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Publication database - Helmholtz-Zentrum Dresden-Rossendorf

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< Seite 1 von 190 >   Gesamtzahl lt. Auswahl: 18973 Title records (100 Title records je Seite)
23347 Publications
Kooperationspartnerschaft: Die Helmholtz-Gesellschaft und die TU Bergakademie
Meyer, B.; Sauerbrey, R.; Gutzmer, J.
Abstract: Die Technische Universität Bergakademie trägt den Namenszusatz "Die Ressourcenuniversität. Seit 1765."
Keywords: Keine Keywords
  • Acamonta 21(2014), 20-23
Registration No. 21372

Observation and manipulation of dipole-forbidden exciton transitions in semiconductors
Schneebeli, L.; Boettge, C. N.; Breddermann, B.; Kira, M.; Koch, S. W.; Rice, W. D.; Kono, J.; Zybell, S.; Winnerl, S.; Bhattacharyya, J.; Esser, F.; Schneider, H.; Helm, M.; Ewers, B.; Chernikov, A.; Koch, M.; Chatterjee, S.; Khitrova, G.; Gibbs, H.; M. Andrews, A.; Strasser, G.
Abstract: We discuss recent experimental and theoretical results that report on the observation of dipole-forbidden intra-exciton transitions in semiconductors via terahertz excitation. Additional manipulation capabilities are gained through the application of a magnetic field.
  • Lecture (Conference)
    CLEO-QELS, 08.-13.06.2014, San José, USA
Registration No. 21351

YMnO3-based photocapacitive detectors in the visible light regime
Bogusz, A.; Choudhary, Om S.; Selvaraj, L.; John, V.; Bürger, D.; Skorupa, I.; Lawerenz, A.; Schmidt, Oliver G.; Schmidt, H.
Abstract: YMnO3 is one of the few materials that exhibit ferroelectricity and antiferromagnetism. Ferroelectricity and antiferromagnetism in case of YMnO3 can be observed up to 900 K and 80 K, respectively. The remanent polarization of YMnO3 amounts to 2 uC/cm2 and metal-YMnO3-metal thin film structures can be switched between a high resistance state (HRS) and a low resistance state (LRS). In case of YMnO3 thin film, the transition from HRS to LRS (set process) occurs at the voltages 10 V and higher, while the transition from LRS to HRS (reset process) is triggered at the smaller voltages. This unipolar resistive switching is nonvolatile and has a resistance ratio of 5 orders of magnitude [1]. In pure YMnO3, absorption occurs throughout the entire visible light region, resulting in its black color [2]. This work investigates the effect of light-irradiation on the capacitance of YMnO3-based metal-ferroelectric-insulator-semiconductor (MFIS) structures. The thickness and optical constants of all layers of the MFIS diodes have been investigated using spectral ellipsometry measurements with a VASE ellipsometer assuming the refraction index of SiN to be 1.95 [3]. The DC bias for the capacitance measurements was swept from +10 to -20 V and back under different light-irradiation at a sweep rate of 230 mV/s. It has been found that under dark conditions two nonvolatile capacitance minima exists at -11 and at -3.55 V, possibly when the YMnO3 is in the LRS and HRS state, respectively. If we rewrite the +10 and -20 V branch in shorter period of time then, low capacitance state (LCS) is non-volatile and pseudo volatile, respectively. Under illumination the capacitance at the two minima increases in the visible spectral range, depending on the wavelength illumination, YMnO3 thickness and capacitance state.
[1] A. Bogusz et al., IEEE Xplore (2013), DOI:10.1109/ISCDG.2013.656319
[2] A. E. Smith et al., J. Am. Chem. Soc. 131, 17084 (2009)
[3] A. Laades et al., Phys. Stat. Sol. C 9, 2124 (2012)
  • Poster
    8th Workshop on Ellipsometry, 10.-12.03.2014, Dresden, Germany
Registration No. 21350

Near-surface density profiling of Fe ion irradiated Si (100) using extremely asymmetric x-ray diffraction by variation of the wavelength
Khanbabaee, B.; Facsko, S.; Doyle, S.; Pietsch, U.
Abstract: In this work, we report on correlations between surface density variations and ion parameters during ion beam-induced surface patterning process. The near-surface density variations of irradi- ated Si(100) surfaces were investigated after off-normal irradiation with 5 keV Fe ions at different fluences. In order to reduce the x-ray probing depth to a thickness below 5 nm, the extremely asym- metrical x-ray diffraction by variation of wavelength was applied, exploiting x-ray refraction at the air-sample interface. Depth profiling was achieved by measuring x-ray rocking curves as function of varying wavelengths providing incidence angles down to 0°. The density variation was extracted from the deviations from kinematical Bragg angle at grazing incidence angles due to refraction of the x-ray beam at the air-sample interface. The simulations based on the dynamical theory of x-ray diffraction revealed that while a net near-surface density decreases with increasing ion fluence which is accompanied by surface patterning, there is a certain threshold of ion fluence to surface density modulation. Our finding suggests that the surface density variation can be relevant with the mechanism of pattern formation.
Keywords: ion irradiation, surface patterning, x-ray diffraction Registration No. 21349

Photocapacitance change in YMnO3 based MFIS in the visible light regime
Choudhary, Om S.; Bogusz, A.; Selvaraj, L.; John, V.; Bürger, D.; Skorupa, I.; Lawerenz, A.; Schmidt, O. G.; Schmidt, H.
Abstract: YMnO3 is one of the few materials that exhibit ferroelectricity and antiferromagnetism. Metal-YMnO3-metal thin film structures can be switched between a high resistance state (HRS) and a low resistance state (LRS), when a positive and negative writing bias is applied, respectively. This work investigates the effect of light-irradiation on the capacitance of YMnO3-based metal-ferroelectric-insulatorsemiconductor (MFIS) structures. The DC bias for the capacitance measurements was swept from +10 to -20 V and back under different light-irradiation at a sweep rate of ca. 103 mV/s. It has been found that under dark conditions two nonvolatile capacitance minima exists at -11 and at -3.55 V, possibly when the YMnO3 is in the LRS and HRS state, respectively. If we rewrite the +10 and -20 V branch in shorter period of time then, low capacitance state (LCS) is non-volatile and pseudo volatile, respectively. Under illumination the capacitance at the two minima increases in the visible spectral range, depending on the wavelength illumination, YMnO3 thickness and YMnO3 capacitance state.
  • Poster
    DPG Spring Meeting, 30.03.-04.04.2014, Dresden, Germany
Registration No. 21348

Resistive switching of flash lamp crystallized YMnO3 thin films prepared on Pt/Ti/SiO2/Si substrates by low temperature pulsed laser deposition
Bogusz, A.; Prucnal, S.; Skorupa, W.; Blaschke, D.; Abendroth, B.; Stöcker, H.; Skorupa, I.; Bürger, D.; Schmidt, O. G.; Schmidt, H.
Abstract: Use of multiferroic oxides as a switching medium presents an opportunity to add the additional or novel functionalities into the switching device. Typically, the growth temperatures of such oxides are above 600°C and so far CMOS compatibility has not been achieved. YMnO3 exhibits unipolar resistive switching [1] however its high crystallization temperature (above 750°C) imposes difficulties in preparation of thin films on metal-coated substrates. This work presents the results of electrical and structural characterization of YMnO3 thin films grown on Pt/Ti/SiO2/Si substrates by pulsed laser deposition at 400°C and crystallized by flash lamp annealing (FLA). It is shown that the FLA process with optimized parameters allows the preparation of polycrystalline YMnO3 films without deformation of the Pt/Ti electrode and interdiffusion processes in the YMnO3/Pt/Ti/SiO2/Si stack.
[1] A. Bogusz et al., IEEE Xplore (2013), DOI:10.1109/ISCDG.2013.656319
  • Lecture (Conference)
    DPG Spring Meeting, 30.03.-04.04.2014, Dresden, Germany
Registration No. 21346

Atomistic modeling of ion-beam and thermally induced processes in Si and Ge
Liedke, B.; Heinig, K.-H.; Schmidt, B.; Bulutay, C.; Böttger, R.; Posselt, M.; Bracht, H.
Abstract: The abstract was not needed
Keywords: Kinetic Monte-Carlo, atomistic simulation, silicon, germanium, molecular dynamics, phase separation, self organization
  • Lecture (others)
    Seminar at the KTH Royal Institute of Technology - Reactor Physics, 12.11.2014, Stockholm, Sweden
Registration No. 21345

Nonvolatile unipolar resistive switching in YMnO3 thin films
Bogusz, A.; Prucnal, S.; Skorupa, W.; Blaschke, D.; Abendroth, B.; Stöcker, H.; Skorupa, I.; Bürger, D.; Schmidt, Oliver G.; Schmidt, H.
Abstract: Due to its promising applications, resistive switching in oxides known also as a memristive effect, has gained a lot of attention both from scientists and industry. The multiferroic oxides as a switching medium offer a novel functionalities of the switching devices. Typically, the growth temperatures of such oxides are above 600°C and so far CMOS compatibility has not been achieved. As an example, the multiferroic YMnO3 exhibits unipolar resistive switching [1]. However, its high crystallization temperature (above 750°C) imposes difficulties in preparation of thin films on metal-coated substrates. This work compares the results of electrical and structural characterization of YMnO3 thin films grown on Pt/Ti/SiO2/Si substrates by pulsed laser deposition with two different approaches. In the first one, the polycrystalline YMnO3 films are deposited at 800°C. In the second approach, amorphous films deposited at 400°C are crystallized by millisecond range flash lamp annealing. It is shown that the ultra short annealing allows the preparation of polycrystalline YMnO3 films without deformation of the Pt/Ti electrode which exhibits improved endurance of resistive switching.
  • Lecture (Conference)
    Workshop AK Materialien für nichtflüchtige Speicher, 28.-29.04.2014, Chemnitz, Germany
Registration No. 21344

Segregation-induced embrittlement in RPV steels: assessment by atomistic simulations
Bakaev, A.; Terentyev, D.; Bonny, G.; Zhurkin, E. E.; van Neck, D.
Abstract: Segregation-induced embrittlement in RPV steels: assessment by atomistic simulations
Keywords: ferrtitic steels, embrittlement, hardening
  • Lecture (Conference)
    FWI seminar, 14.08.2014, HZDR, Germany
Registration No. 21341

Dislocation mechanism of deuterium retention in tungsten under plasma implantation
Dubinko, V. I.; Terentyev, D.; Grigorev, P.; Bakaev, A.; van Oost, G.; Gao, F.; van Neck, D.; Zhurkin, E. E.
Abstract: We have developed a new theoretical model for deuterium (D) retention in tungsten-based alloys on the basis of its being trapped at dislocations and transported to the surface via the dislocation network with parameters determined by ab initio calculations. The model is used to explain experimentally observed trends of D retention under sub-threshold implantation, which does not produce stable lattice defects to act as traps for D in conventional models. Saturation of D retention with implantation dose and effects due to alloying of tungsten with, e.g. tantalum, are evaluated, and comparison of the model predictions with experimental observations under high-flux plasma implantation conditions is presented.
Keywords: dislocations, retention, plasma, hydrogen isotopes, rate theory Registration No. 21340

Deuterium accumulation in tungsten under low-energy high-flux plasma exposure
Grigorev, P. Yu.; Dubinko, V. I.; Terentyev, D. A.; Bakaev, A. V.; Zhurkin, E. E.
Abstract: The accumulation of deuterium implanted in tungsten is simulated within the framework of kinetic diffusion theory. The influence of the tungsten microstructure (dislocation density and impurity concentration) on the process of deuterium capture and accumulation is considered. It is established that, under the chosen irradiation conditions, deuterium accumulation in the near-surface region is determined by capture at defects formed during implantation. The deuterium concentration gradient, together with the material microstructure, determines its accumulation in tungsten. Variation in the dislocation density and impurity concentration does not affect the simulation results, which is, first, related to the fact that the model used does not contain alternative mechanisms for the formation and growth of vacancy clusters under the subthreshold irradiation mode. The simulation results are compared with experimental data, and ways of improving the model are discussed in order to explain the deuterium-saturation effect for high fluences (more than 1023 m−2).
Keywords: tungsten, retention, hydrogen isotopes, plasma, rate theory Registration No. 21339

Many-body central force potentials for tungsten
Bonny, G.; Terentyev, D.; Bakaev, A.; Grigoriev, P.; van Neck, D.
Abstract: Tungsten and tungsten-based alloys are the primary candidate materials for plasma facing components in fusion reactors. The exposure to high-energy radiation, however, severely degrades the performance and lifetime limits of the in-vessel components. In an effort to better understand the mechanisms driving the materials' degradation at the atomic level, large-scale atomistic simulations are performed to complement experimental investigations. At the core of such simulations lies the interatomic potential, on which all subsequent results hinge. In this work we review 19 central force many-body potentials and benchmark their performance against experiments and density functional theory (DFT) calculations. As basic features we consider the relative lattice stability, elastic constants and point-defect properties. In addition, we also investigate extended lattice defects, namely: free surfaces, symmetric tilt grain boundaries, the 1/2〈1 1 1〉{1 1 0} and 1/2〈1 1 1〉 {1 1 2} stacking fault energy profiles and the 1/2〈1 1 1〉 screw dislocation core. We also provide the Peierls stress for the 1/2〈1 1 1〉 edge and screw dislocations as well as the glide path of the latter at zero Kelvin. The presented results serve as an initial guide and reference list for both the modelling of atomically-driven phenomena in bcc tungsten, and the further development of its potentials.
Keywords: tungsten, interatomic potentials, classical molecular dynamics, ab initio Registration No. 21338

Carbon-vacancy interaction controls lattice damage recovery in Iron
Terentyev, D.; Heinola, K.; Bakaev, A.; Zhurkin, E. E.
Abstract: Ab initio techniques are applied to assess the positron lifetime of carbon–vacancy (C–V) complexes in iron for the first time. Positron lifetime is extremely sensitive to C–V arrangement and multiplicity. Following the ab initio lifetime data, a C–V complex can be detected as a single or clustered vacancy, or remain indistinguishable from bulk. Combining ab initio data with kinetic rate theory, we modelled annealing of irradiated Fe–C alloys and performed one-to-one comparison with experiment, which revealed a good agreement.
Keywords: Iron, Interstitial carbon, Lattice damage, Recovery, Annealing Registration No. 21337

Dislocations mediate hydrogen retention in tungsten
Terentyev, D.; Dubinko, V.; Bakaev, A.; Zayachuk, Y.; van Renterghem, W.; Grigorev, P.
Abstract: In this letter, a comprehensive mechanism for the nucleation and growth of bubbles on dislocations under plasma exposure of tungsten is proposed. The mechanism reconciles long-standing experimental observations of hydrogen isotopes retention, essentially defined by material microstructure, and so far not fully explained. Hence, this work provides an important link to unify material's modelling with experimental assessment of W and W-based alloys as candidates for plasma facing components.
Keywords: hydrogen isotopes, retention, tungsten, ab initio, DFT, rate theory Registration No. 21336

Effect of carbon decoration on the absorption of 〈 100 〉 dislocation loops by dislocations in iron
Terentyev, D.; Bakaev, A.; Zhurkin, E. E.
Abstract: This work closes a series of molecular dynamics studies addressing how solute/interstitial segregation at dislocation loops affects their interaction with moving dislocations in bodycentred cubic Fe-based alloys. We consider the interaction of 〈1 0 0〉 interstitial dislocation loops decorated by different numbers of carbon atoms in a wide temperature range. The results reveal clearly that the decoration affects the reaction mechanism and increases the unpinning stress, in general. The most pronounced and reproducible increase of the unpinning stress is found in the intermediate temperature range from 300 up to 600 K. The carbon-decoration effect is related to the modification of the loop–dislocation reaction and its importance at the technologically relevant neutron irradiation conditions is discussed.
Keywords: dislocation, carbon, iron, segregation Registration No. 21335

Atomistic simulation of the interaction between mobile edge dislocations and radiation-induced defects in Fe-Ni-Cr austenitic alloys
Bakaev, A. V.; Terent’Ev, D. A.; Grigor’Ev, P. Yu.; Zhurkin, E. E.
Abstract: The classical molecular dynamics method is employed to simulate the interaction of edge dislocations with interstitial Frank loops (2 and 5 nm in diameter) in the Fe-Ni10-Cr20 model alloy at the temperatures T = 300–900 K. The examined Frank loops are typical extended radiation-induced defects in austenitic steels adapted to nuclear reactors, while the chosen triple alloy (Fe-Ni10-Cr20) has the alloying element concentration maximally resembling these steels. The dislocation-defect interaction mechanisms are ascertained and classified, and their comparison with the previously published data concerning screw dislocations is carried out. The detachment stress needed for a dislocation to overcome the defect acting as an obstacle is calculated depending on the material temperature, defect size, and interaction geometry. It is revealed that edge dislocations more efficiently absorb small loops than screw ones. It is demonstrated that, in the case of small loops, the number of reactions accompanied by loop absorption increases with temperature upon interaction with both edge and screw dislocations. It is established that Frank loops are stronger obstacles to the movement of screw dislocations than to the movement of edge ones.
Keywords: classical molecular dynamics, plastic behaviour, austenitic steels, dislocations Registration No. 21334

Basic Properties of Minor Alloying Elements in High-Cr Ferritic Steels: An Ab Initio Study
Bakaev, A.; Terentyev, D.; Bonny, G.; Klaver, T. P. C.; Olsson, P.; van Neck, D.
Abstract: Basic properties of minor alloying elements, namely Mo, W, Nb, Ta, V, Mn, Si entering the conventional and reduced-activation structural Fe–(9–12)Cr steels have been analyzed using ab initio calculations. The electronic structure calculations were applied to study the interaction of minor alloying elements with a number of important and well defined lattice structures, such as point defects, the 1/2<111> screw dislocation core, high angle symmetric grain boundaries and free surfaces. The studied elements were classified according to their similarities and discrepancies regarding the interaction with the above mentioned defects. The refractory alloying elements are found to follow the same trend whereas Mn and Si exhibit peculiar behavior with respect to the interaction with both point and extended lattice defects. The obtained results are discussed and compared with previously published ab initio and available experimental data.
Keywords: minor alloying elements, ferritic steels, ab initio, DFT, lattice defects Registration No. 21333

