Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32227 Publications
Silicon nanocluster aggregation in SiO2:Si layers
Fitting, H.-J.; Fitting Kourkoutis, L.; Roushdey, S.; Zamoryanskaya, M. V.; Schmidt, B.;
Energy-filtered transmission electron microscopy (EFTEM) in combination with electron energy loss spectroscopy (EELS) and cathodoluminescence (CL) have been used to investigate Si+-implanted amorphous silicon dioxide layers and the formation of Si nanoclusters. Therefore, amorphous, thermally grown SiO2 layers on Si substrate were implanted by Siþ ions with an energy of 150 keV and a dose of 5x1016 ions/cm2 leading to an atomic dopant fraction of about 4 at%. Afterwards a post-implantation thermal annealing has been performed at temperatures Ta=700–1300 °C, for 60 min in vacuum. This thermal annealing leads to Si cluster formation and a change of the SiOx matrix from about x=1.923 to 1.929 connected with additional visible luminescence bands in the green-yellow region. CL spectra in the near infrared (NIR) region indicate such Si aggregation by appearance of an additional band in extension of the common NBOHC band at 1.9 eV towards the NIR region. This band shifts with increasing annealing temperatures of the implanted sample to lower energies, probably, due to cluster growth and quantum confinement effects.
Keywords: ion implantation, SiO2, silivium nanocluster, EFTEM

Publ.-Id: 14800 - Permalink


Mechanism of selective nano structure formation on pre-patterned surfaces
Numazawa, S.; Heinig, K.-H.;
A self-alignment of metal nanoclusters has been observed on ripple like pre-patterned oxidized Si surfaces by oblique angle electron-beam evaporation. During the metal deposition perpendicular to ripples the metal nanoclusters are grown on the slopes which point towards the evaporation source.The self-ordering of metal nanoclusters has not been observed for normal deposition and for low-angle deposition parallel to the ripple direction. This indicates that the features of the metal nanostructure depend strongly on the local deposition angle. With the 3D lattice kinetic Monte Carlo simulations we studied the process of silver deposition on pre-patterned surfaces. The experimentally observed Ag nanostructures could be reproduced by using the many-body potential to estimate the atomistic migration barriers. It was shown that the extremely short range of surface adatom migration causing low sticking probability together with a slope-dependent deposition rate promotes the localization of the Ag nanocluster nucleation distribution. Consequently, the observed selective Ag nano structure formation can be understood by the separation of the Volmer-Weber growth mode and the layer-by-layer growth mode due to the localized coalescence of clusters.
Keywords: Kinetic Monte-Carlo, nanopatterning
  • Lecture (Conference)
    10th International Conference on Computer Simulations of Radiation Effects in Solids COSIRES 2010, 19.-23.07.2010, Krakow, Poland

Publ.-Id: 14799 - Permalink


Ion induced surface pattern evolution described by combined TRIM and kinetic Monte-Carlo simulation
Liedke, B.; Heinig, K.-H.; Facsko, S.; Möller, W.;
Atomistic understanding of surface morphology evolution induced by ion beam sputtering is still strongly limited. Available continuum models cannot explain microscopic processes during ion beam irra-diation. On the other hand, so far atomistic simula-tions could not describe pattern dynamics in the spa-tiotemporal scales of experiments.
However, combined atomistic single ion impacts with continuum equations [1] gives a better under-standing of additional smoothing mechanisms, like an effective mass ‘downhill’ current induced by ballistic atomic drift [2][3].
We developed a novel program package which unifies the collision cascade with kinetic Monte-Carlo simulations. The 3D atom relocations were calculated in the Binary Collision Approximation (BCA), whereas the thermally activated relaxation of ener-getic atomic configurations as well as diffusive proc-esses were simulated by a very efficient bit-coded kinetic 3D Monte Carlo code.
Effects like ballistic mass drift or dependence of local morphology on sputtering yield are automati-cally included in the BCA approach. Distributions presented in Figure 1 show the mean preferential lo-cation of ad-atoms creation and the sputtering re-gions.
Low energy (up to 5 keV) ion a sputtering simula-tions have been performed on the simulation cell of about 17 million atoms, where irradiation fluence goes up to few 1018 cm-2. The pattern topography has been study by means of various intensive parameters like incidence angle (Fig. 2), ion beam energy, ion fluence, and migration energy of defects. Moreover, the scaling behaviour of surface roughness and pat-tern periodicity has been analysed.
Finally, we compare our results with experiments as well as with continuum theory.
[1] S. A. Norris and M. P. Brenner and M. J. Aziz J. Phys. Condens. Matter 21 (2009) 224017.
[2] G. Carter and V. Vishnyakov PRB 54 (1996) 17647.
[3] M. Moseler and P. Gumbsch and C. Casiraghi and A. C. Ferrari and J. Robertson Science 309 (2005) 1545.
Keywords: TRIM, kinetic Monte-Carlo, ion irradiation, ripple formation, scaling, crater function, surface mass current
  • Poster
    Workshop Ion Beam Physics, 29.-31.03.2010, FZD, Germany

Publ.-Id: 14798 - Permalink


Multiphysics program for ion-induced collision cascades and thermally activated phase separation: intermetallic nanolayers by interface mixing
Liedke, B.; Heinig, K.-H.; Facsko, S.; Möller, W.;
Recent developments in computational materials modelling methods have to provide a qualitatively new level of predictive power and insight into materials design. In nature, different physical processes govern simultaneously the evolution of systems. Due to the complexity of the individual processes, so far their simulations are performed separately. One key to computational progress is the multiphysical treatment in a single computer program package.
Here, we consider the evolution of interfaces under energetic ion irradiation. There, the physical process of collisional mixing is in competition with thermally activated diffusion and phase separation. We developed a novel program which treats both physical processes simultaneously. The 3D atom relocations were calculated in the Binary Collision Approximation (BCA), whereas the thermally activated relaxation of energetic, atomic configurations as well as diffusive processes, were simulated by a very efficient bit-coded kinetic 3D Monte Carlo code. Contrary to molecular dynamics simulations, our approach allows studies on experimental spatiotemporal scales.
As applications we present two extremes of interface mixing: (i) Irradiation of interfaces made by immiscible elements, here Al and Pb, with He ions causes ballistic interface mixing accompanied by phase separation. Al and Pb clusters, which form in the interface region, show self-ordering. (ii) Irradiation of interfaces made by metals which form intermetallics, here Pt and Co, with He ions causes the formation of nanometric intermetallic layers with the sequence Pt/Pt3Co/PtCo/PtCo3/Co across the former interface. In the element mapping perpendicular to the interface (e.g. by RBS measurements), this results in step-wise changes of Pt/Co concentrations. Novel magnetic properties of such sandwiched phases are expected. In particular, a very interesting magnetic behaviour of irradiated Pt/Co/Pt multilayers has been observed. It can be shown that the transition between out of plane and in-plane magnetic anisotropy can be triggered by ion beam irradiation, whereas computer experiment can be useful for understanding the physical mechanism.
Keywords: BCA, kinetic Monte-Carlo, collision cascade, ion irradiation, interface mixing, phase seperation, phase ordering, intermetallics
  • Lecture (Conference)
    COSIRES 2010, 19.-23.07.2010, Collegium Maximum Auditorium in Kraków, Poland

Publ.-Id: 14797 - Permalink


Mechanism of metal nanostructure self-ordering during oblique deposition on pre-patterned surfaces
Numazawa, S.; Heinig, K.-H.; Ranjan, M.; Facsko, S.;
By utilizing electron-beam evaporation, metal nanoclusters have been produced on pre-patterned oxidized Si surfaces. During the oblique deposition perpendicular to ripples the metal nanoclusters are grown on the slopes which point towards the evaporation source.The self-ordering of metal nanoclusters has not been observed for normal deposition and for low-angle deposition parallel to the ripple direction. This indicates that the features of the metal nanostructure depend strongly on the local deposition angle. Here, by means of 3D lattice kinetic Monte Carlo simulations, we studied the process of silver deposition on pre-patterned surfaces. The experimentally observed Ag nanostructures could be reproduced by using the many-body potential to estimate the atomistic migration barriers. It was shown that the extremely low sticking probability of deposited Ag together with a slope-dependent local deposition rate leads to a strongly localized Ag nanocluster nucleation distribution on the surface because the nucleation rate depends approximately on the dimer adatom concentration.
Keywords: Kinetic Monte-Carlo, nanopatterninig
  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion Kondensierte Materie (SKM) 2010, 21.-26.03.2010, Regensburg, Germany

Publ.-Id: 14796 - Permalink


Influence of corrosion processes on the head loss across ECCS sump strainers
Kryk, H.; Hoffmann, W.; Waas, U.;
Corrosion of hot-dip galvanized grating treads, installed in the containment, may exacerbate ECCS strainer clogging problems during LOCA incidents in LWR. In order to identify the corrosion mechanisms as well as the nature of particulate corrosion products formed, corrosion investigations were carried out in boric acid solutions as well as in demineralized water using hot-dip galvanized steel samples. For the related experiments, tailored bench-scale facilities have been constructed. The results of batch experiments as well as of long-time corrosion investigations in the KorrVA test facility at FZD suggest that there is a multi-stage corrosion process. The first stage comprises the dissolution of the Zn layer in the acidic coolant forming zinc ions, which can generate crystalline zinc borate in boric acid solutions, if the ion concentration exceeds the saturation concentration. The base material (steel) is cathodically protected as long as the zinc layer is present. During the second stage, a slight head loss rise may occur due to the release of hard zinc (Zn/Fe) particles. After the complete removal of the hard zinc layer, the base material dissolves forming insoluble corrosion particles similarly to a flow accelerated corrosion process, which can subsequently lead to acceleration of the strainer clogging. The main influences on corrosion were identified as jet impact, water chemistry and Zn surface / coolant volume ratio.
  • Kerntechnik 76(2011)1, 46-53

