Publ-26792
Publ.-Id: 26792


Investigation of an 18F-labelled Imidazopyridotriazine for Molecular Imaging of Cyclic Nucleotide Phosphodiesterase 2A

Schröder, S.; Wenzel, B.; Deuther-Conrad, W.; Teodoro, R.; Kranz, M.; Scheunemann, M.; Egerland, U.; Höfgen, N.; Briel, D.; Steinbach, J.; Brust, P.

Specific radioligands for in vivo visualization and quantification of cyclic nucleotide phosphodiesterase 2A (PDE2A) by positron emission tomography (PET) are increasingly gaining interest in brain research. Herein we describe the synthesis, the 18F-labelling as well as the biological evaluation of our latest PDE2A (radio-)ligand 9-(5-Butoxy-2-fluorophenyl)-2-(2-([18F])fluoroethoxy)-7-methylimidazo[5,1-c]pyrido[2,3-e][1,2,4]triazine (([18F])TA5). It is the most potent PDE2A ligand out of our series of imidazopyridotriazine-based derivatives so far (IC50 hPDE2A = 3.0 nM; IC50 hPDE10A > 1000 nM). Radiolabelling was performed in a one-step procedure starting from the corresponding tosylate precursor. In vitro autoradiography on rat and pig brain slices displayed a homogenous and non-specific binding of the radioligand. Investigation of stability in vivo by RP-HPLC and micellar liquid chromatography (MLC) analyses of plasma and brain samples obtained from mice revealed a high fraction of one main radiometabolite. Hence, we concluded that [18F]TA5 is not appropriate for molecular imaging of PDE2A neither in vitro nor in vivo. Our ongoing work is focusing on further structurally modified compounds with enhanced metabolic stability.

Keywords: Phosphodiesterase 2A (PDE2A); secondary messengers; PDE2A radioligands; positron emission tomography (PET); neuroimaging; metabolic stability; micellar liquid chromatography (MLC)

Permalink: https://www.hzdr.de/publications/Publ-26791
Publ.-Id: 26791


Theoretische und experimentelle Untersuchung des Wärmeübergangs an berippten Rohren unter Naturkonvektion

Thiele, J.

In dieser Diplomarbeit werden experimentelle Untersuchungen zum Wärmeübergang an berippten Rohren unter Naturkonvektion bei unterschiedlichen Randbedingungen durchgeführt und ausgewertet. Kernthema dieser Arbeit ist der Einfluss des Rippenabstandes und des Neigungswinkels eines ovalen Rohres bei glatten Rippen und bei Stiftrippen. Untersucht werden Rippenrohre mit einem Rippenabstand von 6 mm, 11 mmund 16 mm. Der Einfluss des Neigungswinkels der Rohre wird bei 0° (horizontale Ausrichtung), 20°, 30° und 40° analysiert. Dafür wird die äußere Rippenrohroberfläche auf 30 °C bis 90 °C (in 10 °C Schritten) erwärmt. Die Oberflächentemperatur der Rippe wird durch Thermoelemente, die an verschiedenen Positionen befestigt sind, gemessen. Daraus lassen sich der Wärmeübergangskoeffizient und der Rippenwirkungsgrad als signifikante Parameter berechnen. In dieser Arbeit wurden folgende Erkenntnisse gewonnen. Das Anwinkeln des Rohres hat keine signifikanten Auswirkungen auf den Wärmeübergangskoeffizienten. Ein Neigungswinkel von 30°weist dabei die beste Performance auf. Eine Vergrößerung des Wärmeübergangskoeffizienten um 14% ist möglich. Die Verwendung von Stiftrippen zeigt keine größeren Werte für den Wärmeübergangskoeffizienten. Lediglich die Rippenrohre mit größeren Rippenabständen verbessern den konvektiven Wärmeübergang. Durch einen Abstand von 16mm kann der Wärmeübergangskoeffizient um bis zu 100 % gegenüber einem Rohr mit einem Rippenabstand von 6 mm gesteigert werden. Der Rippenwirkungsgrad ist am kleinsten, wenn der Rippenabstand am größten ist. Eine Verschlechterung um 25 % ist möglich. Die größten Rippenwirkungsgrade werden bei einem Neigungswinkel von 40° erreicht. Dies gilt sowohl für die Stiftrippe als auch die Glattrippe. Die Untersuchungen liefern einen Beitrag für das Verständnis von Auswirkungen geometrischer Veränderungen an Rippenrohren auf den luftseitigen Wärmeübergang. In Zukunft können diese Erkenntnisse genutzt werden, um die Effizienz von luftgekühlten Wärmeübertragern zu steigern.

This diploma thesis considers the natural convective heat transfer on finned tubes under different boundary conditions. Object of this study is the influence of the fin spacing and the angle of inclination of an oval tube with plain fins or with pin-fins. Finned tubes with a fin spacing of 6mm, 11 mm and 16 mmare examined. The inclination angle of the tubes is evaluated at 0°(horizontal alignment), 20°, 30° and 40°. For that purpose, the finned tubes are heated up between 30 °C and 90 °C in increments of 10 °C. At different position on the fins thermocouples are located to measure the surface temperature. The heat transfer coefficient and the fin efficiency are significant parameters, which can be calculated from the measured temperatures. The increase of the inclination angle has little effect on the heat transfer coefficient. The highest performance improvement has been observed at an inclination angle of 30°, which shows about 14 % enhanced heat transfer coefficient. Pin fins do not enhance the heat transfer coefficient. Finned tubes with larger fin spacing improve the convective heat transfer. The heat transfer coefficient can be enhanced up to 100 % for a spacing of 16mm compare to a tube with a fin spacing of 6 mm. Finned tubes with smaller fin spacing improve the fin efficiency, which can beenhanced up to 25% for a spacing of 6 mm compare to a tube with a fin spacing of 16 mm. The highest values for the fin efficiency have been observes at an inclination angle of40°. The research contributes to understand the effect of geometrical changes on the air-side heat transfer of finned oval tubes. These applications can be used to increase the efficiency of air-cooled heat exchangers in the future.

  • Diploma thesis
    TU Dresden, 2018
    Mentor: Sebastian Unger, Matthias Beyer
    103 Seiten

Permalink: https://www.hzdr.de/publications/Publ-26789
Publ.-Id: 26789


Investigating the structure of crosslinked polymer brushes (brush-gels) by means of Positron Annihilation Spectroscopy

Dehghani, E. S.; Aghion, S.; Anwand, W.; Consolati, G.; Ferragut, R.; Panzarasa, G.

Polymer brushes can be useful as small-scale reactors for the controlled synthesis of nanoparticles, an approach which is gaining increasing interest. In this context, chemical crosslinking of polymer brushes could be considered as a viable approach to control the size and size distribution of the formed nanoparticles. Here we describe the application of Positron Annihilation Spectroscopy (PAS) for the characterization of crosslinked polymer brushes (brush-gels). Poly(hydroxyethyl methacrylate) (PHEMA) brushes were obtained on silicon substrates by means of a surface-initiated atom transfer radical polymerization (SI-ATRP). Crosslinking was achieved during the polymerization by adding different amounts of diethyleneglycol dimethacrylate (DEGDMA) as a difunctional monomer. The resulting brushes, both un- and crosslinked, were then post-modified with carboxylic acid groups, allowing the in situ synthesis of silver nanoparticles after ion exchange with silver nitrate and reduction with sodium borohydride. The detailed characterization of such systems is notoriously challenging and PAS proved to be an effective, non-invasive technique to acquire insight on the structure of the brushes and of their nanoparticle composites.

Keywords: Polymer brushes nanoparticles Positron Annihilation Spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-26788
Publ.-Id: 26788


DFT-MD simulations of mixing properties in warm dense plastic

Vorberger, J.

Mixtures of carbon and hydrogen at megabar conditions and at temperatures below one electronvolt can be found in a variety of planets of our solar system like Uranus and Neptune and are believed to feature prominently in extrasolar planets. The equation of state, transport and mixing properties of carbo-hydrates thus strongly influence the inner structure and evolution of these astrophysical objects.
We present results of density-functional molecular dynamics simulations for the structure and mixing properties of carbo-hydrates at such conditions in order to explain recent experimental results showing the demixing of carbon and hydrogen and the formation of nano-diamonds at double shock conditions.

Keywords: warm dense matter; plastic; CH; DFT-MD; x-ray scattering; planets; planetary interior

  • Lecture (Conference)
    38th Hirschegg meeting on High Energy Density Physics, 28.01.-02.02.2018, Hirschegg, Österreich
  • Invited lecture (Conferences)
    Satellite Meeting to the DESY Photon Science Users' Meeting 2019 'Light-Matter Interaction: Recent Advances in Theory', 23.-25.01.2019, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26787
Publ.-Id: 26787


Rodare - Rossendorf Data Repository

Frust, T.

Rodare (Rossendorf Data Repository) is the data publication platform at HZDR. Rodare is based on the Invenio framework (http://invenio-software.org) and is a fork of the popular data publication service Zenodo which is offered by CERN. Rodare allows HZDR researchers to publish their research data to make them citeable, discoverable and reusable.

Keywords: Rodare; Data repository; Open Science; Open Access

  • Software in external data repository
    Publication year 2018
    Programming language: Python, Javascript
    System requirements: Python 3, Elasticsearch, Postgresql, RabbitMQ, Redis, Nginx, HAproxy
    License: GPLv3 (Link to license text)
    Hosted on HZDR GitLab: Link to location

Permalink: https://www.hzdr.de/publications/Publ-26785
Publ.-Id: 26785


Comparison of tumour hypoxia measured by FMISO-PET and gene signatures for patients with HNSCC

Löck, S.; Linge, A.; Seidlitz, A.; Bandurska-Luque, A.; Großer, M.; Baretton, G. B.; Zöphel, K.; Zips, D.; Troost, E. G. C.; Krause, M.; Baumann, M.

Purpose: Tumour hypoxia is well known to increase radio-resistance of tumours. In a recent prospective biomarker imaging trial, hypoxia has been measured by [18F]fluoromisonidazole positron emission tomography (FMISO-PET) scans [1,2]. Here, we compared hypoxia imaging with the expression of hypoxia-associated gene signatures for patients with locally advanced head and neck squamous cell carcinoma (HNSCC) treated by primary radiochemotherapy (RCHT).

Material and methods: FMISO-PET imaging and gene expression analyses were performed on the cohort of 50 HNSCC patients [1,2]. For this study, the FMISO-PET parameters tumour-to-background ratio (TBPpeak) and hypoxic tumour volume (HV1.6) analysed before RCHT were considered. Expressions of 15-, 26- and 30-gene hypoxia-associated signatures [3-5] were analysed from formalin-fixed paraffin-embedded (FFPE) tumour biopsies obtained before RCHT using the GeneChip® Human Transcriptome Array 2.0 (Affymetrix) and nanoString analysis. Gene expressions were compared between the two methods using the Pearson correlation coefficient. Linear regression was applied to relate TBRpeak and HV1.6 to the mean expression of the gene signatures, including the interaction with tumour volume which was assessed on the planning CT by an experienced radiation oncologist. The association of FMISO-PET parameters and gene expressions to loco-regional control (LRC) and progression-free survival (PFS) was assessed by Cox regression.

Results: The mean expressions of all hypoxia-associated gene signatures were highly correlated between Affymetrix and nanoString analyses (R>0.5). While TBRpeak and HV1.6 were weakly correlated with the expression of hypoxia-associated genes alone, significant correlations were observed if the interaction term of gene expression and tumour volume was included (R>0.5). Both FMISO-PET parameters were significantly correlated with LRC and PFS (p<0.01), while the combination of hypoxia-associated gene expressions and their interaction with tumour volume showed a significant but weaker correlation for the 30-gene signature to LRC and for the 15- and 30-gene signature to PFS (p<0.05). The figure shows patient stratifications using HV1.6 (p=0.02), the 30-gene signature (p=0.07) and their combination (p<0.01).

Conclusion: Hypoxia imaging correlates to the expression of hypoxia-associated genes if the interaction of gene expression and tumour volume is included. Interestingly, both methods may complement each other, which may be of advantage for identifying patients who are at high risk of treatment failure and may benefit from dose escalation. While FMISO-PET directly measures hypoxia, the gene signatures are also associated with other radiobiologic phenomena such stemness of cancer cells.

  • Lecture (Conference)
    ESTRO 36, 05.-09.05.2017, Wien, Österreich
  • Open Access Logo Abstract in refereed journal
    Radiotherapy and Oncology 127(2018), S136-S137
    DOI: 10.1016/S0167-8140(18)30579-6

Permalink: https://www.hzdr.de/publications/Publ-26784
Publ.-Id: 26784


Development of short-pulsed, high-field electromagnets for laser-based proton therapy

Schürer, M.; Herrmannsdörfer, T.; Karsch, L.; Kroll, F.; Masood, U.; Sobiella, M.; Pawelke, J.

The new particle acceleration by high intensity laser promises more compact and economic accelerators for cancer treatment. However, the resulting particle beam is pulsed with an ultra-short pulse-duration (~ ps) and has a large divergence and broad energy spectrum. Within the German joint research project “onCOOPtics” the clinical applicability of laser-driven proton beams is investigated including the development of a laser accelerator and suitable beam transport. The designed magnets are intended for a compact beam transport system (gantry) which efficiently transports proton pulses (≤ 220 MeV) from generation to treatment site. For this purpose the initially divergent proton beam is captured by a cylindrical electromagnet (solenoid), deflected by 45° dipole magnets and focussed by quadrupole magnets, while the energy window is selected by adjustable lead apertures. The implementation as short-pulsed (~ 1 ms) electromagnets allows to generate very high magnetic field strengths (up to 20 T) for short times, which enables the compact construction of both individual magnets and the whole gantry system. The pulse frequency of the magnets can be synchronized with that of the laser accelerator. The high field strengths demand high peak currents (up to 20 kA) and the resultant heating is dissipated by a cooling integrated into the magnets. The in-house developed pulsed magnets will enable a proton gantry 2-3 times smaller than those used in current clinical installations. Pulsed solenoids have been completely engineered and tested, and are routinely applied at laser particle accelerators. Two prototypes of a pulsed dipole and a first pulsed quadrupole were designed and manufactured, and their experimental characterization at the University Proton Therapy Dresden is in progress.
Pulsed electromagnets are crucial components of a compact gantry and after their extensive individual testing they will be combined step-by-step and used at the laser proton accelerator.

  • Poster
    Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreiländertagung der MEDIZINISCHEN PHYSIK, 10.-13.09.2017, Dresden, Deutschland
    DOI: 10.1515/bmt-2017-5078
  • Open Access Logo Abstract in refereed journal
    Biomedical Engineering / Biomedizinische Technik 62(2017)Suppl. 1, S412
    DOI: 10.1515/bmt-2017-5078

Permalink: https://www.hzdr.de/publications/Publ-26783
Publ.-Id: 26783


Saturation correction in pulsed fields of high dose-per-pulse

Gotz, M.; Karsch, L.; Pawelke, J.

Current developments in accelerator technology and beam application have the potential to bring pulsed radiation sources with very high dose-per-pulse into clinical application. In particular, laser-based particle accelerators and pencil beam scanning using synchro-cyclotrons provide intensely pulsed beams. Current methods to determine the saturation correction factor (ks) in ionization chambers are not intended for use at such high dose-per-pulse, possibly leading to an inaccurate dosimetry. We present a method based on the numerical approximation of the ionization, charge reaction and transport processes in an ionization chamber, which is able to overcome the limitations of current procedures used to calculate ks . This numerical work is supported by experimental data of a plane-parallel advanced Markus ionization chamber irradiated with a pulsed electron beam of a dose-per-pulse up to 600 mGy. At a low collection voltage of 100 V a satisfactory description of the saturation correction dependency on dose-per-pulse can be achieved using existing models and tuning their parameter values. However, at the reference voltage of 300 V this is not possible and the newly presented method shows marked improvements. Chief among the additional effects considered in the presented numerical method is the shielding of the electric field by the liberated charges, which alters the dose-per-pulse dependency of ks in a way that can not be replicated by existing approaches.

  • Poster
    Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreiländertagung der MEDIZINISCHEN PHYSIK, 10.-13.09.2017, Dresden, Deutschland
    DOI: 10.1515/bmt-2017-5029
  • Open Access Logo Abstract in refereed journal
    Biomedical Engineering / Biomedizinische Technik 62(2017)Suppl. 1, S129
    DOI: 10.1515/bmt-2017-5029

Permalink: https://www.hzdr.de/publications/Publ-26779
Publ.-Id: 26779


Integration of Vessel‐Based Hyperspectral Scanning and 3D‐Photogrammetry for Mobile Mapping of Steep Coastal Cliffs in the Arctic

Salehi, S.; Lorenz, S.; Sørensen, E. V.; Zimmermann, R.; Fensholt, R.; Heincke, B. H.; Kirsch, M.; Gloaguen, R.