Interaction of carbon-vacancy complex with minor alloying elements of ferritic steels
Bakaev, A.; Terentyev, D.; He, X.; Zhurkin, E. E.; Van Neck, D.
Abstract: Interstitial carbon, dissolved in bcc matrix of ferritic steels, plays an important role in the evolution of radiation-induced microstructure since it exhibits strong interaction with vacancies. Frequent formation and break-up of carbon–vacancy pairs, occurring in the course of irradiation, affect both kinetics of the accumulation of point defect clusters and carbon spatial distribution. The interaction of typical alloying elements (Mn, Ni, Cu, Si, Cr and P) in ferritic steels used as structural materials in nuclear reactors with a carbon–vacancy complex is analyzed using ab initio techniques. It is found that all the considered solutes form stable triple clusters resulting in the increase of the total binding energy by 0.2–0.3 eV. As a result of the formation of energetically favourable solute–carbon–vacancy triplets, the dissociation energy for vacancy/carbon emission is also increased by ~0.2–0.3 eV, suggesting that the solutes enhance thermal stability of carbon–vacancy complex. Association of carbon–vacancy pairs with multiple solute clusters is found to be favorable for Ni, Cu and P. The energetic stability of solute(s)–carbon–vacancy complexes was rationalized on the basis of pairwise interaction data and by analyzing the variation of local magnetic moments on atoms constituting the clusters.
Keywords: ferritic steels, carbon, solute-rich clusters, ab initio, DFT Registration No. 21332

Synergetic Effects of Mn and Si in the Interaction with Point Defects in bcc Fe
Bakaev, A.; Terentyev, D.; He, X.; Van Neck, D.
Abstract: The interaction of Mn, Si and Cr with a vacancy and self-interstitial defects in BCC Fe has been analyzed using ab initio calculations. While the interaction of the considered solute clusters with a single vacancy is linearly additive, there is a considerable synergetic effect in the case of self-interstitial atoms, found to bind strongly with Mn–Si pairs. The latter therefore act as deep trapping configurations for self-interstitials. At the same time, the presence of the point defects nearby weakly attractive Mn–Si pairs significantly enhances the solute–solute binding. The revealed effects are rationalized on the basis of charge density and local magnetic moment distributions.
Keywords: solute clusters, bcc Fe, ab initio, DFT Registration No. 21331

Three-feature dispersed barrier hardening model applied to Cu-bearing low-Ni RPV steels
Bergner, F.; Gillemot, F.; Hernandez-Mayoral, M.; Serrano, M.; Ulbricht, A.
Abstract: The three-feature dispersed-barrier hardening model was successfully applied to neutron-irradiated RPV steels. Estimated values of the obstacle strength of loops, nanovoids and Cu-rich precipitates are largely consistent with reported estimates. For fluences representative of less than 60 years of operation (VVER440 base metal) nanovoids can be ignored, that means a two-feature version is sufficient.
Keywords: RPV steels, neutron irradiation, hardening
  • Lecture (Conference)
    18th Meeting of the International Group on Radiation Damage Mechanisms in Pressure Vessel Steels (IGRDM-18), 23.-28.11.2014, Miyazaki, Japan
Registration No. 21330

Effect of neutron flux on the solute cluster characteristics and hardening in RPV steels
Bergner, F.; Chaouadi, R.; Dohi, K.; Hein, H.; Serrano, M.; Soneda, N.; Wagner, A.
Abstract: Flux is an important variable of RPV steel embrittlement because of several reasons including the consideration of surveillance samples vs. RPV wall material, MTR vs. PWR/BWR irradiations and ions as a neutron substitute in the lab. The approach relies on the reasonable assumption that the flux effect on the mechanical properties is mediated by the flux-dependent evolutiooon of the irradiation-induced nanofeatures. In order to separate flux effects from the effect of the neutron fluence, pairs of samples of one and the same material irradiated at as different as possible flux up to about the same fluence are selected. These pairs of samples were fully characterized with respect to both mechanical property changes and the characteristics of irradiation-induced solute clusters. The results indicate that there is a pronounced effect of flux on cluster size, that there are minor flux effects on number density, volume fraction and composition of clusters and that SANS and APT provide consistent results on size and number density of clusters. The classical dispersed-barrier hardening model combined with deterministic growth and irradiation-enhanced diffusion describes the flux effect on the mechanical properties well.
Keywords: RPV steel, neutron irradiation, flux effect, SANS, APT
  • Lecture (Conference)
    18th Meeting of the International Group on Radiation Damage Mechanisms in Pressure Vessel Steels (IGRDM-18), 23.-28.11.2014, Miyazaki, Japan
Registration No. 21329

Reverse epitaxy on Ge surfaces
Ou, X.; Keller, A.; Helm, M.; Fassbender, J.; Facsko, S.
Abstract: Arrays of semiconductor nanostructures have the potential for nanoelectronic and optoelectronic applications. Besides the conventional low efficiency lithographic techniques broad ion beam irradiation is a simple and mass productive technique to fabricate nanostructure patterns on semiconductor surfaces.[1] Based on a “self-organized” erosion process, periodic ripple, hole, or dot arrays can be produced on various semiconductor surfaces.
However, the main drawback of this method is that the irradiated semiconductor surfaces are amorphized. [1, 2] For device fabrication, a crystalline surface of high quality is indispensable. In this work we report the recent discovery of single crystal Ge nanopattern formation based on a “reverse epitaxy” process.[3] The low energy ion irradiation is performed in a defined temperature window. Vacancies created during ion beam irradiation distribute according to the crystallographic anisotropy, which results in an orientation-dependent pattern formation on single crystal Ge surface. This process shows nicely the equivalence of epitaxy with deposited adatoms and “reverse epitaxy” with ion induced surface vacancies on semiconductors. The formation of these patterns is interpreted as the result of a surface instability due to an Ehrlich-Schwoebel barrier for ion induced surface vacancies. The simulation of the pattern formation is performed by a continuum equation accounting for the effective surface currents.
The formation mechanism of these patterns is quite general and can be extended to other semiconductors, e.g. Si and compound semiconductors. Thus our work establishes an entirely new and complementary epitaxial method for the fabrication of high-quality faceted semiconductor nanostructures. A physical model for nanopatterning of crystalline semiconductor surfaces with ion beam irradiation will be demonstrated based on comparison between experimental results and computer simulations.

[1] Stefan Facsko et al., Science 285, 1551 (1999).
[2] Xin Ou et al., AIP Advances, 1, 042174 (2011).
[3] Xin Ou et al., Physical Review Letters 111, 016101 (2013).

Keywords: Ge and ion irradiation
  • Invited lecture (Conferences)
    23rd Conference on Application of Accelerators in Research and Industry, 25.-30.05.2014, San Antonio, USA
Registration No. 21328

Reverse Epitaxy on Semiconductor Surfaces
Ou, X.; Hübner, R.; Helm, M.; Fassbender, J.; Facsko, S.
Abstract: Arrays of semiconductor nanostructures are emerging as building blocks for next generation of electronic and optoelectronic nanodevices. In molecular beam epitaxy (MBE) the continuous deposition of atoms can lead to growth of self-organized 3D nanostructures. One of the possible surface instabilities, which is responsible for this kind of growth, is caused by the Ehrlich-Schwoebel (ES) barrier, i.e. an additional diffusion barrier for ad-atoms to cross terrace steps [1]. The arriving atoms are trapped on terraces and can again nucleate to form new terraces. This mechanism leads to the growth of pyramidal mounds on the surface with facets corresponding to energetically favored crystal planes. An analogous mechanism is also observed on ion irradiated surfaces. However, ion sputtering leads to the erosion of the surfaces and at room temperature semiconductor surfaces become amorphous. At these conditions various periodic patterns are observed. [2] For device fabrication, a crystalline surface of high quality is indispensable.
In this talk, we demonstrate single crystal elemental (Si and Ge) and compound semiconductor (III-V) nanostructure pattern formation (Figure 1) based on a “reverse epitaxy” process. [3] Vacancies created during ion beam irradiation at elevated temperature distribute according to the crystallographic anisotropy, which results in an orientation-dependent pattern formation on single crystal semiconductor surfaces. This process shows nicely the equivalence of epitaxy with deposited adatoms and “reverse epitaxy” with ion induced surface vacancies on semiconductors. The formation of these patterns is interpreted as the result of a surface instability due to an Ehrlich-Schwoebel barrier for ion induced surface vacancies. The simulation of the pattern formation is performed by a continuum equation accounting for the effective surface currents. Our work establishes an entirely new and complementary epitaxial method for the fabrication of high-quality faceted semiconductor nanostructures. The potential application of reverse epitaxy on fabrication of quantum devices and optical components will be discussed.
*email address: X.Ou@hzdr.de

Keywords: ion sputtering
  • Invited lecture (Conferences)
    The 10th international ESPS-NIS workshop, 20.-23.07.2014, Traunkirchen, Austria
Registration No. 21327

Electrochemical deposition of magnetic ions at electrodes which are exposed to small-scale gradients of the magnetic field
Mutschke, G.; Fröhlich, J.
Abstract: The mechanism responsible for the spatially inhomogeneous thickness of metal layers obtained by
electrochemical deposition in magnetic gradient fields at small scale is controversially discussed in the literature. The
paper presents the results of numerical simulations which support the concept that local convection at the electrode,
driven by the curl of the magnetic gradient force, is responsible for the effects observed. The deposition of paramagnetic and of diamagnetic ions is discussed, and the influence of electrically inert magnetic ions present in the electrolyte is highlighted.

Keywords: Electrochemistry, electrolysis, metal deposition, magnetic field, magnetic gradient force, numerical simulation, spatially-structured deposition
  • Contribution to proceedings
    Strömungstechnische Tagung 2014 anlässlich des 100. Geburtstages von Werner Albring, 10.10.2014, Dresden, Deutschland
    Schriftenreihe aus dem Institut für Strömungsmechanik, Band 10, Dresden: TUDpress Verlag der Wissenschaften GmbH, 978-3-944331-78-2, 373-376
  • Poster
    Strömungstechnische Tagung 2014 anlässlich des 100. Geburtstages von Werner Albring, 10.10.2014, Dresden, Deutschland
Registration No. 21323

“High resolution Positron Emission Tomography for quantitative, spatio-temporal process visualization in geological material (GeoPET)”
Kulenkampff, J.; Lippmann-Pipke, J.
Abstract: Es ist kein Abstract vorhanden.
  • Lecture (others)
    GeoCT Kick off Workhop Hannover, Nationaler Workshop von Forschungseinrichtungen mit tomographischen Methoden in den Geowissenschaften, 19.02.2014, Hannover, Deutschland
Registration No. 21320

Quantification of permeability and porosity changes of cement/clay materials by means of GeoPET.
Lippmann-Pipke, J.; Kulenkampff, J.
Abstract: Es ist kein Abstract vorhanden.
  • Lecture (others)
    Cebama Proposal Consortium Meeting, 11.03.2014, Karlsruhe, Deutschland
Registration No. 21319

Quantifying bioleaching kinetics and efficiency: (3D+t)-visualization of Cu transport through dump material by means of PET - First results from HZDR-IRE (11/2014).
Barthen, R.; Lippmann-Pipke, J.
Abstract: Es ist kein Abstract vorhanden.
  • Lecture (others)
    Ecometals Meeting 2014, 18.-19.11.2014, Orléans, France
Registration No. 21318

Abschlussbericht des DFG-Vorhabens "Imaging and image simulation of organic target compound migration between different biogeochemical interfaces of a soil horizon using positron emission tomography and the lattice Boltzmann equation approach" im Schwerpunktprogramm 1315
Kersten, M.; Lippmann-Pipke, J.
Abstract: Es ist kein Abstract vorhanden.
  • Other report
    Rossendorf: HZDR, 2014
    7 Seiten
Registration No. 21317

Range assessment in particle therapy based on prompt γ-ray timing measurements.
Golnik, C.; Hueso-González, F.; Müller, A.; Dendooven, P.; Enghardt, W.; Fiedler, F.; Kormoll, T.; Roemer, K.; Petzoldt, J.; Wagner, A.; Pausch, G.
Abstract: Proton and ion beams open up new vistas for the curative treatment of tumors, but adequate technologies for monitoring the compliance of dose delivery with treatment plans in real time are still missing. Range assessment, meaning the monitoring of therapy-particle ranges in tissue during dose delivery (treatment), is a continuous challenge considered a key for tapping the full potential of particle therapies. In this context the paper introduces an unconventional concept of range assessment by prompt-gamma timing (PGT), which is based on an elementary physical effect not considered so far: therapy particles penetrating tissue move very fast, but still need a finite transit time--about 1-2 ns in case of protons with a 5-20 cm range--from entering the patient's body until stopping in the target volume. The transit time increases with the particle range. This causes measurable effects in PGT spectra, usable for range verification. The concept was verified by proton irradiation experiments at the AGOR cyclotron, KVI-CART, University of Groningen. Based on the presented kinematical relations, we describe model calculations that very precisely reproduce the experimental results. As the clinical treatment conditions entail measurement constraints (e.g. limited treatment time), we propose a setup, based on clinical irradiation conditions, capable of determining proton range deviations within a few seconds of irradiation, thus allowing for a fast safety survey. Range variations of 2 mm are expected to be clearly detectable. Registration No. 21315

HPV16 DNA status is a strong prognosticator of loco-regional control after postoperative radiochemotherapy of locally advanced oropharyngeal carcinoma: Results from a multicentre explorative study of the German Cancer Consortium Radiation Oncology Group (DKTK-ROG).
Lohaus, F.; Linge, A.; Tinhofer, I.; Budach, V.; Gkika, E.; Stuschke, M.; Balermpas, P.; Rödel, C.; Avlar, M.; Grosu, A.; Abdollahi, A.; Debus, J.; Bayer, C.; Belka, C.; Pigorsch, S.; Combs, S.; Mönnich, D.; Zips, D.; von Neubeck, C.; Baretton, C.; Löck, S.; Thames, H.; Krause, M.; Baumann, M.
Abstract: OBJECTIVE:

To investigate the impact of HPV status in patients with locally advanced head and neck squamous cell carcinoma (HNSCC), who received surgery and cisplatin-based postoperative radiochemotherapy.
MATERIALS AND METHODS:

For 221 patients with locally advanced squamous cell carcinoma of the hypopharynx, oropharynx or oral cavity treated at the 8 partner sites of the German Cancer Consortium, the impact of HPV DNA, p16 overexpression and p53 expression on outcome were retrospectively analysed. The primary endpoint was loco-regional tumour control; secondary endpoints were distant metastases and overall survival.
RESULTS:

In the total patient population, univariate analyses revealed a significant impact of HPV16 DNA positivity, p16 overexpression, p53 positivity and tumour site on loco-regional tumour control. Multivariate analysis stratified for tumour site showed that positive HPV 16 DNA status correlated with loco-regional tumour control in patients with oropharyngeal carcinoma (p=0.02) but not in the oral cavity carcinoma group. Multivariate evaluation of the secondary endpoints in the total population revealed a significant association of HPV16 DNA positivity with overall survival (p<0.01) but not with distant metastases.
CONCLUSIONS:

HPV16 DNA status appears to be a strong prognosticator of loco-regional tumour control after postoperative cisplatin-based radiochemotherapy of locally advanced oropharyngeal carcinoma and is now being explored in a prospective validation trial.

Keywords: DKTK-ROG; HNSCC; HPV; Postoperative radiochemotherapy; p16; p53 Registration No. 21314

Effect of combined irradiation and EGFR/Erb-B inhibition with BIBW 2992 on proliferation and tumour cure in cell lines and xenografts.
Gurtner, K.; Ebert, N.; Pfitzmann, D.; Eicheler, W.; Zips, D.; Baumann, M.; Krause, M.
Abstract: Background and purposeIn previous experiments an enhanced anti-proliterative effect of the EGFR/ErbB tyrosine kinase inhibitor (TKI) BIBW 2992 with single dose irradiation was observed in FaDu tumour xenografts. Aim of the present experiment was to determine if this effect can also be seen in combination with a fractionated radiotherapy. Secondly we investigate the efficacy of BIBW 2992 on local tumour control for UT-SCC-15.Material and methodsTumour pieces of FaDu, UT-SCC-14, A431, UT-SCC-15 (squamous cell carcinomas) and A7 (glioma) tumour models were transplanted onto the right hind leg of NMRI (nu/nu) nude mice. For evaluation of tumour growth mice were either treated daily orally with BIBW 2992 (30 mg/kg body weight), or carrier up to a final tumour size of 15 mm or with a fractionated radiotherapy (15f/15d, 30 Gy) with simultaneous application of BIBW 2992 or carrier. For local tumour control UT-SCC-15 tumours were treated with a fractionated radiotherapy (30f/6weeks) or received 30f/6 weeks in combination with daily orally BIBW 2992 (22.5 mg/kg b.w.) during RT.ResultsA significant effect on tumour growth time was observed in all tumour models for BIBW 2992 application alone. However, substantial intertumoural heterogeneity could be seen. In the UT-SCC-14, UT-SCC-15 and A431 tumour models a total regression of the tumours and no recurrence during treatment time (73 days) were determined where as for the A7 tumour only a slight effect was noticeable. For the combined treatment of fractionated radiotherapy (15f/15d) and BIBW 2992 administration a significant effect on tumour growth time was seen compared to irradiation alone for A7, UT-SCC-15 and A431 (ER 1.2 ¿ 3.7), this advantage could not be demonstrated for FaDu and UT-SCC-14. However, the local tumour control was not altered for the UT-SCC-15 tumour model when adding BIBW 2992 to fractionated irradiation (30f/6weeks).ConclusionA heterogeneous effect on tumour growth time of BIBW 2992 alone as well as in combination with fractionated irradiation could be demonstrated for all tumour models. However, the significant effect on tumour growth time did not translate into an improvement of local tumour control for the UT-SCC-15 tumour model. Registration No. 21313