Publ.-Id: 14795 - Permalink


Einfluss von Korrosionsprozessen auf den Differenzdruck über die Sumpfansaugsiebe von Notkühlsystemen
Kryk, H.; Hoffmann, W.; Waas, U.;
Zur Aufklärung von Korrosionsprozessen und deren Auswirkungen auf die Verstopfung von mit Isoliermaterialfasern belegten Sumpfansaugsieben bei Kühlmittelverluststörfällen in Leichtwasserreaktoren wurden Korrosionsuntersuchungen in speziellen Laboranlagen unter Nutzung von feuerverzinkten Stahlproben durchgeführt. Die Ergebnisse der Batch- sowie der Langzeit-Korrosionsexperimente mit borsäurehaltigen Lösungen lassen auf einen mehrstufigen Korrosionsmechanismus schließen, wobei im ersten Schritt die Auflösung der Reinzinkschicht erfolgt. Die dabei entstehenden Zink-Ionen gehen in Lösung und tragen somit nicht signifikant zur Verstopfung der Sumpfansaugsiebe bei. Im weiteren Verlauf kann es zu einer leichten Differenzdruckerhöhung an den Sumpfsieben durch Ablösung von Partikeln aus der herstellungsbedingten darunterliegenden Hartzinkschicht (Zn/Fe-Legierung) kommen. Nach der kompletten Entfernung der Hartzinkschicht erfolgt eine strömungsinduzierte Korrosion des Basismaterials (Stahl), die zur Bildung unlöslicher Korrosionsprodukte des Eisens in Form kleiner Partikel führt. Diese Partikel lagern sich in die Isoliermaterialfasern an den Sumpfansaugsieben ein, was zu einer starken Erhöhung des Strömungswiderstandes führt. Der Differenzdruckanstieg beginnt, abhängig von den hydrodynamischen Bedingungen, 6 bis 15 Stunden nach Beginn der Beaufschlagung der Proben mit dem Leckwasserstrahl. Eine zweite (theoretische) Quelle für die Bildung partikelförmiger Produkte stellt die Kristallisation von Zinkborat aus einer übersättigten Lösung bei Temperaturerhöhung und/oder Verdampfung des Kühlmittels dar. Haupteinflussfaktoren des Gesamtprozesses sind die Aufprallkraft des Leckstrahls auf die Materialoberfläche, die Wasserchemie (Borsäurekonzentration, pH-Wert) sowie das Verhältnis der Korrosions-Oberfläche zum Kühlmittel-Volumen.
  • Lecture (Conference)
    KTG-Fachtagung „Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland“, 07.-08.10.2010, Dresden, Deutschland

Publ.-Id: 14794 - Permalink


Ion-implanted Silicon detectors ­ - Silicon Strip Detectors
Schmidt, B.; Haberjahn, M.; Lange, H.; Hanf, D.;
Demands on modern silicon detector technology and the detector development for improving analysis in the frame of the EU-Project SPIRIT will be described. For high energy resolution RBS and ERDA experiments large area silicon strip detector with increased sensitivity and energy resolution down to 10 keV FWHM (He+ at max. 2MeV) are required. By applying such strip detectors with certain position resolution kinematic correction procedures will be possible.
Keywords: Silicon radiation detectors, ion implantation, high resolution IBA
  • Lecture (Conference)
    1st SPIRIT Workshop on New detector technologies for advanced materials research using ion beam analysis, 25.-26.10.2010, Plitvice Lakes National Park, Croatia

Publ.-Id: 14793 - Permalink


Transition metal diffusion in diluted magnetic Si and GaAs prepared by pulsed laser processing
Bürger, D.; Seeger, M.; Zhou, S.; Skorupa, W.; Schmidt, H.;
Starting from a random or ordered distribution of 0.8, 1.6, 3.7 and 12.5 % dopants over the lattice sites of a simple cubic host lattice, we estimate the fraction of unclustered dopants after pulsed laser quenching of different host:dopant systems. Initial clustering events are simulated with a greedy algorithm implemented in a Monte-Carlo study. The greedy algorithm gives adequate results for dopants with low diffusity and low solubility.
The absolute initial dopant concentration and declustering strongly in influence the kinetics of clustering. Particularly, we consider transition metal doped Si and GaAs after pulsed laser annealing, which are of interest for spintronics applications. An uncritical integral diffusion of Mn in GaAs:Mn and a tendency of Mn to form silicides in Si:Mn are simulated. These results are in good agreement with experimental observations.
Keywords: diluted magnetic semiconductor, implantation, pulsed laser annealing, ferromagnetism, secondary phase formation, nanoscale clustering

Publ.-Id: 14792 - Permalink


Channeling as a means to obtain information on crystal quality and structure
Munnik, F.; Heller, R.;
Rutherford Backscattering Spectrometry (RBS) is an analysis technique that uses fast ions like He+ to obtain information about the chemical composition in the surface region. In case of crystalline samples, the ion beam can be aligned with the crystal orientation thereby allowing the ions to penetrate the sample much deeper than in a random direction. This results in a large reduction of the yield of backscattered ions, the so-called channeling dip. Information about crystal quality can be obtained from the width and the depth of the channeling dip. The position of atoms of a certain species in the crystal can de deduced from the yield reduction in various crystal orientations.

In this presentation, the basic principles of channeling are explained. Channeling can be used to obtain information about the position of impurities in a crystal and to assess damage caused by implantation and the quality of the crystal after subsequent annealing. Examples of these types of analysis are presented. Complementary PIXE (Particle Induced X-ray Emission) channeling can be applied to obtain information about elements that have a mass similar to the main elements, which cannot be measured with RBS. An example of PIXE channeling is also presented.
  • Invited lecture (Conferences)
    New detector technologies for advanced materials research using ion beam analysis, 25.-26.10.2010, Plitvice Lakes, Croatia

Publ.-Id: 14790 - Permalink


Hysteresis in the magneto-transport of Manganese-doped Germanium: evidence for carrier-mediated ferromagnetism
Bürger, D.; Zhou, S.; Baumgart, C.; Skorupa, W.; Timm, C.; Oesterlin, P.; Helm, M.; Schmidt, H.;
The III-V compound GaMnAs is considered as being the prototype diluted ferromagnetic semiconductor (FMS), exhibiting negative magneto-resistance (MR) and anomalous Hall-effect (AHE) related to carrier-mediated ferromagnetism. However, it would be very desirable to have a group-IV FMS, being compatible with silicon technology. In particular manganese-doped germanium prepared using low-temperature molecular beam epitaxy (LT-MBE) has been proven to be a very promising material [1]. Still, no direct correspondence between transport and magnetization data has been reported yet to date. We believe that the origin of these observations lies in the less effective substitution of Mn at Ge sites, which results in too low a hole concentration, making carrier-mediated ferromagnetism impossible. The hole concentrations realized in Ge:Mn grown by LT-MBE are mostly well below 1019 cm-3, which indicates the possible unsuitability of LT-MBE to achieve a large hole concentration in Ge:Mn.
In this contribution, we show that the hole concentration can be increased by two orders of magnitude, from 1018 to 1020 cm-3, through Mn-ion implantation into Ge followed by pulsed laser annealing [2]. This non-equilibrium technique allows the preparation of metastable materials with interesting material properties, e.g. diluted ferromagnetic GaMnAs [3]. In Mn-doped Ge with a hole-concentration of around 2.1×1020 cm-3, we observe that the longitudinal and the Hall resistance exhibit the same hysteresis as the magnetization at temperatures below 10 K. This hysteresis in magneto-transport is usually considered as a direct evidence of carrier-mediated ferromagnetism. We will present a comprehensive correlation between the magnetic, transport and structural properties of Ge:Mn samples with different hole concentrations, as well as a comparison with literature. Note that ion implantation followed by pulsed laser annealing is an established scalable chip technology and may have a significant industry impact.

[1] Y. D. Park et al., Science 295, 651 (2002); M. Jamet et al., Nature Mater. 5, 653 (2006).
[2] S. Zhou et al., Phys. Rev. B 81, 165204 (2010).
[3] D. Bürger et al., Phys. Rev. B 81, 115202 (2010).
  • Lecture (others)
    47. Punktdefekttreffen, 07.-08.10.2010, Dresden, Deutschland

Publ.-Id: 14789 - Permalink


Synchrotron Radiation in Materials Science
Baehtz, C.;
In Material Science (powder) diffraction methods are a common sample characterisation tool. Beside the laboratory sources synchrotron radiation offers the advantages of high brilliance and tuneable wavelength. As an example for high resolution diffraction the localisation of incorporated guest molecule in zeolites faujasite by crystal structure refinement will be presented.
Heavy load goniometer allows also experiments with high sophisticated sample environments to perform in-situ investigations. Hereby solid state reactions can be monitored or catalyst characterized. Carbon nano tubes (CNT) are synthesized by chemical vapour deposition and the use of iron nano particles. The catalyst processing and CNT synthesis was observed by XRD and the catalytic active species determinated.
By the use of hard X-rays absorption effects are minimized and more complex system like a secondary lithium ion battery can be investigated. Hereby the diffraction pattern of the system in operation can be collected. The charge-discharge behaviour of lithium manganese oxide will be discussed.
In general in-situ investigations have the advantage to monitor different processes directly and being more time efficient. Misleading results of ex-situ measurements by metastable phases, subsequent reactions or aging of the material are avoided.
Keywords: synchrotron radiation, in-situ investigation, zeolites, carbon nano tubes, lithium ion battery
  • Lecture (Conference)
    Seminarvortrag an der TU BA Freiberg, 03.05.2010, Freiberg, Germany