Remote and extreme regions such as in the Arctic remain a challenging ground for geological mapping and mineral exploration. Coastal cliffs are often the only major well-exposed outcrops, but are mostly not observable by air/spaceborne nadir remote sensing sensors. Current outcrop mapping efforts rely on the interpretation of Terrestrial Laser Scanning and oblique photogrammetry, which have inadequate spectral resolution to allow for detection of subtle lithological differences. This study aims to integrate 3D-photogrammetry with vessel-based hyperspectral imaging to complement geological outcrop models with quantitative information regarding mineral variations and thus enables the differentiation of barren rocks from potential economic ore deposits. We propose an innovative workflow based on: 1) the correction of hyperspectral images by eliminating the distortion effects originating from the periodic movements of the vessel, 2) lithological mapping based on spectral information and 3) accurate 3D integration of spectral products with photogrammetric terrain data. The method is tested using experimental data acquired from near-vertical cliff sections in two parts of Greenland, in Karrat (Central West) and Søndre Strømfjord (South West). Root-Mean-Square Error of (6.7, 8.4) pixels for Karrat and (3.9, 4.5) pixels for Søndre Strømfjord in X and Y directions demonstrate the geometric accuracy of final 3D products and allow a precise mapping of the targets identified using the hyperspectral data contents. This study highlights the potential of using other operational mobile platforms (e.g. unmanned systems) for regional mineral mapping based on horizontal viewing geometry and multi-source and multi-scale data fusion approaches.

Keywords: Hyperspectral Remote Sensing; Digital Outcrop Models; Spectral Mobile Mapping; Scale Invariant Feature Transform Method; Multi-Source Data Integration; Near-Vertical Topography

Permalink: https://www.hzdr.de/publications/Publ-26778
Publ.-Id: 26778


Swift heavy ion shaping of oxide-structures at (sub)-micrometer scales

Ferhati, R.; Amirthapandian, S.; Fritzsche, M.; Bischoff, L.; Bolse, W.

100 nm thin NiO-films on oxidized Si-substrates were pre-structured into small platelets of 100-5000 nm side-lengths utilizing the focused ion beam technique. The development of the individual platelets under grazing angle swift heavy ion irradiation was monitored using our "High Resolution In Situ Scanning Electron Microscope" installed in the beam line of the UNILAC ion accelerator at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt/Germany. This instrument allows us to in situ investigate the structural and compositional development of individual objects in the μm- and nm-range under swift heavy ion bombardment, from the very first ion impact up to fluences of some 1015 ions/cm-2. The sample is irradiated in small fluence steps and in between SEM-images (and EDX-scans) of one-and-the-same surface area are taken. Swift heavy ion irradiation at grazing incidence (tilt angle ≥80°) and continuous azimuthal sample rotation results in lateral shrinking and vertical growth of the platelets. At intermediate fluences additional rounding of edges and corners can be observed. At high fluences the deformation finally saturates. The deformation of the platelets is accompanied by huge sputtering of the exposed SiO2-layer, which due to the retracting edges of the platelets results in a pyramidal-like base underneath of the NiO-structures. In our presentation we will illustrate and discuss the reshaping mechanisms and underlying driving forces.

Keywords: Ion hammering; Ion shaping; NiO; Surface tension; Swift heavy ions

Downloads:

  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-26777
Publ.-Id: 26777


Narrow-band Tunable Spintronic THz Emission from Ferrimagnetic Nanofilms

Awari, N.; Kovalev, S.; Fowley, C.; Rode, K.; Lau, Y.-C.; Betto, D.; Thiyagarajah, N.; Green, B.; Yildrim, O.; Lindner, J.; Fassbender, J.; Coey, M.; Deac, A.; Gensch, M.

We report on narrow-band THz emission from ferrimagnetic Mn3-xGa nano-films based. The emission originates from coherently excited spin precession. The central frequency of the emitted radiation is determined by the anisotropy field, while the bandwidth relates to Gilbert damping. It is shown how THz emission can be used for the characterization of dynamic properties of ultra-thin magnetic films. We furthermore study the dependence of THz emission on laser power and applied external magnetic field.

Keywords: THz emission; Heusler alloys

  • Poster
    Ultrafast Magnetism Conference 2017, 09.-13.10.2017, Kaiserslautern, Germany

Permalink: https://www.hzdr.de/publications/Publ-26776
Publ.-Id: 26776


Frequency dependence of THz induced ultrafast demagnetization dynamics in amorphous ferromagnetic films

Awari, N.; Hudl, M.; Polley, D.; Kovalev, S.; Gensch, M.; Bonetti, S.

The interaction between magnetism and light is receiving considerable interest in recent years, after the ground-breaking experiments that showed that ultrashort (~100 fs) infrared light pulses can be used to demagnetize [1] or even switch [2] the magnetization of thin film ferromagnets. However, the fundamental physical processes governing the ultrafast magnetization have proven to be challenging to understand. Two main mechanisms have been put forward as possible ways of absorbing spin angular momentum: dissipation of spins through the electronic system, via the creation of super diffusive spin-currents [3], or via the phonon bath, through spin- orbit scattering of Elliot-Yafet type [4]. Although experimental evidence for both mechanisms has been reported, their relative contributions to ultrafast demagnetization remain debated with the accurate modelling of the infrared fs laser-induced highly non-equilibrium state remaining a key obstacle.
Here, we represent our recent work on thin amorphous ferromagnetic films using unique multicycle, strong THz fields from the High-field THz user facility TELBE [5] to drive ultrafast magnetization dynamics. With the THz pulse duration of the order of the electronic and spin scattering events, it was possible to assess the influence of elementary scattering processes on the sample magnetization while a non-equilibrium current is flowing in the magnetic material. Preliminary result shows that ultrafast magnetization depends both on the lattice ordering and the frequency of THz pulses used. This effect was quadratic in the THz field strength and could be separated from the magnetization precession around the THz magnetic field. Complementary THz conductivity measurements allow us to relate these observations to defect-induced spin-lattice scattering processes of Elliot-Yafet type [6].

References:
[1] E. Beaurepaire et al., Phys. Rev. Lett. 76, 4250 (1996).
[2] C. D. Stanciu et al., Phys. Rev. Lett. 99, 047601 (2007).
[3] M. Battiato et al., Phys. Rev. Lett. 105, 027203 (2010).
[4] B. Koopmans et al., Phys. Rev. Lett. 95, 267207 (2005).
[5] B. Green et. al., Sci. Rep. 5, 22256 (2016).
[6] B. Koopmans, et al. Nature Mat. 9, 259 (2010).

Keywords: ultrafast magnetization; Demagnetization; spin- orbit scattering of Elliot-Yafet type

  • Poster
    Ultrafast Magnetism Conference 2017, 09.-13.10.2017, Kaiserslautern, Germany

Permalink: https://www.hzdr.de/publications/Publ-26775
Publ.-Id: 26775


An activation database for materials used at high-intensity laser acceleration facilities

Fasso', A.; Ferrari, A.; Olsovcova, V.; Shetty, N.; Versaci, R.

The ELI Beamlines facility will be the high-energy, high repetition-rate laser pillar of the Extreme Light Infrastructure (ELI). The goal of ELI Beamlines is to deliver ultra-short, high-energy laser pulses for the generation and applications of high-brightness X-ray sources and accelerated particles. Particle beams are expected to operate in an unprecedented energy range for laser-driven accelerators, going up to 10 GeV for electrons and 250 MeV for protons, with envisaged upgrade to higher energies (up to 50 GeV for electrons and to 3 GeV for protons). Depending on the experimental setup, the number of particles per laser shot is expected to be 109 -1011. The high energy and the large current per shot of the produced beams, together with the possibility to operate at 10 Hz laser repetition rate, require an adequate evaluation of activation in structural materials. Several radiation protection problems, such as minimization of residual dose rates and management of activated materials (short and long-term storage and eventual decommissioning), must be assessed.
A comprehensive database covering all the energies and materials of interest is being developed using FLUKA, a Monte Carlo transport code successfully benchmarked for the production of radioactive nuclides. Results for electrons and protons at different energies are presented. These results, although focused on the needs of laser-driven accelerators, are likely to be useful also when designing more conventional facilities.

  • Open Access Logo Contribution to proceedings
    SATIF-13: 13th Meeting of the task- force on Shielding aspects of Accelerators, Targets and Irradiation Facilities, 10.-12.10.2016, Dresden, Germany
    Proceedings of SATIF-13, Paris: OECD/NEA, 422-429

Permalink: https://www.hzdr.de/publications/Publ-26774
Publ.-Id: 26774


Shielding and activation calculations around the reactor core for the MYRRHA ADS design

Ferrari, A.; Mueller, S.; Konheiser, J.; Castelliti, D.; Sarotto, M.; Stankovskiy, A.

In the frame of the FP7 European project MAXSIMA, an extensive simulation study has been done to assess the main shielding problems in view of the construction of the MYRRHA accelerator-driven system at SCK·CEN in Mol (Belgium). An innovative method based on the combined use of the two state-of-the-art Monte Carlo codes MCNPX and FLUKA has been used, with the goal to characterize complex, realistic neutron fields around the core barrel, to be used as source terms in detailed analyses of the radiation fields due to the system in operation, and of the coupled residual radiation. The main results of the shielding analysis are presented, as well as the construction of an activation database of all the key structural materials. The results evidenced a powerful way to analyse the shielding and activation problems, with direct and clear implications on the design solutions.

Keywords: Shielding; ADS systems; Monte Carlo; FLUKA; MCNPX

  • Open Access Logo Contribution to proceedings
    ICRS-13 & RPSD-2016, 13th International Conference on Radiation Shielding & 19th Topical Meeting of the Radiation Protection and Shielding Division of the American Nuclear Society - 2016, 03.-06.10.2016, Paris, France
    EPJ Web Conferences, 153 (2017) 05001
    DOI: 10.1051/epjconf/201715305001
  • Lecture (Conference)
    ICRS-13 & RPSD-2016, 13th International Conference on Radiation Shielding & 19th Topical Meeting of the Radiation Protection and Shielding Division of the American Nuclear Society - 2016, 03.-06.10.2016, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-26773
Publ.-Id: 26773


Electromagnetically driven convection suitable for mass transfer enhancement in liquid metal batteries

Weber, N.; Nimtz, M.; Personnettaz, P.; Salas, A.; Weier, T.

Liquid metal batteries (LMBs) were recently proposed as cheap large scale energy storage. Such devices are urgently required for balancing highly fluctuating renewable energies. During discharge, LMBs tend to form intermetallic phases. These do not only limit the up-scalability, but also the efficiency of the cells. Generating a mild fluid flow in the fully liquid cell will smoothen concentration gradients and minimise the formation of intermetallics. In this context we study electro-vortex flow numerically. We simulate a recent LMB related experiment and discuss how the feeding lines to the cell can be optimised to enhance mass
transfer. The Lorentz forces have to overcome the stable thermal stratification in the cathode of the cell; we show that thermal effects may reduce electro-vortex flow velocities considerable. Finally, we study the influence of the Earth magnetic field on the flow.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-26772
Publ.-Id: 26772


Residual activity evaluation: benchmark and intercomparison between ANITA, FISPACT, FLUKA and PHITS codes

Firpo, G.; Viberti, C. M.; Ferrari, A.; Frisoni, M.

The activity of residual nuclides dictates the radiation fields in periodic inspections/repairs (maintenance periods) and dismantling operations (decommissioning phase) of accelerator facilities (i.e., medical, industrial, research) and nuclear reactors. Therefore, the correct prediction of the material activation allows for a more accurate planning of the activities, in line with the ALARA (As Low As Reasonably Achievable) principles. The scope of the present work is to show the results of a comparison between residual total specific activity versus a set of cooling time instants (from zero up to 10 years after irradiation) as obtained by two analytical (FISPACT and ANITA) and two Monte Carlo (FLUKA and PHITS) codes, making use of their default nuclear data libraries. A set of ~40 irradiating scenarios is considered, i.e. neutron and proton particles of different energies, ranging from zero to many hundreds MeV, impinging on pure elements or materials of standard composition typically used in industrial applications (namely, AISI SS316 and Portland concrete). In some cases, experimental results were also available for a more thorough benchmark.

Keywords: Activation; Monte Carlo; Benchmarks; Decommissioning

  • Open Access Logo Contribution to proceedings
    ICRS-13 & RPSD-2016, 13th International Conference on Radiation Shielding & 19th Topical Meeting of the Radiation Protection and Shielding Division of the American Nuclear Society - 2016, 03.-06.10.2016, Paris, France
    EPJ Web of Conferences 153, (2017), 02006
    DOI: 10.1051/epjconf/201715302006
  • Lecture (Conference)
    ICRS-13 & RPSD-2016, 13th International Conference on Radiation Shielding & 19th Topical Meeting of the Radiation Protection and Shielding Division of the American Nuclear Society - 2016, 03.-06.10.2016, Paris, France
  • Poster
    SATIF-13: 13th Meeting of the task- force on Shielding aspects of Accelerators, Targets and Irradiation Facilities, 10.-12.10.2016, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-26771
Publ.-Id: 26771


Herstellung und Charakterisierung von Spin-Hall Effekt-basierten Nano-Mikrowellenoszillatoren

Hache, T.

Spin-Hall nano-oscillators (SHNOs) are modern auto-oscillation devices. Their simple geometry allows for an optical characterization by Brillouin-Light-Scattering microscopy at room temperature. Here we report on the observation of auto-oscillations in constriction based SHNOs. These are devices where the current density is increased locally due to lateral confinement. Hence, the spin current generated by the spin Hall effect can create well defined hot-spots for auto-oscillations.
We present BLS measurements of auto-oscillations in Co60Fe20B20(5 nm)/Pt(7 nm) based samples with two interacting, neighbouring nanoconstrictions.
The precession amplitude in these samples can be driven far from equilibrium, resulting in clear nonlinear signatures in the spinwave spectra. The spatial distributions of the observed modes and current dependencies are shown.

Keywords: spin Hall; spin Hall nano-oscillators; Spin-Hall Nanooszillatoren; spin current; auto-oscillations; Autooszillationen

  • Master thesis
    Westsächsische Hochschule Zwickau, 2017, 2017
    Mentor: Prof. Dr. Wieland Zahn, Dr. Helmut Schultheiss
    96 Seiten
  • Invited lecture (Conferences)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, TU Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26770
Publ.-Id: 26770


Shielding assessment for the HED Science Instrument at the European XFEL

Ferrari, A.; Nakatsutsumi, M.; Pelka, A.; Tschentscher, T.; Cowan, T.

Interaction with plasma of high-power, high-intensity lasers of multi-TW and PW class always produces ‘hot’ electrons with a quasi-Maxwellian energy spectrum, with temperatures between about 10 keV and several MeV for intensities ranging from 1016 W/cm2 up to about 1022 W/cm2. Those electrons interact in turn with the target and the surrounding materials, producing Bremsstrahlung and possibly photo-neutrons. The resulting radiation field is present in all laser-plasma experiments, and drives the shielding design of every facility dedicated to high energy density research.
The proper definition of the radiation source term is a challenging aspect, and the shielding cannot therefore be designed with the conventional tools used in nuclear and accelerator physics. Different, complementary approaches are possible: relying only on analytical formulas, combining those predictions with experimental results to characterize source terms in input to established Monte Carlo codes, and/or interfacing those codes with specialized Particle-In-Cell programs. At the Helmholtz-Beamline of the European XFEL, the shielding design of the High Energy Density (HED) Physics Instrument has been evaluated by using analytical calculations, cross-checked with measurements done at the DRACO laser of the Helmholtz-Zentrum Dresden-Rossendorf. In this work the characterization of the radiation fields and the resulting shielding solutions are summarized.

Keywords: Shielding; Source Terms; HIBEF; HED Instrument

  • Open Access Logo Contribution to proceedings
    SATIF-13, 13th Meeting of the task-force on Shielding aspects of Accelerators, Targets and Irradiation Facilities, 10.-12.10.2016, Dresden, Germany
    Proceedings of SATIF-13, Paris: OECD-NEA
  • Lecture (Conference)
    SATIF-13, 13th Meeting of the task- force on Shielding aspects of Accelerators, Targets and Irradiation Facilities, 10.-12.10.2016, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-26769
Publ.-Id: 26769


Magnetic e-skins enabled somatic and touchless interactive devices

Jin, G.; Xu, W.; Gilbert Santiago, C. B.; Changan, W.; Shengqiang, Z.; Jürgen, F.; Denys, M.

Humans skin provide perceptions of the temperature of objects, strain and pressure on skin, friction for holding objects, which help humans interact very precisely with unstructured surroundings [1]. Electronic skins [2-4] allow for the realization of similar sensing functions and also having the possibility of integrating other sensing functions beyond humans, for example, touchless feeling. Very recently we demonstrated magnetosensitive e-skins, which is an important step towards the realization of artificial magnetoception for humans [5,6].
Here, we present a magnetic e-skin that not only has the ability to detect the position and movement of magnetic objects in a touchless mode but also is sensitive to mechanical forces. The magnetic skin is a stack of a magnetoresistive (MR) sensor layer and a surface-pyramid-structured magnetic foil. The MR sensor of the magnetic skin is sensitive to the surrounding magnetic field change. When the surface of the target object is fixed with a magnet, the magnetic e-skin will have the ability to detect the distance change between itself and the target object in a touchless mold. Furthermore, when a pressure is applied on the surface of the magnetic e-skin, the induced distance change between the MR sensor and the magnetic foil will also result in the resistance change of the MR sensor. As a result, this magnetic e-skin also has the ability to detect the pressure change applied on its surface in a touch mold (somatic interaction). This multi-functional magnetic e-skin will hold a great promise for the realization of advanced humanoid robots, biomedical prostheses, and surgical electronic gloves.