Creating a data exchange strategy for radiotherapy research: Towards federated databases and anonymised public datasets.
Skripcak, T.; Belka, C.; Bosch, W.; Brink, C.; Brunner, T.; Budach, V.; Büttner, D.; Debus, J.; Dekker, A.; Grau, C.; Gulliford, S.; Hurkmans, C.; Just, U.; Krause, M.; Lambin, P.; Langendijk, J.; Lewensohn, R.; Lühr, A.; Maingon, P.; Masucci, M.; Niyazi, M.; Poortmans, P.; Simon, M.; Schmidberger, H.; Spezi, E.; Stuschke, M.; Valentini, V.; Verheij, M.; Whitfield, G.; Zackrisson, B.; Zips, D.; Baumann, M.
Abstract: Disconnected cancer research data management and lack of information exchange about planned and ongoing research are complicating the utilisation of internationally collected medical information for improving cancer patient care. Rapidly collecting/pooling data can accelerate translational research in radiation therapy and oncology. The exchange of study data is one of the fundamental principles behind data aggregation and data mining. The possibilities of reproducing the original study results, performing further analyses on existing research data to generate new hypotheses or developing computational models to support medical decisions (e.g. risk/benefit analysis of treatment options) represent just a fraction of the potential benefits of medical data-pooling. Distributed machine learning and knowledge exchange from federated databases can be considered as one beyond other attractive approaches for knowledge generation within "Big Data". Data interoperability between research institutions should be the major concern behind a wider collaboration. Information captured in electronic patient records (EPRs) and study case report forms (eCRFs), linked together with medical imaging and treatment planning data, are deemed to be fundamental elements for large multi-centre studies in the field of radiation therapy and oncology. To fully utilise the captured medical information, the study data have to be more than just an electronic version of a traditional (un-modifiable) paper CRF. Challenges that have to be addressed are data interoperability, utilisation of standards, data quality and privacy concerns, data ownership, rights to publish, data pooling architecture and storage. This paper discusses a framework for conceptual packages of ideas focused on a strategic development for international research data exchange in the field of radiation therapy and oncology.
Keywords: Data exchange; Data pooling; Interoperability; Large scale studies; Public data; Radiotherapy Registration No. 21312

Pre-clinical research in small animals using radiotherapy technology - a bidirectional translational approach.
Tillner, F.; Thute, P.; Bütof, R.; Krause, M.; Enghardt, W.
Abstract: For translational cancer research, pre-clinical in-vivo studies using small animals have become indispensable in bridging the gap between in-vitro cell experiments and clinical implementation. When setting up such small animal experiments, various biological, technical and methodical aspects have to be considered. In this work we present a comprehensive topical review based on relevant publications on irradiation techniques used for pre-clinical cancer research in mice and rats. Clinical radiotherapy treatment devices for the application of external beam radiotherapy and brachytherapy as well as dedicated research irradiation devices are feasible for small animal irradiation depending on the animal model and the experimental goals. In this work, appropriate solutions for the technological transfer of human radiation oncology to small animal radiation research are summarised. Additionally, important information concerning the experimental design is provided such that reliable and clinically relevant results can be attained.
Keywords: Kleintiere; Krebsforschung; Pre-clinical research; Präklinische Forschung; bildgeführte Strahlentherapie (IGRT); cancer research; image-guided radiation therapy (IGRT); small animals; translational research; translationale Forschung Registration No. 21311

Effect of [(18)F]FMISO stratified dose-escalation on local control in FaDu hSCC in nude mice.
Schütze, C.; Bergmann, R.; Brüchner, K.; Mosch, B.; Yaromina, A.; Zips, D.; Hessel, F.; Krause, M.; Thames, H.; Kotzerke, J.; Steinbach, J.; Baumann, M.; Beuthien-Baumann, B.
Abstract: OBJECTIVE:

To investigate the effect of radiation dose-escalation on local control in hypoxic versus non-hypoxic hypoxic tumours defined using [(18)F]fluoromisonidazole ([(18)F]FMISO) PET.
MATERIALS AND METHODS:

FaDu human squamous cell carcinomas (hSCCs) growing subcutaneously in nude mice were subjected to [(18)F]FMISO PET before irradiation with single doses of 25 or 35Gy under normal blood flow conditions. [(18)F]FMISO hypoxic volume (HV) and maximum standardised uptake value (SUVmax) were used to quantify tracer uptake. The animals were followed up for at least 120days after irradiation. The endpoints were permanent local tumour control and time to local recurrence.
RESULTS:

HV varied between 38 and 291mm(3) (median 105mm(3)). Non-hypoxic tumours (HV below median) showed significantly better local control after single dose irradiation than hypoxic tumours (HV above median) (p=0.046). The effect of dose was significant and not different in non-hypoxic and in hypoxic tumours (HR=0.82 [95% CI 0.71; 0.93], p=0.002 and HR=0.86 [0.78; 0.95], p=0.001, respectively). Dose escalation resulted in an incremental increase of local tumour control from low-dose hypoxic, over low-dose non-hypoxic and high-dose hypoxic to high-dose non-hypoxic tumours. SUVmax did not reveal significant association with local control at any dose level.
CONCLUSIONS:

The negative effect of [(18)F]FMISO HV on permanent local tumour control supports the prognostic value of the pre-treatment [(18)F]FMISO HV. Making the assumption that variable [(18)F]FMISO uptake in different FaDu tumours which all have the same genetic background may serve as an experimental model of intratumoural heterogeneity, the data support the concept of dose-escalation with inhomogeneous dose distribution based on pre-treatment [(18)F]FMISO uptake. This result needs to be confirmed in other tumour models and using fractionated radiotherapy schedules.

Keywords: Dose escalation; Human tumour xenografts; Hypoxic volume; Local control; Single dose irradiation; Squamous cell carcinoma; [(18)F]FMISO positron emission tomography Registration No. 21310

Radiolabeled Cetuximab Conjugates for EGFR Targeted Cancer Diagnostics and Therapy.
Sihver, W.; Pietzsch, J.; Krause, M.; Baumann, M.; Steinbach, J.; Pietzsch, H.
Abstract: The epidermal growth factor receptor (EGFR) has evolved over years into a main molecular target for the treatment of different cancer entities. In this regard, the anti-EGFR antibody cetuximab has been approved alone or in combination with: (a) chemotherapy for treatment of colorectal and head and neck squamous cell carcinoma and (b) with external radiotherapy for treatment of head and neck squamous cell carcinoma. The conjugation of radionuclides to cetuximab in combination with the specific targeting properties of this antibody might increase its therapeutic efficiency. This review article gives an overview of the preclinical studies that have been performed with radiolabeled cetuximab for imaging and/or treatment of different tumor models. A particularly promising approach seems to be the treatment with therapeutic radionuclide-labeled cetuximab in combination with external radiotherapy. Present data support an important impact of the tumor micromilieu on treatment response that needs to be further validated in patients. Another important challenge is the reduction of nonspecific uptake of the radioactive substance in metabolic organs like liver and radiosensitive organs like bone marrow and kidneys. Overall, the integration of diagnosis, treatment and monitoring as a theranostic approach appears to be a promising strategy for improvement of individualized cancer treatment. Registration No. 21309

Waiting time and overall treatment timeof postoperative radiotherapy of non-small cell lung cancer (NSCLC).
Bütof, R.; Kirchner, K.; Appold, S.; Löck, S.; Rolle, A.; Höffken, G.; Krause, M.; Baumann, M.
Abstract: Aim

The aim of this analysis was to investigate the impact of tumour-, treatment- and patient-related cofactors on local control and survival after postoperative adjuvant radiotherapy in patients with non-small cell lung cancer (NSCLC), with special focus on waiting and overall treatment times.

Patients and methods

For 100 NSCLC patients who had received postoperative radiotherapy, overall, relapse-free and metastases-free survival was retrospectively analysed using Kaplan–Meier methods. The impact of tumour-, treatment- and patient-related cofactors on treatment outcome was evaluated in uni- and multivariate Cox regression analysis.

Results

No statistically significant difference between the survival curves of the groups with a short versus a long time interval between surgery and radiotherapy could be shown in uni- or multivariate analysis. Multivariate analysis revealed a significant decrease in overall survival times for patients with prolonged overall radiotherapy treatment times exceeding 42 days (16 vs. 36 months) and for patients with radiation-induced pneumonitis (8 vs. 29 months).

Conclusion

Radiation-induced pneumonitis and prolonged radiation treatment times significantly reduced overall survival after adjuvant radiotherapy in NSCLC patients. The negative impact of a longer radiotherapy treatment time could be shown for the first time in an adjuvant setting. The hypothesis of a negative impact of longer waiting times prior to commencement of adjuvant radiotherapy could not be confirmed.
Registration No. 21308

Be smart against cancer! A school-based program covering cancer-related risk behavior.
Stölzel, F.; Seidel, N.; Uhmann, S.; Baumann, M.; Berth, H.; Hoyer, J.; Ehninger, G.
Abstract: BACKGROUND:
Several studies suggest that most school-age children are poorly informed about cancer risk factors. This study examines the effectiveness of the 'Be smart against cancer' (BSAC) program in promoting cancer awareness and intentions to engage in health-promoting behavior.

METHODS:
235 seventh-grade students were randomized to either the intervention (N = 152) or the wait-control group (N = 83). The intervention included the modules: "What is cancer?," "Sun protection," "Non smoking," and "Physical activity, Healthy nutrition, and Limited alcohol consumption." Outcomes measured at baseline and at the end of the one week BSAC program included knowledge of cancer and its behavioral risk factors, health-promoting intentions, and reported risk behavior.

RESULTS:
BSAC was effective in increasing knowledge about cancer and risk factors for cancer (p < .001), as well as in increasing intentions to engage in health-promoting behavior (p < .001), independent of a student's risk profile. Knowledge did not serve as a mediator for intention building.

CONCLUSIONS:
The BSAC is an effective school-based program for raising awareness of cancer, associated risk factors and intentions to engage in cancer-preventive behavior. The results indicate that the effectiveness of BSAC is independent of a student's risk profile. Therefore, it holds considerable promise as a broadly applicable program to raise cancer awareness and promote healthy behavior intentions.
Registration No. 21307

Application of organ tolerance dose-constraints in clinical studies in radiation oncology.
Dörr, W.; Herrmann, T.; Baumann, M.
Abstract: In modern radiation oncology, tolerance dose-constraints for organs at risk (OAR) must be considered for treatment planning, but particularly in order to design clinical studies. Tolerance dose tables, however, only address one aspect of the therapeutic ratio of any clinical study, i.e., the limitation of adverse events, but not the desired potential improvement in the tumor effect of a novel treatment strategy. A sensible application of "tolerance doses" in a clinical situation requires consideration of various critical aspects addressed here: definition of tolerance dose, specification of an endpoint/symptom, consideration of radiation quality and irradiation protocol, exposed volume and dose distribution, and patient-related factors of radiosensitivity. The currently most comprehensive estimates of OAR radiation tolerance are in the QUANTEC compilations (2010). However, these tolerance dose values must only be regarded as a rough orientation and cannot answer the relevant question for the patients, i.e., if the study can achieve a therapeutic advantage; this can obviously be answered only by the final scientific analysis of the study results. Despite all limitations, the design of clinical studies should currently refer to the QUANTEC values for appreciation of the risk of complications, if needed supplemented by one's own data or further information from the literature. The implementation of a consensus on the safety interests of the patients and on an application and approval process committed to progress in medicine, with transparent quality-assuring requirements with regard to the structural safeguarding of the study activities, plays a central role in clinical research in radiation oncology. Registration No. 21305

Radiolabeled anti-EGFR-antibody improves local tumor control after external beam radiotherapy and offers theragnostic potential.
Koi, L.; Bergmann, R.; Brüchner, K.; Pietzsch, J.; Pietzsch, Hj.; Krause, M.; Steinbach, J.; Zips, D.; Baumann, M.
Abstract: PURPOSE:
The effect of radioimmunotherapy (RIT) using the therapeutic radionuclide Y-90 bound to the anti-EGFR antibody cetuximab combined with external beam irradiation (EBRT) (EBRIT) on permanent local tumor control in vivo was examined.

METHODS:
Growth delay was evaluated in three human squamous cell carcinoma models after RIT with [(90)Y]Y-(CHX-A''-DTPA)₄-cetuximab (Y-90-cetuximab). The EBRT dose required to cure 50% of the tumors (TCD₅₀) for EBRT alone or EBRIT was evaluated in one RIT-responder (FaDu) and one RIT-non-responder (UT-SCC-5). EGFR expression and microenvironmental parameters were evaluated in untreated tumors, bioavailability was visualized by PET using ([(86)Y]Y-(CHX-A''-DTPA)₄-cetuximab (Y-86-cetuximab) and biodistribution using Y-90-cetuximab.

RESULTS:
In UT-SCC-8 and FaDu but not in UT-SCC-5 radiolabeled cetuximab led to significant tumor growth delay. TCD₅₀ after EBRT was significantly decreased by EGFR-targeted RIT in FaDu but not in UT-SCC-5. In contrast to EGFR expression, parameters of the tumor micromilieu and in particular the Y-90-cetuximab biodistribution or Y-86-cetuximab visualization in PET correlated with the responsiveness to RIT or EBRIT.

CONCLUSION:
EGFR-targeted EBRIT can improve permanent local tumor control compared to EBRT alone. PET imaging of bioavailability of labeled cetuximab appears to be a suitable predictor for response to EBRIT. This theragnostic approach should be further explored for clinical translation.

Keywords: Cetuximab; Combined treatment; Epidermal growth factor receptor (EGFR) inhibition; Radioimmunotherapy; Radiotherapy Registration No. 21304

Radiosynthesis, in vitro and in vivo evaluation of 8-[4-(2-[18F]fluoroethoxy)benzyl]-1,4-dioxa-8-azaspiro[4.5]decane, a spirocyclic σ1 receptor ligand for tumor targeting
Kniess, T.; Bergmann, R.; Xie, F.; Jia, H.; Deuther-Conrad, W.; Steinbach, J.; Pietzsch, J.
Abstract: Aim: Sigma (σ) receptors have a characteristic distribution in the brain and are implicated in many diseases of the central nervous system. In the past years a number of PET and SPECT radiotracers for visualization of σ‐receptors in the brain have been developed. In addition, σ‐receptors are up‐regulated in various tumor cells motivating us to develop a series of novel spirocyclic receptor ligands showing high affinity and good selectivity for σ1. One candidate was radiolabeled with fluorine‐18 as potential radiotracer for tumor targeting.
Methods: Six novel spirocyclic σ1 receptor ligands were designed, synthesized, and characterized. The affinity to σ1 and σ2 receptors was tested, one derivative, 8‐[4‐(2‐[18F]fluoroethoxy)benzyl]‐1,4‐dioxa‐8‐azaspiro[4.5]decane, was chosen for radiolabeling with fluorine‐18. The stability of the radiotracer in vitro and in vivo was evaluated, the logP value was determined. Biodistribution studies in rats and mice as well as dynamic small animal PET studies in nude mice xenografted with DU145 human prostate tumors were performed.
Results: The Ki values of the spirocyclic ligands were determined to be in the range 3.26‐11.2 nM for σ1 and 164.4‐312.2 nM for σ2. The radiotracer was prepared by 18F‐fluoroethylation of the corresponding hydroxyl precursor via a two‐step automated procedure in 20% yield and 99% radiochemical purity with a specific activity about 45 GBq/μmol. The logP value was determined 0.81 ± 0.13, and it was found to be stable in vitro in saline, ethanol, and human plasma. Biodistribution in normal mice and Wistar rats showed radiotracer uptake in σ1‐rich regions like brain and pancreas that could be blocked by pre‐administration of haloperidol. In mice fast degradation of the radiotracer
resulting in four metabolites was observed. However, PET studies in mouse tumor models showed tumor uptake of about 0.77+/‐0.45 (SUV, 1 h p.i.), which likewise could be substantially blocked by haloperidol.
Conclusion: We have developed an 18F‐labeled spirocyclic receptor ligand with high selectivity for σ1 and excellent hydrophilicity. We demonstrated by successful PET imaging in mice bearing σ1‐expressing DU‐145 tumors the principle of targeting tumors with radiolabeled σ‐ligands. However, the unfavorable in vivo stability of this spirocyclic derivative limits a broader application as an imaging agent.
  • Poster
    Annual Congress of the European Association of Nuclear Medicine (EANM), 18.-22.10.2014, Gothenburg, Sweden
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 41(2014), S416
    DOI-Link: http://dx.doi.org/10.1007/s00259-014-2901-9
Registration No. 21303

Focal adhesion signaling and therapy resistance in cancer.
Eke, I.; Cordes, N.
Abstract: Interlocking gene mutations, epigenetic alterations and microenvironmental features perpetuate tumor development, growth, infiltration and spread. Consequently, intrinsic and acquired therapy resistance arises and presents one of the major goals to solve in oncologic research today. Among the myriad of microenvironmental factors impacting on cancer cell resistance, cell adhesion to the extracellular matrix (ECM) has recently been identified as key determinant. Despite the differentiation between cell adhesion-mediated drug resistance (CAMDR) and cell adhesion-mediated radioresistance (CAMRR), the underlying mechanisms share great overlap in integrin and focal adhesion hub signaling and differ further downstream in the complexity of signaling networks between tumor entities. Intriguingly, cell adhesion to ECM is per se also essential for cancer cells similar to their normal counterparts. However, based on the overexpression of focal adhesion hub signaling receptors and proteins and a distinct addiction to particular integrin receptors, targeting of focal adhesion proteins has been shown to potently sensitize cancer cells to different treatment regimes including radiotherapy, chemotherapy and novel molecular therapeutics. In this review, we will give insight into the role of integrins in carcinogenesis, tumor progression and metastasis. Additionally, literature and data about the function of focal adhesion molecules including integrins, integrin-associated proteins and growth factor receptors in tumor cell resistance to radio- and chemotherapy will be elucidated and discussed.
Keywords: Extracellular matrix; Focal adhesion; Integrins; Small molecules; Targeted therapy Registration No. 21302