Publ.-Id: 14787 - Permalink


In-situ investigations at ROBL-MRH
Baehtz, C.; von Borany, J.; Wirth, C. T.; Bayer, B. C.; Hofmann, S.;
The last few years have seen an increasing interest in in-situ investigations using different diffraction methods. This is one of the main applications of the Material Research Station of the Rossendorf Beamline (ROBL) at the ESRF. The beamline operates with a monochromatic beam in the energy range of 6 to 36 keV and an energy resolution of ΔE/E of 5*10-4. Equipped with a six circle goniometer, different high temperature chambers can be mounted and various diffraction experiments can be performed, e.g. under controlled reaction conditions. A detector bank behind the goniometer allows the use of additional heavy weight detectors. One field of interest is the synthesis of carbon nanotubes (CNT) by chemical vapor deposition. Here, CNTs were grown from iron nanoparticles acting as the catalyst. The particles were formed by annealing Fe thin films with thicknesses ranging from 1-10 nm. The Fe films were evaporated on Si substrates covered with a SiO2 or Al2O3 buffer layer respectively. The splitting was initiated by annealing the initial Fe films at a temperature of up to 760°C in an Argon/Hydrogen atmosphere at ~200 mbar. The reducing atmosphere also removed initially amorphous iron oxide layers. The splitting temperature depends on the buffer layer, and the particle size of the formed nanocrystals depends on the initial film thickness of the pristine material. Adding acetylene (C2H2) to the gas stream initiated CNT-growth. Two different reaction pathways were observed. A very high α/γ iron ratio at high temperature under reducing atmosphere led to the formation of iron carbide when acetylene is added. If the ratio is around 1, no carbide was observed during CNT synthesis. SEM images show a comparable yield of CNTs in both scenarios. Therefore, the catalytic activity of iron carbide in this process is doubtful [1]. The influence of the buffer layer will be discussed. Thick Ni films (>170 nm) can be used to synthesize graphene also by chemical vapour deposition [2]. Compared with the usual increase of the lattice parameter with temperature due thermal expansion (measured at 5*10-6 mbar), an unusual increase of the the lattice parameter is observed when acetylene is introduced (at 2*10-3 mbar). Also, Rietveld refinement does not reveal any structural changes. This effect can only be explained by cracking of the acetylene molecules on the surface and subsequent carbon storage on interstitials. Upon cooling to room temperature, the differences in lattice parameter are negligible. These examples show that in-situ investigations are a powerful and versatile tool to monitor the deposition of nanosized materials from chemical processes.
Keywords: synchrotron radiation, carbon nano tubes
  • Lecture (Conference)
    12th European Powder Diffraction Conference, 27.-30.08.2010, Darmstadt, Germany

Publ.-Id: 14786 - Permalink


Interstitial nitrogen induced decomposition of austenitic stainless steel
Martinavičius, A.; Abrasonis, G.; Möller, W.;
The nature of the S phase in austenitic stainless steel (ASS) produced by incorporation of large amounts of nitrogen is investigated. The S phase has been produced by plasma nitriding of AISI 304L ASS at 400 °C for 30 h. The S phase structure was studied using a combination of global (X-ray diffraction (XRD), nuclear reaction analysis, glow discharge optical emission spectroscopy) and local (Conversion Electron Mössbauer, X-ray absorption near edge structure, extended X-ray absorption fine structure (EXAFS) spectroscopies) probe techniques. This combination of analytical methods allows direct comparison of the data obtained from atomic up to macroscopic levels. The results show that Fe, Cr and Ni have different local chemical environments: Cr is very similar to CrN, Fe is in a phase similar to Fe4N, while Ni stays metallic. The N coordination is by a factor of 3 higher around than around Fe while negligible around Ni. Three lattice parameters for Fe, Cr and Ni, and a large disorder have been detected by EXAFS analysis. None of these phases could be identified by XRD, except a set of broad peaks which are commonly attributed to the supersaturated nitrogen solid solution in the literature. It is suggested that the incorporation of interstitial nitrogen destabilizes homogeneous distribution of ASS constituents and leads to the segregation of elements with the zones rich in Cr and Ni being small and coherent with the Fe-rich matrix. The data provide strong evidence that the decomposition of the nitrogen saturated ASS is of spinodal nature. The findings of this work on S phase microstructure are correlated to mechanical, magnetic and electrochemical properties.
  • Lecture (Conference)
    Interaction'2010 "Radiation interaction with material and its use on technologies 2010", 20.09.10, Kaunas, Lithuania

Publ.-Id: 14785 - Permalink


In-situ Thin Film and Nano Structure Characterization at ROBL
Baehtz, C.; Jeutter, N.; Grenzer, J.; von Borany, J.;
The last few years have seen an increasing interest in in-situ investigations on thin filmor nano structured systems. The advantages of these methods are clear: The (x-ray)investigations are done at the time of the phase or structure formation. Misleading results of ex-situ investigation due to altering or decomposition of the sample were avoided, metastable intermediate states were observed and additionally these experiments are less time consuming.The presented experiments were carried out at Material Research Station of the instrument BM20 at ESRF that is operated by the Forschungszentrum Dresden- Rossendorf. Our experimental station focuses on in-situ studies using different X-Ray diffraction and scattering methods in the energy range of 6 to 30 keV. The experiments can be combined with XRF and electrical resistivity measurements on demand. Two different topics of synthesis and processing are given. First, results on the formation of isolated Ge nano particles with well defined size by disproportion of germanium oxides in a silicondioxid matrix at higher temperatures of corresponding multilayer system were presented. Such materials are potential candidates for solar cells, extending the working spectral range for energy conversion. The size and ordering of the Ge nano crystallite can be controlled by the layer thicknesses as well as growth and annealing temperatures. Different in-situ growth techniques like reactive DC magentron sputtering of Si and RF- sputtering of SiO2 are compared. Secondly, the phase behavior of different metal catalyst onto different buffer layers for the carbon nanotube and graphene synthesis will be shown and discussed. Hereby diffraction experiments under controlled and reactive atmosphere were performed. As shown by in-situ investigations process were characterized on-line and structural as well as functional properties are correlated directly with each other. This increases the comprehension of synthesis and processing of functional materials.
Keywords: synchrotron radiation, in-situ diffraction, magnetron sputtering
  • Lecture (Conference)
    Materials Science and Engineering 2010, 24.-26.08.2010, Darmstadt, Germany

Publ.-Id: 14784 - Permalink


Effects of volume mismatch and electronic structure on the decomposition of ScAlN and TiAlN solid solutions
Höglund, C.; Alling, B.; Birch, J.; Beckers, M.; Persson, P. O. Å.; Baehtz, C.; Czigány, Z.; Jensen, J.; Hultman, L.;
Thin solid films of metastable rocksalt structure (c-) Sc1−xAlxN and Ti1−xAlxN were employed as model systems to investigate the relative influence of volume mismatch and electronic structure driving forces for phase separation. Reactive dual magnetron sputtering was used to deposit stoichiometric Sc0.57Al0.43N (111) and Ti0.51Al0.49N (111) thin films, at 675 °C and 600 °C, respectively, followed by stepwise annealing to a maximum temperature of 1100 °C. Phase transformations during growth and annealing were followed in situ using x-ray scattering. The results show that the as-deposited Sc0.57Al0.43N films phase separate at 1000–1100 °C into nonisostructural c-ScN and wurtzite structure (w-) AlN, via nucleation and growth at domain boundaries. Ti0.51Al0.49N, however, exhibits spinodal decomposition into isostructural coherent c-TiN and c-AlN, in the temperature interval of 800–1000 °C. X-ray pole figures show the coherency between c-ScN and w-AlN, with AlN(0001)|| ScN(001) and AlN(01-10)|| ScN(1-10). First-principles calculations of mixing energy-lattice spacing curves explain the results on a fundamental physics level and open a route for design of novel metastable pseudobinary phases for hard coatings and electronic materials.
Keywords: magnetron sputtering, synchrotron radiation

Publ.-Id: 14783 - Permalink


Effect of Internal Interfaces on Hardness and Thermal Stability of Nanocrystalline Ti0.5Al0.5N Coatings
Rafaja, D.; Wuestefeld, C.; Baehtz, C.; Klemm, V.; Dopita, M.; Motylenko, M.; Michotte, C.; Kathrein, M.;
The effect of microstructure on the thermal stability and hardness of the cathodic arc evaporated Ti0.5Al0.5N coatings was investigated with the aid of the in-situ high-temperature X-ray diffraction experiments, which were accompanied by high-resolution transmission electron microscopy (HRTEM) and nanoindentation measurements. The microstructure of the coatings was modified through the choice of the bias voltage in the deposition process. It was found that the bias voltage affects strongly the uniformity of the local distribution of titanium and aluminum in the coatings. The nonuniform distribution of the elements contributes to the formation of lattice strains at the crystallite and phase boundaries. The lattice strains at the crystallite boundaries increase the hardness of the coatings; the lattice strains at the phase boundaries improve their thermal stability. A certain nonuniformity of the distribution of the metallic species in the coatings is regarded as advantageous. However, a great nonuniformity in the distribution of the metallic species accelerates the degradation of the coatings at high temperatures. As a measure for the nonuniformity of the distribution of the atomic species in the as-deposited (Ti, Al) N samples, the stress-free lattice parameter of fcc-(Ti, Al) N is suggested.
Keywords: hard coating, synchrotron radiation, internal interfaces

Publ.-Id: 14782 - Permalink


Formation of basal plane fiber-textured Ti2AlN films on amorphous substrates
Beckers, M.; Eriksson, F.; Lauridsen, J.; Baehtz, C.; Jensen, J.; Hultman, L.;
The synthesis of fiber-textured Ti2AlN(0001) films on SiO2 was characterized by in-situ and ex-situ X-ray scattering and Rutherford backscattering spectrometry. Ti2AlN was formed by solid-state reaction between sequentially deposited Ti and AlN layers. A deposition at 275 °C yields a Ti(0001) outof-plane orientation which is maintained for the following AlN(0001)/Ti(0001) layers. Annealing to 600 °C yields AlN decomposition and diffusion of Al and N into Ti, with consecutive transformation into Ti3AlN(111) and Ti2AlN(0001) plus AlN residuals. Despite preferred Ti2AlN(0001) out-ofplane orientation, the in-plane distribution is random, as expected from the self-organized pseudo-epitaxial growth.
Keywords: X-ray diffraction, thin films, growth, sputtering