1. A. Zimmerman, et al. Science 346, 950 (2014).
2. T. Someya, et al. Proc. Natl. Acad. Sci. U.S.A. 101, 9966 (2004).
3. Z. Ma, et al. Science 333, 830 (2011).
4. Z. Bao, et al. Adv. Mater. 25, 5997 (2013).
5. M. Melzer, et al, Nat. Commun. 6, 6080 (2015).
6. D. Makarov, et al., Appl. Phys. Rev. 3, 011101 (2016).

Keywords: e-skin; pressure sensor; flexible; magnetic sensor; multi-functional

  • Lecture (Conference)
    2017 MRS Fall Meeting, 26.11.-01.12.2017, Boston, America

Permalink: https://www.hzdr.de/publications/Publ-26768
Publ.-Id: 26768


Bridging from Brain to Tumor imaging: (S)- and (R)-[18F]Fluspidine for investigation of Sigma-1 Receptors in Tumor-bearing Mice

Kranz, M.; Bergmann, R.; Kniess, T.; Belter, B.; Neuber, C.; Cai, Z.; Deng, G.; Fischer, S.; Steinbach, J.; Zhou, J.; Huang, H.; Brust, P.; Deuther-Conrad, W.; Pietzsch, J.

Sigma-1-receptors (Sig1R) are highly expressed in various human cancer cells and hence imaging of this target with positron emission tomography (PET) can contribute to a better understanding of tumor pathophysiology and support the development of antineoplastic drugs. Two Sig1R-specific radiolabeled enantiomers (S)-(−)- and (R)-(+)-[18F]fluspidine were investigated in several tumor cell lines including melanoma, squamous cell/epidermoid carcinoma, prostate carcinoma and glioblastoma. Dynamic PET scans were performed in mice to investigate the suitability of both radiotracers for tumor imaging. The Sig1R expression in the respective mice tumors was confirmed by Western blot. Rather low radiotracer uptake was found in heterotopically implanted tumors. Therefore, a brain tumor model (U87-MG) with orthotopic implantation was chosen to investigate the suitability of the two Sig1R radiotracers for brain tumor imaging. A high tumor uptake as well as a favorable tumor-to background ratio was found. These results suggest that Sig1R PET imaging of brain tumors with [18F]fluspidine could be possible. Further studies with this tumor model will be performed to confirm specific binding and the integrity of the blood-brain barrier (BBB).

Keywords: : [18F]fluspidine; carcinoma; glioblastoma; melanoma; Sigma-1 receptor; dedicated small animal PET/CT

Permalink: https://www.hzdr.de/publications/Publ-26767
Publ.-Id: 26767


The timing of deglaciation on the northern Swiss Plateau inferred by cosmogenic 10Be surface exposure dating

Groos, A. R.; Struck, J.; Wüthrich, L.; Veit, H.; Gnägi, C.; Merchel, S.; Scharf, A.; Rugel, G.; Zech, R.

During the Last Glacial Maximum (19-30 ka) extensive ice caps and large outlet glaciers covered the alpine valleys and forelands in the Swiss Alps (e.g. Ivy-Ochs, 2015). The former Rhône Glacier expanded onto the Swiss Plateau, was deflected and bounded by the Jura Mountain Range, and reached 'Wangen an der Aare' (Niederbipp Stade). Various studies have investigated respective glacial deposits, but the maximum extent of glaciation and the exact timing of deglaciation is still under discussion (Wüthrich et al. 2018, 2017). We investigated 18 additional samples from 15 erratic boulders from the region by cosmogenic 10Be surface exposure dating to constrain the timing of deglaciation. The 10Be exposure ages from seven different locations vary mainly between 17-30 ka. Five outliers show three younger ages (4 ka, 7 ka, and 10 ka, respectively) and two older ages (42 ka and 87 ka, respectively) than expected, proofing again that geomorphological processes and inheritance can affect the exposure ages of the erratic boulders.
Ivy-Ochs, S. (2015). Glacier variations in the European Alps at the end of the Last Glaciation. Cuadernos de Investigación Geográfica 41, 295–315.
Wüthrich, L., Brändli, C., Braucher, R., Veit, H., Haghipour, N., Terrizzano, C., Christl, M., Gnägi, C., Zech, R. (2018): 10Be depth profiles in glacial sediments on the Swiss Plateau: deposition age, denudation and (pseudo-)inheritance, E&G Quaternary Sci. J., 66, 57–68.
Wüthrich, L., Garcia Morabito, E., Zech, J., Gnägi, C., Trauerstein, M., Veit, H., Merchel, S., Scharf, A., Rugel, G., Christl, M., Zech, R. (under review, 2017): 10Be surface exposure dating of the last deglaciation in the Aare Valley, Switzerland. Swiss Journal of Geosciences.

Keywords: AMS; glaciation; LGM

  • Poster
    European Geosciences Union (EGU) General Assembly, 08.-13.04.2018, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-26766
Publ.-Id: 26766


Mesoscale Dzyaloshinskii-Moriya interaction in curvilinear geometries: one-dimensional and two-dimensional cases

Volkov, O.; Kravchuk, V.; Sheka, D.; Makarov, D.; Fassbender, J.; Gaididei, Y.; Roessler, U.; van den Brink, J.; Fuchs, H.; Fangohr, H.

A broken chiral symmetry in a magnetic system manifests itself as the appearance of either periodical (e.g. helical or cycloid modulations [1]) or localized magnetization structures (e.g. chiral domain walls and skyrmions [2]). The origin of these magnetic textures is spin-orbit Dzyaloshinskii-Moriya interaction (DMI), which is observed in bulk magnetic crystals with low symmetry [3-4] or at interfaces between a ferromagnet and a nonmagnetic material with strong spin-orbit coupling [5]. This DMI is intrinsic to the crystal or layer stack. Recently, it was reported that geometrically-broken symmetry in curvilinear magnetic systems leads to the appearance of curvature-driven DMI-like chiral contribution in the energy functional [6]. This chiral term is determined by the sample geometry, e.g local curvature and torsion, and is therefore extrinsic to the crystal or layer stack. It reveals itself in the domain wall pinning at a localized wire bend and is responsible for the existence of magnetochiral effects in curvilinear magnetic
systems, e.g. in ferromagnetic Möbius rings, nanorings and helix wires [7].
The intrinsic and extrinsic DMI act at different length scales and, hence, their combination can be referred to as a mesoscale DMI. The symmetry and strength of this term are determined by the geometrical and material properties of the three-dimensional (3D) object. Although, intrinsic and extrinsic terms separately are broadly investigated, their synergistic impact is not known yet. Here, we study the properties of the mesoscale DMI in a 1D curvilinear wire and in 2D curvilinear shells. We derive the general expressions for the mesoscale DMI term and analyze the magnetization states which arise in a helix wire and in a thin spherical shell with intrinsic DMI.
[1] I. E. Dzyaloshinskii, Sov. Phys. JETP, vol. 19, pp. 964–971 (1964).
[2] N. Nagaosa and Y. Tokura, Nature Nanotechnology, vol. 8, pp. 899–911 (2013).
[3] I. E. Dzialoshinskii, Sov. Phys. JETP, vol. 5, pp. 1259–1272 (1957).
[4] T. Moriya, Phys. Rev. Lett., vol. 4, pp. 228–230 (1960).
[5] A. Fert, Materials Science Forum, vol. 59-60, pp. 439–480 (1990).
[6] Y. Gaididei, V. P. Kravchuk, and D. D. Sheka, Phys. Rev. Lett., vol. 112, p. 257203 (2014).
[7] R. Streubel, P. Fischer, F. Kronast, V. P. Kravchuk, D. D. Sheka, Y. Gaididei, O. G. Schmidt, and D. Makarov, Journal of Physics D: Applied Physics, vol. 49, p. 363001 (2016)

Keywords: Dzyaloshinskii-Moriya interaction; curved geometry; helical wire; magnetochirality; mesoscale; skyrmion

  • Lecture (Conference)
    TOP-SPIN 3: Spin and Topological Phenomena in Nanostructures - Towards Topological Materials Science, 25.-28.04.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-26765
Publ.-Id: 26765


Mesoscale Dzyaloshinskii-Moriya interaction: one-dimensional and two-dimensional cases

Volkov, O.; Kravchuk, V.; Sheka, D.; Makarov, D.; Fassbender, J.; Gaididei, Y.; Roessler, U.; van den Brink, J.; Fuchs, H.; Fangohr, H.; Kosub, T.

A broken chiral symmetry in a magnetic system manifests itself as the appearance of either periodical (e.g. helical or cycloid modulations [1-3]) or localized magnetization structures (e.g. chiral domain walls and skyrmions [3-6]). The origin of these magnetic textures is spin-orbit Dzyaloshinskii-Moriya interaction (DMI), which is observed in bulk magnetic crystals with low symmetry [7-8] or at interfaces between a ferromagnet and a nonmagnetic material with strong spin-orbit coupling [9]. This DMI is intrinsic to the crystal or layer stack. Recently, it was reported that geometrically-broken symmetry in curvilinear magnetic systems leads to the appearance of curvature-driven DMI-like chiral contribution in the energy functional [10-14]. This chiral term is determined by the sample geometry, e.g local curvature and torsion, and is therefore extrinsic to the crystal or layer stack. It reveals itself in the domain wall pinning at a localized wire bend [15] and is responsible for the existence of magnetochiral effects in curvilinear magnetic systems, e.g. in ferromagnetic Möbius rings [16], nanorings [11] and helix wires [12, 13, 17].
The intrinsic and extrinsic DMI act at different length scales and, hence, their combination can be reffered to as a mesoscale DMI. The symmetry and strength of this term are determined by the geometrical and material properties of a three-dimensional (3D) object. Although, intrinsic and extrinsic terms separately are broadly investigated, their synergistic impact is not known yet. Here, we study the properties of the mesoscale DMI in a 1D curvilinear wire and in 2D curvilinear shells. We derive the general expressions for the mesoscale DMI term and analyse the magnetization states which arise in a helix wire and in a thin spherical shell with intrinsic DMI.
The clear cut comparison a helix wire with a straight wire with homogeneous tangential intrinsic DMI reveals: (i) The magnetic states of a curved wire is governed by a single vector of magnetochirality — a vector of the mesoscale DMI — originating from the vector sum of the intrinsic and extrinsic DMI vectors; (ii) The symmetry and period of the chiral structures are determined by the strength and direction of the vector of the mesoscale DMI, which depends on both material and geometrical parameters of a curvilinear wire (Figure, panel a); (iii) Similarly to the case of the straight wire [18] both types of phase transitions (of the first and the second order) are found in the helix. The appearance of
each state can be determined by measuring of the average values of the magnetization components and/or by establishing space Fourier spectra of the coordinate-dependent magnetic signals from the helices.
In the case of 2D curvilinear magnetic shells, it’s shown the existence of a skyrmion solution on a thin magnetic spherical shell even without any additional intrinsic DMI [19]. Such skyrmions can be stabilized by curvature effects only, namely by the curvature-induced, extrinsic DMI (Figure, panel b). In addition to the striking difference to the case of a planar skyrmion, magnetic skyrmions on a spherical shell are topologically trivial. This is due to a shift of the topological index of the magnetization field caused by topology of the surface itself. As a result, a skyrmion on a spherical shell can be induced by a uniform external magnetic field. Further, the curvature stabilized skyrmions are very small, with a lateral extension of several nm only (Figure, panel b). The size of the skyrmion core can be tailored e.g. by an additional intrinsic DMI (Figure, panel c). One can note here, that the curvature stabilized skyrmions are always of Neel type (at least, for a surface of rotation). Due to their small sizes and ease in manipulating using homogeneous magnetic fields, we envision those topological objects to be relevant for the realization of on-demand tunable topological logic. Indeed, topological Hall effect can be digitally switched on or off by exposing a sample withferromagnetic spherical shells submerged by a nonmagnetic conductor.
References:
[1] I. E. Dzyaloshinskii, “Theory of helicoidal structures in antiferromagnets. i. nonmetals,” Sov. Phys. JETP, vol. 19, pp. 964–971 (1964).
[2] A. Bogdanov, U. Rössler, and C. Pfleiderer, “Modulated and localized structures in cubic helimagnets,” Physica B: Condensed Matter, vol. 359-361, pp. 1162–1164 (2005).
[3] S. Rohart and A. Thiaville, “Skyrmion confinement in ultrathin film nanostructures in the presence of dzyaloshinskii-moriya interaction,” Physical Review B, vol. 88, p. 184422 (2013).
[4] A. Thiaville, S. Rohart, É. Jué, V. Cros, and A. Fert, “Dynamics of Dzyaloshinskii domain walls in ultrathin magnetic films,” EPL (Europhysics Letters), vol. 100, p. 57002 (2012).
[5] A. Bogdanov and A. Hubert, “The stability of vortex-like structures in uniaxial ferromagnets,” Journal of Magnetism and Magnetic Materials, vol. 195, pp. 182–192 (1999).
[6] N. Nagaosa and Y. Tokura, “Topological properties and dynamics of magnetic skyrmions,” Nature Nanotechnology, vol. 8, pp. 899–911 (2013).
[7] I. E. Dzialoshinskii, “Thermodynamic theory of “weak” ferromagnetism in antiferromagnetic substances,” Sov. Phys. JETP, vol. 5, pp. 1259–1272 (1957).
[8] T. Moriya, “New mechanism of anisotropic superexchange interaction,” Phys. Rev. Lett., vol. 4, pp. 228–230 (1960).
[9] A. Fert, “Magnetic and transport properties of metallic multilayers,” Materials Science Forum, vol. 59-60, pp. 439–480 (1990).
[10] Y. Gaididei, V. P. Kravchuk, and D. D. Sheka, “Curvature effects in thin magnetic shells,” Phys. Rev. Lett., vol. 112, p. 257203 (2014).
[11] D. D. Sheka, V. P. Kravchuk, and Y. Gaididei, “Curvature effects in statics and dynamics of low dimensional magnets,” Journal of Physics A: Mathematical and Theoretical, vol. 48, p. 125202 (2015).
[12] D. D. Sheka, V. P. Kravchuk, K. V. Yershov, and Y. Gaididei, “Torsion-induced effects in magnetic nanowires,” Phys. Rev. B, vol. 92, p. 054417 (2015).
[13] O. V. Pylypovskyi, D. D. Sheka, V. P. Kravchuk, K. V. Yershov, D. Makarov, and Y. Gaididei, “Rashba torque driven domain wall motion in magnetic helices,” Scientific Reports, vol. 6, p. 23316 (2016).
[14] R. Streubel, P. Fischer, F. Kronast, V. P. Kravchuk, D. D. Sheka, Y. Gaididei, O. G. Schmidt, and D. Makarov, “Magnetism in curved geometries (topical review),” Journal of Physics D: Applied Physics, vol. 49, p. 363001 (2016).
[15] K. V. Yershov, V. P. Kravchuk, D. D. Sheka, and Y. Gaididei, “Curvature-induced domain wall pinning,” Phys. Rev. B, vol. 92, p. 104412 (2015).
[16] O. V. Pylypovskyi, V. P. Kravchuk, D. D. Sheka, D. Makarov, O. G. Schmidt, and Y. Gaididei, “Coupling of chiralities in spin and physical spaces: The Möbius ring as a case study,” Phys. Rev. Lett., vol. 114, p. 197204 (2015).
[17] K. V. Yershov, V. P. Kravchuk, D. D. Sheka, and Y. Gaididei, “Curvature and torsion effects in spin-current driven domain wall motion,” Phys. Rev. B, vol. 93, p. 094418 (2016).
[18] M. Heide, G. Bihlmayer, and S. Blügel, “Non-planar dzyaloshinskii spirals and magnetic domain walls in noncentrosymmetric systems with orthorhombic anisotropy,” Journal of Nanoscience and Nanotechnology, vol. 11,
pp. 3005–3015 (2011).
[19] V. P. Kravchuk, U. K. Rößler, O. M. Volkov, D. D. Sheka, J. van den Brink, D. Makarov, H. Fuchs, H. Fangohr, and Y. Gaididei, “Topologically stable magnetization states on a spherical shell: Curvature-stabilized skyrmions,” Phys. Rev. B, vol. 94, p. 144402 (2016).

Keywords: Dzyaloshinskii-Moriya interaction; curved geometry; helical wire; magnetochirality; mesoscale; skyrmion

  • Poster
    2017 IEEE International Magnetics Conference, 24.-28.04.2017, Dublin, Ireland

Permalink: https://www.hzdr.de/publications/Publ-26764
Publ.-Id: 26764


An attempt to enrich holmium ions in a flow system by inhomogeneous magnetic fields.

Kolczyk, K.; Wojnicki, M.; Zabinski, P.; Yang, X.; Mutschke, G.

Recent experimental results regarding an attempt to enrich holmium ions in a flow system by inhomogeneous magnetic fields
are presented.

Keywords: magnetic field; magnetic separation

  • Invited lecture (Conferences)
    International Workshop ECMAG - Magnetic Field Effects on Aqueous Solutions, 20.-21.04.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26763
Publ.-Id: 26763


Magnetic e-skins enabled somatic and touch-less interactive devices

Jin, G.; Xu, W.; Gilbert Santiago, C. B.; Jürgen, F.; Denys, M.