Detection of Radiation-Induced Changes in Healthy Mouse Brain Using Diffusion-weighted MRI and 18F-FDG-PET
Máthé, D.; Kovács, N.; Szigeti, K.; Bergmann, R.
Abstract: Aim: To evaluate in vivo longitudinal PET and MRI parameter changes in images can be sensitively read out with radiation‐induced tissue changes in healthy mouse brain.
Materials and Methods: We irradiated a group of c57bl6 mice (n=6) with 5 Gy and another (n=6) with 20 Gy in the left hemisphere using an X‐ray tube (Yxlon Maxishot). Animals were imaged before, and 3‐7‐30 and 60 days post irradiation. For 18F‐Fluoro‐Deoxy‐Glucose (FDG) PET we injected 10 to 15 MBq FDG iv. PET and MR imaging was performed subsequently with a Mediso nanoScan PET/CT and a Bruker Biospec 7T MRI system. Arterial spin labeling (ASL) was probed using a FAIR‐EPI sequence. For DWI, a SE EPI‐based sequence was used. Standardized brain FDG‐PET uptake (SUV) values were determined for righ/left hemispheres and cerebellum using Rover software. ASL data and water apparent diffusion coefficients (ADC) were read out using a Matlab code after atlas coregistration. We determined statistical differences between readout results in both groups and between the time points in the same groups in these regions.
Results: There was no significant difference in ASL values neither in ADC values in the 5 Gy group compared to baseline or between time points. If both hemisphere’s respective VOI data were taken into account we could observe significant ADC differences between early (3 days) and late (30 to 60 days) changes in almost all VOIs of the brains. Using hemisphere VOI PET data we see a change at 7 days and 60 days both compared to baseline and all other time points in both groups by a decrease in SUVs of both hemispheres at Day 7 and and an increase at Day 60.
Conclusion: In our study ASL had no readout value on radiation‐induced changes. Using ADC maps, as early as 3 days and after one month post irradiation the late changes are visible throughout the brain. FDG‐PET provided us with a readable change at day 7. The direction of increased metabolism in the hemisphere 60 days read out with PET coregisters with the increase in ADC values at Day 60. These late changes are possibly due to second‐phase neuro‐inflammation and cell content increase in accordance with PET imaging results. Combined DWI MR/FDG PET is a promising means for radiation therapy side effect follow‐up.
This research reading to these results has received funding from the European Union Seventh Framework Programme FP7/2007‐2013 under grant agreement n° 305311/INSERT.
  • Poster
    Annual Congress of the European Association of Nuclear Medicine (EANM), 18.-22.10.2014, Gothenburg, Sweden
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 41(2014), S415
    DOI-Link: http://dx.doi.org/10.1007/s00259-014-2901-9
Registration No. 21301

The Role of Phospholipid Headgroup Composition and Trehalose in the Desiccation Tolerance of Caenorhabditis elegans
Abusharkh, S. E.; Erkut, C.; Oertel, J.; Kurzchalia, T. V.; Fahmy, K.
Abstract: Anhydrobiotic organisms have the remarkable ability to lose extensive amounts of body water and survive in an ametabolic state. Distributed to various taxa of life, these organisms have developed strategies to efficiently protect their cell membranes and proteins against extreme water loss. Recently, we showed that the dauer larva of the nematode Caenorhabditis elegans is anhydrobiotic and accumulates high amounts of trehalose during preparation to harsh desiccation
(preconditioning). Here, we have used this genetic model to study the biophysical manifestations of anhydrobiosis and show that, in addition to trehalose accumulation, dauer larvae dramatically reduce their phosphatidylcholine (PC) content. The chemical composition of the phospholipids (PLs) has key consequences not only for their interaction with trehalose, as we demonstrate with Langmuir−Blodgett monolayers, but also, the kinetic response of PLs to hydration transients is strongly influenced as evidenced by time-resolved FTIR spectroscopy. PLs from preconditioned larvae with reduced PC content exhibit a higher trehalose affinity, a stronger hydration-induced gain in acyl chain free volume, and a wider spread of structural relaxation rates of their lyotropic transitions and sub-headgroup H-bond interactions. The different hydration properties of PC and phosphatidylethanolamine (PE) headgroups are crucial for the hydration-dependent rearrangement of the trehalose-mediated H-bond network. As a consequence, the compressibility modulus of PLs from preconditioned larvae is about 2.6-fold smaller than that from non-preconditioned ones. Thus, the biological relevance of reducing the PC:PE ratio by PL headgroup adaptation should be the preservation of plasma membrane integrity by relieving mechanical strain from desiccated trehalose-containing cells during fast rehydration.

Keywords: Fourier transform infrared spectroscopy biomembrane preservation hydration Registration No. 21300

In-situ investigations of ion implantation at ROBL-MRH
Baehtz, C.; Grenzer, J.; von Borany, J.; Posselt, M.
Abstract: The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) operates since 1998 a bending magnet beamline with two end stations at the ESRF, Grenoble. In 2011 the complete beamline optics was renewed with new focusing mirrors and a double crystal monochromator equipped with3 pairs of differently oriented Si-crystals and two sets of multilayers. The Materials Research Station is focusing on in-situ measurements using different scattering techniques like XRR, GISAXS, HRXRD or GIXRD that can be combined with spectroscopy measurements. In the center of interest are the CVD growth of graphite materials, phase change materials under operation and hydrogen storage materials. Additionally the syntheses of various nano-structured materials by magnetron sputtering were explored. A similar sample environment is used to investigate in-operando the He and Ar-ion implantation processes on single crystalline Si and Al2O3. Ions were provided by an ion gun operated at 5 keV, an additional potential of up to 20keV on the sample was applied to accelerate the ions further. Using a Mythen detector, a series of reciprocal space maps were recorded with duration of less than 1 minute per map. The crystal truncation rod vanished within the first seconds of He-ion bombardment. In the following the Si (004) reflection broadens, forming a layer peak that give clearly a hint of increasing strain in the material. After 50 minutes a steadystate that correspond to a heavily damaged or amorphized Si layer is reached
Keywords: Synchrotron radiation, in-Situ investigation, magnetron sputtering, ion implantation
  • Poster
    Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten 2014, 21.-23.09.2014, Bonn, Deutschland
Registration No. 21299

Synthese neuartiger Vesamicolanaloga als potentielle Liganden für den vesikulären Acetylcholintransporter
Lindemann, M.
Abstract: Es ist kein Abstract vorhanden.
  • Master thesis
    Universität Leipzig, Fakultät für Chemie und Mineralogie, 2014
    Mentor: Dr. Barbara Wenzel
    94 Seiten
Registration No. 21298

Pretherapeutic scan time-normalized tumor to blood standard uptake ratio (SUR) is superior to SUV as a prognostic factor in patients with esophageal carcinoma
Hofheinz, F.; Bütof, R.; Zöphel, K.; Schütze, C.; Löck, S.; Steffen, I. G.; Stadelmann, T.; Kotzerke, J.; Baumann, M.; van den Hoff, J.
Abstract: Aim: Determination of tumor SUV is widely used for quantitative assessment of tumor metabolism in FDG PET and its potential for therapy outcome prediction in various cancer diseases is under scrutiny. However, the SUV approach has several well known limitations compromising its ability to act as a surrogate parameter of glucose consumption. Recently, we have shown that SUR overcomes most of these limitations as long as FDG kinetics in the target structure can be considered irreversible [1,2]. The aim of this work was to evaluate the prognostic value of SUR in comparison to SUV in patients with esophageal carcinoma.
Methods: FDG-PET/CT was performed in 97 consecutive patients ((64+/-10)y, 83 males) with newly diagnosed esophageal cancer prior to definitive radiochemotherapy. In the PET images the metabolic active volume (MTV) of the primary tumor was delineated with an adaptive threshold method. For determination of the blood SUV the aorta was delineated manually in the attenuation CT. The aorta ROI was transferred to the PET image. Blood SUV was computed as the mean value of the aorta ROI. SUR values were computed as ratio of tumor SUV and blood SUV. SUR values were scan-time-normalized to 60 min p.i. as described in [2]. Univariate Cox regression with respect to overall survival (OS), locoregional control (LRC), and distant-metastases-free survival (DM) was performed for SUVmax, SURmax and clinically relevant parameters. Additionally, a multivariate Cox regression including N stage and smoking status (univariate significant) as confounding parameters was performed.
Results: Both, SUVmax and SURmax, were prognostic factors for OS and DM, but not for LRC. With respect to OS a univariate Cox regression showed a slightly increased hazard ratio (HR) for SURmax (HR=2.3, p=0.001) compared to SUVmax (HR=2.1, p=0.001). With respect to DM HR of SURmax was notably larger than HR of SUVmax (HR=5.7, p=0.005 compared to 3.1, p=0.006). Moreover, in a multivariate Cox regression the prognostic value of SUR was slightly higher for OS and notably higher for DM.
Conclusion: Our results indicate an increased prognostic value if lesion uptake is characterized by time-normalized SUR instead of SUV in pretherapeutic FDG PET of patients with esophageal carcinoma. More comprehensive investigations are necessary to confirm these results.
Literature: [1] van den Hoff et al, EJNMMI Res 2013, 3:77 [2] van den Hoff et al, EJNMMI Res 2014, 4:18
  • Lecture (Conference)
    Annual Congress of the European Association of Nuclear Medicine (EANM), 18.-22.10.2014, Gothenburg, Sweden
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 41(2014), S232-S233
    DOI-Link: http://dx.doi.org/10.1007/s00259-014-2901-9
Registration No. 21297

Capability of X-ray diffraction for the study of microstructure of metastable thin films
Rafaja, D.; Wüstefeld, C.; Dopita, M.; Motylenko, M.; Baehtz, C.
Abstract: Metastable phases are often used to design materials with outstanding properties, which cannot be achieved with thermodynamically stable compounds. In many cases, the metastable phases are employed as precursors for controlled formation of nanocomposites. This contribution shows how the microstructure of crystalline metastable phases and the formation of nanocomposites can be concluded from X-ray diffraction experiments by taking advantage of the high sensitivity of X-ray diffraction to macroscopic and microscopic lattice deformations and to the dependence of the lattice deformations on the crystallographic direction. The lattice deformations were determined from the positions and from the widths of the diffraction lines, the dependence of the lattice deformations on the crystallographic direction from the anisotropy of the line shift and the line broadening. As an example of the metastable system, the supersaturated solid solution of titanium nitride and aluminium nitride was investigated, which was prepared in the form of thin films by using cathodic arc evaporation of titanium and aluminium in a nitrogen atmosphere. The microstructure of the (Ti,Al)N samples under study was tailored by modifying the [Al]/[Ti] ratio in the thin films and the surface mobility of the deposited species.
Keywords: metastable thin films; microstructure; X-ray diffraction Registration No. 21296

Crystallography of phase transitions in metastable titanium aluminium nitride nanocomposites
Rafaja, D.; Wüstefeld, C.; Dopita, M.; Motylenkoa, M.; Baehtz, C.; Michotte, C.; Kathrein, M.
Abstract: The isostructural decomposition of the titanium aluminium nitride supersaturated solid solution crystallising in the face centred cubic (fcc) crystal structure into the titanium-rich fcc-(Ti,Al)N and almost titanium-free fcc-(Al, Ti)N and the transformation of metastable fcc-(Ti,Al)N into the wurtzitic aluminium nitride are discussed from the crystallographic point of view by taking the observed orientation relationships between the adjacent phases into account. It is shown that the isostructural decomposition of fcc-(Ti,Al)N into Ti-rich fcc-(Ti,Al)N and fcc-(Al, Ti)N and the transformation of themetastable fcc-(Ti,Al)N into the thermodynamically stablewurtzitic phase are concurrent processes, which are controlled not only by the thermodynamic stability of the respective compound and by the diffusivity of Al and Ti, but also by the local lattice strains. A part of the local lattice strains is regarded to result from the lattice misfit at the interfaces between the titanium aluminium nitrides having different [Al]/ [Ti] concentration ratios and, in the case of the fcc/wurtzite-type interface, also having different crystal structures. The phase transition of the fcc-(Ti,Al)N to thewurtzitic onewas predicted to be facilitated by stacking faults. The results of crystallographic considerations were verified experimentally by using in situ high-temperature synchrotron diffraction experiments that were performed on cathodic arc evaporated (Ti,Al)N thin films containing titanium and aluminium in different amounts.
Keywords: Ti–Al–N Cathodic arc evaporation X-ray diffraction Phase transformation Stacking faults High-resolution transmission electron microscopy Registration No. 21295

Density change upon crystallization of Ga-Sb films
Putero, M.; Coulet, M.-V.; Muller, C.; Cohen, G.; Hopstaken, M.; Baehtz, C.; Raoux, S.
Abstract: Besides crystallization time and temperature, the mass density change upon crystallization is a key parameter governing the reliability of phase change random access memory. Indeed, few percentages density change induces considerable mechanical stress in memory cells, leading to film delamination with subsequent electrical failures. This letter presents an extensive study of density change upon crystallization in a series of Ga-Sb thin films with various antimony contents. The mass density of the films is precisely determined by x-ray reflectivity in both their amorphous and crystalline states. The variations of the density in crystalline and amorphous films according to the Sb content found to cross with a zero-density change for 70 at. % Sb. The peculiar behavior of Ga-Sb thin films upon crystallization may be linked to their stress state and mechanical properties.
Keywords: phase change material, x-ray, diffraction, reflectivity Registration No. 21294

Nitrogen controlled iron catalyst phase during carbon nanotube growth
Bayer, B. C.; Baehtz, C.; Kidambi, P. R.; Weatherup, R. S.; Mangler, C.; Kotakoski, J.; Goddard, C. J. L.; Caneva, S.; Cabrero-Vilatela, A.; Meyer, J. C.; Hofmann, S.
Abstract: Close control over the active catalyst phase and hence carbon nanotube structure remains challenging in catalytic chemical vapor deposition since multiple competing active catalyst phases typically co-exist under realistic synthesis conditions. Here, using in-situ X-ray diffractometry, we show that the phase of supported iron catalyst particles can be reliably controlled via the addition of NH3 during nanotube synthesis. Unlike polydisperse catalyst phase mixtures during H2 diluted nanotube growth, nitrogen addition controllably leads to phase-pure c-Fe during pre-treatment and to phase-pure Fe3C during growth. We rationalize these findings in the context of ternary Fe-C-N phase diagram calculations and, thus, highlight the use of pre-treatment- and add-gases as a key parameter towards controlled carbon nanotube growth.
Keywords: Carbon nano tubes, x-ray diffraction, xps Registration No. 21293

In Situ Phase Evolution of Ni/Ti Reactive Multilayers
Cavaleiro, A. J.; Ramos, A. S.; Martins, R. M. S.; Baehtz, C.; Vieira, M. T.; Braz Fernandes, F. M.
Abstract: Joining shape-memory alloys (SMA) to other materials is strongly required in order to enlarge their fields of application. Fusion welding induces strong compositional and microstructural changes that significantly affect the shape-memory effect and the superelastic behavior of these alloys. The exothermic and in some cases self-propagating character of some nano-multilayer reactions is explored in this study as an alternative for joining SMA. To follow these very fast reactions, high brilliance sources, such as synchrotron radiation, are required. In situ high-resolution x-ray diffraction data, giving the phase evolution sequence with temperature of the Ni/Ti multilayer thin films under study, are presented. A correlation between the multilayer design and the tendency for the sequence of phase formation is established.
Keywords: advanced characterization, intermetallic, x-ray Registration No. 21292

Influence of a passivation layer on strain relaxation and lattice disorder in thin nano-crystalline Pt films during in-situ annealing
Gruber, W.; Rahn, J.; Baehtz, C.; Horisberger, M.; Geckle, U.; Schmidt, H.
Abstract: In this work we compared the relaxation of strain and lattice disorder in thin nano-crystalline Pt films for samples covered with a Si3N4 layer and samples without a cover layer, respectively.We measured thickness and interplanar distance of the Pt film by X-ray reflectometry and X-ray diffractometry during insitu annealing using synchrotron radiation. The results show that strain and lattice disorder relaxation are impeded if the Pt film is sealed with a cover layer to suppress the creation of vacancies at the Pt surface. This emphasizes the postulated important role of the generation of vacancies at the free surface of thin metal films for strain relaxation during isothermal annealing.
Keywords: Nano-crystalline platinum Thin films Strain relaxation Vacancy creation Registration No. 21291

An inverted cylindrical sputter magnetron as metal vapour supply for electron cyclotron resonance ion sources
Weichsel, T.; Hartung, U.; Kopte, T.; Zschornack, G.; Kreller, M.; Silze, A.
Abstract: An inverted cylindrical sputter magnetron device has been developed. The magnetron is acting as a metal vapor supply for an electron cyclotron resonance (ECR) ion source. FEM simulation of magnetic flux density was used to ensure that there is no critical interaction between both magnetic fields of magnetron and ECR ion source. Spatially resolved double Langmuir probe and optical emission spectroscopy measurements show an increase in electron density by one order of magnitude from 1 × 1010 cm−3 to 1 × 1011 cm−3, when the magnetron plasma is exposed to the magnetic mirror field of the ECR ion source. Electron density enhancement is also indicated by magnetron plasma emission photography with a CCD camera. Furthermore, photographs visualize the formation of a localized loss-cone - area, when the magnetron is operated at magnetic mirror field conditions. The inverted cylindrical magnetron supplies a metal atom load rate of R > 1 × 1018 atoms/s for aluminum, which meets the demand for the production of a milliampere Al+ ion beam. Registration No. 21290

Electron beam ion sources for use in second generation synchrotrons for medical particle therapy
Zschornack, G.; Ritter, E.; Schmidt, M.; Schwan, A.
Abstract: Cyclotrons and first generation synchrotrons are the commonly applied accelerators in medical particle therapy nowadays. Next generation accelerators such as Rapid Cycling Medical Synchrotrons (RCMS), direct drive accelerators, or dielectric wall accelerators have the potential to improve the existing accelerator techniques in this field. Innovative accelerator concepts for medical particle therapy can benefit from ion sources which meet their special requirements. In the present paper we report on measurements with a superconducting Electron Beam Ion Source, the Dresden EBIS-SC, under the aspect of application in combination with RCMS as a well proven technology. The measurements indicate that this ion source can offer significant advantages for medical particle therapy. We show that a superconducting EBIS can deliver ion pulses of medically relevant ions such as protons, C4 + and C6 + ions with intensities and frequencies required for RCMS [S. Peggs and T. Satogata, “A survey of Hadron therapy accelerator technology,” in Proceedings of PAC07, BNL-79826- 2008-CP, Albuquerque, New Mexico, USA, 2007; A. Garonna, U. Amaldi et al., “Cyclinac medical accelerators using pulsed C6 +/ H+2 ion sources,” in Proceedings of EBIST 2010, Stockholm, Sweden, July 2010]. Ion extraction spectra as well as individual ion pulses have been measured. For example, we report on the generation of proton pulses with up to 3 × 109 protons per pulse and with frequencies of up to 1000 Hz at electron beam currents of 600 mA. Registration No. 21289