Publ.-Id: 14781 - Permalink


Fano signatures in the intersubband THz response of GaAs/AlGaAs quantum wells after interband photoexcitation
Wagner, M.; Golde, D.; Stehr, D.; Schneider, H.; Helm, M.; Andrews, A. M.; Roch, T.; Strasser, G.; Kira, M.; Koch, S. W.;
THz spectroscopy on semiconductor heterostructures has revealed new insight in low-energy excitations such as intersubband transitions (ISTs). A microscopic analysis has to consider the true THz transitions, but also the so-called ponderomotive response as a charge current of carriers generated by the alternating classical electric field. In former experiments the ponderomotive contribution could only be seen rather indirectly [1].
Here, we directly study the interplay between ponderomotive contribution and true IST [2]. In our experiment we create electrons in the conduction band of an undoped GaAs/Al0.34Ga0.66As multiple quantum well by resonant interband excitation at the 1s heavy-hole exciton, using either a broad- or narrowband laser. Broadband THz pulses probe the IST and are detected by electro-optic sampling. The observed differential THz transmission transient as the pump-induced change in the transmitted THz field shows a strong beating. In the frequency domain this results in an intersubband resonance with a broad additional low-frequency peak. The line shape of this intersubband resonance strongly resembles a Fano-resonance with an undershoot at the low-frequency side and an asymmetric peak to higher frequencies. However, since we are able to measure differential transmission and total THz absorption separately, we find that the absorption does not show such a Fano-asymmetry, but reveals the expected Lorentzian-like line shape of the intersubband resonance. Especially, it is a single peak and therefore the beating in the time domain cannot originate from an adjacent second absorptive resonance next to the true intersubband resonance.
In our microscopic theory these features can be explained unambiguously by a phase-sensitive superposition of the true THz intersubband current and the ponderomotive current.
[1] J. R. Danielson et al. ,”Interaction of Strong Single-Cycle Terahertz Pulses with Semiconductor Quantum Wells“, Phys. Rev. Lett. 99, 237401 (2007).
[2] D. Golde et al., “Fano Signatures in the Intersubband Terahertz Response of Optically Excited Semiconductor Quantum Wells”, Phys. Rev. Lett. 102, 127403 (2009)
Keywords: intersubband, terahertz, Fano, ponderomotive
  • Poster
    ICPS 2010, 30th International Conference on the Physics of Semiconductors, 25.-30.07.2010, Seoul, Südkorea

Publ.-Id: 14780 - Permalink


Thallium distribution in sediments from the Pearl River Basin, China
Liu, J.; Wang, J.; Chen, Y.; Qi, J.; Lippold, H.; Wang, C.;
Thallium (Tl) is a rare element of high toxicity. Sediments sampled in three representative locations near industries utilizing Tl-containing raw materials from the Pearl River Basin, China, were analyzed for their total Tl contents and the Tl contents in four sequentially extracted fractions (i.e., weak acid exchangeable, reducible, oxidizable, and residual fraction). The results reveal that the total Tl contents (1.25–19.1 µg/g) in the studied sediments were slightly high to quite high compared with those in the Chinese background sediments. This indicates the apparent Tl contamination of the investigated sediments. However, with respect to the chemical fractions, Tl is mainly associated with the residual fraction (>60%) of the sediments, especially of those from the mining area of Tl-bearing pyrite minerals, indicating the relatively low mobility, and low bioavailability of Tl in these sediments. This obviously contrasts with the previous findings that Tl is mainly entrapped in the first three labile fractions of the contaminated samples. Possible reasons were given for the dominating association of Tl with the residual fraction (>95%) of the mining area sediments. The significant role of certain K-containing silicates or minerals of these sediments on retaining Tl in the residual fraction, discovered by this study, provides a special field of research opportunity for the Tl-containing wastewater treatment.
Keywords: Pearl River Basin, Sediment, Sequential extraction, Thallium

Publ.-Id: 14779 - Permalink


Östrogennachweis in wässrigen Lösungen mit Hilfe Silzium-basierter Lichtemitter
Cherkouk, C.;
In dieser Arbeit wurde ein Sensorkonzept mit Hilfe der Si-basierten Lichtemitter (MOSLED) zum Östrogennachweis in wässrigen Lösungen entwickelt. Das Sensorkonzept basiert auf einer direkten Fluoreszenzanalyse und besteht aus der Anordnung der Bio-Komponenten und dem Verfahren zu ihrer Herstellung sowie dem eigentlichen Meßverfahren. Die Anordnung besteht aus drei Teilen: die Funktionalisierung der MOSLED-Oberfläche, die Immobilisierung des hER-Rezeptors und die Herstellung der Referenzlösung. Den Schwerpunkt dieser Arbeit bildet die Ausführung dieser drei Teile.
Die Funktionalisierung der SiO2-Oberfläche der MOSLED wurde mit Hilfe eines im Rahmen dieser Arbeit entwickelten SSC (Spraying Spin Coating)- Verfahrens realisiert. Die Ausgangsmaterialien dieses Verfahrens sind organofunktionelle Silangruppen mit drei unterschiedlichen funktionellen Gruppen, nämlich die Amino-, Carboxyl- und die Thiolgruppen. Die Optimierung dieser Methode erfolgte mittels der zwei Silangruppen APMS ((3- Aminopropyl)trimethoxysilane und Triamino-APMS (N-[3-(Trimethoxysilyl)propyl]ethylenediamine mit der gleichen Molekülstruktur, aber mit einer unterschiedlichen Anzahl an funktionellen Gruppen. Diese Resultate wurden mit in der Literatur beschriebenen Verfahren verglichen. Die Optimierung der SSC-Methode wurde zuerst auf einfache SiO2-Oberflächen und dann auf der Oberfläche der MOSLED angewendet. Die Proben wurden mit Hilfe üblicher Methoden der Oberflächenphysik- wie FTIR-, Raman- und XPS-Spektroskopie untersucht.Die Oberflächenrauhigkeit wurde mittels AFM-Spektroskopie ermittelt, deren Aufnahmen eine glatte Oberfläche bei den mit der SSC-Methode silanisierten Proben zeigen. Während die Hydrophobizität der funktionalisierten SiO2-Oberflächen zunimmt, sinkt dabei die Oberflächenenergie, welche die Anbindung eines hER-Rezeptors mit großer Bindungsenergie begünstigt. Zur Immobilisierung des hER-Rezeptors wurde dieser erst an das Hüllenmolekül des QDots R-655-Farbstoffs gebunden und anschließend an der SSC-silanisierten SiO2-Oberflächen adsorbiert. Der Anteil der immobilisierten Rezeptoren wurde mittels PL-Messung kontrolliert.
Eine andere Immobilisierungstrategie des hER-Rezeptors an die SiO2-Oberfläche kann mit Hilfe eines Aminosäure-Derivates um den Rezeptor realisiert werden. Eine Adsorption der Lysinaminosäure an die SSC-APMS silanisierten SiO2- Oberflächen als Funktion des pH-Wertes wurde durchgeführt, und der Adsorbatsanteil des Lysins mittels XPS-Messung durch die Bindungsenergien der Energieniveaus C1s und N1s berechnet. Eine Referenzlösung mit QDots R 800-Farbstoff markierten Östrogenmolekülen kommt zum Einsatz. Dabei wird die Position 17 des β-Estradiolmoleküls, welches mit einem N-Hydroxysuccinimide Derivat versehen ist, an das Hüllenmolekül des QDots R 800-Farbstoff gebunden,sodass der Phenolring des β-Estradiols frei bleibt. Insbesondere ist bei den FTIR-Spektren
eine nichtgebunden OH-Gruppe des β-Estradiolmoleküls gut erkennbar. Das gesamte Sensorkonzept wurde an zwei mit Östrogen mit einer Konzentration von 1mM und 1μM versetzten Wasserproben getestet. Die Anordnung der Bio-Komponenten wurde mittels PL nachgewiesen. Der Östrogennachweis wurde mit Hilfe des Ge- und Tb-basierten Lichtemitters demonstriert.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-542 2010

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Publ.-Id: 14778 - Permalink


Ultrafast and nonlinear terahertz spectroscopy of semiconductor quantum structures
Schneider, H.;
This seminar gives an overview on our recent experimental studies involving terahertz (THz) radiation from photoconducting antennae and from the free-electron laser in Dresden, Germany. In particular, microstructured scalable antennae for photoconductive THz emitters and semiconductor quantum well detectors for quadratic autocorrelation of pulsed THz radiation will be discussed. The final part of my talk will concentrate on nonlinear THz spectroscopy, in particular THz sideband generation and coherent dynamics of excitons dressed by strong THz beams.
Keywords: two-photon absorption, quadratic autocorrelation, terahertz spectroscopy
  • Lecture (others)
    Condensed Matter Physics Colloquium, 21.09.2010, Hefei, China