Humans skin provide perceptions of the temperature of objects, strain and pressure on skin, friction for holding objects, which help humans interact with unstructured surroundings very precisely. Electronic skins [1,2] allow for the realization of similar sensing functions and also having the possibility of integrating other sensing functions beyond humans. Very recently we demonstrated magnetosensitive e-skins, which is an important step towards the realization of artificial magnetoception for humans [3,4].
Here, we present a magnetic e-skin that not only is sensitive to mechanical forces and deformation, but also has the ability to detect the position and movement of magnetic objects in a touch-less manner. The magnetic skin is a stack of a wrinkled magnetic sensor layer and a pyramid-structured magnetic foil. The GMR sensor enables the sensing of the movement of the remote magnetic objects (touch-less interaction). Furthermore, the distance change between the sensor and the magnetic foil make the magnetic skin sensitive to pressure, stretch and flexion (somatic interaction). This magnetic e-skin will hold great promise for the realization of humanoid robots, biomedical prostheses, and surgical electronic gloves.

1. Z. Ma et al. Science 333, 830 (2011).
2. Z. Bao et al. Adv. Mater. 25, 5997 (2013).
3. M. Melzer et al, Nat. Commun. 6, 6080 (2015).
4. D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).

Keywords: e-skin; pressure sensor; magnetoresistance; artificial skin; GMR sensor

  • Lecture (Conference)
    DPG Spring Meeting 2017, 19.-24.03.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-26762
Publ.-Id: 26762


Multiplexing of imperceptible temperature sensor arrays for on-skin applications

Voitsekhivska, T.; Fassbender, J.; Makarov, D.

Beside the direct temperature measurement resembling the standard health indicator, the access to the body core temperature and its temporal variations provides the information, which is absolutely crucial to assess the psycho-physiological conditions of the patient, e.g. level of stress. To measure spatial and temporal temperature gradients, multiple temperature sensors have to be attached and processed on the human body surface [1, 2].
Here, we introduce a thermal characterization technology for real - time monitoring the human body temperature using arrays of highly compliant on-skin temperature sensors, realized on 6-micrometer-thick polymeric foils, which are haptically not perceived when worn on the skin. Beside the realization of the arrays of imperceptible temperature sensors, we put strong emphasis on the integration of a multiplexing unit on flexible foils in order to achieve measurements with mapping capabilities.
[1] R. Chad Webb et al., Nature Materials 12, pp. 938-944 (2013).
[2] Tomoyuki Yokota et al., PNAS 112, pp. 14533-14538 (2015).

Keywords: multiplexing; temperature sensor arrays

  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-26761
Publ.-Id: 26761


Mesoscale Dzyaloshinskii-Moriya interaction

Volkov, O.; Sheka, D.; Makarov, D.; Fassbender, J.; Kravchuk, V.; Gaididei, Y.

A broken chiral symmetry in a magnetic system leads to the appearance of both periodical and localized magnetization structures. Intrinsic to the crystal spin-orbit driven Dzyaloshinskii-Moriya interaction (DMI) is the origin of all those magnetic textures [1]. Recently, we reported [2,3] that geometrically broken symmetry in curvilinear magnetic systems also leads to the appearance of shape-induced effective DMI.
The combined intrinsic and shape-induced DMI can be reffered to as a mesoscale DMI, whose symmetry and strength depend on the geometrical and material parameters. The mesoscale DMI determines chiral properties of 3D curved systems. We derive the general expression for the mesoscopic DMI terms and determined the conditions for periodical magnetisation structures to appear in one-dimensional ferromagnetic helix wires.
[1] A. Soumyanarayanan et. al., Nature 539, 509-517 (2016).
[2] Y. Gaididei et. al, Phys. Rev. Lett. 112, 257203 (2014).
[3] D. D. Sheka et. al., J. Phys. A: Math. Theor. 48, 125202 (2015).

Keywords: Dzyaloshinskii-Moriya interaction; curved geometry; helical wire; magnetochirality; mesoscale

  • Lecture (Conference)
    DPG Spring Meeting 2017, 19.-24.03.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-26760
Publ.-Id: 26760


Programmed Magnetically-Triggered Ultrathin Soft Robots with Fast Actuation Speed

Wang, X.; Ge, J.; Canon Bermudez, G. S.; Fassbender, J.; Makarov, D.

Soft robots have been designed and developed to fulfil the demands of better deformability and adaptability to changing environment [1-2]. These soft robots could be made of various stimuli responsive materials that can be actuated by magnetic field [3], light [4], temperature [5], electric fields [6], chemicals [7], pressure [8], etc. In contrast to other actuation mechanisms, magnetic fields are appealing for numerous application scenarios (e.g. environmental, biological, medical), where the benefits stem from their long range penetration, easy accessibility and controllability [2]. There are already impressive demonstrations of magnetically triggered actuators performing as walkers, swimmers and grippers [9]. However, most of these robots are bulky (0.2 mm thick) [11], reveal low actuation speed (2.7 s deflection time) [11] and not sufficiently soft to demonstrate reversible large scale actuation amplitude (less than 1 micron) [12]. Furthermore, they require rather large magnetic fields (42 mT) [13] for actuation, which limits their application potential.

Here, we present an ultrathin and lightweight soft robot that can be actuated in a tiny magnetic field of 0.2 mT reaching full actuation amplitude with reaction times of 10 ms only. The Young’s modulus of the developed magnetic elastomer (NdFeB particles are dispersed into a PDMS host) goes down to remarkable 5 MPa while still maintaining stretchability levels of 50%. The weight of the magnetic foil is 4 mg/cm2 and it can provide 0.16 mN/mg. By programming the foils into different geometries, these soft robots are readily used for different applications, such as quick gripper that can pick, transport and release objects in a controllable manner.

[1] D. Rus et al., Nature 521, 467 (2015)
[2] M. Sitti et al., Adv. Mater. 29, 13 (2017)
[3] S. Kwon et al., Nature materials 10, 747 (2011)
[4] S.H Peng et al., J. Am. Chem. Soc. 138, 225 (2016)
[5] M. Takata et al., Nature Materials 14, 1002 (2015)
[6] J. D. W. Madden et al., Materials Today, 10, 30 (2007)
[7] J.Y. Yuan et al., Nature communications 5 (2014).
[8] G. M. Whitesides et al., Science, 337, 828 (2012)
[9] O. Sandre et al., Chem. Soc. Rev., 42, 7099 (2013).
[10] R. V. Ramanujan et al., Adv Mater., 24, 4041-54 (2012).
[11] H. Z. Liu. et al., ACS Appl. Mater. Interfaces, 8, 14182 (2016)
[12] M. Sitti et al., Nature Communications 5, 3124 (2014)
[13] D. Fragouli et al., ACS Appl. Mater. Interfaces 7, 19112 (2015).

Keywords: soft robot; magnetic field; human-mimic motion; ultra-fast actuation; super durable

  • Lecture (Conference)
    2017 MRS Fall Meeting, 26.11.-01.12.2017, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-26759
Publ.-Id: 26759


Multifunctional Highly Compliant Implants for Cancer

Kruv, A.; Canon Bermudez, G. S.; Voitsekhivska, T.; Lebanov, A.; Fassbender, J.; Yevsa, T.; Makarov, D.

Cancer is one of the main death reasons worldwide [1]. Radio- and chemotherapies, which are the most common approaches to combat this disease, cause severe side effects due to their non-selective nature [2]. As an alternative paradigm, a targeted cancer therapy has recently emerged. This method aims to affect only cancer cells thus spare the healthy tissues [3].
The large fraction of the targeted therapies relay on drug delivery in nanovectors (e.g. micelles, dendrimers) to the tumour site via vascular system followed by the drug release in response to binding to a certain molecule, local environment (e.g. pH) or externally provided heat [4]. These methods suffer from delivery complexity (e.g. due to multiple physiological barriers), non-reliability of the release mechanism, difficulty in organising the feedback for precise control over the process as well as toxicity and stability concerns [4,5].
In order to overcome these limitations, we propose an alternative approach to the targeted cancer treatment (liver cancer is used as a case study) which relies on the implantation at the tumour site of an ultra-thin flexible device comprising a resistive heater and temperature sensor. The devices are prepared on a 6 micrometer thick PET foil. This foil thickness was found to be optimal as it provides the best compliancy to the very soft liver tissue and does not mechanically damage the tissue. The heater can heat the tissue to a pre-defined temperature of up to 55 °C even when the driving current is in the range of 10 mA. The integrated temperature sensor provides a real-time feedback about the on-site thermal impact. We demonstrate a proof-of-the-concept prototype together with the evaluation of its electrical and mechanical performance and the results of the first clinical trials on mice models.
This device allows realizing several negative for tumour interactions including thermal impact all the way up to burning the tissue, highly localized drug release, enhancement of immune response and drug uptake [6]. In addition, it raises the possibility to establish precise control over temperature and potentially evaluate the treatment effects which are of fundamental importance for the development of the new models for cancer research especially in the case of such a severe one as liver cancer.

[1] A. Jemal et al., CA: a cancer journal for clinicians, 61(2), 69-90 (2011).
[2] Padma, V. V. (2015). An overview of targeted cancer therapy. BioMedicine, 5(4), 19-19.
[3] A. A. Alexander-Bryant et al., Advances in cancer research, 118, 1 (2012).
[4] J. Shi et al., Nature Reviews Cancer, 17, 20 (2017).
[5] M. Ferrari, Nature Reviews Cancer 5, 161 (2005).
[6] K. F. Chu et al., Nature Reviews Cancer 14, 199 (2014).

Keywords: cancer threatment; ultra-thin flexible heater

  • Lecture (Conference)
    2017 MRS Fall Meeting & Exhibit, 26.11.-01.12.2017, Boston, Massachussets, USA

Permalink: https://www.hzdr.de/publications/Publ-26758
Publ.-Id: 26758


Mesoscale Dzyaloshinskii-Moriya interaction in curved geometry

Volkov, O.; Sheka, D.; Kravchuk, V.; Makarov, D.; Fassbender, J.; Gaididei, Y.

A broken chiral symmetry in magnetic systems manifests itself at the appearance of either periodical (e.g. helical or cycloid modulations) or localized magnetization structures (e.g. chiral domain walls and skyrmions) [1,2]. The origin of these magnetic textures is spin-orbit driven Dzyaloshinskii-Moriya interaction (DMI), which is intrinsic to the crystal or layer stack. Recently, it was reported that geometrically broken symmetry in curvilinear systems leads to the appearance of exchange-driven DMI-like chiral term in energy functional [3,4]. This term is determined by the sample geometry (it is linear with respect to curvature and torsion) and is therefore extrinsic to the crystal or layer stack. The magnetic properties of curvilinear magnets with intrinsic DMI will be necessarily determined by the interplay between two types of chiral interactions. Hence, the resulting chiral term in such type of objects is referred to as a vector of mesoscale DMI, which is the vector sum of the intrinsic and extrinsic DMI vectors. The symmetry and strength of this term are determined by the geometrical and material properties of the curvilinear magnet. Here we study the properties of the mesoscale DMI using a one-dimensional helical wire as a case of study. The clear cut comparison with the straight wire with intrinsic DMI reveals: (i) a single vector of magnetochirality, which is referred to as vector of the mesoscale DMI, originates from the vector sum of the intrinsic and extrinsic DMI vectors; (ii) a symmetry and period of the chiral modulated structures are determined by the strength and direction of the mesoscale DMI vector; (iii) a phase transition between homogeneous and chiral modulated states in the case of mesoscale DMI is a complex second-order phase transition with the intermediate conical state.

References

[1] U. K. Rößler, A. N. Bogdanov, C. Pfleiderer, Nature 442, 797801 (2006)
[2] N. Nagaosa, Y. Tokura, Nature Nanotechnology 8, 899-911 (2013)
[3] Y. Gaididei, V. P. Kravchuk, D. D. Sheka, Phys. Rev. Lett. 112, 257203 (2014)
[4] O. V. Pylypovskyi, V. P. Kravchuk, D. D. Sheka, D. Makarov, O. G. Schmidt, Y. Gaididei, Phys. Rev. Lett. 114, 197204 (2015)

Keywords: Dzyaloshinskii-Moriya interaction; curved geometry; helical wire; magnetochirality; mesoscale

  • Poster
    633. Wilhelm und Else Heraeus-Seminar, Spin Orbit Dynamics, 04.-06.01.2017, Physikzentrum Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-26757
Publ.-Id: 26757


Compliant on-skin compass for artificial magnetoception and interactive devices

Cañón Bermúdez, G. S.; Makarov, D.

Flexible electronics has inspired novel concepts like electronic skins [1] equipped with e.g. pressure and temperature sensing capabilities, which could replicate the 5 empirical senses of humans. Very recently, magnetosensitive skins enabled by shapeable magnetoelectronics [2] were reported providing humans with perception of magnetic fields, which is beyond the senses developed during the evolution.
Here, we present a technology platform to realize a functional on-skin compass system. The highly compliant compasses are prepared on 6-μm-thick polymeric foils and rely on the anisotropic magnetoresistance effect. The response of these sensors is tailored to be linear and possess maximum sensitivity around the earth’s magnetic field by using a barber pole configuration and Wheatstone bridge arrangement.
We envision that these on-skin compasses can enable humans to electronically emulate the magnetoceptive sense which some mammals possess naturally. This feat could open new possibilities to support research efforts on biomagnetic orientation and novel magnetic interactive devices. In the latter case, the applications span a plethora of tasks from virtual or augmented reality systems to touchless security systems and magnetic tags.
REFERENCES:
1. M. L. Hammock, A. Chortos, B. C.-K. Tee, J. B.-H. Tok, Z. Bao. The Evolution of Electronic Skin (E-Skin): A Brief History, Design Considerations, and Recent Progress. Adv. Mater. 25, 5997 (2013).
2. D. Makarov, M. Melzer, D. Karnaushenko, O. G. Schmidt. Shapeable Magnetoelectronics. Appl. Phys. Rev. 3, 011101 (2016).

Keywords: Magnetic properties; Performance/Functionality/sensor; Composition & Microstructure/Material Type/polymer

  • Lecture (Conference)
    NanoBioSensor Conference, 04.-05.09.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-26756
Publ.-Id: 26756


Simplified expression and production of small metal binding peptides for biosorptive materials

Braun, R.; Schönberger, N.; Jain, R.; Matys, S.; Lederer, F.; Pollmann, K.

Phage display for discovery of specific binding peptides is nowadays widely used in the pharmaceutical industry and in many biotechnological applications. Using state-of-the-art cloning techniques we developed an easy-to-use cloning and expression system, allowing the fast production of identified peptides while avoiding proteolysis.

Keywords: protein expression; metal binding; peptide; biosorption; phage display; molecular genetics; gibson assembly; metal interaction; biomaterials

  • Poster
    HZDR Doktorandenseminar 2017, 16.-18.10.2017, Seiffen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26755
Publ.-Id: 26755


A 3D geometrical and geometallurgical model of a chromite mine

Menzel, P.; Bachmann, K.; Prior-Arche, A.; Tolosana-Delgado, R.; van den Boogaart, K. G.; Gutzmer, J.

This contribution introduces a 3D geometallurgical model that has been developed to assess the resource potential of PGE (+Ni and Cu) recovery at the Thaba chromite mine, South Africa. The Thaba Mine is located on the northwestern limb of the Bushveld Complex and is operated by Cronimet SA. The geometallurgical model is based on a structural model and geostatistical interpolation of primary geometallurgical properties, obtained from mineral liberation analysis (MLA) and geochemical exploration data.

More than 250 MLA samples and 750 geochemical measurements cover four target seams (lower group chromitite seams: LG 6 and LG6a; middle group chromitite seams: MG1 and MG2). The data provides information about chemistry, modal mineralogy and micro-fabric from the platinum group minerals and associated base metal sulfides.
The 3D model is based on the geometry and lithological interpretations of 300 drill cores and the known main faults in the study area and covers all stratigraphic units. The MLA measurements are linked to the 3D geometry of the target seams by the sampling positions in the associated boreholes. This allows to interpolate the information based on the MLA measurements over the horizontal extension of the target seams. The model can be enhanced with further information, e.g the distance to a volume of alterated silicate host rock. The final step is to transfer the geometallurgical model to a block model, that allows to predict for each block the parameters for an optimized processing.
Our approach shows how the different ore types are spatially related to geological features and that a separate extraction of different geometallurgical ore types would be sensible.

Keywords: Geometallurgy; geological model; geometallurgical model; geostatistics

  • Lecture (Conference)
    Resources for Future Generations - RFG 2018, 16.-21.06.2018, Vancouver, Canada

Permalink: https://www.hzdr.de/publications/Publ-26754
Publ.-Id: 26754


Compliant on-skin compass for artificial magnetoception

Cañon Bermúdez, G. S.; Makarov, D.; Fassbender, J.