Ridge waveguides in Nd:ABC3O7 disordered crystals produced by swift C5+ ion irradiation and precise diamond dicing: Broad band guidance and spectroscopic properties
Chen, C.; Luan, Q.; He, R.; Cheng, C.; Akhmadaliev, S.; Zhou, S.; Yu, H.; Zhang, H.; Chen, F.
Abstract: Optical ridge waveguides have been manufactured in the crystals of Nd:SrLaGa3O7 and Nd:SrGdGa3O7 by combining techniques of swift carbon ion irradiation with precise diamond blade dicing. The guiding properties of the waveguides are investigated at broadband (at wavelength of 633 nm, 1064 nm, and 4 µm). After annealing treatment at 200 °C for 1 h, the propagation losses of ridge waveguides could be reduced to as low as 1 dB/cm. The confocal microfluorescence emission spectra confirm that the fluorescence properties of Nd3+ ions are almost unchanged after the ion irradiation processing, showing promising potentials as application of miniature light sources in integrated optics.
Keywords: Optical ridge waveguides; Swift heavy ion irradiation; Diamond saw dicing Registration No. 21287

Electron spin resonance study in the chiral ferromagnet Cu2OSeO3 using pulsed magnetic fields up to 64 T and terahertz free electron laser
Ozerov, M.
Abstract: The recent discovery of skyrmions in Cu2OSeO3 has established a new platform to create and manipulate skyrmionic spin textures. We use high-field electorn spin resonance (ESR) spectroscopy combining a terahertz free electron laser and pulsed magnetic fields up to 64 T to probe and quantify ist microscopic spin-spin interactions. Besides providing direct access to the long-wavelength Goldstone mode, this technique probes also the high-energy part of the excitation spectrum which is inaccessible by Standard low-frequency ESR. Fitting the behavior of the observed modes in magnetic field to a theroretical Framework establishes experimentally that the fundamental magnetic building blocks of this skyrmionic magnet are rigid, highly entangled and weakly coupled tetrahedra.
  • Lecture (Conference)
    Science at FEL, 15.08.2014, Villligen, Switzerland
Registration No. 21285

Quantum spin chains with frustration due to Dzyaloshinskii-Moriya interactions
Hälg, M.; Lorenz, W. E. A.; Povarov, K. Y.; Mansson, M.; Skourski, Y.; Zheludev, A.
Abstract: The properties of two quantum spin chain materials, K2CuSO4Cl2 and K2CuSO42, are studied by a variety of experimental techniques, including bulk measurements, neutron spectroscopy, and electron spin resonance. The hierarchy of relevant terms in the magnetic Hamiltonian is established. It is shown that these two compounds feature substantial Dzyaloshinskii-Moriya interactions that are uniform within each chain, but antiparallel in adjacent chains. The result is a peculiar type of frustration of interchain interactions, which leads to an unusual fielderature phase diagram. Registration No. 21284

Materials Research at the Dresden High Magnetic Field Laboratory
Wosnitza, J.
Abstract: es hat kein Abstract vorgelegen
  • Invited lecture (Conferences)
    Functionalized Molecule-Based Magnetic Materials, 24.-27.11.2014, Bielefeld, Deutschland
Registration No. 21283

The Tesla Race - Materials Research in Very High Magnetic Fields
Wosnitza, J.
Abstract: es hat kein Abstract vorgelegen
  • Invited lecture (Conferences)
    International Conference "Materials Science and Engineering", 23.-25.09.2014, Darmstadt, Deutschland
Registration No. 21282

Spin dynamics in triangular-lattice antiferromagnets Cs2CuBr4 and Cs2CuCl4: high-field ESR studies
Zvyagin, S.
Abstract: A spin-1/2 Heisenberg antiferromagnet (AF) on a triangular lattice is the paradigmatic model in quantum magnetism, which was intensively studied. In spite of numerous theoretical studies (which predict a rich variety of grounds states, ranging from a gapless spin liquid to Néel order), many important details of the phase diagram of triangular-lattice AFs remain controversial or even missing. In order to test the theory experimentally, a precise information on the spin-Hamiltonian parameters for the materials of interest is highly demanded. Here, we present results of high-field electron spin resonance (ESR) studies of spin-1/2 Heisenberg AFs Cs2CuCl4 and Cs2CuBr4 with distorted triangular-lattice structures in magnetic fields up to 50 T. In the magnetically saturated phase (H > Hsat), quantum fluctuations are fully suppressed, and the spin dynamics is defined by ordinary magnons. This allows us to accurately describe the magnetic excitation spectra in both materials and, using the harmonic spin-wave theory, to determine their exchange parameters. The viability of the proposed method was first proven by applying it to Cs2CuCl4, revealing good agreement with inelastic neutron-scattering results. For the isostructural Cs2CuBr4 we obtain J/kB = 14.9(7) K, J'/kB = 6.1(3) K, [J'/J ~ 0.41], providing exact and conclusive information on the exchange coupling parameters in this frustrated spin system. The approach has a broader impact and can be potentially used for any quantum magnet with reduced (e.g., by the staggered Dzyaloshinskii-Moriya interaction) translational symmetry, resulting, as predicted, in emergence of a new exchange mode above Hsat
  • Lecture (Conference)
    From Exotic Excitations to Novel Transport and Non-Equilibrium Phenomena, 01.-05.09.2014, Dresden, Deutschland
Registration No. 21280

Europium(III)-Calcite study with site-selective TRLFS
Peschel, S.; Schmidt, M.; Stumpf, T.
Abstract: Calcite is an important mineral that plays a significant role in nuclear waste disposal concerning the safety and performance in geological formations. At these sites it can be found in the near field as a secondary phase (weathering of the geochemical barrier) and as a rock-forming mineral in the surrounding rocks. Geochemically, calcite has the potential to adsorb as well as incorporate guest ions with a similar ionic radius, such as europium and curium, for calcium in the host lattice. Because of the long half-lives of actinides like curium and americium, they and their lanthanide homologues (i.e., europium) are the subject of recent research.
Calcite samples were doped with Eu(III) in batch experiments. Calcium carbonate powder was contacted with a Eu(III) solution (5 x 10-7 M) in a calcium carbonate saturated solution with a NaCl (10 mM) background electrolyte solution. Batch samples were analyzed at varying contact times to understand the step-by-step kinetic and mechanistic behavior of incorporation of Eu(III) into the solid phase. After the contact period, the supernatant was investigated with ICP-MS. The Eu(III) concentration in solution varies from 0.1 to 3.2 % of the initial concentration, which indicates that almost all Eu(III) is adsorbed.
The calcite powder was examined with site-selective TRLFS at temperatures below 20 K. The direct excitation of the 7F0 →5D0 transition in the range of 576-581 nm and the integration of the respective emission spectra yields a characteristic excitation spectrum. These excitation spectra show only one broad peak with a maximum at ~579.2 nm, independent of the sorption time (up to 31 days). This behavior is dissimilar to that determined by Stumpf and Fanghänel [1] who investigated Cm(III) sorption on calcite with NaClO4 as background electrolyte and found 2 peaks, which change over time. Lifetime measurements of our samples exhibit biexponential decay indicative of two species. The first specie has a lifetime of 460 to 985 µs and the second 2155 to 4577 µs. Using Horrock´s equation[2] the number of coordinating water molecules in the first sphere surrounding the Eu(III) can be determined. This value corresponds to its location (surface sorbed vs incorporated) on or within the calcite lattice. Therefore, calculated values of 0.5 to 1.7 indicate the formation of an inner sphere sorption species whereas a value of 0 is indicative of incorporation of the Eu(III) within the calcite. The emission spectrum shows a threefold splitting of the 7F1 band.This indicates a ligand field with low symmetry. To better understand these surface species, future measurements with CTR and RAXR will be performed.

[1] Stumpf, T. and T. Fanghanel (2002). J. of Colloid and Interface Science 249(1), 119-122.
[2] Horrocks (1979) J. Am. Chem. Soc. 101, 334.

Keywords: site-selective TRLFS Europium Calcite
  • Poster
    Advanced Techniques in Actinide Spectroscopy 2014 (ATAS 2014), 03.-07.11.2014, Dresden, Deutschland
Registration No. 21276

Sorption of (trivalent) actinides and lanthanides
Hellebrandt, S.; Schmidt, M.; Stumpf, T.
Abstract: Introduction
The study of trivalent actinides is of particular importance for the safety assessment of nuclear waste disposal sites due to the predominance of this valence in deep geological formations. In particular, studying the solution-solid interface chemistry of these trivalent radioelements in the aqueous phase with a mineral is fundamental for better understanding their interactions at or within the surface of a host phase in a repository. As a relevant near field material (geotechnical barrier) for nuclear waste disposal sites, clay minerals are very important due to their retardation properties. Muscovite, a phyllosilicate material of aluminum and potassium, is very similar to clay minerals but less complex, so we are able to assign results from muscovite to clay minerals. Additionally, investigations concerning trace concentration of actinides appearing in the far field of a nuclear waste disposal are also of interest. Site-Selective Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) is a characterizational technique that can probe the behavior of low concentrated actinides on a molecular level. As a complementary technique resonant anomalous x-ray reflectivity (RAXR) will be used to get a deeper insight and a verification of the TRLFS results.

TRLFS, the main tool
The aim of this study focuses on understanding the surface interactions of muscovite with aqueous trivalent actinides and lanthanides using Eu(III) and Cm(III), and characterization of the solid and aqueous phase species using TRLFS. Europium (III) is used as a non-radioactive homologue for trivalent actinides due to its similar chemical behavior and its spectroscopic properties as a probe for TRLFS. Direct excitation of the 7F05D0 electron transition and consecutive integration of the respective emission generates information pertaining to the chemical coordination and environment of the Eu(III). First investigations in the muscovite-europium system show that there appears one poorly defined species (broad excitation peak) present at one site. Lifetime measurements of the luminescence are used in accordance with the Horrocks equation (europium) [1] and the number of coordinated waters can be determined. The lifetimes between 208 and 230 µs indicates 4 to 5 coordinated water ligands in the inner sphere. As a consequence of this the europium species is interpreted as inner-sphere sorption on the surface of muscovite.

[1] Horrocks, W.D. and Sudnick, D.R. (1979) J. Am. Chem. Soc. 101, 334-340.
  • Poster
    2nd International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS 2014), 03.-07.11.2014, Dresden, Deutschland
Registration No. 21275

AER Working Group D on VVER safety analysis – report of the 2014 meeting
Kliem, S.
Abstract: The AER Working Group D on VVER reactor safety analysis held its 23th meeting in Garching, Germany, during the period 12-13 May, 2014. The meeting was hosted by the GRS Garching and was held in conjunction with the eighth workshop on the OECD Benchmark for Uncertainty Analysis in Best-Estimate Modelling (UAM) for Design, Operation and Safety Analysis of LWRs. Altogether 21 participants attended the meeting of the working group D, 19 from AER member organizations and 2 guests from non-member organization. The co-ordinator of the working group, Mr. S. Kliem, served as chairman of the meeting.
The meeting started with a general information exchange about the recent activities in the participating organizations.
The given presentations and the discussions can be attributed to the following topics:
• Safety analyses methods and results
• Code development and benchmarking including the calculation of the OECD/NEA Benchmark for the Kalinin-3 VVER-1000 NPP and 7th AER Dynamic Benchmark
• Future activities
A list of the participants and a list of the handouts distributed at the meeting are attached to the report. The corresponding PDF-files of the handouts can be obtained from the chairman.
  • Lecture (Conference)
    24th Symposium of AER on VVER Reactor Physics and Reactor Safety, 14.-18.10.2014, Sochi, Russian Federation
  • Contribution to proceedings
    24th Symposium of AER on VVER Reactor Physics and Reactor Safety, 14.-18.10.2014, Sochi, Russian Federation
    Proceedings of the 24th Symposium of AER on VVER Reactor Physics and Reactor Safety, Budapest: MTA Energoatom, 415-420
Registration No. 21274

Recent developments in (H)LM measurement techniques
Wondrak, T.; Eckert, S.; Franke, S.; Shevchenko, N.; Buchenau, D.; Stefani, F.; Gerbeth, G.
Abstract: In the field of advanced heavy-liquid-metal (HLM) cooled systems the knowledge of flow properties of the liquid metal is important for the design, the operation and the safety of such systems. The measurement of the flow properties is usually hampered by the high temperature and the opaqueness of liquid melts. We will give an overview of the recent developments of measurement techniques which can be used for model experiments as wells as for instrumenting a HLM cooled system. This includes ultrasound Doppler velocimetry, x-ray radioscopy and several inductive techniques like inductive flow meters and the contacless inductive flow tomography.
Keywords: liquid metal, flow measurement
  • Invited lecture (Conferences)
    SEARCH/MAXSIMA 2014 International Workshop, 07.-10.10.2014, Karlsruhe, Germany
Registration No. 21272

Measurement techniques for the flow in a model of a continuous caster
Wondrak, T.; Timmel, K.; Stefani, F.; Eckert, S.; Shevchenko, N.; Röder, M.
Abstract: In order to examine the flow structure in a continuous casting mold which is important for the quality of the produced steel, at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) three different models of a continuous caster are available to study the flow in a continuous casting mold. Those cold liquid metal models which use metallic alloys with low melting point e.g. up to 200 °C offer the application of different measurement techniques like ultrasound doppler velocimetry, x-ray and potential probes for flow investigation. Second, these models can be used to study the influence of magnetic actuators to the flow due to their high conductivity, contrary to water models. Third, these models can be used to develop new measurement techniques which can be applied in a real caster.
We will give a short overview of the measurement techniques available for those models. Additionally we will present the newly developed Contactless Inductive Flow Tomography which can reconstruct the flow in the mold by measuring the flow induced perturbation of an applied magnetic field. This technique has the ability to be deployed in a real caster.

Keywords: liquid metal model, measurement techniques, contactless inductive flow tomography
  • Contribution to proceedings
    8th European Continuous Casting Conference, 23.-26.06.2014, Graz, Österreich
    Proceedings of the 8th eccc
  • Lecture (Conference)
    8th European Continuous Casting Conference, 23.-26.06.2014, Graz, Österreich
Downloads:
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Registration No. 21270

Quantitative assessment of the asphericity of pretherapeutic FDG uptake as an independent predictor of outcome in NSCLC.
Apostolova, I.; Rogasch, J.; Buchert, R.; Wertzel, H.; Achenbach, H. Jost; Schreiber, J.; Riedel, S.; Furth, C.; Lougovski, A.; Schramm, G.; Hofheinz, F.; Amthauer, H.; Steffen, I. G.
Abstract: Background:
The aim of the present study was to evaluate the predictive value of a novel quantitative measure for the spatial heterogeneity of FDG uptake, the asphericity (ASP) in patients with non-small cell lung cancer (NSCLC).

Methods:
FDG-PET/CT had been performed in 60 patients (15 women, 45 men; median age, 65.5 years) with newly diagnosed NSCLC prior to therapy. The FDG-PET image of the primary tumor was segmented using the ROVER 3D segmentation tool based on thresholding at the volume-reproducing intensity threshold after subtraction of local background. ASP was defined as the relative deviation of the tumor's shape from a sphere. Univariate and multivariate Cox regression as well as Kaplan-Meier (KM) analysis and log-rank test with respect to overall
(OAS) and progression-free survival (PFS) were performed for clinical variables, SUVmax/mean, metabolically active tumor volume (MTV), total lesion glycolysis (TLG), ASP and "solidity", another measure of shape irregularity.

Results:
ASP, solidity and "primary surgical treatment" were significant independent predictors of PFS in multivariate Cox regression with binarized parameters (HR, 3.66; p < 0.001, HR, 2.11; p = 0.05 and HR, 2.09; p = 0.05), ASP and "primary surgical treatment" of OAS (HR, 3.19; p = 0.02 and HR, 3.78; p = 0.01, respectively). None of the other semi-quantitative PET parameters showed significant predictive value with respect to OAS or PFS. Kaplan-Meier analysis revealed a probability of 2-year PFS of 52% in patients with low ASP compared to 12% in patients with high ASP (p < 0.001). Furthermore, it showed a higher OAS rate in the case of low versus high ASP (1-year-OAS, 91% vs. 67%: p = 0.02).

Conclusions:
The novel parameter asphericity of pretherapeutic FDG uptake seems to provide better prognostic value for PFS and OAS in NCSLC compared to SUV, metabolic tumor volume, total lesion glycolysis and solidity.
Registration No. 21268

Abschlussbericht zum BMBF-Verbundprojekt Partitioning II: Multifunktionelle Komplexbildner mit N, O, S-Donorliganden für d- und f-Elemente - Synthese, Komplexbildung, Struktur und Transportverhalten
Günther, A.; Mansel, A.; Schulz, K.; Paulik, S.; Poetsch, M.; Bernhard, G.
Abstract: Hauptziel des Verbundprojektes war es, die Wechselwirkung von neu synthetisierten supramolekularen Komplexbildnern mit N,O,S-Donorfunktionen gegenüber d- und f-Elementen zu untersuchen. Dabei standen für das HZDR im Teilprojekt 1 die Komplexierung von N,O-Donorliganden insbesondere mit den Aktiniden U(VI) und Cm(III) und den Lanthaniden Eu(III), Ce(III) und Yb(III) in wässriger und erstmalig in organischer Lösung in Abhängigkeit vom pH-Wert bzw. Redoxspannung im Mittelpunkt. Es wurden die entsprechenden Komplexstöchiometrien und die spektroskopischen Eigenschaften der gebildeten Komplexe mittels UV-Vis-Spektroskopie, verschiedener laserinduzierter Methoden als auch IR-Spektroskopie bestimmt. Durch Anwendung der NMR-und EXAFS-Spektroskopie konnten strukturelle Aussagen zu den Metallkomplexen in Lösung gemacht werden. Mit Hilfe von UV-Vis Daten war es möglich, reproduzierbare Komplexbildungskonstanten von Aktinid- bzw.- Lanthanidkomplexen mit verschiedenen ß-Diketonen sowie Schiffschen Basen in Lösung zu bestimmen. Ergebnisse der Arbeiten des HZDR im Teilprojekt 2 zeigten, dass die Wechselwirkung von wasserlöslichen Calixarenen mit Radionuklidmetallionen sowie das Adsorptionsverhalten von Calixarenen an Geomatrizes unter naturnahen Bedingungen (pH 4 - 9) vernachlässigbar sind. Für die Flüssig-Flüssig-Extraktion von divalenten Metallionen mittels Radiotracertechnik wurden wasserunlösliche Calixarene ermittelt, die elementselektiv die Radionuklide 85Sr, 56Co, 64Cu und 65Zn aus der wässrigen Phase separieren können. Für Strontium eignet sich Bis-Salicyliden-diamino-calixaren, welches sich unter milden Bedingungen rückextrahieren lässt. Dicarboxy-calixaren extrahiert die d-Elemente quantitativ. Diese Extraktion ist nicht vollständig reversibel. Für die gebildeten Calixaren-Komplexe wurden spektroskopische Daten ermittelt. Die Extraktionsverfahren wurden für vier natürliche Wässer erfolgreich angewendet. Festphasenfixierte Calixarene sorbieren die Radionuklide quantitativ, jedoch ist eine vollständige Desorption nicht realisierbar.
Keywords: radionuclide, actinide, lanthanide, Schiff base, ß-diketone, calixarene, complexation, spectroscopy, extraction, radiotracer technique
  • Other report
    Dresden-Rossendorf: HZDR, 2014
    128 Seiten
Registration No. 21265

Source and shielding calculations at a PET cyclotron and possible activation in the soil
Konheiser, J.; Ferrari, A.; Naumann, B.; Müller, S.; Brachem, C.
Abstract: This presentation summarizes the results of the Monte Carlo simulation of the shielding calculations and estimates of the soil activation for the new cyclotron of the HZDR (Helmholtz-Zentrum Dresden-Rossendorf). The dose values were determined on base of the resulting neutron flux at the 18F production. The calculations were carried out with the Monte Carlo code MCNP5. The neutron source was used both calculated with ALICE-91 code (manufacturer) and calculated with MCNP6. The comparison of the sources shows that ALICE-91 produced significantly fewer neutrons. The calculation of the soil activations was performed with FLUKA. In addition the effects of the energy increasing of the protons from 24 to 28 MeV were evaluated.
It could be shown that the expected total dose rate in the public area is about 0.1 mSv/h and thus significantly below the permissible value of 0.5 microSv/h. The activities generated in the soil are mainly determined by radionuclides with short half-life. After 5 years of continuous beam operation and a subsequent decay time of 30 days, the allowable value is used up only to 0.2%.