Publ.-Id: 14777 - Permalink


Two-photon quantum well infrared photodetectors for terahertz autocorrelation
Schneider, H.; Winnerl, S.; Drachenko, O.; Helm, M.; Liu, H. C.; Walther, M.; Faist, J.;
Two-photon quantum well infrared photodetectors (QWIPs) are based on quantum wells comprising three energetically equidistant states, namely two bound subbands and one resonant state in the continuum. This configuration is extremely efficient for two-photon transitions, giving rise to strong resonant enhancement and to optical nonlinearities which are six orders of magnitude stronger than in bulk crystals. Using this approach, extremely sensitive quadratic detectors for mid-infrared and THz radiation can thus be realized. These devices are very useful for quadratic autocorrelation measurements of THz radiation from free-electron lasers, nonlinear optical converters, and modelocked quantum cascade lasers.
Exploiting the two-photon QWIP approach, we have investigated various detectors based on different epitaxial structures, covering operation wavelengths from the mid-wavelength infrared to the THz regime. In particular, we have demonstrated a two-photon QWIP which operates below the Reststrahlen band at 42 μm (7.1 THz) [1]. At shorter wavelengths, quadratic detection also works at higher temperatures, which is crucial for applications in practical systems. In particular, room temperature operation has been achieved at 5.5 μm (54.5 THz) [2].
In this talk, we will concentrate on the detection properties of two-photon QWIPs. We confirm their quadratic intensity dependence and demonstrate autocorrelation measurements and pulse monitoring of far-infrared picosecond pulses from the free-electron laser at the Forschungszentrum Dresden Rossendorf. Huge optical nonlinearities allow for quadratic detection at THz pulse energies as low as a few pJ. The time resolution of this detector is limited by the intersubband dynamics associated with the intermediate state. Besides applications in THz pulse diagnostics, the two-photon QWIP thus also provides interesting opportunities for studies of the associated intersubband population and polarization lifetimes.
[1] H. Schneider, H. C. Liu, S. Winnerl, C. Y. Song, M. Walther, M. Helm, Opt. Express 17, 12279 (2009)
[2] H. Schneider, H. C. Liu, S. Winnerl, O. Drachenko, M. Helm, J. Faist, Appl. Phys. Lett. 93, 101114 (2008)
Keywords: Quantum well infrared photodetector, QWIP, terahertz, autocorrelation
  • Invited lecture (Conferences)
    5th International Symposium on Ultrafast Phenomena & Terahertz Waves (ISUPTW'2010), 12.-16.09.2010, Xi'an, China

Publ.-Id: 14776 - Permalink


Hydrogen desorption kinetics of melt-spun and hydrogenated Mg90Ni10 and Mg80Ni10Y10 using in-situ synchrotron X-ray diffraction and thermogravimetry
Kalinichenka, S.; Roentzsch, L.; Baehtz, C.; Kieback, B.;
Two nanocrystalline magnesium-rich alloys, Mg90Ni10 and Mg80Ni10Y10, were produced by meltspinning. After hydrogenation they consist of a MgH2 matrix with finely dispersed Mg2NiH4 grains of about 2m in size. In the case of Mg80Ni10Y10, nanocrystalline YH3 grains are found, additionally. The desorption kinetics of hydrogenated Mg90Ni10 and Mg80Ni10Y10 was investigated by thermogravimetry at different temperatures in the range from 150°C to 250°C. It was observed that Mg80Ni10Y10 exhibits a much faster desorption kinetics in comparison toMg90Ni10 of up to 1.3 wt.%H2/min. Differential scanning calorimetry indicates that these alloys undergo a two-step desorption process. The corresponding phase transformations were investigated in detail by in situ synchrotron X-ray diffraction, thus, the different hydrogen desorption kinetics can be explained.
Keywords: Hydrogen storage Lightweight metal hydrides Mg-rich alloys Melt-spinning X-ray diffraction Synchrotron radiation

Publ.-Id: 14775 - Permalink


Longitudinal THz electric fields in the focus of radially polarized beams
Winnerl, S.; Hubrich, R.; Peter, F.; Helm, M.; Schneider, H.;
While typical pulsed terahertz (THz) systems operate with freely propagating THz waves of linear polarization and Gaussian beam profile, modes of different polarization can also be attractive. In particular, radially polarized beams exhibit longitudinal fields at the focus and smaller spot sizes as compared to linearly polarized beams. These key properties of radially polarized beams have been demonstrated indirectly for visible light [1]. Recently radially polarized single cycle THz beams have been generated by velocity-mismatched optical rectification [2] and photoconductive antennas [3,4]. However, longitudinal THz fields have been observed so far only in the near field of plasmon-polariton excitations in a metal tip [5].

We report on longitudinal THz fields in the focus of freely propagating waves. Single cycle THz pulses with radial polarization are generated by photoexcitation of emitters with an electrode structure consisting of concentric rings [4]. By means of electro-optic detection we determine the phase relation between transverse and longitudinal field components. The radiation is focused onto ZnTe sensing crystals oriented along the (110) and (100) axis, respectively, in order to detect transverse and longitudinal THz fields. While the THz beam is kept fixed, the electro-optic detection system is scanned along the x-axis, which denotes the horizontal direction perpendicular to the axis of propagation. For comparison, emitters for linearly polarized beams are operated under the same conditions.

The transverse field changes sign, as the detector is moved across the propagation axis located at x = 0, as expected for a radially polarized wave. The longitudinal field, however, is located around the propagation axis and does not change sign as x changes from negative to positive. At t = 0 where the transverse fields exhibits extrema (dashed line), the longitudinal field is zero. This phase difference of pi/2 has been predicted theoretically as a consequence of Maxwell’s equation div E = 0. To our knowledge, this phase relation has not been measured previously in the entire range of the electromagnetic spectrum. Furthermore we show that the spot size of the longitudinal component is smaller than the diffraction limited spot of a linearly polarized THz beam. The results are analyzed by calculations based on the vector Helmholtz equation beyond the paraxial approximation.

[1] R. Dorn, S. Quabis, G. Leuchs, Sharper focus for a radially polarized light beam, Phys. Rev. Lett. 91, 233901 (2003).
[2] G. Chang, Ch.J. Divin, C.-H. Liu, S.L. Williamson, A. Galvanauskas, T.B. Norris, Generation of radially polarized terahertz pulses via velocity-mismatched optical rectification, Opt. Lett. 32, 433 (2006).
[3] J.A. Deibel, K. Wang, M.D. Escarra, D. Mittleman, Enhanced coupling of terahertz radiation to cylindrical wire waveguides, Opt. Express. 14, 279 (2006).
[4] S. Winnerl, B. Zimmermann, F. Peter, H. Schneider, M. Helm, Thz Bessel-Gauss beams of radial and azimuthal polarization from microstructured photoconductive antennas, Opt. Express 17, 1571 (2009).
[5] N.C.J. van der Valk and P.C.M. Planken, Electro-optic detection of subwavelength terahertz spot sizes in the near field of a metal tip, Appl. Phys. Lett. 81, 1558 (2002).
Keywords: terahertz waves, longitudinal and azimuthal fields, radial polarization
  • Lecture (Conference)
    5th International Symposium on Ultrafast Phenomena & Terahertz Waves (ISUPTW'2010), 12.-16.09.2010, Xi'an, China

Publ.-Id: 14774 - Permalink


Aqueous uranyl benzoate species characterized by different spectroscopic techniques
Frost, L.; Moll, H.; Bernhard, G.;
In this study UV-vis spectroscopy as well as RT and cryo time-resolved laser-induced fluorescence spectroscopy (TRLFS) were applied to reinvestigate the complexation of uranium(VI) by benzoic acid (BA). For the first time in the liquid phase the existence of a U(VI)-BA complex with a 1:2 stoichiometry could be proven.
RT TRLFS measurements revealed a static as well as a dynamic ligand-initiated quench process in the U(VI)-BA system. At these conditions no luminescence emission resulting from complex formation was found. Consequently cryo TRLFS was applied to increase the maximum detect-able BA:U(VI) ratio. By this for the first time a lumines-cence spectrum of the 1:2 U(VI)-BA complex could be determined. This species is characterized by emission bands at 467, 485, 505, 526, and 550 nm which are blue-shifted compared to the ones of the uranyl ion. The luminescence lifetime of the 1:2 complex amounts to 9.21 ± 0.01 µs at -18°C compared to 150.4 ± 0.5 µs for uranyl.
Stability constants of both, the 1:1 and the 1:2 species, have been calculated to be log β110 = 2.66 ± 0.18 and log β120 = 4.48 ± 0.24, respectively. UV-vis spectroscopy combined with factor analysis yielded the molar absorption spectrum of the 1:2 U(VI)-BA species which is characterized by absorption bands at 406, 418, 432.5, 447, and 461 nm and a molar absorption coefficient of 22 L•mol-1•cm-1.
Keywords: Uranium, Benzoic Acid, Complexation, UV-vis spectroscopy, Cryo TRLFS

Publ.-Id: 14773 - Permalink


Electromagnetic inspection of a two-phase flow of GaInSn and Argon
Terzija, N.; Yin, W.; Gerbeth, G.; Stefani, F.; Timmel, K.; Wondrak, T.; Peyton, A.;
In the continuous casting process, an adequate control of liquid steel flow through the submerged entry nozzle is essential for maintaining steel cleanliness and ensuring good surface quality in downstream processing. Monitoring the flow in the nozzle presents a challenge for the instrumentation system because of the high temperature environment and the limited access to the nozzle in between the tundish and the mould.
In this paper, the distribution of a two-phase liquid metal/gas flow is studied by using a liquid metal laboratory model of an industrial steel caster and an inductive sensor array. The experiments were performed with the liquid eutectic alloy GaInSn as an analogue for liquid steel, which has similar conductive properties as molten steel and allows the measurements at room temperature. A scaled (approx. 1:10) experimental rig consisting of a tundish, a stopper rod, a nozzle and a mould was used. Argon gas was injected through the centre of the stopper rod and the behavior of two phase GaInSn/Argon flows was studied.
The electromagnetic system used in the experiments to monitor the behavior of two phase GaInSn/Argon flows consists of an array of 8 equally spaced inductive coils arranged around the object, a data acquisition system and a host computer. The present system operates at 10 kHz and has a capture rate of 10 frames per second.
The results show clearly that the injection of the Argon gas is distinguishable from the single phase flow by observing the appearance of oscillation patterns. These oscillations become more dominant with the increase of the Argon flow. In some cases two main oscillation patterns were present in the raw signals. In general, the signals and the reconstructed void fractions in the nozzles are highly correlated with the observed oscillations of the level height in the mould and the pressure in the nozzle.