Flexible electronics has inspired novel concepts like electronic skins[1] and more recently, magnetosensitive skins[2], i. e., artificial skins which allow humans to perceive magnetic fields. This ability to detect and respond to magnetic fields, commonly referred to as magnetoception, has sparked several legends since the old sailing times. Back then, it was believed that compass rose tattoos would allow sailors to always find the way home. Here, we present a flexible electronics platform to turn this ancient belief into a functional on-skin compass system.
The highly compliant compass is prepared on 6-micron-thick polymeric foils and relies on the anisotropic magnetoresistance (AMR) effect in magnetic thin film sensors. Its response is tailored to be linear and possess maximum sensitivity around the earth’s magnetic field by using a barber pole scheme, which forces the current in the sensor to flow 45 degrees skewed with respect to the easy axis of the AMR stripes. We envision that this on-skin compass could support research efforts on biomagnetic orientation and novel magnetic interactive devices. In the latter case, the applications span a plethora of tasks from virtual or augmented reality systems to touchless security systems and magnetic tags.
[1] D. H. Kim et al., Science 333, 838 (2011).
[2] M. Melzer, DM et al., Nature Commun. 6, 6080 (2015).

Keywords: Functional Materials (Actuators; catalysts; energy storage; energy conversion; filters; sensors; shape memory)

  • Lecture (Conference)
    DPG Spring Meeting, 19.-24.03.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-26753
Publ.-Id: 26753


Electronic On-skin Compass for Magnetoception and Interactive Devices

Cañón Bermúdez, G. S.; Makarov, D.; Fassbender, J.

Flexible electronics has inspired novel concepts like electronic skins [1-3] equipped with e.g. pressure [4] and temperature [5] sensing capabilities, which could potentially replicate the 5 empirical senses of humans. Very recently, magnetosensitive skins [6-8] enabled by shapeable magnetoelectronics [9] were reported, allowing humans to perceive magnetic fields, which is beyond the senses developed during the evolution.

Magnetoception for humans, i.e., the ability to detect and respond to magnetic fields, has been a subject of debate and dreams since the early days of navigation when sailors used compasses to orient themselves with respect to earth’s magnetic field. Sailors of old times often had compass rose tattoos to “enable” magnetoception, assuring success and luck in their trips [10,11].

Here, we present a technology platform to turn these dreams into a functional on-skin compass system. The highly compliant compasses are prepared on 6-µm-thick polymeric foils and rely on the anisotropic magnetoresistance (AMR) effect in magnetic thin film sensors. The response of these sensors is tailored to be linear and possess maximum sensitivity around the earth’s magnetic field by using a barber pole [12] configuration and preconditioned via a Wheatstone bridge arrangement. In a barber pole configuration, conductive slabs with a 45 degrees tilt are fabricated on top of Permalloy sensing stripes to force the current to flow skewed with respect to the easy axis of the stripes. By defining the tilt angle and properly adjusting the inter-slab separation, the magnetic field dependence of the AMR on the stripes becomes even and linear around zero.

We envision that this on-skin compass can enable humans to electronically emulate the magnetoceptive sense which some mammals possess naturally [13]. Thereby, allowing us to orient ourselves with respect to earth’s magnetic field ubiquitously. This feat could open new possibilities to support research efforts on biomagnetic orientation and novel magnetic interactive devices. In the latter case, the applications span a plethora of tasks from virtual or augmented reality systems to touchless security systems and magnetic tags.

[1] T. Someya et al., Proc. Natl. Acad. Sci. U. S. A. 101, 9966 (2004).
[2] D. H. Kim et al., Science 333, 838 (2011).
[3] S. Bauer et al., Adv. Mater. 26 149 (2014)
[4] S. Lee et al., Nature Nanotechnology 11, 472 (2016).
[5] X. Ren et al., Adv. Mater. 28, 4832 (2016).
[6] M. Melzer, DM et al., Nature Commun. 6, 6080 (2015).
[7] M. Melzer et al., Adv. Mater. 27, 1274 (2015).
[8] N. Münzenrieder et al., Adv. Electron. Mater. 2, 1600188 (2016).
[9] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
[10] F. Fahlander et al., The skin I live in. The materiality of body imagery, (2015).
[11] Taylor, E.G.R. Journal of Navigation, 4, 351 (1951).
[12] Phillips Semicond., Electronic Compass Design using KMZ51 and KMZ52, (2000).
[13] W. Wiltschko et al., J. Comp. Physiol. A 191, 675 (2005).

Keywords: Properties; Magnetic; magnetic properties; Performance; Functionality/sensor; Composition & Microstructure/Material Type/polymer

  • Lecture (Conference)
    2017 MRS Spring Meeting & Exhibit, 17.-21.04.2017, Phoenix, Arizona, USA

Permalink: https://www.hzdr.de/publications/Publ-26752
Publ.-Id: 26752


On-site Multiplexing of Mechanically Imperceptible Sensor Arrays

Voitsekhivska, T.; Cañon Bermúdez, G. S.; Lebanov, A.; Kruv, A.; Fassbender, J.; Makarov, D.

Flexible electronics is a rapidly growing research field which enables a wide range of applications, as for consumer electronics, healthcare, environmental monitoring and a smart skins [1-3]. There are already impressive demonstrations of different types of sensors developments prepared on flexible or elastomeric support [4-9]. However, to mimic the human skin sensory ability will require the combination of multiple, distributed sensor arrays (i.e. temperature, tactile, strain) integrated on a flexible substrate. One of the challenges here is to connect each sensor with the read-out electronics. For example, if 10 sensors are to be connected, one would require at least 20 wires, which would increase the overall complexity of whole system, make it bulky and diminish its flexibility. In electrical engineering the standard approach to solve this issue is to use a multiplexing unit to minimize the amount of wires to be addressed. Yet, as there are no flexible multiplexers available, the integration of their rigid counterparts into flexible wearable systems becomes crucial [10]. Therefore, it is key point is to have a small size yet high performance multiplexer which improves the conformability and integration level of the system. As an improvement over the smallest commercially available CMOS multiplexer (32 to 1 multiplexer, overall size 7 mm x 7 mm) we have developed a monolithic CMOS analog multiplexer comprised of 96 CMOS transfer gates arranged as 3 x 32:1 multiplexers. It allows addressing up to 32 sensors simultaneously usingby 9 wires going outside and has having a footprint of just 1 mm x 4 mm.

Here, we applied the developed multiplexer for interfacing ultra-thin and mechanically imperceptible resistive temperature sensor arrays realized on imperceptible 6-µm-thick polymeric foils. As a case study, we used temperature sensor arrays. The multiplexer was integrated on a flexible printed circuit board connectedand coupled to the ultrathin sensors part by using of Z-conductive tape ora novel combination of soldering and encapsulation processes to establish reliable contacts. Using this method, we could perform real time measurements on distributed arrays of on-skin sensors. By placing these arrays on the fingers of a human hand, wWe demonstrated their use ability of this sensor array to capture and quantify the temperature information of cold/hot objects as approached by a test subject. This concept is promising for robotics, rehabilitation and, human-machine interfaces, where precise determination of local variables (e.g. temperature, pressure) is of high importance.
[1] Y. Zhang et al., Adv. Healthcare Mater. 5, (2016).
[2] W. Gao et al., Nature 529, (2016).
[3] G. Schwartz et al., Nature Communication 4, 1859 (2013).
[4] M. Kaltenbrunner et al., Nature 499, 458 (2013).
[5] X. Wang et al., Advanced Materials 26, pp. 1336–1342 (2014).
[6] M. Melzer, D. Makarov et al., Nature Communication 6, 6080 (2015).
[7] M. Drack et al., Advanced Materials, 27, pp. 34-40 (2015).
[8] R. Chad Webb et al., Nature Materials, 12, pp. 938–944 (2013).
[9] T. Yokota et al., PNAS, 112, pp. 14533–14538 (2015).
[10] J. Viventi et al., Nature Neuroscience 14, pp. 1599–1605 (2011).

Keywords: Flexible electronics; multiplexing; soft matter; polymer

  • Lecture (Conference)
    2017 MRS Fall Meeting & Exhibit, 26.11.-01.12.2017, Boston, Massachussets, USA

Permalink: https://www.hzdr.de/publications/Publ-26751
Publ.-Id: 26751


Touchless Omnidirectional Magnetosensitive Skins for Interactive Electronics

Cañón Bermúdez, G. S.; Fassbender, J.; Makarov, D.

The widespread permeation of electronic devices into our daily life has increased the importance ofseamless interaction schemes that simplify the user’s experience. Electronic skins [1-3] contribute naturally to this development by combining sensor [4,5] and actuator elements in a compliant and mechanically imperceptible [6] format, thus eliminating the need for rigid interfaces. To advance beyond the conventional tactile interactions, we have recently proposed magnetosensitive skins [7-10] as a novel way to interact with objects in a touchless manner. This vision implies that basic building blocks of any interaction like pressing (proximity sensing) or turning (direction sensing) have to be replicated in a touchless format. In order to do so, our methodology utilizes magnetic fields as external stimuli to magnetosensitive circuits which provide a 3D reconstruction of motion in space. Moreover, to expand the breadth of applications, these interactive devices should operate over the whole range of typically available magnetic fields, spanning from the geomagnetic field of 40 μT up to regular permanent magnet fields of ~10 mT.
Here, we introduce a technology platform that addresses this vision to extend the potential of magnetosensitive skins. At its core, the platform utilizes metallic thin films as magnetoresistive (MR) and Hall-effect sensor elements, which are prepared on 6-μm-thick polymeric foils. This combination of out-of-plane (Hall) and in-plane (MR) sensors allows omnidirectional sensing on a single substrate. In addition, by using geometrical modifications like barber poles [11] or measurement schemes like zero-offset anomalous Hall magnetometry [12,13], the output sensitivity and offset can be optimized for a wide variety of applications.
We foresee that these highly compliant magnetic skins could be used to digitize fine motion, e.g. fingers with respect to the palm. This feat could enable the integration of usually rigid magnetic detection systems into on-skin, textilebased or Internet of Things (IoT) applications. A successful implementation could lead to a new class of virtual or augmented reality systems and interactive input devices which extract information from their surroundings through magnetic tags.
[1] T. Someya et al., Proc. Natl. Acad. Sci. U. S. A. 101, 9966 (2004).
[2] D. H. Kim et al., Science 333, 838 (2011).
[3] S. Bauer et al., Adv. Mater. 26 149 (2014)
[4] S. Lee et al., Nature Nanotechnology 11, 472 (2016).
[5] X. Ren et al., Adv. Mater. 28, 4832 (2016).
[6] M. Kaltenbrunner et al., Nature 499, 458 (2013).
[7] M. Melzer, DM et al., Nature Commun. 6, 6080 (2015).
[8] M. Melzer et al., Adv. Mater. 27, 1274 (2015).
[9] N. Münzenrieder et al., Adv. Electron. Mater. 2, 1600188 (2016).
[10] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
[11] Phillips Semicond., Electronic Compass Design using KMZ51 and KMZ52, (2000).
[12] T. Kosub et al. Phys. Rev. Lett. 115, 097201 (2015).
[13] T. Kosub et al., Nat. Commun. 8, 13985 (2017).

Keywords: Properties/Magnetic/magnetic properties; Performance/Functionality/sensor; Composition & Microstructure/Material Type/polymer

  • Lecture (Conference)
    2017 MRS Fall Meeting & Exhibit, 26.11.-01.12.2017, Boston, Massachussets, USA

Permalink: https://www.hzdr.de/publications/Publ-26750
Publ.-Id: 26750


A novel method for the measurement of flotation recovery by means of 4D particle tracking velocimetry

Sommer, A.-E.; Nikpay, M.; Heitkam, S.; Rudolph, M.; Eckert, K.

This work focuses on the analysis of the collection process in flotation by a simultaneous time-resolved measurement of particle and bubble trajectories. We introduced a new method that determined the probability of collision and attachment by a 3D particle tracking method with high temporal (1000 fps) and spatial (0.03 mm/pixel) resolution in the dense particle flow (5000 particles/ml). A tomographic particle image velocimetry device with three high-speed cameras recorded the three-phase flow in a rectangular bubble column (bubble chain). Particles made of fluorescent polystyrene were employed so that particles appeared bright and bubbles dark on the captured images. An attachment occurred if the trajectory of a particle coincided with that of a bubble. The recovery was calculated based on the number of particles attached to a bubble compared to the total particles density. With this method, the true flotation depending on the particle diameter (30 µm - 100 µm) was investigated and compared the results with an existing model of the bubble-particle collection microprocess.

Keywords: Collection zone recovery; Particle tracking velocimetry; Polystyrene flotation; Bubble-particle interaction

  • Open Access Logo Minerals Engineering 124(2018), 116-122
    DOI: 10.1016/j.mineng.2018.05.006
  • Lecture (Conference)
    Flotation '17, 13.-16.11.2017, Cape Town, South Africa
  • Lecture (Conference)
    89th GAMM Annual Meeting, 19.-23.03.2018, München, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-26749
Publ.-Id: 26749


Geostatistics for Geometallurgical Property Prediction

van den Boogaart, K. G.; Menzel, P.; Bachmann, K.; Krupko, N.; Prior, A.; Tolosana Delgado, R.; Gutzmer, J.

Geometallurgy distinguishes primary and secondary ore properties. Primary properties are describing the analytically observable properties of the ore, such as chemical composition, modal mineralogy or microstructure. Secondary properties describe the properties observable in processing experiments, like milling energy consumption, recovery and concentrate grade and thus finally monetary return as a function of processing decisions. While only the primary properties can be obtained in a sufficiently dense spatial grid at reasonable costs, the secondary properties determine processing decisions and the ultimate value.

The standard approach is to estimate two things: A geostatistical block model of primary properties based on a spatial dataset and a regression model mapping the observable primary properties to experimental secondary properties on a smaller dataset. This regression model is then applied to the predicted primary properties. Due to the nonlinearity of the dependence and due to the difference in covariance structure between observed and predicted primary properties this is however misleading and will lead to suboptimal processing decisions and a loss in resource and energy efficiency.

We solve this problem by defining intermediate properties, which can be computed directly from automated mineralogy data, on which processing properties depend approximately linearily. In this approach each particle observed is separated, remilled and circulated in virtual plants according to their observed microstructures. Nonlinear effects like the influence of the microstructure on the recovery are handled in this transformation. In this way most value relevant properties (recovery, dillution and mass pull, etc.) become a linear function of the virtual distribution of microstructures. This multivariate dataset of intermediate values is then predicted by standard geostatistical techniques.

The methodology will be exemplified with a 2D case study from a chromite mine based on local geological knowledge and automated mineralogy data acquired on a suite of samples from known locations. The resultant model readily illustrates domains of differing processing characteristics

Keywords: Geometallurgy; Particle based modelling; Geostatistics; Secondary Properties

  • Lecture (Conference)
    IAMG2018 - 19th Annual Conference of the International Association for Mathematical Geosciences, 02.-08.09.2018, Olomouc, Česká republika

Permalink: https://www.hzdr.de/publications/Publ-26748
Publ.-Id: 26748


Analysis of the defect clusters in the congruent lithium tantalate

Vyalikh, A.; Zschornak, M.; Köhler, T.; Nentwich, M.; Weigel, T.; Hanzig, J.; Zaripov, R.; Vavilova, E.; Gemming, S.; Brendler, E.; Meyer, D. C.

A wide range of technological applications of lithium tantalate LiTaO3 (LT) is closely related to the defect chemistry. Several cation substitution defect models have been considered in literature since decades. Here we report a combinational approach based on DFT calculations of electric field gradients (EFG) and solid-state NMR in order to reveal the defect structure in congruent lithium tantalate. Using this approach, we were able to identify the cation substitution structure attributed to the Empty site defect model in one of two congruent LT crystals studied in our work. This observation is supported by the calculation of the energy for defect formation as well as by evaluation of the defect models based on the structural refinements and chemical reasonability reported in literature. After thermal treatment, hydrogen out diffusion and homogenation of other defects in lithium tantalate have been observed by electron spin resonance (ESR), NMR and FTIR spectroscopies. Identification of the defect structure in the second LT sample seems to be more challenging, as the extrinsic defects for balancing other impurities and/or an inhomogeneous defect distribution have to be taken into account. We have found that, although grown by the same method; the two congruent LT samples provided by two manufacturers show rather different defect structures, which is manifested not only in the distribution of EFGs at 7Li, but also in the FTIR and ESR spectra and in the 7Li spin-lattice relaxation behaviour. This observation has to be taken into account when attempting to favour one specific defect model within the scientific community and when studying the physical – particularly, magneto-optical – phenomena in the systems where lithium tantalate is used as a substrate.

Keywords: Lithium tantalate; defect models; cation substitution; DFT; solid-state 7Li NMR; spin-lattice relaxation; ESR; ferroic

Permalink: https://www.hzdr.de/publications/Publ-26747
Publ.-Id: 26747


A comparative biocompatibility study of graded TiC/a-C coatings prepared by dcMS and chopped-HiPIMS

Meško, M.; Gotzmann, G.; Bohovičová, J.; Zacková, P.; Čaplovič, Ľ.; Munnik, F.; Čaplovičová, M.; Vančo, Ľ.; Skákalová, V.; Krause, M.

Differences in the structural and biocompatibility properties of graded TiC/a-C coatings prepared by direct current magnetron sputtering (dcMS) and chopped -high power impulse magnetron sputtering (c-HiPIMS) were studied. The higher ID/IG ratio in c-HiPIMS a-C films is due to the clustering of the sp2 phase as indicated by Raman spectroscopy. C-HiPIMS a-C films are more hydrophobic with contact angle difference of about 9 % in comparison to the dcMS films at average power of 250W. The metabolic activity of human fibroblast cells cultivated on the samples grown by c-HiPIMS is of about 20 % higher than that of the samples deposited by dcMS. The increased metabolic activity is due to a confluent cell layer on these surfaces. The investigation of the cell morphology revealed no negative influence on biocompatibility for both deposition methods.