Keywords: Monte Carlo simulation, cyclotron, 18F production, dose rate, neutron soure
  • Lecture (others)
    14. AAA Workshop, 01.12.2014, Garching, Germany
Registration No. 21261

Charge Exchange and energy loss of slow highly charged ions in 1nm thick carbon nanomembranes
Wilhelm, R. A.; Gruber, E.; Ritter, R.; Heller, R.; Facsko, S.; Aumayr, F.
Abstract: It has been demonstrated in recent years that slow highly charged ions can be used as an efficient tool for nano-structure formation on in- sulating solid surfaces mainly by deposition of their potential energy. By reducing the solid thickness into the nano-meter range a limit is reached where on the one hand the ion may not be completely neutralized in the solid membrane and on the other hand dissipation of the deposited energy may be limited to two spacial dimensions. To investigate the energy deposition and neutralization processes in 2D- materials by slow highly charged ions we performed charge exchange and energy loss measurements of slow highly charged Xe ions transmitted through ultra thin polymeric carbon membranes. Surprisingly, two distinct exit charge state distributions accompanied by charge ex- change dependent kinetic energy losses are observed. The energy loss for ions exhibiting large charge loss shows a quadratic dependency on the incident charge state, indicating that equilibrium stopping force values do not apply in this case. The combination of charge transfer and kinetic energy loss measurements allows us to link the two differ- ent exit charge state distributions to ion trajectories through distinct local electron densities distributions in the membrane.
  • Lecture (Conference)
    Frühjahrestagung der Deutschen Physikalischen Gesellschaft - Sektion Festkörperphysik, 31.03.-04.04.2014, Dresden, Deutschland
  • Poster
    73th IUVSTA Workshop on Nanostructures on two-dimensional solids, 22.-26.09.2014, Eisenerz, Österreich
  • Lecture (Conference)
    Ionenstrahlworkshop 2014, 20.-22.07.2014, Paderborn, Deutschland
  • Lecture (Conference)
    Physics on a Boat, 03.-05.06.2014, Helsinki, Finnland
Registration No. 21258

Ion beam synthesis for hybrid nanoelectronics: beyond silicon limits
Prucnal, S.; Lugstein, A.; Glaser, M.; Helm, M.; Zhou, S.; Skorupa, W.
Abstract: A key milestone for the next generation of high-performance nanoelectronic devices is the monolithic integration of III-V compound semiconductor materials with silicon technology. The incorporation of different functional III-V nano- and optoelectronic elements on a single chip enables performance progress, which can overcome the downsizing limit in silicon technology. Conventionally, the integration of III-V semiconductors with Si is based on the heteroepitaxial growth of multi-layered structures on Si or a variety of wafer bonding techniques. Devices based on such structures combine the high carrier mobility and high luminescence efficiency of III-V semiconductors with the advantages of well-developed silicon technology. We have shown that the ion beam implantation technique (fluences of 1x1016 ion/cm2 to 4x1016 ion/cm2) followed by millisecond-range flash lamp annealing can be successfully utilised for the fabrication of different Si/III-V heterojunctions on bulk Si and SOI substrates [1-3]. Recently, we have extended the application of ion beam implantation followed by ms liquid-phase processing into the fabrication of hybrid 1D materials. We have demonstrated axial heteronanowires consisting of III-V compound semiconductor and Si using advanced processing steps of silicon technology [4]. The clou of this approach is the phase formation within milliseconds via the liquid phase leading to excellent crystalline properties in the volume and at the interface of the nanocrystals. This paves the way for a hybrid 1D nano-/optoelectronics with high-mobility and optically active materials, compatible to standard Si technology. Moreover, this kind of processing on the nanoscale could lead to a renewed interest in the field of ion beam synthesis. 1. S. Prucnal, et al., Nano Lett. 11, 2814 (2011). 2. S. Prucnal, et al., Nanotechnology 23, 485204 (2012). 3. S. Prucnal, et al., J. Appl. Phys. 115, 074306 (2014). 4. S. Prucnal, et al., Nano Research, submitted (2014).
Keywords: III-V, ion implantation, liquid-phase processing, FLA
  • Lecture (Conference)
    19th International Conference on Ion Beam Modification of Materials (IBMM 2014), 14.-19.09.2014, Leuven, Belgium
Registration No. 21257

OFOCell concept for low cost silicon photovoltaics
Prucnal, S.; Skorupa, W.
Abstract: The incredible growth rates of the PV solar industry have allowed manufacturing efficiencies that are unheard of in other industries. Nowadays in the solar cells industry the main effort is directed to the cost reduction of the solar panels fabrication which will decrease the average price per kWh from presence 0.20 €/kWh down to 0.07 €/kWh in 2020. Generally it is realized by using much cheaper polycrystalline wafers, reduction of the overall wafer thickness and/or simplification of the production complexity. We propose the simplification of the production process of silicon solar cells using only one step millisecond annealing for the whole solar cell processing and replacing standard phosphorous thermal diffusion by plasma immersion ion implantation. Our technology can be directly transferred to an in-line production process leading to significant cost reduction and decreasing the amount of chemicals used during solar cell manufacturing. Due to one step millisecond range flash lamp annealing (FLA) the overall thermal budget needed for the solar cell fabrication is significantly reduced. Moreover the emitter formed by ion implantation and FLA is clean and allows the precise control of the dopant concentration and width of the p-n junction.
Keywords: FLA, solar cells, silicon
  • Poster
    E-MRS 2014 SPRING MEETING, 26.-30.05.2014, Lille, France
Registration No. 21256

Purification of SoG silicon by millisecond range internal gettering of metal impurities
Prucnal, S.; Bregolin, F. L.; Krockert, K.; Wiesenhütter, U.; Skorupa, W.
Abstract: Cost reduction is the overall goal in the further development of the photovoltaic technologies. The solar-grade (SoG) mc-Si produced by upgrading metallurgical-grade silicon is an attractive material for low-cost solar cells. The remaining impurities after the purification process, mainly transition metals, are the main obstacle towards highly efficient solar cells, effectively limiting the minority carrier lifetime. Here we propose a novel method for the purification of SoG silicon by a millisecond range low thermal budget internal gettering process. The solar cells were produced by Plasma Immersion Ion Implantation of phosphorous using PH3 gas source and millisecond range Flash Lamp Annealing (ms-FLA). To study the metal distribution during ms-FLA, Cz-Silicon wafer were intentionally doped with iron. An influence of different thermal treatments on the diffusion of iron and the optoelectronic properties of metal contaminated silicon wafers were investigated by RBS, cross-section TEM, Raman spectroscopy, photoluminescence and surface photovoltage spectroscopy. We have shown that diffusion of metal impurities into the space charge region can be avoided by an one step ms-FLA step, only. It will be presented that the implanted phosphorous is electrically activated and all defects introduced into silicon during the ion implantation process are removed while metal impurities are kept far away from the p-n junction region. The effect of hydrogen co-implanted with phosphorous on the redistribution of iron will be explored. ms-FLA is demonstrated here as a very promising technique for the emitter formation in SoG silicon using an low thermal budget, only.
Keywords: Si, solar cells, FLA, photovoltaics
  • Lecture (Conference)
    E-MRS 2014 SPRING MEETING, 26.-30.05.2014, Lille, France
Registration No. 21255

Improved SoG silicon substrates produced by internal gettering of metal impurities induced by millisecond-range flash lamp annealing
Bregolin, F. L.; Prucnal, S.; Krockert, K.; Mathey, A.; Wiesenhütter, U.; Skorupa, W.
Abstract: The research highlights for the further development of silicon based solar cell technologies focus on the cost reduction by applying inexpensive materials such as Solar Grade Multicrystalline Silicon (SoG mc-Si) and/or the simplification of the production process. Replacement of standard diffusion based doping by ion implantation reduces two of the solar cell production steps: elimination of the phosphosilicate glass (PSG) cleaning and edge isolation steps. Although ion implantation doping got very recently distinct consideration for doping of monocrystalline solar material, efficient doping of multicrystalline solar material remains the main challenge to reduce the costs. The usefulness of the plasma immersion ion implantation system (PIII) combined with advanced flash lamp annealing (FLA) was already validated. We have shown that within the millisecond annealing time, implanted phosphorous is electrically activated and silicon is recrystallized. Simultaneously, the diffusion of metal impurities and their activation is suppressed.
Keywords: Multicrystalline Silicon, flash lamp annealing , plasma immersion ion implantation
  • Lecture (Conference)
    X-th International Conference Ion Implantation and other Applications of Ions and Electrons, 23.-26.06.2014, Kazimierz Dolny, Poland
Registration No. 21254

Hyperdoping of semiconductors by ion implantation and ultrafast annealing: solid vs. liquid phase epitaxy
Prucnal, S.; Gao, K.; Skorupa, I.; Liu, F.; Skorupa, W.; Zhou, S.
Abstract: Hyperdoped semiconductors exhibit exotic physical properties opening new routes for the fabrication of highly-sensitive photodetectors, intermediate band solar cells and ultra-fast nanoelectronics. The engineering of the electronic band structure in semiconductors by hyperdoping allows the strong enhancement of the below-band-gap photocurrent generation, insulator-to-metal transition (IMT) or creation of new magneto-optoelectronic devices. Hyperdoping requires an incorporation of foreign elements into the lattice side of the semiconductor far above the solid solubility limits. To this day the hyperdoping was realised either by the low-temperature molecular beam epitaxy or by the femtosecond or nanosecond liquid phase epitaxy during laser annealing. Here, we propose the novel millisecond range solid phase epitaxy performed by the flash lamp annealing (FLA) technique with a time range in between rapid thermal annealing and laser melting. The FLA was successfully utilised to fabricate ferromagnetic GaMnAs alloys with excellent optical properties, an IMT in the chalcogen doped Si with a substitutional rate higher than 70% or highly-conductive TCO (aluminium doped ZnO). Experimental data show that ion implantation followed by the millisecond range FLA is a cost-effective and high-throughput alternative for the processing of the hyperdoped semiconductors with outstanding properties.
Keywords: Hyperdoping, Si, GaAs, insulator-to-metal transition
  • Invited lecture (Conferences)
    ION 2014 - X-th International Conference on Ion Implantation and Other Applications of Ions and Electrons, 23.-26.06.2014, Kazimierz Dolny, Poland
Registration No. 21253

Utilization of flash lamp annealing for processing of low-cost TCO layers
Mathey, A.; Prucnal, S.; Wiesenhütter, K.; Vines, L.; Lindberg, P.; Svensson, B.; Bregolin, F. L.; Skorupa, W.
Abstract: Aluminum-doped zinc oxide (AZO) is one of the most promising transparent conductive oxides (TCO) characterized by low resistivity, high transparency and most of all, by low cost of fabrication. AZO thin-films were deposited on p-type Si wafers via r.f. magnetron sputtering either at room temperature or at 400 oC and subsequently annealed in the millisecond-range, utilizing flash lamp annealing (FLA). Here, we have investigated the influence of the deposition parameters and post-deposition FLA treatment on the optoelectronic properties of the AZO layer. It is shown that the millisecond range flash lamp annealing significantly enhances the electrical activation of Al and suppresses secondary phase formation during post-deposition annealing. Moreover, the optoelectronic and microstructural properties of the FLA treated samples are independent on the deposition temperature. This, in turn opens the possibility for a further, highly-desired cost reduction of the overall fabrication process. The FLA technique is cost-effective and a high-throughput alternative for processing of AZO films.
Keywords: AZO, flash lamp annealing, magnetron sputtering
  • Poster
    ION 2014 X-th International Conference on Ion Implantation and Other Applications of Ions and Electrons, 23.-26.06.2014, Kazimierz Dolny, Poland
Registration No. 21252

Influence of Flash Lamp Annealing on the Optical Properties of CIGS Layer
Prucnal, S.; Jiao, F.; Reichel, D.; Zhao, K.; Cornelius, S.; Turek, M.; Pyszniak, K.; Drozdziel, A.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: Copper indium gallium diselenide (CIGS) becomes more significant for solar cell applications as an alternative to silicon. The quality of the layer has a critical impact on the final efficiency of the solar cell. An influence of the post-deposition millisecond range flash lamp annealing on the optical and microstructural properties of the GIGS films was investigated. Based on the Raman and photoluminescence spectroscopy, it is shown that flash lamp annealing reduces the defect concentration and leads to an increase of the photoluminescence intensity by a factor of six compared to the nonannealed sample. Moreover, after flash lamp annealing the degradation of the photoluminescence is significantly suppressed and the absolute absorption in the wavelength range of 200-1200 nm increases by 25%.
Keywords: CIGS, flash lamp annealing, solar cells, photoluminescence Registration No. 21251

III–V semiconductor nanocrystal formation in silicon nanowires via liquid-phase epitaxy
Prucnal, S.; Glaser, M.; Lugstein, A.; Bertagnolli, E.; Stöger-Pollach, M.; Zhou, S.; Helm, M.; Reichel, D.; Rebohle, L.; Turek, M.; Zuk, J.; Skorupa, W.
Abstract: Direct integration of high-mobility III-V compound semiconductors with existing Si based CMOS processing platforms presents a main challenge to increase the CMOS performance and the scaling trend. Silicon hetero-nanowires with integrated III-V segments are one of the most promising candidates for advanced nano-optoelectronics as first demonstrated using molecular beam epitaxy techniques. Here we demonstrate a novel route for InAs/Si hybrid nanowire fabrication via millisecond range liquid-phase epitaxy regrowth using sequential ion beam implantation and flash-lamp annealing. We show that such highly mismatched systems can be monolithically integrated within a single nanowire. Optical and microstructural investigations confirm the high quality hetero-nanowire fabrication coupled with the formation of atomically sharp interface between Si and InAs segments. Such hybrid systems open new routes for future high-speed and multifunctional nanoelectronic devices on a single chip.
Keywords: liquid phase epitaxy, InAs, heteronanowires, silicon, ion implantation Registration No. 21250

Optoelectronic properties of ZnO film on silicon after SF6 plasma treatment and milliseconds annealing
Prucnal, S.; Gao, K.; Zhou, S.; Wu, J.; Cai, H.; Gordan, O. D.; Zahn, D. R. T.; Larkin, G.; Helm, M.; Skorupa, W.
Abstract: Zinc oxide thin film is one of the most promising candidates for the transparent conductive layer in microelectronic and photovoltaic applications, due to its low resistivity and high transmittance in the visible spectral range. In this letter we present optoelectronic and structural properties of fluorine doped ZnO films deposited at low temperature on a silicon substrate. The fluorine doping was made by post-deposition SF6 plasma treatment and activation by the millisecond range flash lamp annealing. Both the microstructural and optical investigations confirm the formation of a high-quality, highly-doped n-type ZnO layer. The current-voltage characteristics show a heterojunction between n++-ZnO and Si. Moreover, it is shown that the SF6 plasma treatment efficiently passivates the surface state and bulk defects in the ZnO film.
Keywords: ZnO, plasma immersion ion implantation, pulsed laser deposition, flash lamp annealing, SF6 Registration No. 21249

Increased evidence for the prognostic value of primary tumor asphericity in pretherapeutic FDG PET for risk stratification in patients with head and neck cancer
Hofheinz, F.; Lougovski, A.; Zöphel, K.; Hentschel, M.; Steffen, Ingo G.; Apostolova, I.; Wedel, F.; Buchert, R.; Baumann, M.; Brenner, W.; Kotzerke, J.; van den Hoff, J.
Abstract: Purpose

In a previous study, we demonstrated the first evidence that the asphericity (ASP) of pretherapeutic FDG uptake in the primary tumor provides independent prognostic information in patients with head and neck cancer. The aim of this work was to confirm these results in an independent patient group examined at a different site.

Methods

FDG-PET/CT was performed in 37 patients. The primary tumor was delineated by an automatic algorithm based on adaptive thresholding. For the resulting ROIs, the metabolically active part of the tumor (MTV), SUVmax, SUVmean, total lesion glycolysis (TLG) and ASP were computed. Univariate Cox regression with respect to progression free survival (PFS) and overall survival (OS) was performed. For survival analysis, patients were divided in groups of high and low risk according to the parameter cut-offs defined in our previous work. In a second step, the cut-offs were adjusted to the present data. Univariate and multivariate Cox regression was performed for the pooled data consisting of the current and the previously described patient group (N = 68). In multivariate Cox regression, clinically relevant parameters were included.

Results

Univariate Cox regression using the previously published cut-off values revealed TLG (hazard ratio (HR) = 3) and ASP (HR = 3) as significant predictors for PFS. For OS MTV (HR = 2.7) and ASP (HR =
5.9) were significant predictors. Using the adjusted cutoffs MTV (HR = 2.9/3.3), TLG (HR = 3.1/3.3) and ASP (HR = 3.1/5.9) were prognostic for PFS/OS. In the pooled data, multivariate Cox regression revealed a significant prognostic value with respect to PFS/OS for MTV (HR = 2.3/2.1), SUVmax (HR = 2.1/2.5), TLG (HR = 3.5/3.6), and ASP (HR = 3.4/4.4).