Publ.-Id: 14772 - Permalink


Ternary uranium(VI) carbonato humate complex studied by cryo-TRLFS
Steudtner, R.; Sachs, S.; Schmeide, K.; Brendler, V.; Bernhard, G.;
The complex formation of U(VI) with humic acid (HA) in the presence of carbonate was studied by time-resolved laser-induced fluorescence spectroscopy at low temperature (cryo-TRLFS) at pH 8.5. In the prescence of HA, a decrease of the luminescence intensity of U(VI) and no shift of the emission band maxima in compari-son to the luminescence spectrum of the UO2(CO3)34- complex, the dominating U(VI) species under the applied experimental conditions in the absence of HA, was observed. The formation of a ternary U(VI) carbonato hu-mate complex of the type UO2(CO3)2HA(II)4− starting from UO2(CO3)34- was calculated from the luminescence data. A complex stability constant of log K = 2.83 ± 0.17 was determined and the result of the slope analysis with a slope of 1.12 ± 0.11 verifies the postulated complex reaction. These results agrees very well with literature data. Speciation calculations show, that the formation of the ternary U(VI) carbonato humate complex can significantly influence the U(VI) speciation under environmental conditions.
Keywords: Uranium(VI), Humic acid, Carbonate, Complexation, Ternary complex, cryo-TRLFS

Publ.-Id: 14771 - Permalink


P0902 - Anordnung zur Elektronenstrahltomographie
Hampel, U.;
Aufgabe der vorliegenden Erfindung ist es, eine Anordnung zur Elektronenstrahltomographie anzugeben, die eine kontinuierliche und gleichzeitige Aufnahme zweidimensionaler Schnittbilder eines Objektes in verschiedenen Durchstrahlungsebenen mit hoher zeitlicher und räumlicher Auflösung gestattet.
Die Erfindung beinhaltet, dass die Targets (5) von Öffnungen (14) gegebener Breite und regelmäßiger Anordnung in Umfangsrichtung durchbrochen sind, wobei die Öffnungen (14) in den Targets (5) jeweils auf einer Bahnkurve liegen, die den Schnitt der Mantelfläche des Elektronenstrahlkegels (11) mit dem jeweiligen Target (5) bilden; die in Strahlrichtung aufeinanderfolgenden Targets (5) mit jeweils einem kleinen Winkelversatz zum davorliegenden Target (5) bezüglich der optischen Achse (10) angeordnet sind, so dass ein entlang der Mantelfläche des Elektronenstrahlkegels (11) zirkulierender Elektronenstrahl (4) mit mindestens einem Teil seines Querschnitts nacheinander die Materialstege (15) zwischen den Öffnungen (14) aller Targets (5) bestrahlt und zu jedem Target (5) ein Röntgendetektorbogen (6) koplanar radial vor oder hinter dem jeweiligen Target (5) angeordnet ist.
  • Patent
    Anmeldung: DE 10 2009 002 114 A1 14.10.2010
  • Patent
    EP 2238908 B1 - 24.08.2011
  • Patent
    DE 102009002114B4 - 15.03.2012
  • Patent
    US 8130899B2 - 06.03.2012

Publ.-Id: 14770 - Permalink


Große Laufwasserkraftwerke im Einzugsgebiet der Elbe
Rindelhardt, U.;
In Deutschland ist die Grenze zwischen großen und kleinen Wasserkraftanlagen (WKA) bei einer Generator-Leistung von 1 MW festgelegt. Die vorliegende Untersuchung stellt den aktuellen Stand der großen WKA im deutschen Elbe-Einzugsgebiet dar. An der Elbe selbst bestehen heute keine Voraussetzungen (Staustufen) für die Nutzung der erheblichen Wasserkräfte (etwa 1 TWh/a). Die 31 an den Nebenflüssen der Elbe bestehenden WKA haben eine Leistung von insgesamt etwa 59 MW, wovon 50 MW etwa zu gleichen Teilen auf die Flussgebiete der Saale und der Mulde entfallen. Neubaumöglichkeiten für weitere WKA an bestehenden Stauanlagen mit einer Leistung von 6 bis 8 MW werden derzeit untersucht.
Keywords: hydropower, Elbe river
  • Wasserwirtschaft 101(2011)3, 31-36

Publ.-Id: 14769 - Permalink


Activation study of the 40Ca(alpha,gamma)44Ti reaction at the Dresden Felsenkeller
Bemmerer, D.;
The strength of selected resonances in the 40Ca(alpha,gamma)44Ti reaction is studied by activation, using the Felsenkeller low-level gamma-counting facility. In addition, the background conditions for possible accelerator experiments inside Felsenkeller are reviewed.
  • Lecture (Conference)
    10th Meeting Collaboration of European Low-level Underground Laboratories (CELLAR), 14.-15.10.2010, Dresden, Deutschland

Publ.-Id: 14768 - Permalink


Anisotropic magneto-optical response of metallic thin films probed by Vector-Magneto-Optical Generalized Ellipsometry
Mok, K. M.; Du, N.; Schmidt, H.;
Magneto-optical generalized ellipsometry is the most general approach to characterize the magneto-optical response of materials. We extended this experimental approach to Vector-Magneto-Optical Generalized Ellipsometry (VMOGE) in the IR-UV spectral range, by constructing a generalized spectroscopic ellipsometer combined with a 3D vector magnet. VMOGE measures the upper 3 x 4 submatrix of the 4 x 4 Mueller matrix in a magnetic field of arbitrary orientation and magnitude up to 0.4 T at room temperature. Searching the best match model between experimental and calculated VMOGE data, the complex-valued magneto-optical dielectric tensor ε MO is determined. Comparison with vector magnetometry measurements can provide the complex and anisotropic magneto-optical coupling constant Qx, Qy, Qz. We have determined the wavelength dependence of the isotropic Qx and Qy of ferromagnetic Co, Fe, and Ni films. Besides, VMOGE is also employed to study Co nanowires with very strong anisotropic optical response. Having knowledge of the magneto-optical coupling constant Q(λ), one can design magneto-optical devices, e.g., ferromagnetic thin film and nanowire structures, with a strong magneto-optical response for a selected wavelength.
Keywords: Magneto optics, Mueller matrix, generalized ellipsometry, dielectric tensor, ferromagnetism, magnetic anisotropy, nanowires
  • Lecture (Conference)
    3rd NanoCharm Workshop on Non-Destructive Real Time Process Control, 13.-15.10.2010, Berlin, Germany
  • Lecture (Conference)
    Trends in Spintronics and Nanomagnetism (TSN-2010), 24.-28.05.2010, Lecce, Italy

Publ.-Id: 14767 - Permalink


Optimization of the pulp process regarding energy efficiency and fibre pulp quality
Mäbert, M.; Bieberle, A.; Krug, D.; Hampel, U.;
Zur Herstellung von Mitteldichten Faserplatten (MDF) werden Holzfasern definierter Qualität benötigt. Für die Prozess- und Energieoptimierung soll die Holzfaserverteilung im Laborrefiner des Institut für Holztechnologie Dresden gGmbH (IHD) erfasst werden.
Keywords: Refiner, MDF-Plattenherstellung, Faserstoffproduktion
  • Lecture (Conference)
    7th European Wood-based Panel Symposium, 13.-15.10.10, Hannover, Deutschland

Publ.-Id: 14766 - Permalink


Spatial Resolution of Thin-Walled High-Pressure Drift Tubes
Davkov, V. I.; Gregor, I.; Haas, D.; Mouraviev, S. V.; Myalkovskiy, V. V.; Naumann, L.; Peshekhonov, V. D.; Rembser, C.; Rufanov, I. А.; Russakovich, N. А.; Senger, P.; Smirnov, S. Y.; Tikhomirov, V. O.;
A small prototype detector based on high pressure thin-walled tubes (straws) has been developed and its parameters have been studied on a bench at JINR, Dubna, and SPS at CERN. The inner diameter of the straws is 9.53 mm. The pressure of the active gas mixture Ar/CO2 (80/20) has been varied from 1 to 5 bar. The best spatial resolution achieved in this pressure range is ~40 μm. Both the high efficiency and high rate capability are retained.
Keywords: Coordinate Detector; High Pressure; Thin-Walled Drift Tube; Straw; Spatial Resolution

Publ.-Id: 14765 - Permalink


Influence of humic acid on the Am(III) sorption onto kaolinite
Krepelova, A.; Sachs, S.; Bernhard, G.;
The sorption of americium(III), (Am(III)), onto kaolinite was studied in batch experiments in the absence and presence of humic acid (HA) ([Am(III)]0 = 1x10-6 M, [HA]0 = 0 or 10 mg/L, I = 0.01 M NaClO4, pH = 3–10, pCO2 = 10-3.5 atm, solid-to-liquid ratio (S/L) = 1 or 4 g/L). The results show that the Am(III) sorption onto kaolinite is influenced by S/L, the presence of HA and the pH value. In the absence of HA, Am(III) exhibits a very strong and almost pH independent sorption onto kaolinite at the S/L ratio of 4 g/L. In the presence of HA, there are small differences in the Am(III) sorption compared to the HA free system. At pH values < 5, HA very slightly enhances the sorption of Am(III). Conversely, at pH values ≥ 5.5, the presence of HA decreases the sorption of Am(III) due to the formation of dissolved Am(III) humate complexes. The decrease of S/L from 4 to 1 g/L has a significant effect on the Am(III) sorption onto kaolinite. A sorption edge occurs at pH 6 and the influence of carbonate on the Am(III) sorption at higher pH values becomes evident. Furthermore, the influence of HA on the Am(III) sorption onto kaolinite is more pronounced. The Am(III) sorption results are compared to literature and to those of U(VI) sorption onto kaolinite obtained under the same experimental conditions.
Keywords: Americium, Kaolinite, Humic Acid, Sorption, Clay

Publ.-Id: 14764 - Permalink


Alteration of magnetic anisotropy of Pt/Co/Pt trilayers by FIB irradiation
Mazalski, P.; Dobrogowski, W.; Maziewski, A.; Sveklo, I.; Fritzsche, M.; Liedke, M. O.; Fassbender, J.ORC; Wawro, A.; Baczewski, L. T.
Ion beam irradiation enables to modify magnetic properties of magnetic ultrathin films and multilayers [1, 2]. Such a method is a very promising technique for magnetic patterning [3]. In films with initial perpendicular magnetization the decrease of perpendicular magnetic anisotropy, followed by the magnetization rotation to the in-plane orientation and finally a transition to superparamagnetic state has been observed with increasing irradiation dose D [1-3]. Recently a double magnetisation reorientation from in-plane to out-of-plane direction and back to in-plane alignment, driven by Ga+ ion 30 keV irradiation, has been observed in sputtered Pt/(Co 2.6 nm)/Pt films [4].
In this work we report the influence of focused ion beam (FIB) irradiation on magnetic properties of MBE grown Mo/Pt/(Co 3.3nm)/Pt sandwiches. In the as deposited sample magnetization was aligned in the film plane. The numerous areas of the sample (squares 100x100μm² or 50x50μm²) have been irradiated by Ga+ ions with doses D ranging between 2x1012 and 1x1016 ions/cm². A development of perpendicular magnetic anisotropy in irradiated regions has been correlated with modifications of a surface morphology using polar Kerr effect magnetometry (sensitive to perpendicular magnetization component), as well as atomic/magnetic force microscopy techniques.