  • Contribution to proceedings
    The Fourteenth International Symposium on Sputtering and Plasma Processes (ISSP 2017), 05.-07.07.2017, Kanazawa, Japan, ISSN 2187-7637, 256-259
  • Poster
    The Fourteenth International Symposium on Sputtering and Plasma Processes (ISSP 2017), 05.-07.07.2017, Kanazawa, Japan

Permalink: https://www.hzdr.de/publications/Publ-26745
Publ.-Id: 26745


Beneficiation potential of complex Sn deposits in the Erzgebirge

Kern, M.

Presentation for the 15th Freiberger Short Course on Economic Geology (2017)

  • Invited lecture (Conferences)
    15th Freiberger Short Course on Economic Geology, 03.-06.12.2017, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-26744
Publ.-Id: 26744


Electrical characterization of Si nanocrystal devices suitable for RT-SET operation

Belli, M.; Alia, M.; Xu, X.; Laviron, C.; Gharbi, A.; Rommel, M.; Stumpf, F.; Prüfer, T.; Wolf, D.; Bischoff, L.; Hübner, R.; Hlawacek, G.; Facsko, S.; Heinig, K.-H.; von Borany, J.; Fanciulli, M.

The contribution addresses two needs of the current micro/nanoelectronics field: the creation of low-power consumption devices, together with the compatibility with CMOS technology. Both can be potentially fulfilled adopting single electron transistors (SETs), prepared by opportune methods, to be inserted into hybrid SET-CMOS devices.
Here we focus on the electrical characterization of structures whose preparation method is suited for large-scale production of SET devices, potentially operative at room temperature: the device core is represented by few-nanometer size nanocrystals embedded in a SiO2 matrix, and is produced by ion beam mixing and subsequent thermal annealing. The preparation starts with a Si/SiO2/Si stack characterized by a few nm-size inner SiO2 layer. Ion bombardment induces atom displacements between the layers, which can be partly recovered by thermal annealing. Thanks to the joint use of process simulations and experiment, it is possible to find an opportune thermal annealing process to yield few nm-size silicon crystals embedded in the middle of the SiO2 layer. The small crystal size (< 5 nm) and the extremely narrow SiO2 bridges (~ 2 nm) between the nanocrystals and the electrical contacts are designed to ensure high tunneling probability towards the Si quantum dot and room temperature operation. The production method should allow fast transfer to industrial processes, being scalable to standard full wafer-size processing. Results on the electrical characterization in the 5 K – 350 K range of preliminary structures will be presented, in view of the realization of SET and hybrid SET-CMOS devices.
The authors acknowledge support from H2020 project “IONS4SET”, contract number 688072.

  • Lecture (Conference)
    EUROMAT 2017, 17.-22.09.2017, Thessaloniki, Greece

Permalink: https://www.hzdr.de/publications/Publ-26743
Publ.-Id: 26743


Challenges of digitalizing the circular economy: Assessment of the state-of-the-art of metallurgical carrier metal platform for lead and its associated technology elements

van Schalkwyk, R. F.; Reuter, M. A.; Gutzmer, J.; Stelter, M.

The circular economy (CE) paradigm in its broadest sense is key to our survival as a species. Due to this critical importance, understanding its fundamental limitations is thus of significant importance. Especially understanding the losses to Nature are key as these represent the true limitation to circularity. This requires at the minimum an understand of the thermodynamics and entropy of the losses. Most CE work as well as the many depictions to date neglect to address this in detail, the many losses are brushed aside. Many texts in CE do not use the words entropy, thermodynamics, mass and heat transfer, technology etc. which all ultimately fundamentally affect both the circularity as well as economic viability of the system. Using lead as carrier for the narrative of this paper, the state-of-the art from technology to the thermodynamics as well as heat and mass transfer, product design, modularity, environmental impact, system simulation etc. will be critically discussed. This will reveal what key knowledge and data is presently missing to the achieve the economically viable circularity of materials and products This paper goes further to offer pointers what should be researched and developed to “close” the circular economy system. It thus provides a “ground zero” or baseline for the evaluation of the true economic viability of the CE paradigm relative to what we are presently achieving in our linear economy paradigm.

Keywords: Circular Economy; Lead; Technology Elements; Process metallurgy; Resource efficiency; Sustainability

Permalink: https://www.hzdr.de/publications/Publ-26742
Publ.-Id: 26742


Chancen und Grenzen der Circular Economy: Wie recycelbar sind Mobiltelefone?

Reuter, M. A.; Weigl, A.

Um Ressourcen verantwortungsvoll und effizient zu nutzen, ist eine fortschrittliche Circular Economy (CE ─ Kreislaufwirtschaft), in der Recycling ein Kernelement ist, der vielversprechendste Ansatz. Auf der politischen Agenda Europas ist die CE ganz oben angekommen. Circular Economy und Recycling sollten, so fordert zum Beispiel der französische Premierminister, Emmanuel Macron, eine wichtige Säule bei der Rohstoffsicherung für die heimische Industrie bilden (1). Auch verhandeln derzeit die EU-Mitgliedstaaten über ein europäisches Kreislaufwirtschaftspaket (2).
Wieviel Recycling ist aber angesichts von immer komplexeren elektronischen Geräten und anderen Hochtechnologieanwendungen derzeit überhaupt möglich? Eine aktuelle Recyclingstudie zeigt am Beispiel eines Mobiltelefons die Chancen und Grenzen der Circular Economy auf.

Keywords: Circular Economy; Kreislaufwirtschaft; CE; Recycling; Recyclingstudie; Mobiltelefon; Rohstoffe; Recycelbarkeit; Metallurgie

  • ACAMONTA - Zeitschrift für Freunde und Förderer der TU Bergakademie Freiberg 24(2017), 65-68

Permalink: https://www.hzdr.de/publications/Publ-26740
Publ.-Id: 26740


Property-based Modelling and Simulation of Mechanical Separation Processes using Dynamic Binning and Neural Networks

Hannula, J.; Kern, M.; Luukkanen, S.; Roine, A.; van den Boogaart, K. G.; Reuter, M. A.

To fully understand the limits of the Circular Economy (CE), a comprehensive model taking into account its different stages (product design, mechanical pre-processing, metallurgy, etc.) is required. A crucial aspect is to understand the inevitable losses at different stages of recycling. The complexity of the material streams in mechanical separation processes requires a detailed description of particles and their properties to successfully simulate unit processes. This paper presents a new approach that connects measurement-based particle properties to statistical modelling and simulation of mechanical separation processes. The proposed approach combines particle tracking with the generalization ability of neural networks. Above all it advances the present particle binning and tracking methods utilizing property-based binning rather than liberation-based binning for modelling purposes of complex systems. In order to demonstrate the new approach, this paper uses Mineral Liberation Analysis (MLA) data from magnetic and gravity separation processes of a complex ore and shows the benefits of property based binning over for example liberation based binning. The proposed approach can be integrated into present simulation platforms such as HSC Sim.

Keywords: Particle Tracking; Particle-based model; Modelling; Simulation; Circular Economy

  • Minerals Engineering 126(2018), 52-63
    DOI: 10.1016/j.mineng.2018.06.017
  • Lecture (Conference)
    Sustainable Minerals '18, 15.06.2018, Windhoek, Namibia

Permalink: https://www.hzdr.de/publications/Publ-26739
Publ.-Id: 26739


Central receiver coatings for high-temperature concentrated solar power studied by in situ RBS, Raman spectroscopy and spectroscopic ellipsometry

Lungwitz, F.; Heras, I.; Janke, D.; Wenisch, R.; Schumann, E.; Guillén Rodriguez, E.; Escobar Galindo, R.; Gemming, S.; Krause, M.

The development of solar-selective CSP receiver coatings with high-temperature and environmental stability requires new concepts of design and in operando monitoring. Solar receiver tubes are a key component of solar thermal power plants. The increase of their operation temperature from today’s maximum of 550°C to about 800°C could increase the CSP efficiency by approximately 15 to 20% and improve the competiveness of this technology compared to other ones of carbon-free electricity generation. Potential alternatives to fast degrading state-of-the-art pigment paint receiver tube coatings are based on refractive metal carbides, nitrides, and oxides because of their high thermal stability and oxidation resistance.
New types of solar-selective coatings were studied in situ at temperatures of up to 830°C by Rutherford backscattering spectrometry, Raman spectroscopy, and spectroscopic ellipsometry within a cluster tool. High-temperature stability in high-vacuum is demonstrated for carbon-metal- and oxynitride-absorber-based multilayers as well as for a solar-selective transmitter based on a transparent conductive oxide.
Financial support by the EU, grant No. 645725, project FRIENDS2, and the HGF via the W3 program (S.G.) is gratefully acknowledged.

Keywords: Solar selective coatings; Oxynitrides; Thermosolar energy; Optical simulation; in situ analysis

  • Poster
    X Iberian Vacuum Conference, RIVA, 04.-06.10.2017, Bilbao, Espana

Permalink: https://www.hzdr.de/publications/Publ-26738
Publ.-Id: 26738


An update on possibilities of metals recovery from Polish copperores by biotechnology. Project Ecometals

Szubert, A.; Guezennec, A.-G.; Bodénan, F.; Dirlich, S.; Pawłowska, A.; Grotowski, A.; Sadowski, Z.; Witecki, K.

The possibilities of metals recovery from copper ores with the biotechnological methods are widely known. The methods consist in bioleaching of copper ores, copper concentrates and byproducts of their production, as well as metals recovery from leaching solutions. Biohydrometallurgical methods were tested for years to be applied at KGHM Polska Miedź S.A., in order to improve efficiency of copper production. Several different research units worked on the topic, and the most significant and wide range initiatives in this area are mentioned in this article. One of the initiatives is an ongoing German and French Ecometals project. KGHM Polska Miedź S.A. and KGHM Cuprum Ltd. Research and Development Centre are this project Partners. In the frame of the project different metals bearing materials (ores, concentrates and tailings) are tested. Among them three lithological types of the copper ore from Rudna mine and the copper concentrate from Lubin concentrator are used for studies. The article gives a general overview of these activities, with the main focus on results of bioleaching studies of selected materials, conducted by KGHM Cuprum. In these studies sandstone and shale, as well as so called “shale concentrate” (containing 39% of the shale) were used for experiments, and possibilities of their bioleaching were evaluated.

Keywords: Biohydrometallurgie; biohydrometallurgy; Biolaugung; bioleaching, Kupfer; copper

  • Open Access Logo Contribution to proceedings
    Mineral Engineering Conference MEC2017, 20.-23.09.2017, Wisła, Polska
    E3S Web of Conferences 18 , 01015
    DOI: 10.1051/e3sconf/201712301015

Permalink: https://www.hzdr.de/publications/Publ-26736
Publ.-Id: 26736


Bewertung - zwischen Vollständigkeit und Praxisnähe

Dirlich, S.

Der Buchbeitrag beschäftigt sich mit der Bewertung von Handlungsoptionen in verschiedenen Themenfelder der Siedlungsentwicklung, die in einem Projekt im BMBF-Förderprogramm "Nachhaltiges Landmanagement" entwickelt wurde. Eine Bewertung der vorgeschlagenen Handlungsoptionen ist erforderlich, um deren Wirkungen aus Sicht der Ressourceneffizienz und Emissionsarmut einzuschätzen und miteinander zu vergleichen. Aufgrund der Bandbreite der Themenfelder von der Abfallwirtschaft bis hin zur Siedlungsentwicklung und der transdisziplinären Herangehensweise ist ein projektspezifischer angepasster Ansatz nötig, der sowohl den Erfordenissen der Wissenschaft nach Vollständigkeit und Vergleichbarkeit gerecht wird, als auch den Anforderungen der beteiligten Akteure entspricht.

Keywords: nachhaltiges Landmanagement; sustainable land management; Bewertung; assessment; Siedlungsentwicklung; settlement development

  • Open Access Logo Book chapter
    Schiller, Georg: Wege zur Umsetzung von Ressourceneffizienzstrategien in der Siedlungs- und Infrastrukturplanung IÖR Schriften Band 74, Berlin: RHOMBOS-Verlag, 2017, 978-3-944101-74-3

Permalink: https://www.hzdr.de/publications/Publ-26735
Publ.-Id: 26735


Relativistic Effects in Laser Plasmas -Plasma Birefringence and Generation of Mega-Tesla Magnetic Field-

Arefiev, A.; Stark, D. J.; Toncian, T.; Murakami, M.

と呼ばれる物理現象は,高強度レーザーとプラズマとの相互作用に対する近年の当該領 域の研究の中でもパラダイムシフトとも言うべき極めて興味深いものである.超高強度レーザーの照射によりプ ラズマ中の電子温度が急速に相対論領域(!500 keV)にまで上昇すると,たとえ非相対論領域においてレーザー が完全反射されるほどの高密度のプラズマでも,レーザー光はプラズマの奥深く浸透することが可能となり,こ の特性は「相対論的透明性」と呼ばれる.本章では,相対論的透明性が顕著に見られる2つの集団現象にスポッ トを当てることにより,レーザーと物質との相互作用において同特性が演じる重要な役割を俯瞰する.第一の現 象は,相対論領域におけるプラズマ中で見られる複屈折である.この相対論的複屈折では超高強度レーザー照射 によってプラズマが非等方性を持ち,結果としてその光学特性がレーザーの偏光に強く依存する.第二の現象は, 高密度プラズマと超高強度レーザーとの(極小幅を持つ境界面ではなく奥行きを持った有限空間に分布する)体 積的相互作用により誘起される超高強度の準静磁場の生成である.このような相対論的高エネルギー密度領域で は MeV オーダーの

Keywords: relativistic transparency; laser-matter interaction; megatesta magnetic field; plasma birefringence

  • Open Access Logo Journal of Plasma and Fusion Research 93(2017)11, 535-544

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Permalink: https://www.hzdr.de/publications/Publ-26734
Publ.-Id: 26734


Se behaviour in Pb pyrometallurgical processes

van Schalkwyk, R. F.; Reuter, M.; Stelter, M.

Lead pyrometallurgical infrastructure plays an important role in the circular economy, due to the application of existing lead infrastructure and smelters for processing of secondary materials (e.g. electronics, flue dusts and waste slags). However, as the proportion of non-traditional secondary feed materials to smelters increases, so does the complexity. Better understanding is required of non-traditional and minor elements in lead metallurgy, e.g. Se.
During direct lead smelting, molten metal and slag phases form and minor elements are distributed amongst these. Se typically reports to the lead bullion and is removed from the bullion during refining stages. It is important to determine the metal/slag distribution in order to understand downstream process impacts and to avoid contamination of the final product.
Equilibration experiments are carried out in a laboratory furnace to determine slag/metal distributions of minor elements. At thermodynamic equilibrium, the distribution is affected by the temperature, slag composition, oxygen potential and interactions between elements in the melt. Results from equilibrium measurements and process implications will be discussed.

Keywords: Metallurgy; Lead; Selenium; Technology Elements

  • Lecture (Conference)
    Sustainable Minerals 2018, 14.-16.06.2018, Windhoek, Namibia

Permalink: https://www.hzdr.de/publications/Publ-26732
Publ.-Id: 26732


Integration of mineralogical and hyperspectral data for drill-core characterization

Tusa, L.; Andreani, L.; Contreras, C. I.; Ivascanu, P.; Gloaguen, R.; Gutzmer, J.

Mineral exploration and resource definition require extensive drilling campaigns that are generally done with tight deadlines and often rely only on visual qualitative evaluation of the rock characteristics (core logging) and limited chemical analyses. The aim of these campaigns is to understand the genesis and zonality of mineral deposits. The ore, in many cases, is closely related to the distribution of hydrothermal alterations and their associated structures. Therefore, the host characteristics are analysed in order to build a distribution model of the mineralization. However, traditional techniques such as core logging can present limitations in the identification of often subtle and therefore similar mineral assemblages and the acquired data are only qualitative. Additionally, the identification and quantification of other textural and structural features, such as veins, is slow, laborious and frequently limited by the subjectivity of the observer.
Our aim is to develop new methods which respond to the need for rapid, automated and precise extraction of mineralogical, textural and structural information from cores. We propose to process hyperspectral VNIR/SWIR data from core scanners, using innovative image segmentation and classification techniques in order to quickly extract precise numerical parameters of both mineralogical and structural information. We use scanning electron microscopy (SEM)-based analyses on selected samples to train the classifier and validate the results. SEM shows great potential in the identification of the main alteration assemblages as well as of the main hydrothermal events they are associated with. Even though it requires extensive sample preparation and the measurements are time consuming, by analysing representative samples for different alteration types, SEM-based analyses provide control information for the interpretation and classification of hyperspectral data. Hyperspectral data allow the identification of the main alteration phases and the distribution of specific mineral assemblages as each vein type displays a specific signature in the VNIR-SWIR region of the electromagnetic spectrum. Image segmentation techniques allow us to extract veins and additional parameters such as orientations and densities. The interest of this approach is that it (1) allows the combined analysis of compositional and structural features, (2) provides a very rapid and validated mapping of the cores that is based on (3) the upscaling of SEM data.
The proposed methodology has been tested on selected core samples from the Bolcana copper-gold porphyry system (Romania). This site is located in the Golden Quadrilateral (Apuseni Mountains) where extensive drilling has been performed by Eldorado Gold using state of art methodology that includes thorough chemical analyses, detailed logging and spectral characterization of assay pulps. The mineralization in Bolcana is hosted in Neogene subvolcanic dioritic intrusions and associated magmatic-hydrothermal breccias that intruded in a shallow volcanic environment. The system is characterized by complex transitions on lithological and alteration assemblages. The porphyry mineralization is also overprinted by later epithermal events that lead to different alteration patterns than those usually encountered in porphyry systems.
The analyses of the cores collected from the Bolcana site have shown a preferential association of specific alteration assemblages with different vein generations such as white mica dominant assemblages for late stage pyrite veins, a chlorite-epidote dominant assemblage on early chalcopyrite veins and low intensity white mica dominant assemblage associated with early quartz veins. At core scale a preferential orientation of these veins was additionally observed.
The integration of this new approach with traditional logging methods performed by site geologists as well as with structural data (Reflex IQ-logger) provided by Eldorado Gold gives us an insight on the spatial and directional distribution of the main vein types and their characteristic alteration assemblages in the Bolcana site. The integration of such new methodologies in the exploration campaign allows for better and faster exploration targeting based on key mineral assemblages and structural features, as well as a more comprehensive preliminary ore evaluation and resource modelling. This would be achieved by the implementation of on-site drill-core scanning.