Conclusions

Our results confirm the independent prognostic value of ASP of the pretherapeutic FDG uptake in the primary tumor in patients with head and neck cancer. Moreover, these results demonstrate that ASP can be determined unambiguously across different sites

Keywords: PET; FDG; Head and neck cancer; Tumor heterogeneity; Asphericity; Prognostic value Registration No. 21248

The influence of different signal-to-background ratios on spatial resolution and F18-FDG-PET quantification using point spread function and time-of-flight reconstruction
Rogasch, J. M. M.; Hofheinz, F.; Lougovski, A.; Furth, C.; Ruf, J.; Großer, O. S.; Mohnike, K.; Hass, P.; Walke, M.; Amthauer, H.; Steffen, I. G.
Abstract: Background

F18-fluorodeoxyglucose positron-emission tomography (FDG-PET) reconstruction algorithms can have substantial influence on quantitative image data used, e.g., for therapy planning or monitoring in oncology. We analyzed radial activity concentration profiles of differently reconstructed FDG-PET images to determine the influence of varying signal-to-background ratios (SBRs) on the respective spatial resolution, activity concentration distribution, and quantification (standardized uptake value [SUV], metabolic tumor volume [MTV]).

Methods

Measurements were performed on a Siemens Biograph mCT 64 using a cylindrical phantom containing four spheres (diameter, 30 to 70 mm) filled with F18-FDG applying three SBRs (SBR1, 16:1; SBR2, 6:1; SBR3, 2:1). Images were reconstructed employing six algorithms (filtered backprojection [FBP], FBP + time-of-flight analysis [FBP + TOF], 3D-ordered subset expectation maximization [3D-OSEM], 3D-OSEM + TOF, point spread function [PSF], PSF + TOF). Spatial resolution was determined by fitting the convolution of the object geometry with a Gaussian point spread function to radial activity concentration profiles. MTV delineation was performed using fixed thresholds and semiautomatic background-adapted thresholding (ROVER, ABX, Radeberg, Germany).

Results

The pairwise Wilcoxon test revealed significantly higher spatial resolutions for PSF + TOF (up to 4.0 mm) compared to PSF, FBP, FBP + TOF, 3D-OSEM, and 3D-OSEM + TOF at all SBRs (each P < 0.05) with the highest differences for SBR1 decreasing to the lowest for SBR3. Edge elevations in radial activity profiles (Gibbs artifacts) were highest for PSF and PSF + TOF declining with decreasing SBR (PSF + TOF largest sphere; SBR1, 6.3%; SBR3, 2.7%). These artifacts induce substantial SUVmax overestimation compared to the reference SUV for PSF algorithms at SBR1 and SBR2 leading to substantial MTV underestimation in threshold-based segmentation. In contrast, both PSF algorithms provided the lowest deviation of SUVmean from reference SUV at SBR1 and SBR2.

Conclusions

At high contrast, the PSF algorithms provided the highest spatial resolution and lowest SUVmean deviation from the reference SUV. In contrast, both algorithms showed the highest deviations in SUVmax and threshold-based MTV definition. At low contrast, all investigated reconstruction algorithms performed approximately equally. The use of PSF algorithms for quantitative PET data, e.g., for target volume definition or in serial PET studies, should be performed with caution
- especially if comparing SUV of lesions with high and low contrasts.

Keywords: FDG-PET/CT reconstruction; PSF; TOF; Spatial resolution; Metabolic tumor volume delineation; Signal-to-background ratio; Radial activity concentration profile; Gibbs artifact; Ringing artifact; Gibbs phenomenon Registration No. 21247

Spin coated targets for filamentation studies
Kraft, S.
Abstract: In our presentation we report on the experimental observation of spatially modulated proton beams.
  • Lecture (Conference)
    Targert Fabrication Workshop 5, 06.-11.07.2014, St. Andrews, Great Britain
Registration No. 21246

Status of laser ion acceleration at HZDR
Kraft, S.
Abstract: Within the last years, numerous activities in laser particle acceleration have been taken place at the 100TW ultra-short pulse Laser system Draco at HZDR. Special emphasis was laid on developing an ion beam suitable for applications. In order to achieve high proton energies various approaches such as mass limited targets and active pre-plasma formation have been tested.

Recently, the laser is upgraded to a dual beam system delivering 30f pulses with 100TW as well as synchronized 1PW pulses. The talk will give an overview over the particle acceleration activities focussing on Laser ion acceleration as well as a current status of the laser upgrade in Dresden.
  • Invited lecture (Conferences)
    Seminar der Plasmaphysik, 12.11.2014, Darmstadt, Deutschland
Registration No. 21245

Uranium sorption on montmorillonite at high ionic strengths: Surface complexation modelling
Fritsch, K.; Schmeide, K.
Abstract: The current results of surface complexation modelling of U(VI) complexes on montmorillonite in NaCl and a NaCl/CaCl2/MgCl2 mixed electrolyte of high ionic strength are presented.
Keywords: uranium sorption, argillaceous rock,clay, uranium, montmorillonite, high ionic strength, surface complexation modelling
  • Lecture (others)
    7. Workshop des Verbundprojekts „Rückhaltung endlagerrelevanter Radionuklide im natürlichen Tongestein und in salinaren Systemen“, 28.-29.10.2014, Saarbrücken, Deutschland
Registration No. 21240

Simulations of precessing flows in cylindrical geometry
Giesecke, A.
Abstract: no abstract available
Keywords: Precession DRESDYN DYNAMO
  • Lecture (Conference)
    MHD Days 2014, 02.-03.12.2014, Potsdam, Germany
Registration No. 21239

Radiolabelling of colloids for highly sensitive detection in transport studies Vortrag im Rahmen des BELBaR WP2 und WP4 Projekttreffens, 30.-31. Oktober, Prag
Hildebrand, H.; Schymura, S.; Kulenkampff, J.; Lippmann-Pipke, J.; Franke, K.
Abstract: In dem Vortrag wurde für einen Teil des BELBaR Konsortiums ein Überblick über am HZDR/FSL vorhandene Radiomarkierungsmöglichkeiten für Kolloide bzw. Nanopartikel gegeben.
  • Lecture (others)
    Joined meeting of WP2 and WP4 within the EC project BELBaR, 30.-31.10.2014, Prag, Tschechische Republik
Registration No. 21238

Colloidal Probe Atomic Force Microscopy to determine the Floatability of Minerals in Ores
Rudolph, M.
Abstract: Flotation is without a doubt one of the major processes for the separation of fine minerals and it has been applied for more than a century. A key task of a successful flotation separation is to find the proper chemical treatment to selectively hydrophobize and thus float a certain mineral phase using molecules or ions referred to as collectors, depressants, regulators and frothers. Commonly floatability is determined by microflotation tests using the Hallimond tube with pure mineral phases. This method however requires the pure mineral phase which is very often not even taken from the same deposit which is going to be processed. In this paper we present a new approach to in-situ determine and even map the floatability of finely disseminated mineral phases within cross-sections of an ore. It is based on measuring hydrophobic effects using colloidal probe atomic force microscopy with a hydrophobic polystyrene probe based on force spectroscopy with a lateral resolution of only a few nanometers. Coupled confocal Raman spectroscopy on the same locality enables the identification of the mineral phase. We present the working principles of the method and show which signals in the force spectra characteristic for hydrophobic interactions can be used to define floatability and which can then be mapped as single quantities, e.g. jump-into-contact events due to nanobubble occurrence or parameters of the long range interaction curves most probably due to capillary effects.
A finely grained silicate ore containing the valuable rare earth mineral eudialyte from southern Sweden as well as pure samples of magnetite are presented as substrates to demonstrate the capability of this new approach.
This method will not only help to find the proper flotation chemistry but it can furthermore help in researching and unravelling problems of floatability within similar mineral phases.
  • Contribution to proceedings
    International Mineral Processing Congress 2014, 20.-24.10.2014, Santiago de Chile, Chile
    Proceedings of the XXVII International Mineral Processing Congress – IMPC 2014
Registration No. 21236

Subcritical bifurcation to turbulence in precessing flow
Gundrum, T.; Herault, J.; Steglich, C.; Giesecke, A.; Stefani, F.; Gerbeth, G.
Abstract: Subcritical bifurcation to turbulence in precessing flow in the water mockup for the DRESDYN Experiment
Keywords: Precession driven dynamo, Subcritical bifurcation, metastable transition
  • Lecture (Conference)
    MHD Days 2014, 02.-03.12.2014, Potsdam, Deutschland
Registration No. 21235

Interaction of uranium with isolated microorganisms of the former uranium mine Königstein (Saxony, Germany)
Gerber, U.; Krawczyk-Bärsch, E.; Arnold, T.; Stumpf, T.
Abstract: The uranium waste mine Königstein (Saxony, Germany) is heavily polluted with heavy metals, especially with uranium. Despite the high concentrations of heavy metals, the mine is a reservoir for many different microorganisms that have evolved special strategies to survive in these extreme environments. Their ubiquitous occurrence is of fundamental interest to understand the migration behavior of radionuclides within the biosphere. Furthermore, microorganisms are the beginning of the food chain, and therefore the transfer of bound uranium along this food chain could rise to a serious threat to human health. Biosorption of radionuclides especially uranium by microorganisms regulates the mobility of the metal in the environment. Thus, microorganisms could be used to clean-up contaminated soils, sediments, and waters by removing uranium and other radionuclides, due to bioremediation processes.
Keywords: Uranium, Königstein, Interaction, Microorganisms
  • Poster
    Projekttreffen TransAqua, 25.-27.11.2014, Karlsruhe, Deutschland
Registration No. 21230

Kontaminationsfreie Injektion von Radiotracern für die Prozesstomographie von Transportprozessen in Geomaterialien
Kulenkampff, J.
Abstract: Prozessverständnis und Modellierung von Transport in natürlichen geklüfteten oder porösen Geomaterialien (Böden, Gesteine) sind aufgrund der komplizierten geometrischen Randbedingungen auf der Mikroskala und der heterogenen Struktur und Zusammensetzung des Materials besonders schwierige Aufgaben. Gewöhnlich werden wie in weniger komplexen technischen Materialien, wie Filtern oder Reaktoren, einfache Modelle zur Beschreibung der Porzesse angewendet, die nur eine grobe Beschreibung der Prozesse erlauben und außerhalb ihres begrenzten Gültigkeitsbereichs versagen. Bei einer solchen Parametrisierung anhand von Durchbruchkurven wird das Material als Blackbox betrachtet und mit wenigen Parametern beschrieben (Abb. 1). Die Nutzung von Radioisotopen als Tracer für den mobilen Stoff ermöglicht Einblicke in den räumlich-zeitlichen Verlauf des Transports im Innern des opaken Versuchskörpers mit höchster Sensitivität und ohne chemische oder physikalische Rückwirkung auf den Prozess. Außerdem ist die einfache und selektive Detektierbarkeit geringster Konzentrationen von Radiotracern oft vorteilhaft. Präferentielle Transportwege, die Verzögerung des Transports durch Wechselwirkungen und gegebenenfalls auch die Immobilisierung der beobachteten Spezies im Versuchskörper können so erfasst werden (Abb. 2).
Es werden zylindrische Probekörper hergestellt (Durchmesser bis 30-100 mm, Länge 50-300 mm), mit Fluidanschlüssen an den Stirnflächen. Im Transportversuch wird kontinuierlich eine Trägerlösung mit Fließraten von 5 µL/min bis 5 mL/min injiziert. In Abhängigkeit vom Probenvolumen wird der Trägerlösung ein Tracerpuls (1-5 mL) hinzugefügt. Dieser Tracerpuls wird mit Positronen-Emissions-Tomographie quantitativ in seinem räumlich-zeitlichen Verlauf mit einer räumlichen Auflösung im Bereich von 1 mm erfasst. Für den Tracerpuls eingesetzte Aktivitäten betragen zwischen 1 MBq und 500 MBq. Sie werden mit einer Empfindlichkeit von 10 – 100 Bq/µL erfasst, was einer Sensitivität im picomolaren Bereich entspricht. Geeignete Radionuklide sind z.B. 18F, 124I, 64Cu, 58Co, 22Na mit Halbwertszeiten von Stunden bis Jahren. Mögliche Beobachtungszeiten sind etwa 10 Halbwertszeiten – also Tage bis Jahrzehnte.
Positronen-Emissions-Tomographie (PET) (Abb. 3) ist als höchst sensitive Methode der funktionellen medizinischen Diagnostik bekannt und wird vor allem in der Krebsdiagnostik und der biomedizinischen Forschung angewendet. Wegen des hohen Aufwandes gibt es wenige examplarische Anwendungen auf technischen Gebieten. Insbesondere wird PET in der Forschungsstelle Leipzig des HZDR seit über 10 Jahren erfolgreich für die Untersuchung von Prozessen in Geomaterialien eingesetzt (s. Literaturangaben).
Eine wichtige Rolle nimmt die zuverlässige Injektion des Tracers ein. Dabei sind Sicherheits- und Strahlenschutzaspekte zu berücksichtigen. Je nach Untersuchungsaufgabe werden unterschiedliche Pumpen eingesetzt (Schlauchpumpen, einfache Spritzenpumpen mit handelsüblichen Injektionsspritzen, HPLC-Pumpen, ISCO-Spritzenpumpen). Bei den zwei letzteren kann die Kontamination der Pumpe durch die Nutzung von Injektionsschleifen für den Radiotracer vermieden werden. Insbesondere bei langlebigen Tracern (58Co, 22Na) ist dabei aber besondere Vorsicht geboten.
Ergbebnis der Untersuchung sind zeitlich aufgelöste tomographische Darstellungen der Tracerkonzentration (Abb. 4). Hieraus lassen sich
- lokale Tracerverteilungen
- prozessabhängiges effektives Volumen
- effektiv wirksamer Anteil innere Oberfläche (bei Wechselwirkungen)
- Geschwindigkeitsverteilung
bestimmen. Gegenüber der Parametrisierung von Transportuntersuchungen durch Modellanpassung an Durchbruchkurven ergeben sich so verlässlichere real gemessenen Parametersätze und gleichzeitig eine bisher nicht erreichbare Verbesserung des Prozessverständnisses.

Literatur:
Richter, M., Gruendig, M., Zieger, K., Seese, A. and Sabri, O., 2005. Positron emission tomography for modelling of geochemical transport processes in clay. Radiochimica Acta, 93: 643-651.
Kulenkampff, J., Gründig, M., Richter, M. and Enzmann, F., 2008. Evaluation of positron-emission-tomography for visualisation of migration processes in geomaterials. Physics and Chemistry of the Earth, Parts A/B/C, 33(14–16): 937-942.
Wolf, M.; Kulenkampff, J.; Enzmann, F.; Gründig, M.; Richter, M.; Lippmann-Pipke, J.; Mittmann, H., 2010. 3D-Visualisierung und Quantifizierung von Fluidströmungen in Salinargestein mittels Positronen-Emissions-Tomographie. EDGG Exkursionsführer & Tagungspublikationen 244(2010), Hannover: Deutschen Gesellschaft für Geowissenschaften e.V.
Kulenkampff, J.; Gründig, M.; Korn, N.; Zakhnini, A.; Barth, T.; Lippmann-Pipke, J., 2013. Application of high-resolution positron-emission-tomography for quantitative spatiotemporal process monitoring in dense material. 7. World Congress on Industrial Process Tomography, 02.-05.09.2013, Krakow, Poland.
Bittner, L.; Kulenkampff, J.; Gründig, M.; Lippmann-Pipke, J.; Enzmann, F. , 2014. Direct Observation of Waterglass Impregnation of Fractured Salt Rock with Positron Emission Tomography. International Conference on the Performance of Engineered Barriers: Backfill, Plugs & Seals, 06.-07.02.2014, Hannover, Deutschland
  • Lecture (others)
    ISCO-Anwendertreffen, 09.12.2014, Potsdam, Deutschland
Registration No. 21229

Undesired air entrainment by vortex formation - experimental investigations on the resulting phase fraction distributions in a centrifugal pump using gamma-ray computed tomography
Schäfer, T.; Bieberle, A.; Neumann, M.; Hampel, U.
Abstract: Air entrainment may occur in situations, where water is conveyed from a reservoir. There hollow vortices may form as a consequence of low liquid level and pre-existing fluid swirling. Particularly, such a situation may be prevailing in nuclear power plants, e.g. when emergency cooling water is taken from a liquid reservoir, like the condensation chamber. Presence of gas in pumps may lead to abrasion at impeller blades, strong vibrations with damaging of bearings and loss of cooling for shaft and bearings and early fatigue as a consequence. At least it will lead to decreasing pump performance even to the point of abrupt collapse of flow rate. The presented work contributes quantitative measurements, visualizations and analyses of gas-liquid phase distributions to the fundamental understanding of the effects of air entrainment in centrifugal pumps. Advanced tomographic measuring methods with high spatial resolution were applied to investigate the two-phase distribution in the impeller region of an industrial centrifugal pump.
Keywords: gamma-ray computed tomography, centrifugal pump, gas entrainment, two-phase flow
  • Poster
    East German Centre of Competence in Nuclear Technology Workshop of Doctoral Candidates, 04.12.2014, Zittau, Deutschland
Registration No. 21226

P1313-Magnetisierbare Halbleiter und Oxide mit permanenter Magnetisierung, deren Herstellung und Verwendung
Schmidt, H.; Kaspar, T.; Bürger, D.; Skorupa, I.; Fiedler, J.
Abstract: Die Erfindung beschreibt die Herstellung und den Aufbau einer Anordnung mit mindestens einer Raumladungszone, bei der sich im Bereich der Raumladungszone magnetische Polaronen stabil ausbilden. Weiterhin beschreibt die Erfindung, die Integration und die Verwendung der Anordnung in einem Spin-FET, in einem Spin-Ventil und in einer Spin-LED.
  • Patent
    DE102013209278.4 - Offenlegung-20.11.2014; Nachanmeldung-WO
Registration No. 21221

PolCarr: Smart carriers for advanced manufacturing in biotechnology.
Wiesenhütter, K.; Urban, B.; Müller, M.; Müller, A.-D.; Skorupa, I.; Rüb, M.; Skorupa, W.; Schmidt, O. G.; Schmidt, H.
Abstract: Further development of intelligent, highly-efficient and low-cost concepts in biosensors is a prime drive of the dynamically expanding biotechnology industry. As majority of the available market for biosensors is based on the functionalization of substrates, new approaches offering carriers with superior performance i.e. with easy-to-control immobilization, modification, transport and detection of the target analytes are strongly required. Consequently, herein we propose a novel, promising concept for fabrication of the smart carriers (PolCarr) for diverse applications in biotechnology. The PolCarr substrate consists of a doped Si wafer with an ultra-thin insulating top layer and a characteristic pattern of surface near electrostatic forces (SNEF) [Baumgart 2009]. The selective binding and release of the electrically polarizable molecules onto the PolCarr medium is purely driven by SNEF [Schmidt 2013]. Though, chemical-covalent and biological immobilization mechanisms are widely used by conventional biotechnology industry, they suffer from limited control. In stark contrast, the physical interaction via SNEF offers an excellent degree of control on the mm-nm scale. By attaching a structured bottom electrode to a locally doped Si wafer and voltage altering, SNEF can be precisely modulated in the nm range. Since SNEF are characterized by excellent environmental stability, the PolCarr carriers can be successfully utilized under a broad-spectrum of environmental conditions i.e. temperature, pH and humidity. The exceptional functionality of PolCarr makes it a suitable medium for typical biotechnology processing e.g. autoclaving for sterilization, incubation for cell growth, and for cryogenic applications for shock freezing, where conventional substrates may undergo critical failure. Finally, as the PolCarr technology originates from a standard, well-established semiconductor manufacture [Skorupa and Schmidt Springer 2014], the exceptionally facile carrier processing allows for realization of significant throughput and overall cost-reduction. Based on the highly-desirable and unique features of the PolCarr technology presented above, we strongly believe that our concept constitutes a high-value solution to the challenges faced by state-of-the-art biotechnology industry and may have a decisive impact on design and development of carriers for biotechnological manufacturing [Müller in preparation].
To protect the valuable IP, patent applications were filed in 2011 and 2012. To commercialize the PolCarr technology, a spin-off company is planned.