[1] C. Chappert, H. Bernas, et al., Science 280, 1919 (1998).
[2] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320, 579 (2008).
[3] J. Ferré, J.-P. Jamet, in Handbook of Magnetism and Advanced Magnetic Materials, Vol. 3, p.1710 H. Kronmüller, S. Parkin Ed. (John Wiley & Sons, Ltd, 2007).
[4] J.Jaworowicz et al., APL 95, 022502 (2009).
  • Poster
    NANOSMAT 2010, 19.-21.10.2010, Reims, France

Publ.-Id: 14763 - Permalink


Preparation and characterization of 90Y- and 177Lu-labeled cetuximab for therapeutic applications in vitro and in vivo
Zenker, M.; Bergmann, R.; Walther, M.; Heldt, J.-M.; Pietzsch, J.; Pietzsch, H.-J.; Steinbach, J.;
Cetuximab (C225) as a chimeric monoclonal antibody specifically targets the epidermal growth factor receptor (EGFR) that is often overexpressed in human malignancies. This phenotype is associated with tumor aggressiveness, treatment
resistance and biological heterogeneity with potential to bypass the blockade of the EGFR signaling pathways.
The aim of this work was to modify the C225 for radiolabeling with therapeutic radionuclides like 90Y and 177Lu as a prerequisite for combination of endoradionuclide therapy with antibody-, chemo- or external radiation therapy for routine application.
C225 was conjugated with the bifunctional chelator CHX-A″-DTPA up to a molar DTPA to C225 ratio of 5. The EGFR-affinity of the immunoconjugate resulted in 94% versus 100% of the unmodified C225 measured with enzyme-linked immunosorbent assay on EGFR-positive tumor cell line A431. DTPA-C225 was labeled with 90YCl3 or 177LuCl3 within 30 min with a radiolabeling yield of N95%. The radio-immunoconjugates exhibited high accumulation in squamous cell carcinoma xenotransplanted tumors shown by single photon emission computed tomography and autoradiography. The radiolabeled C225 can be produced in routine with high avidity and specific activity as prerequisite for long term preclinical therapeutic studies.
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 723
    DOI: 10.1016/j.nulmedbio.2010.04.053
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 553-554

Publ.-Id: 14762 - Permalink


Cu-61 production and purification
Thieme, S.; Walther, M.; Pietzsch, H.-J.; Steinbach, J.;
Cu-61 (T1/2=3.32 h, Eβ+=1.22 MeV 60%) is a positron emitter from the set of medically useful copper radioisotopes. Its nuclear properties and ease of production make it suitable for positron emission tomography imaging. The 64Zn (p,α)61Cu reaction with enriched Zn-64 as target material seems to be more convenient for the routine production of Cu-61 than the 61Ni(p,n)61Cu route, due to the higher costs of enriched Ni-61. As reported, the 64Zn(p,α)61Cu reaction delivers adequate yields of Cu-61 in an energy window of 19à10MeV with low contaminants like Cu-60/62 which occur at higher proton energies.
Cu-61 was generated using the 64Zn(p,α)61Cu reaction utilizing 16 MeV. For the purification of Cu-61, a system of cation- and anion-exchange columns was applied which allows recycling of the target material for uncomplicated electro deposition for the next irradiation cycle. The abandonment of heating and drying steps, applying pumps or any pressure to the columns makes this process suitable for remote handling in hot cells and causing fewer sources of contaminants and enables good/reasonable yields. An overview of the key data (yield at EOB and after processing, specific activity and radiochemical purity) will be presented.
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 719
    DOI: 10.1016/j.nulmedbio.2010.04.049
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 475-478
  • Lecture (Conference)
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy

Publ.-Id: 14761 - Permalink


[188Re(N)(cys∼)(PNP)]+/0 mixed ligand compounds as models for target specific agents
Bolzati, C.; Thieme, S.; Agostini, S.; Carta, D.; Salvarese, N.; Refosco, F.; Bergmann, R.; Pietzsch, J.; Pietzsch, H.-J.;
An efficient procedure for the preparation of [188Re(N)(PNP)]-based complexes is reported. The radiochemical yield (RCY) of the compounds was optimized considering reaction parameters such as: nature of nitrido nitrogen donors, reaction times and pH.
The chemical identity of 188Re-agents was determined by high-performance liquid chromatography comparison with the corresponding well characterized cold Re-compounds. The stability of the [188Re(N)(PNP)] complexes toward transchelation with glutathione and degradation by serum enzymes was assessed. The clearance of selected radiolabeled agents from normal tissues was evaluated in rats.
[188Re(N)(cys∼)(PNP)]+/0 asymmetrical compounds were prepared in aqueous solution from perrhenate using a multistep procedure based on the preliminary formation of the labile 188ReIIIEDTA species which easily undergo to oxidation/ligand exchange reaction to afford in presence of DTCZ the [188ReV≡N]2+core. The final compounds were obtained by adding to the [188ReV≡N]int 2+ the two bidentate ligands. However, a relative high amount of cys∼ ligand was required to obtain a quantitative RCY. The complexes were stable toward reoxidation to perrhenate and ligand exchange reactions. In vivo studies showed a rapid distribution and elimination of the complexes from the body. No specific uptakes in radiation sensitive tissues/organs were detected.
A positive correlation of the distribution of the complexes estimated with biodistribution studies (% injected dose) andwithmicro-single photon emission computed tomography semiquantification imaging analysis was observed. The low labeling efficiency limits but not excludes the possibility to apply [188Re(N)(PNP)]-technology to the preparation of target specific radiotherapeutical agents.
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 711-712
    DOI: 10.1016/j.nulmedbio.2010.04.001
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 407-408

Publ.-Id: 14760 - Permalink


Radiolabeled L-oligonucleotides with tunable pharmacokinetics — a suitable complementary system for pretargeting technologies
Förster, C.; Bergmann, R.; Schubert, M.; Walther, M.; Pietzsch, J.; Vonhoff, S.; Klussmann, S.; Pietzsch, H.-J.; Steinbach, J.;
Complementary mirror-image L-oligonucleotides (L-ON) and tumorspecific antibodies appear as a suitable system for pretargeting technologies. However, optimization of the radiopharmacological characteristics of the LON is a prerequisite for high accumulation in the target. The objective was to decrease the kidney uptake, to increase the area under the blood curve (AUC), and to minimize the nonspecific accumulation in the body. Therefore the L-ON were conjugated with PEG units of increasing size (2, 5, 10, 20 kDa) and subsequently derivatized with NOTA and DOTA for radiolabeling with Ga-68, Cu-64, Y-86, Y-90, Lu-177.
We investigated the impact of size and structure of the radiolabeled (Ga-68, Cu-64) L-ON on biodistribution and positron emission tomography kinetics. The increasing PEG units, up to 20 kDa PEG, decreased the kidney uptake, increased the activity concentration in the blood, e.g., the AUC, but also increased the liver uptake. We can decisively influence the pharmacokinetics resulting in optimal L-ON kinetics and distribution. These results, combined with the option of different radionuclides and high specific activities of the radiolabeled L-ON, emphasizes the attractiveness of this complementary system for pretargeting approaches.
  • Lecture (Conference)
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 706
    DOI: 10.1016/j.nulmedbio.2010.04.100
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 357-362

Publ.-Id: 14759 - Permalink


99mTc-labelled vasopressin peptide as a potential radiopharmaceutical for small-cell lung cancer imaging
Koźmiński, P.; Gniazdowska, E.; Bańkowski, K.; Pietzsch, H.-J.;
The aim of the paper was to synthesize and investigate the conjugate of the “4+1” mixed-ligand technetium(III) complex with the vasopressin peptide-99mTc(NS3)(CN-AVP). The overexpression of vasopressin receptor V2 has been found in the case of small-cell lung cancer.
The “4+1” mixed-ligand technetium complex consists of central metal ion Tc(III) coordinated simultaneously by a tetradentate NS3 tripodal chelator tris(2-mercaptoethyl)-amine and a monodentate isocyanide ligand, previously coupled with the selected biomolecule. The identity of the 99mTclabelled vasopressin peptide was corroborated by investigation of the analogous rhenium compound. The 99mTc-labelling vasopressin conjugate was formed in two-step synthesis, via the 99mTc-EDTA intermediate complex, with the final yield of 95%. After 24 h of incubation of the conjugate in the 10 mM solution of histidine or cysteine, the obtained highperformance liquid chromatography chromatograms have shown the existence of one radioactive species, with the retention time characteristic for the complex studied. The log D value of −0.48±0.02 for the 99mTclabelled vasopressin peptide was found. This value (higher than the lipophilicity of the free vasopressin peptide equal to −2.15) can be corrected by introducing a hydrophilic group, R, at the periphery of the NS3 ligand.
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, I
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 704
    DOI: 10.1016/j.nulmedbio.2010.04.128
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 337-338