  • Poster
    Applied Geological Remote Sensing, 12.-15.12.2017, Lisbon, Portugal

Permalink: https://www.hzdr.de/publications/Publ-26731
Publ.-Id: 26731


Distribution of lead- and zinc-bearing minerals in the gossan of the Gamsberg Zn deposit, South Africa

Tusa, L.; Moeckel, R.; Gutzmer, J.

The giant Gamsberg massive sulphide deposit is currently being developed by Vedanta Resources. During mine development, the massive gossan zone is stripped in order to expose the sulphide orebody. During a field visit In September 2016, a suite of samples was collected from the gossan in the developing open pit. Three lithologically distinct zones were recognized. The topmost zone is a goethitic hard cap that is also well exposed at the present-day land surface (Rozendaal, 1986). The goethitic hard cap grades down into an iron oxide-poor zone that comprises of very friable siliceous material. The latter is cross-cut by fractures filled by hematite. The third zone of the gossan is marked by an abundance of fine-grained earthy hematite intergrown with semi-friable silica. Vugs are commonly lined by chalcedony. A detailed study revealed the presence of a complex suite of secondary lead and zinc minerals. Zinc is most abundant in the goethite cap – apparently related to the occurrence iron-rich smectite group minerals. Minor amounts of Pb-rich minerals, such as anglesite and members of the corkite-beaudantite were also identified. Most abundant, however, is lead below the goethitic cap where anglesite and members of the mimetite- pyromorphite and corkite-beaudantite series are very common. The lowermost gossan zone consists of mainly fine grained silica and hematite. Lead- and zinc-bearing minerals are conspicuously absent. The results obtained are consistent with observations by Rozendaal (1986) – and the apparent enrichment of lead-bearing secondary minerals in the gossan - relative to scarce nature of galena in the sulphide orebody. This apparent enrichment is attributed to the greater mobility of zinc – relative to lead - in the supergene environment.

  • Poster
    Geology of Ore Deposits, 08.-11.03.2017, Hannover, Germany

Permalink: https://www.hzdr.de/publications/Publ-26730
Publ.-Id: 26730


3D Si-SiO2 nano-networks formed by diode laser-induced liquid- and solid-state decomposition of SiOx

Schumann, E.; Hübner, R.; Carcelen, V.; Grenzer, J.; Heinig, K.-H.; Gemming, S.; Krause, M.

Thin films of nano-structured crystalline silicon (nc-Si) are potential absorber and supporting layers for next-generation Si solar cells. As one candidate, Si-SiO2 nanocomposites with percolated nc-Si have been fabricated by rapid thermal annealing (RTA) of sputter-deposited SiOx films (x≈1). A percolated silicon network has been formed by solid state phase separation into nc-Si and SiO2 [1, 2].
In the present study, SiO0.6 layers of ~500nm thickness are grown on quartz by ion beam sputter (IBS) as well as by reactive magnetron sputter (RMS) deposition. Formation of percolated Si-SiO2 nanocomposites is achieved by two different modes of thermal treatment: (i) Furnace annealing at 950°C and (ii) scanning laser processing. In case (ii), a diode laser with dwell times in the ms range, power densities of ~30 kW/cm², a wavelength of λ= 808nm and a line focus of 100µm x 11mm is applied. This process is ~106 times faster than isothermal treatment and ~103 times faster than RTA. Another advantage of this method is the usability of temperature sensitive substrates and maintaining homogeneous processing.
Rutherford backscattering spectra of as-deposited and processed SiO0.6 reveals a compositional change in thin surface and interface layers, but no significant change in the bulk composition. Raman spectroscopy and X-ray diffraction show that the crystallinity of the nc-Si is higher for the laser-treated sample.
High resolution- and energy-filtered transmission electron microscopy (HTEM, EFTEM) show additionally, that in both cases the as-deposited SiO0.6 is transformed into a percolated nanocomposite consisting of amorphous SiO2 and nc-Si.
In more detail, laser processing of IBS-deposited layers leads to isotropic morphologies self-similar to furnace-annealed samples, but scaled up by a factor of ~5. This is explained by a phase separation in the liquid state and the solid state, respectively, which cause diffusion coefficients differing by several orders of magnitude.
During the deposition by RMS, phase separated filament-like morphologies form. Here, furnace annealing leads to enhanced phase separation accompanied by crystallization. In contrast laser processing erases the as-deposited filaments and produces isotropic morphologies similar to IBS-deposited and laser-processed samples

[1] Friedrich, D. et al. Sponge-like Si-SiO2 nanocomposite - Morphology studies of spinodally decomposed silicon-rich oxide. Appl. Phys. Lett. 103, 131911 (2013).
[2] Ilday, S. et al. Multiscale Self-Assembly of Silicon Quantum Dots into an Anisotropic Three-Dimensional Random Network. Nano Lett. 16, 1942–1948 (2016).

  • Lecture (Conference)
    2017 MRS Spring Meeting & Exhibit, 17.-21.04.2017, Phoenix, USA

Permalink: https://www.hzdr.de/publications/Publ-26728
Publ.-Id: 26728


Design of high-temperature solar-selective coatings based on aluminium titanium oxynitrides AlyTi1-y(OxN1-x). Part 1: Advanced microstructural characterisation and optical simulation

Heras, I.; Guillén, E.; Lungwitz, F.; Rincón-Llorente, G.; Munnik, F.; Schumann, E.; Azkona, I.; Krause, M.; Escobar-Galindo, R.

Aluminium titanium oxynitrides were studied as candidate materials for high temperature absorbers in solar selective coatings due to their excellent stability and their tuneable optical behaviour. A set of individual AlyTi1-y(OxN1-x) layers with different oxygen content was prepared by cathodic vacuum arc (CVA) deposition. The composition, morphology, phase structure and microstructure of the films were characterized by elastic recoil detection (ERD), scanning and transmission electron microscopy and X-ray diffraction. An fcc phase structure is found in a broad compositional range of AlyTi1-y(OxN1-x). Simultaneously, sample microstructure and morphology undergo systematic changes from a columnar growth to the development of a heterogeneous structure with spherical nanoparticle inclusions when the oxygen concentration is increased. The optical properties were determined by spectroscopic ellipsometry and UV–Vis–NIR and FTIR spectrophotometry. A comprehensive analysis of the film properties allowed an accurate modelling of the optical constants of the AlyTi1-y(OxN1-x) in the whole wavelength range of solar interest (from 190 nm to 25 µm). It points to a transition from metallic to dielectric behaviour with increasing oxygen content. Consequently, it is demonstrated that the optical properties of these AlyTi1-y(OxN1-x) deposited films can be controlled in a wide range from metallic to dielectric character by adjusting the oxygen concentration, opening a huge range of possibilities for the design of solar selective coatings (SSC) based on this material. Complete SSC, including a TiN layer as IR reflector, were designed by applying optical simulations, obtaining excellent optical selective properties of α=94.0% and εRT = 4.8%.

Keywords: Solar selective coatings; Oxynitrides; Thermosolar energy; Optical simulation

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Permalink: https://www.hzdr.de/publications/Publ-26727
Publ.-Id: 26727


Phase Transitions in C:Ni Nanocomposite Templates during Diameter-Selective CVD Synthesis of SWCNTs

Krause, M.; Melkhanova, S.; Hübner, R.; Haluska, M.; Gemming, S.

Phase transitions in carbon: nickel nanocomposite templates during diameter-selective CVD synthesis of SWCNTs were studied. While almost conserving their pre-defined diameter distribution, as-deposited Ni3C nanoparticles transform into fcc-NiO during activation in low-pressure air atmosphere, and are reduced to a mixture of fcc-Ni and Ni3C under nanotube growth conditions. The first phase transition leads to a substitutional replacement of the protective carbon matrix by a protective oxide layer. The second one reflects competing reduction processes of NiO. A mechanism for the complementary roles of carbon matrix and Ni species in the three-step CVD synthesis is proposed that includes nanoparticle immobilization, carbon delivery and catalysis of nanotube growth.

Keywords: nanocomposites; single-walled carbon nanotubes; catalysis; transmission electron microscopy; Raman spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-26726
Publ.-Id: 26726


On the synchronizability of Tayler–Spruit and Babcock–Leighton type dynamos

Stefani, F.; Giesecke, A.; Weber, N.; Weier, T.

The solar cycle appears to be remarkably synchronized with the gravitational torques exerted by the tidally dominant planets Venus, Earth and Jupiter. Recently, a possible synchronization mechanism was proposed that relies on the intrinsic helicity oscillation of the current-driven Tayler instability which can be stoked by tidal-like perturbations with a period of 11.07 years. Inserted into a simple alpha-Omega dynamo model these resonantly excited helicity oscillations led to a 22.14 years dynamo cycle. Here, we assess various alternative mechanisms of synchronization. Specifically we study a simple time-delay model of Babcock–Leighton type dynamos and ask whether periodic changes of either the minimal amplitude for rising toroidal flux tubes or the Omega effect could eventually lead to synchronization. In contrast to the easy and robust synchronizability of Tayler–Spruit dynamo models, our answer for those Babcock–Leighton type models is less propitious.

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Permalink: https://www.hzdr.de/publications/Publ-26725
Publ.-Id: 26725


Metallurgie und Recycling im HIF - Gegenwart und Zukunft

Kelly, N.; Scharf, C.

  • Lecture (others)
    Topictreffen „Ressourcentechnologie“, 03.-04.07.2017, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26724
Publ.-Id: 26724


FWGM - Division METALLURGY & RECYCLING - Helmholtz Institute Freiberg for Resource Technology

Kelly, N.; Scharf, C.

  • Lecture (others)
    Meeting VITO - FWGM, 26.-27.01.2017, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26723
Publ.-Id: 26723


FWGM - Division METALLURGY & RECYCLING - Helmholtz Institute Freiberg for Resource Technology

Kelly, N.; Scharf, C.

  • Lecture (others)
    Meeting IWKS - FWGM, 13.02.2017, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26722
Publ.-Id: 26722


Current Projects and Objectives at Helmholtz Institute Freiberg – Department of Metallurgy and Recycling

Kelly, N.; Scharf, C.

Current Projects and Objectives at Helmholtz Institute Freiberg – Department of Metallurgy and Recycling

  • Poster
    International Workshop ECMAG - Magnetic Field Effects on Aqueous Solutions, 20.-21.04.2017, Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26721
Publ.-Id: 26721


Screening the potential of Halophilic bacteria for Pyrite bio depression

Luque Consuegra, G.; Kutschke, S.; Rudolph, M.; Pollmann, K.

The separation of minerals has been a pressing issue in the last decades. One of the most common techniques to separate useful minerals from gangue minerals is Froth Flotation. Flotation is a relatively cheap and efficient process but the use of harmful chemicals and continuous decrease in ore quality due to the scarcity of high grade ores has motivated researchers to find alternative solutions to the standard flotation reagent scheme in order to make the process more efficient and environmentally friendly. Bioflotation has the potential of making the beneficiation of minerals more efficient and environmentally friendlier. Different bacteria and bacterial products have demonstrated to have prospective applications in bio flotation of different minerals (Behera and Mulaba-Bafubiandi, 2016). Halophilic bacteria are adapted to high salinity environments and other extreme conditions. Halophilic bacteria produce Extracellular Polymeric Substances (EPS) that aid them in the formation of biofilms and resist abrupt changes in salinity, pH, temperature and pressure. These EPS could have potential applications in flotation operations performed in sea water, such as the Copper-Molybdenum flotation operations in Chile. To date, there are no reports of halophilic bacteria been used in bio flotation experiments.
Halomonas boliviensis, Marinobacter spp, Halobacillus sp, Marinococcus sp and Halomonas eurihalina were studied to examine their potential as pyrite bio depressants, a gangue mineral common in Cu-Mo flotation. Micro flotation experiments using Hallimond tubes as well as flocculation, adsorption and Zeta potential experiments were performed in order to report the potential of these bacteria in the flotation process. In this study we will show the first results of using halophilic bacteria as Pyrite bio depressants, as well as an initial characterisation of the Extracellular Polymeric Substances excreted by these bacteria that could have an influence on the adsorption and mechanism by which these bacteria alter the surface of Pyrite.

Keywords: Biodepression; Halophilic bacteria; Pyrite

  • Poster
    Tagung 2017 Aufbereitung und Recycling, 08.-09.11.2017, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26720
Publ.-Id: 26720


Whole exome sequencing identifies mTOR and KEAP1 as potential targets for radiosensitization of HNSCC cells refractory to EGFR and β1 integrin inhibition

Klapproth, E.; Dickreuter, E.; Zakrzewski, F.; Seifert, M.; Petzold, A.; Dahl, A.; Schröck, E.; Klink, B.; Cordes, N.

Intrinsic and acquired resistances are major obstacles in cancer therapy. Genetic characterization is commonly used to identify predictive or prognostic biomarker signatures and potential cancer targets in samples from therapy-naïve patients. By far less common are such investigations to identify specific, predictive and/or prognostic gene signatures in patients or cancer cells refractory to a specific molecular-targeted intervention. This, however, might have a great value to foster the development of tailored, personalized cancer therapy. Based on our identification of a differential radiosensitization by single and combined β1 integrin (AIIB2) and EGFR (Cetuximab) targeting in more physiological, three-dimensional head and neck squamous cell carcinoma (HNSCC) cell cultures, we performed comparative whole exome sequencing, phosphoproteome analyses and RNAi knockdown screens in responder and non-responder cell lines. We found a higher rate of gene mutations with putative protein-changing characteristics in non-responders and different mutational profiles of responders and non-responders. These profiles allow stratification of HNSCC patients and identification of potential targets to address treatment resistance. Consecutively, pharmacological inhibition of mTOR and KEAP1 effectively diminished non-responder insusceptibility to β1 integrin and EGFR targeting for radiosensitization. Our data pinpoint the added value of genetic biomarker identification after selection for cancer subgroup responsiveness to targeted therapies.

Keywords: β1 integrin; EGFR; Exome; ionizing radiation; HNSCC

Permalink: https://www.hzdr.de/publications/Publ-26719
Publ.-Id: 26719


Carbonate and silicate intercomparison materials for cosmogenic 36Cl measurements

Mechernich, S.; Dunai, T. J.; Binnie, S. A.; Goral, T.; Heinze, S.; Dewald, A.; Schimmelpfennig, I.; Keddadouche, K.; Aumaître, G.; Bourlès, D.; Marrero, S. M.; Wilcken, K.; Simon, K.; Fink, D.; Phillips, F. M.; Caffee, M. W.; Gregory, L. C.; Phillips, R.; Freeman, S. P. H. T.; Shanks, R. P.; Sarıkaya, M. A.; Pavetich, S.; Rugel, G.; Merchel, S.; Akçar, N.; Yesiyurt, S.; Ivy-Ochs, S.; Vockenhuber, C.

Two natural mineral separates, labeled CoCal-N and CoFsp-N, have been prepared to serve as intercomparison material (ICM) for in situ-produced cosmogenic 36Cl and natural chlorine (Clnat) analysis. The sample CoCal-N is derived from calcite crystals in a Namibian lag deposit, while the sample CoFsp-N is derived from a single crystal of alkali-feldspar from a Namibian pegmatite. The sample preparation took place at the University of Cologne and a rotating splitter was used to obtain homogeneous splits of both ICMs. Forty-five measurements of CoCal-N (between 1 and 16 per facility) and forty-four measurements of CoFsp-N (between 2 and 20 per facility) have been undertaken by ten target preparation laboratories measured by seven different AMS facilities. The internal laboratory scatter of the 36Cl concentrations indicate no overdispersion for half of the laboratories and 3.9 to 7.3% (1σ) overdispersion for the others. We show that the CoCal-N and CoFsp-N splits are homogeneous regarding their 36Cl and Clnat concentrations. The grand average (average calculated from the average of each laboratory) yields initial consensus 36Cl concentrations of (3.74 ± 0.10) x 106 at 36Cl/g (CoCal-N) and (2.93 ± 0.07) x 106 at 36Cl/g (CoFsp-N) at 95% confidence intervals. The coefficient of variation is 5.1% and 4.2% for CoCal-N and CoFsp-N, respectively. The Clnat concentration corresponds to the lower and intermediate range of typical rock samples with 0.73 ± 0.18 μg/g in CoCal-N and 73.9 ± 6.8 μg/g in CoFsp-N. We discuss the most relevant points of the sample preparation and measurement and the chlorine concentration calculation to further approach intra-laboratory comparability. We propose to use continuous measurements of the ICMs to provide a valuable quality control for future determination of 36Cl and Clnat concentrations.