Keywords: biotechnology, biomaterials immobilization, carrier materials, biosensors, tissue engineering, doped Si-wafer, surface-near electrostatic forces, semiconductor industry
  • Lecture (others)
    Bionection Partnering Conference for Technology Transfer in Life Sciences, 09.-10.10.2014, Dresden, Deutschland
Registration No. 21217

Advanced ms-annealing concepts for semiconducting oxides for PV applications.
Wiesenhuetter, K.; Lindberg, P.; Bregolin, F. L.; Prucnal, S.; Vines, L.; Mathey, A.; Wiesenhuetter, U.; Monakhov, E. V.; Svensson, B. G.; Skorupa, W.
Abstract: The demand for high performance PV devices has led to vast advances in novel concepts for highly efficient PV products to be realized. Transparent conductive oxides (TCO) is one of the materials with a great potential towards PV applications and their indium tin oxide (ITO) is an industry viable option. The excellent set of properties demonstrated by ITO are stipled by its high cost and as a result given impetus to scientists to research for cheaper materials as an alternative. Consequently, Al- and Ga-doped ZnO (AZO and GZO) were identified as attractive candidates to replace the ITO-based PV components. However, to simultaneously ensure a higher conversion of solar energy to electricity and a significant reduction of the processing costs, further improvements of the AZO characteristics need to be achieved. Herein the authors propose application of advanced, millisecond annealing technologies e.g. flash lamp annealing (FLA) for the fabrication of the enhanced quality AZO for PV industry. As it will be shown, FLA offers effective recrystallization of the as-processed AZO films, activation of the Al dopants and creation of a defect-depleted AZO/c-Si interface. Superior opto-electrical response of the fabricated semiconductor heterostructures is achieved as a result. The application of ultra-short annealing times and selective heating option lead to an extraordinary time and energy conservation, opening up novel and low cost fabrication strategies for innovative PV products.
Keywords: transparent conductive oxide, thin-films, Al-doped ZnO, millisecond flash lamp annealing, interface, PV applications
  • Invited lecture (Conferences)
    E-MRS Fall Meeting 2014, 15.-18.09.2014, Warszawa, Polska
Registration No. 21216

PolCarr®: Smart carriers for advanced nano-sensors and tissue engineering applications.
Wiesenhütter, K.; Urban, B.; Müller, M.; Müller, A.-D.; Skorupa, I.; Rüb, M.; Skorupa, W.; Schmidt, O. G.; Schmidt, H.
Abstract: Further development of intelligent, highly-efficient and low-cost concepts in biosensors is a prime drive of the dynamically expanding biotechnology industry. As majority of the available market for biosensors is based on the functionalization of substrates, new approaches offering carriers with superior performance i.e. with easy-to-control immobilization, modification, transport and detection of the target analytes are required. Consequently, herein we propose a novel concept for fabrication of the smart carriers (PolCarr®) for diverse applications in biotechnology e.g. nano-sensors. The PolCarr® substrate consists of a doped Si wafer with an ultra-thin insulating top layer and a characteristic pattern of surface near electrostatic forces (SNEF). The selective binding and release of the electrically polarizable molecules onto the PolCarr® medium is purely driven by SNEF. Due to the excellent control degree at both the nm- and µm-range and the superb inertness of SNEF to environmental conditions, the PolCarr® carriers are very attractive candidates for tissue engineering and regenerative medicine, as they allow for directed cell growth. The exceptional functionality of PolCarr® makes it a suitable medium for typical biotechnology processing e.g. autoclaving for sterilization. As the PolCarr® technology originates from a standard semiconductor manufacture, the exceptionally facile carrier processing offers realization of significant throughput and overall cost-reduction.
Keywords: biotechnology, biosensors, controlled cell growth, carriers, biomaterials immobilization, doped-Si wafer, semiconductors manufacturing, surface-near electrostatic forces
  • Lecture (Conference)
    E-MRS Fall Meeting 2014, 15.-18.09.2014, Warszawa, Polska
Registration No. 21215

Surface solid and liquid phase processing in the ms-range using flash lamp annealing.
Wiesenhütter, K.; Schumann, T.; Prucnal, S.; Bregolin, F.; Wutzler, R.; Reichel, D.; Mathey, A.; Zichner, R.; Lindberg, P.; Vines, L.; Wiesenhütter, U.; Svensson, B. G.; Skorupa, W.
Abstract: Annealing is one of the oldest methods utilized by mankind for the manufacture of materials. Over the past millennium, thermal processing has evolved from its simple form to a highly sophisticated, mature technology. However, to meet modern requirements for novel, high performance products and to respond to dynamic progress in technology, new concepts in heat treatment that allow realization of innovative materials structures with superior functionality are required. Consequently, herein we demonstrate a successful application of ultra-short millisecond flash lamp annealing (for short FLA) for surface solid and liquid phase processing of advanced materials fabricated in the form of bulk, thin-films or complex nano-heterostructures [1]. Overall principles of FLA, the state-of-the-art facilities as well as selected FLA-applications developed at the HZDR will be presented. The ms-range FLA has already proven to be a highly promising alternative to standard heating technologies e.g. furnace annealing, which cannot meet the material-manufacture-property requirements imposed by modern devices e.g. large-area electronics printed on flexible, low-thermal budget media. As FLA enables a selective surface-near high temperature heating in ultra-short cycles, the high processing efficiencies with a substantial drop of the overall fabrication costs can be achieved. The numerous advantages of ms-range FLA are already widely exploited in the semiconductor industry. However, we believe there is still plenty of room for novel innovative applications of the ms-FLA to be identified and be successfully developed.
References
1. W. Skorupa and H. Schmidt, Springer Series in Materials Science, 192 (2014)

Keywords: millisecond flash lamp annealing, liquid phase processing, large-area electronics, thin-films, transparent conducting oxides, Al-doped ZnO, photovoltaics
  • Poster
    4th International Conference on Advances in Solidification Processes (ICASP-4), 08.-11.07.2014, Beaumont Estates, Old Windsor, United Kingdom
Registration No. 21214

Functionalization of Printed Metal-Particle Suspensions by Millisecond Thermal Processing.
Wiesenhütter, K.; Schumann, T.; Zichner, R.; Gebel, T.; Wiesenhütter, U.; Skorupa, W.
Abstract: The global quest towards novel, flexible and low-cost electronic products with functionality far beyond that offered by conventional size-restricted and rigid semiconductor devices, demands a rapid development of advanced material and deposition technology concepts. One of the most promising pathways to realize this ambitious goal is printed flexible electronics (PFE). Over the past years, printing has successfully demonstrated its potential for manufacture of manifold electronic products such as flexible displays, thin-film solar cells, large-area sensors etc. Importantly, by employing bendable, inexpensive media (e.g.: polymer foils, paper-like substrates) and high-throughput roll-to-roll (R2R) processing, a significant reduction of the overall costs associated with electronic device fabrication has been achieved.
Herein, we report on a successful application of ultra-fast millisecond flash lamp annealing (FLA) as a highly-attractive technique for the functionalization of Ag- and Cu-layers screen printed on low-thermal budget PET and paper-like media for e.g. antenna applications. The effect of the FLA parameters (i.e. pulse duration and energy density), on the substrate behavior as well as on the microstructure and electrical response of the as-flashed films was studied. A significant drop of the sheet resistance of the FL-treated layers as compared to the as-printed films was observed for the selected samples. As ms-FLA permits selective, near-surface heating, a damage of the sensitive substrates was avoided. Being highly-efficient (ultra-short), “non-destructive” (suitable for low-thermal tolerance flexible media) and compatible with R2R processing, FLA offers the realization of advanced PFE products.

Keywords: printed electronics, flash lamp annealing, roll-to-roll, flexible inexpensive substrates, Ag- and Cu-based inks
  • Poster
    E-MRS Spring Meeting 2014, 26.-30.05.2014, Lille, France
Registration No. 21213

Advanced AZO processing via flash lamp annealing.
Bregolin, F. L.; Lindberg, P.; Wiesenhütter, K.; Vines, L.; Prucnal, S.; Svensson, B.; Skorupa, W.
Abstract: Currently, indium tin oxide (ITO) is the most widely used transparent conductive oxide due to its outstanding properties. However, because of its high cost, several alternatives are being sought to replace it. Among them, the aluminum-doped zinc oxide (AZO) films are one of the most promising candidates for PV applications due their low resistivity, high transparency and most of all, their relative low cost of fabrication.
In this work, AZO films were deposited over Si wafers via r.f. magnetron sputtering and subsequently treated by millisecond-range flash lamp annealing (FLA). The fabricated layers were then characterized by sheet resistance, photoluminescence spectroscopy, X-ray diffraction and Hall effect measurements. The influence of the deposition temperature and FLA parameters on the microstructure and optoelectronic response of the AZO layers was studied in detail. It was demonstrated that the FLA technique significantly improves the electrical conductivity of the as-deposited AZO layers due to the Al activation, the increase in crystallinity as well as the passivation of defects and grain boundaries. In particular, the room temperature sputtered AZO films subsequently treated by FLA have shown performance characteristics similar to those sputtered at 400 ºC, opening the possibility for further cost reductions in the fabrication process. The FLA technique is a cost-effective and high-throughput alternative for the processing of Si-based heterojunction solar cells.

Keywords: Transparent Conductive Oxides, Al-doped ZnO, Flash Lamp Annealig, Photovoltaics
  • Poster
    E-MRS Spring Meeting 2014, 26.-30.05.2014, Lille, France
Registration No. 21212

PolCarr - Smarte Trägermaterialien für die Biotechnologie
Schmidt, H.; Wiesenhütter, K.; Teichmann, D.
Abstract: Das smarte Trägermaterial PolCarr® besteht aus dotiertem Silizium und umfasst eine isolierende Deckschicht sowie eine strukturierte Rückseitenelektrode. Die Dotierung des Siliziums verursacht die Ausbildung oberflächennaher, elektrostatischer Kräfte, deren Stärke und Richtung durch die Konzentration und Spezies der implantierten Ionen auf der Nanometer- bis Millimeterlängenskale kontrolliert eingestellt wird. Elektrisch polarisierbare Zellen oder Moleküle können an PolCarr® angezogen, ausgerichtet und immobilisiert werden.
Keywords: Trägermaterialien, Biosensoren, Zellwachstumsplatten
  • Lecture (others)
    Cross Cluster Cooperation-Projekt „C3-Saxony“, IDEA CALL zum 9. Silicon Saxony Day, 03.07.2014, Dresden, Deutschland
  • Lecture (others)
    Cross Cluster Cooperation-Projekt „C3-Saxony“ IDEA CALL zum 9. Silicon Saxony Day, 03.07.2014, Dresden, Deutschland
Registration No. 21211

Smart carriers for advanced nano-sensors and tissue engineering applications.
Wiesenhütter, K.; Skorupa, I.; Rüb, M.; Müller, M.; Skorupa, W.; Schmidt, O. G.; Schmidt, H.
Abstract: A paramount drive of the rapidly growing biotechnology sector is the further development of intelligent, highly-efficient and inexpensive concepts for biosensors. As the key component of a biochip platform, biosensors hold a responsibility for immobilization, modification, transport and detection of a variety of biological analytes broadly utilized in health care, food industry and environmental monitoring. To augment the overall biosensor performance, much effort has been dedicated to designate the new, superior carrier materials, which permit easy-to-control immobilization of the target analytes. Consequently, herein we do propose a novel, promising concept for the smart carriers’ fabrication which is named PolCarr. PolCarr consists of doped silicon wafers and ultra-thin insulating top layers and exploits surface-near electrostatic forces (SNEF) [1-2] for the selective adsorption of electrically polarizable bioanalytes and functionalized polymers [3]. The binding and release of molecules onto the PolCarr substrate is purely driven by SNEF. By attaching a structured bottom electrode to locally doped silicon wafers and by a careful voltage altering, the SNEF can precisely be controlled on the nm-length scale, enabling realization of new, advanced products for manifold medical applications (for instance: nano-sensors). Further on, the excellent control degree at both the nm- and µm-range and the superb inertness of SNEF to environmental influences make PolCarr carriers very attractive candidates for tissue engineering and regenerative medicine, as they allow the growth of the target cells in a highly-desirable ordered manner. As PolCarr permits exceptionally facile manufacture by ion implantation and thermal dopant activation [4] and as PolCarr is compatible with well-developed standard semiconductor processing, the significant throughput and overall cost-reduction associated with the entire carrier’s production and its subsequent use as an integral part of a medical device (e.g.: biochip), can be achieved. Considering the whole benefits offered by our smart carriers, we strongly believe that the PolCarr concept can thoroughly transform traditional biosensor- and tissue engineering-oriented technologies [5]. Finally, the unique selling points of the innovative and proprietary technology offer from our point of view a high value proposition compared to state of the art technology. In order to protect the valuable intellectual property, patent applications were filed in 2011 and 2012. For the future commercialization of the technology a spin-off company is planned. The start-up team is formed by an experienced business developer and key scientists. Cooperations for the biochip development are already established. In addition, the team is supported by technology transfer partners of the Helmholtz Zentrum Dresden Rossendorf. [1] Quantitative dopant profiling in semiconductors: A Kelvin probe force microscopy model, C. Baumgart, M. Helm, H. Schmidt, Phys. Rev. B 80 (2009) 085305. [2] Kelvin probe force microscopy in the presence of intrinsic local electric fields, C. Baumgart, A.-D. Müller, F. Müller, H. Schmidt, Phys. Stat. Sol. (A) 208 (2011) 777–789. [3] Kelvin probe force microscopy for characterizing doped semiconductors for future sensor applications in nano- and biotechnology, H. Schmidt, S. Habicht, S. Feste, A.D. Müller, O.G. Schmidt, Appl. Surf. Sci. 281 (2013) 24-29 (invited). [4] Subsecond Annealing of Advanced Materials Annealing by Lasers, Flash Lamps and Swift Heavy Ions (Eds.: Wolfgang Skorupa, Heidemarie Schmidt), Springer-Verlag, ISBN: 978-3-319-03130-9 (2014). [5] Selective polyelectrolyte adsorption at novel charge patterned carrier materials for future biosensor applications, M. Müller, B. Urban, A.-D. Müller, M. Rüb, K. Wiesenhütter, I. Skorupa, O.G. Schmidt, H. Schmidt, Materials (2014), in preparation (invited).
Keywords: Biotechnology, biosensors, tissue engineering, carriers, doped Si-wafers, Surface-Near Electrostatic Forces
  • Poster
    Saxon Biotechnology Symposium 2014, Dresden, 19.03.2014, Dresden, Deutschland
Registration No. 21210

Pressure-induced shift of energy levels and structural phase transition in CdSe/ZnS quantum dots
Tauch, J.; Braun, J. M.; Keller, J.; Hinz, C.; Haase, J.; Seletskiy, D. V.; Leitenstorfer, A.; Pashkin, A.
Abstract: Electronic band structure of CdSe/ZnS quantum dots under high pressures is studied using fluorescence spectroscopy. We observe a strong blue shift of about 50 meV/GPa for the emission line at 655 nm. At moderate pressures (below 3 GPa) this shift is linear and it is dominated by increase of the fundamental band gap of CdSe under pressure [1]. In contrast to bulk CdSe where the fluorescence is quenched above 3 GPa as a results of the phase transition into the rock-salt structure, the CdSe/ZnS quantum dots remain structurally stable up to 6.5 GPa. The shift of the fluorescence line below this pressure is strongly nonlinear with tendency to saturation. This behavior can be well described using the Murnaghan equation of state giving the deformation potential value of -3.5 eV.
The remarkably high pressure of the structural phase transition in the studied CdSe/ZnS quantum dots exceeds previously reported values for CdSe nanocrystals [2] and bulk CdSe [1]. Presumably, the wurtzite structure of the quantum dots is stabilized by the ZnS shell. This structural robustness together with the high fluorescence yield and the large pressure coefficient of the wavelength shift make CdSe quantum dots a promising alternative to bulk ruby crystals for precise pressure calibration at moderate pressures.

[1] W. Shan et al., Appl. Phys. Lett. 84, 67 (2004).
[2] S. H. Tolbert and A. P. Alivisatos, J. Chem. Phys. 102, 4642 (1995).

Keywords: quantum dots, high pressure, structural phase transition
  • Poster
    Pressure and Strain Effects in Correlated Electron Materials, 06.-10.10.2014, Dresden, Germany
Registration No. 21209
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