Keywords: Accelerator mass spectrometry; Terrestrial cosmogenic nuclides (TCN); Round Robin; Intercomparison material (ICM); Consensus values

Permalink: https://www.hzdr.de/publications/Publ-26718
Publ.-Id: 26718


Optimization of an SRF Gun for High Bunch Charge Applications at ELBE

Lu, P.

As a cutting-edge type of photoinjectors, SRF gun is expected to provide a CW electron beam with high bunch charge and low emittance, which is highly demanded by the development of future FELs, ERLs and 4th/5th generation light sources. However, existing researches have not explored the full potential of SRF gun predicted by theory.

Keywords: photo injector; superconducting RF; SRF gun; ELBE facility; electron beam transport; simulation

  • Doctoral thesis
    TU Dresden, 2017
    Mentor: Dr. Jochen Teichert
    134 Seiten

Permalink: https://www.hzdr.de/publications/Publ-26717
Publ.-Id: 26717


Operation of the SRF Gun with Mg Photocathodes for Production of Neutrons and THz Radiation at ELBE

Teichert, J.

Status Report on Superconducting Rf Photoinjector application at ELBE

Keywords: SRF gun; photo injector; ELBE

  • Lecture (Conference)
    PITZ Collaboration Meeting, 05.-06.12.2017, Zeuthen, Germany

Permalink: https://www.hzdr.de/publications/Publ-26716
Publ.-Id: 26716


The Superconducting RF Photoinjector and its Present and Future Use at the ELBE Accelerator

Teichert, J.

The Superconducting RF Photoinjector and its Present and Future Use at the ELBE Accelerator

Keywords: SRF Gun; ELBE facility; superconducting RF; photocathodes; Nb resonator

  • Lecture (others)
    Seminar talk, 06.-10.11.2017, Chengdu, China

Permalink: https://www.hzdr.de/publications/Publ-26715
Publ.-Id: 26715


Operational Aspects of Photocathodes for SRF Guns

Teichert, J.; Xiang, R.

The talk reports on operational aspects and experiences of photocathodes for the superconducting Rf photo injector at the ELBE accelerator

Keywords: photocathode; SRF gun; photo injector; cathode handling

  • Invited lecture (Conferences)
    EWPAA workshop, 20.-22.09.2017, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-26714
Publ.-Id: 26714


Using the Mineral Liberation Analyzer for mineralogical studies of a carbonaceous apatite ore

Hoang, D. H.; Leißner, T.; Haser, S.; Rudolph, M.; Peuker, U. A.

Liberation analysis on grinding products is a very important subject for application in respect of both mineralogical characteristics and beneficiation process relevant parameters. The Mineral Liberation Analyzer (MLA) combines a large specimen chamber automated Scanning Electron Microscope (SEM), multiple Energy Dispersive X-ray detectors (EDX) with automated quantitative mineralogy software. SEM-based automated mineralogy tools are essential in measuring parameters, such as modal mineralogy, mineral locking, mineral association, theoretical grade - recovery and mineral liberation.
Such quantitative information is fundamental to investigate and evaluate the mineral processing of ores. In this study carbonaceous apatite ore samples from Lao Cai deposit (Vietnam) was used. The petrographic, mineralogical and mineral liberation observations showed that the ore sample is quite
complex, containing carbonate impurities (dolomite and calcite) and having very fine intergrown texture. The separation of carbonate from apatite has been recognized as one of the most difficult subjects in mineral processing due to the similarities in their physiochemical properties.

Keywords: Mineral Liberation Analyzer; automated mineralogy; carbonaceous apatite; flotation

  • Contribution to proceedings
    International Conferences on Earth Sciences and Sustainable Geo-Resources Development, 12.-15.11.2016, Hanoi, Vietnam
    Proceedings of the ESASGD 2016, Hanoi, Vietnam: Transport Publishing House, 978-604-76-1171-3, 42-51

Permalink: https://www.hzdr.de/publications/Publ-26713
Publ.-Id: 26713


Diagnostics of ELBE SRF Gun - Status and Future Design

Lu, P. N.; Arnold, A.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.

Report on the Diagnostics for Beam Characterization of the ELBE SRF-Gun

Keywords: SRF gun; photo injector; transverse emittance; beam charactetization

  • Poster
    IBIC 2017 - International Beam Instrumentation Conference, 20.-24.08.2017, Grand Rapids, USA
  • Open Access Logo Contribution to proceedings
    IBIC 2017 - International Beam Instrumentation Conference, 20.-24.08.2017, Grand Rapids, USA
    Proceedings of IBIC 2017, Genf: JACoW, 53-56

Permalink: https://www.hzdr.de/publications/Publ-26712
Publ.-Id: 26712


Optimization of ELBE SRF Gun II for high-bunch-charge applications

Lu, P.; Arnold, A.; Vennekate, H.; Murcek, P.; Teichert, J.; Xiang, R.

Report on the beam transport simulation of the ELBE accelerator for injection with the SRF gun for THz, neutron and CBS applications.

Keywords: SRF gun; electron source; superconducting acceleerator

  • Poster
    The 3rd annual meeting of Matter and Technologies, 31.01.-02.02.2017, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-26711
Publ.-Id: 26711


Metal and Semiconductor Photocathodes in the HZDR SRF Gun

Teichert, J.; Arnold, A.; Lu, P.; Murcek, P.; Vennekate, H.; Xiang, R.

The superconducting RF photoelectron gun at the ELBE accelerator facility is a high-repetition rate electron injector for CW operation and can provide high average current and high brightness electron beams. During commissioning and operating time different types of photocathodes, metallic (Cu, Mg) and semiconductors (Cs2Te), have been used. We present the preparation processes, properties as well as performance and operational experience of the cathodes in the SRF gun. Furthermore, specific issues like cathode cooling, multipacting, and dark current will be discussed.

Keywords: SRF gun; electron source; photocathode; Mg; Cu; Cs2Te

  • Invited lecture (Conferences)
    ERL 17 - The 59th ICFA Advanced Beam Dynamics Workshop on Energy recovery Linacs, 18.-23.06.2017, Geneva, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-26710
Publ.-Id: 26710


RF Performance and Beam Parameter Measurement of the 2nd 3.5 cell SRF Gun for ELBE

Arnold, A.; Freitag, M.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.; Kneisel, P.; Ciovati, G.; Turlington, L.

In May 2014 the 1st superconducting photo injector (SRF gun) at HZDR was replaced by a new gun, featuring a new resonator and cryostat. The intention for this upgrade was to reach higher beam energy, higher bunch charge and lower emittance at the same time in order to serve user experiments at the superconducting CW accelerator ELBE. In our contribution we will report on the commissioning of the SRF gun by presenting a full set of RF performance results as well as detailed beam parameter measurements up to a bunch charge of 300 pC. Additionally, we will present the results of the first two user experiments (neutron and THz generation) that demonstrated the reliability of this gun concept.

Keywords: SRF gun; electron source; superconducting accelerator; ELBE; beam parameter

  • Poster
    ERL 17 The 59th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, 18.-23.06.2017, Geneva, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-26709
Publ.-Id: 26709


Application status of SRF gun II as the injector for the ELBE radiation center

Xiang, R.; Arnold, A.; Lehnert, U.; Lu, P.; Michel, P.; Murcek, P.; Teichert, J.; Vennekate, H.

An improved SRF gun (ELBE SRF Gun II) has been installed at the ELBE radiation center as an additional electron source since 2014. This new gun is able to produce up to 300 pC bunch charges in CW mode. This poster summarizes the latest results of user application with SRF Gun II

Keywords: SRF Gun; photo injector; ELBE; CW mode

  • Poster
    IPAC 2017 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark

Permalink: https://www.hzdr.de/publications/Publ-26708
Publ.-Id: 26708


Beam Transport Optimization for Applying an SRF Gun at the ELBE Center

Lu, P. N.; Arnold, A.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.

An SRF gun at the ELBE center has been operated with a magnesium cathode. Electron beams were produced with a maximum bunch charge of 200 pC and an emittance of 7.7 μm. Simulations have been conducted with ASTRA and Elegant for applying the SRF gun to ELBE user experiments, including neutron beam generation, positron beam generation, THz radiation and Compton backscattering experiment. Beam transport has been optimized to solve the best beam performance for these user stations at the bunch charge of 200 pC. Simulation results indicate that the SRF gun is potential to benefit the high bunch charge applications at ELBE.

Keywords: SRF gun; photo injector; electron source; ELBE; simulation; electron accelerator

  • Poster
    IPAC 2017- 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark
  • Open Access Logo Contribution to proceedings
    IPAC 2017 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark
    Proceedings of the 8th International Particle Accelerator Conference, G: JACoW

Permalink: https://www.hzdr.de/publications/Publ-26707
Publ.-Id: 26707


Pre-production and quality assurance of the Mu2e calorimeter Silicon Photomultipliers

Cordelli, M.; Cervelli, F.; Diociaiuti, E.; Donati, S.; Donghia, R.; Di Falco, S.; Ferrari, A.; Giovannella, S.; Happacher, F.; Martini, M.; Morescalchi, L.; Miscetti, S.; Mueller, S.; Pedreschi, E.; Pezzullo, G.; Sarra, I.; Spinella, F.

The Mu2e electromagnetic calorimeter has to provide precise information on energy, time and position for ~100 MeV electrons. It is composed of 1348 un-doped CsI crystals, each coupled to two large area Silicon Photomultipliers (SiPMs). A modular and custom SiPM layout consisting of a 3 x 2 array of 6 x 6 mm UV-extended monolithic SiPMs has been developed to fulfill the Mu2e calorimeter requirements and a pre-production of 150 prototypes has been procured by three international firms (Hamamatsu, SensL and Advansid). A detailed quality assurance process has been carried out on this first batch of photosensors: the breakdown voltage, the gain, the quenching time, the dark current and the Photon Detection Efficiency (PDE) have been determined for each monolithic cell of each SiPMs array. One sample for each vendor has been exposed to a neutron fluency up to ~8.5 x 10^11 1 MeV (Si) eq. n/cm2 and a linear increase of the dark current up to tens of mA has been observed. Others 5 samples for each vendor have undergone an accelerated aging in order to verify a Mean Time To Failure (MTTF) higher than ~10^6 h.

Keywords: Calorimeter; Silicon Photomultiplier; Quality assurance; Radiation damage

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Permalink: https://www.hzdr.de/publications/Publ-26706
Publ.-Id: 26706


The neutron transmission of natFe, 197Au and natW

Beyer, R.; Junghans, A. R.; Schillebeeckx, P.; Sirakov, I.; Song, T.-Y.; Bemmerer, D.; Capote, R.; Ferrari, A.; Hartmann, A.; Hannaske, R.; Heyse, J.; Kim, H. I.; Kim, J. W.; Kögler, T.; Lee, C. W.; Lee, Y.-O.; Massarczyk, R.; Müller, S. E.; Reinhardt, T. P.; Röder, M.; Schmidt, K.; Schwengner, R.; Szücs, T.; Takacs, M. P.; Wagner, A.; Wagner, L.; Yang, S.-C.

Neutron total cross sections of natFe, 197Au and natW have been measured at the nELBE neutron time-of-flight facility in the energy range from 0.2 - 8 MeV with an uncertainty due to counting statistics of up to 2 % and a total uncertainty due to systematic effects of 1 %. The neutrons are produced with the superconducting electron accelerator ELBE using a liquid lead circuit as photo-neutron target. By periodical sample-in-sample-out measurements the transmission of the sample materials has been determined using a low-threshold plastic scintillation detector. The resulting effective total cross sections show good agreement with previously measured data that cover only part of the energy range available at nELBE. The results have also been compared to evaluated library files and recent calculations based on a dispersive coupled channel optical model potential.

Keywords: nELBE; fast neutrons; total cross section; transmission; iron; gold; tungsten

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Permalink: https://www.hzdr.de/publications/Publ-26704
Publ.-Id: 26704


Phage surface display derived short peptides for the development of new biosorbents for the recovery of valuable elements from primary and secondary sources

Matys, S.; Lederer, F.; Schönberger, N.; Braun, R.; Pollmann, K.

In the course of evolution, nature has developed diverse strategies to avoid toxic effects of metals in the surrounding environment. Many organisms are able to bind metals to their surface via a variety of structurally diverse biomolecules carrying different functional groups. Because of the need for green and sustainable economic solutions, innovative biotechnological processes using biomolecules have become increasingly important.Biomolecules as sorbents are not only attractive for bioremediation, but also for the recovery of elements from recycling or mining. Currently, we are focusing on the development of new biosorbents based on short peptides for the selective recovery of valuable or toxic elements in complex process water streams such as Co, Ni, Ga or As and microparticles containing rare earth elements from fluorescent lamp powder. To select and identify these peptides we recently established Phage Surface Display Technology (PSD) as novel biotechnological platform in our group. Different adapted experimental setups for the peptide selection of each respective target material could be established and will be presented in detail. Specific and selectively metal binding peptides for particulate materials as well as for ionic species could be identified from commercially available phage libraries. These libraries contain a pool of genetically engineered phage of up to 10^9 different peptide motifs presented at their surface, which will be reduced in variability in an iterative biopanning process to capture the best binders. This contribution will give an insight into current research activities in our group focusing on PSD, introducing suitable spectroscopic techniques to characterize the metal-peptide complexes and discuss strategies for technical applications.

Keywords: peptides; metal binding; phage surface display; metal peptide complexes

  • Lecture (Conference)
    Jahrestagung der Vereinigung für Allgemeine und Angewandte Mikrobiologie, 15.-18.04.2018, Wolfsburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26703
Publ.-Id: 26703


In situ RBS and Raman spectroscopy study of nickel-catalyzed amorphous carbon graphitization

Janke, D.; Hulman, M.; Wenisch, R.; Munnik, F.; Gemming, S.; Rafaja, D.; Krause, M.

Session: Thin films type of contribution: Poster
Metal-induced crystallization with and without layer exchange (MIC w/o LE) is a method to decrease the crystallization temperature of amorphous group 14 elements (G14E) by up to several hundred degrees. In situ experiments are expected to provide new insights into thin film evolution and elementary process steps of MIC w/o LE and to improve existing models of this type of phase transformation. While MIC w/o LE has been widely studied for Si and Ge in contact with catalytic metals, there exist only a few studies for the crystallization of amorphous carbon. Therefore, in this contribution in situ Rutherford backscattering spectrometry (RBS), Raman spectroscopy and spectroscopic ellipsometry studies were performed during annealing of amorphous carbon/nickel (a-C/Ni) layer stacks at temperatures up to 750°C.
Due to its small lattice mismatch with the basal plane of graphite and high diffusivity of C atoms, Ni is a suitable catalyst for the growth of graphene and crystalline graphitic nanostructures. During the annealing of an a-C/Ni layer stack covalent bonds between the carbon atoms at the catalyst interface are weakened. Liberated carbon atoms can move along the interface and diffuse along the grain boundaries into the Ni layer towards the catalyst surface, where nucleation and grain growth of graphitic crystallites occur. Our in situ studies showed a change in the stacking sequence between C and Ni layers under defined experimental conditions. According to in situ Raman measurements, this mechanism occurs independent of the stacking sequence, while the velocity of the LE differs significantly. As observed in time and temperature resolved Raman spectra, the position of the G peak and the I(D)/I(G) ratio changed according to the Three-Stage-Model by Ferrari and Robertson, confirming the transformation of amorphous carbon to nc-graphite. With the in situ RBS measurements more insight into LE was given. Here peak positions of C and Ni were shifted, indicating a change of the energy of the scattered ions for both layers respectively and proving the combination of the observed graphitization process with LE during annealing. The thickness of the synthesized crystalline graphitic layer is controlled by the finite carbon source – the deposited a-C film, which is a decisive advantage of this process compared to CVD. It is demonstrated that the structure and the crystallite size of the metallic catalyst layer has a strong influence on the crystallite size and the quality of the graphitic film.
LE is potentially interesting for industrial applications, as it allows the formation of polycrystalline thin films of G14E at much lower temperatures - than during thermal annealing without the metallic catalyst. Depending on the initial stacking sequence, the crystalline graphitic film can be deposited on a suitable device-ready substrate or transferred to another substrate after the dissolution of the transition metal catalyst.

  • Poster
    Iberian Vacuum Conference, RIVA-X, 04.-05.10.2017, Bilbao, Spanien

Permalink: https://www.hzdr.de/publications/Publ-26702
Publ.-Id: 26702


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