Publ.-Id: 14758 - Permalink


Studies of new [Tc(N)(PS)]-based mixed compounds as analogues of WAY 100635
Bolzati, C.; Salvarese, N.; Carta, D.; Pietzsch, H.-J.; Bergmann, R.; Dolmella, A.; Bandolini, G.;
This study was focused on evaluating the applicability of a new labelling procedure to the preparation of 99mTc(N)-based target specific compounds. The chemistry is based on the use of the [Tc(N)Cl(PS)(PPh3)] species (PS=alkyl-phosphino-thiolate ligand), which selectively reacts with an appropriate mono-negative chelate, such as a dithiocarbamate (DTC), to give neutral [Tc(N)(PS)(DTC)] compounds. The 2-methoxyphenylpiperazine (L) pharmacophore, which displays a potent and specific affinity for 5HT1A receptors, was selected as functional group and conjugated to the dithiocarbamate unit through different spacers.
The synthesis of [99m/99gTc(N)(PS)(Ln)] complexes, and their stability as well as their biological in vitro and in vivo assays were investigated. [99mTc(N)(PS)(Ln)] compounds were prepared in high yield (N90%) using a multi-step procedure and their chemical identity was determined by highperformance liquid chromatrography comparison with the 99gTc-analogues. All complexes were found to be inert toward transchelation with glutathione and sufficiently stable to the in-vitro action of serum and liver enzymes. Nanomolar affinities for the 5-HT1A receptor were obtained for [99mTc(N) (PSiso)L3] (IC50=1.5 nM). However, a negligible brain uptake was observed after in-vivo administration of the complex.
This work describes the application of a new labelling procedure for incorporating a bioactive molecule into a stable dissymmetric 99mTc(N)-complex. Despite the lack of BBB penetration of [99mTc(N)(PSiso)L3] the favourable binding properties of this compound strongly support the possibility to apply [Tc(N)(PS)]-technology to the preparation of target specific agents useful in peripheral applications.
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 700
    DOI: 10.1016/j.nulmedbio.2010.04.026
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 313-314

Publ.-Id: 14757 - Permalink


Induction heating for pendent-drop melt extraction from a metallic sheet
Park, J.-S.; Pal, J.; Cramer, A.; Gerbeth, G.; Taniguchi, S.;
Induction heating for pendent-drop melt extraction (PDME) from a metallic sheet is simulated and optimized. This numerical study aims at concentrating dissipated powers on the lower edge of the metallic sheet so that multi-extraction of fine fibers from the wide metallic drop is realized. The solutions on the electromagnetic field are obtained numerically by three-dimensional (3D) modeling based on Finite Element Method (FEM) using ANSOFT Maxwell software, then verified experimentally by lab-scale tests. Subjects to variation are (1) the extension of the substrate (extraction wheel) in both directions parallel and perpendicular to the inductor, (2) the protrusion depth of the edge below the lower face of the inductor and (3) the shape of the inductor. The numerical simulations suggest that the vertical position of the inductor has to be significantly higher than that in Reference 1 in order to increase the efficiency of the process.
  • Lecture (Conference)
    The 4th Asian Workshop on EPM, 03.-06.10.2010, Jeju, Korea
  • Contribution to proceedings
    The 4th Asian Workshop on EPM, 03.-06.10.2010, Jeju, Korea
    Induction heating for pendent-drop melt extraction from a metallic sheet, pp. 252-256

Publ.-Id: 14756 - Permalink


Direct evidence of long lived trapped carriers in InGaAs/GaAs quantum dots studied using terahertz-activated luminescence measurements
Bhattacharyya, J.; Wagner, M.; Helm, M.; Hopkinson, M.; Wilson, L. R.; Schneider, H.;
Trapped carrier dynamics in semiconductor quantum dots (QDs) have been studied using terahertz activated luminescence. This technique enabled us to isolate the luminescence emitted by the trapped carriers from the photoluminescence due to interband excitation. Trapped carriers having long lifetimes ~ 250 ns at 8 K were observed. Temperature dependence of the trapped carrier lifetime was measured. Activation energy for the trapped carrier decay rate was found to be close to the intersublevel transition energy of the QDs.
Keywords: trapped carriers, quantum dots, terahertz activated luminescence
  • Lecture (Conference)
    ICPS-30, 25.07.2010, Seoul, South Korea
  • Contribution to proceedings
    ICPS 2010, 30th International Conference on the Physics of Semiconductors, 25.-30.07.2010, Seoul, South Korea
    AIP Conference Proceedings 1399(2011)593

Publ.-Id: 14755 - Permalink


Results from the LIMMCAST programme: Modelling the steel flow in the mould with cold liquid metals
Gerbeth, G.; Eckert, S.; Timmel, K.; Miao, X.;
Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications. We present the new experimental facility LIMMCAST for modelling the continuous casting process of steel using the alloy SnBi at temperatures of 200-400°C. The possibilities for flow investigations in tundish, submerged entry nozzle and mould will be discussed. In addition, experimental results will be presented on the impact of a steady magnetic field on the outlet flow from the nozzle, obtained at a smaller-scale set-up working with the room-temperature alloy GaInSn. Local velocities are measured by Ultrasound Doppler Velocimetry and contactless inductive flow tomography. The magnetic field significantly changes the jet-type flow in the mould. Surprisingly, in some parameter ranges the DC field creates low-frequency oscillations of the flow structure which resulted in increased velocity fluctuations. Numerical simulations using the CFX code confirm this magnetic field action.
  • Lecture (Conference)
    The 4th Asian Workshop on EPM, 03.-06.10.2010, Jeju, Korea
  • Contribution to proceedings
    The 4th Asian Workshop on EPM, 03.-06.10.2010, Jeju, Korea
    Results from the LIMMCAST programme: modelling the steel flow in the mould with cold liquid metals, 9-12

Publ.-Id: 14754 - Permalink


Preparation of DOTA-dendron Cetuximab bioconjugates for radioimmunotherapy using 90Y, 177Lu and 67Cu
Heldt, J.-M.; Zenker, M.; Pietzsch, H.-J.; Bergmann, R.; Steinbach, J.;
In order to improve the efficiency of radioimmunotherapy by augmenting the specific activity of the radiolabeled bioconjugates while preserving their immunoreactivity, we prepared a water-soluble dendron bearing four 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid moieties by solidphase peptide synthesis. An N-hydoxysuccinimide ester of the dendron was synthesized and the dendron conjugated to lysine amino groups of the therapeutic monoclonal antibody Cetuximab which is specific for the epidermal growth factor receptor and overexpressed by various tumours. Dendron-bearing Cetuximab is thus used for treatment of colon, head, and neck cancer, so as to combine high specific activities brought by multilabeling to achieve a more effective targeted radionuclide therapy as it has been shown for Zevalin and Rituximab. The dendron to antibody ratio was determined by MALDI-TOF MS. These new conjugates have been radiolabeled by 64Cu and 90Y and higher specific activities have been obtained compared to monochelator- labeled antibody. positron emission tomography imaging in mice showed a significant tumour accumulation. Here we discuss the relationships between dendron to antibody ratio, antigen affinity and specific activity of monochelator and dendron-labeled Cetuximab conjugates.
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 696-697
    DOI: 10.1016/j.nucmedbio.2010.04.005
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 255-256

Publ.-Id: 14753 - Permalink


Ga-68 Microspheres and Galligas for lung scintigraphy with PET
Wunderlich, G.; Schiller, E.; Pietzsch, H.-J.; Bergmann, R.;
To handle the present shortage of Mo-99 in the nuclear medicine community, we offer alternative preparations for lung scintigraphy, Ga-68-labelled DOTA microspheres (DOTA MS) and labelled aerosol, analogously to well-known Technegas.
Over the last three decades, several trials have been made to label HSA microspheres with Ga-68 in an efficient manner and with stability. Biodegradable albumin microspheres (HSAM) have been widely applied for lung perfusion scintigraphy (Tc-99m HSAM) or labelled with Re-188 for internal radiation therapy. We present in vitro and in vivo stability data of Ga-68 DOTA HSAM in Wistar rats.
DOTA-Bz-NCS was reacted with HSAM and labelled with Ga-68 from a Ge-68/Ga-68 generator by a simple and reproducible method in high yields. The in vitro stability of Ga-68-labelled DOTA-HSAM was checked by incubation in human plasma and by challenging with DTPA.
After intravenous injection into a tail vain, the Ga-68 DOTA MS was rapidly filtered from venous blood and accumulated almost quantitatively in the lungs. Radioactivity level then remains constant for at least 30 min (PET studies with microPET P4). Ga-68-labelled particles showed high in vitro stability and almost quantitative accumulation in the lungs after intravenous application. We consider that Ga-68 DOTA HSAM is a potential radiotracer for lung and other organ perfusion studies.
On the other hand, for ventilation, Ga-68 Galligas aerosol for PET imaging is simple to produce in a Technegas apparatus which can produce Ga-68 eluate concentrated in acetone/HCl. It was stable in vivo (tested over 3.5 h) and allows PET imaging in man with 5–10 MBq Ga-68 only.
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 694
    DOI: 10.1016/j.nucmedbio.2010.04.016
  • Contribution to external collection
    U. Mazzi, W. C. Eckelman, W. A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali Padova, 2010, 235-236

Publ.-Id: 14752 - Permalink


Effect of carrier redistribution on spin polarization in n-doped InGaAs quantum dot ensemble
Bhattacharyya, J.; Wagner, M.; Helm, M.; Hopkinson, M.; Wilson, L. R.; Schneider, H.;
Semiconductor quantum dots (QDs) are found to have relatively long spin depolarization times, which makes them promising candidates for practical realization of qubits for spintronics based computation. For doped QDs the presence of the excess carriers in the dots modifies the electron-hole interaction leading to unusual spin polarization properties like negative spin polarization. From our experiments we found that the sign and magnitude of the spin polarization depended on the excitation energy and the QD transition involved. Therefore, to understand the spin dynamics in doped QDs and the role of excited states, we performed photoluminescence quenching measurements using circularly polarized interband excitation and temporally synchronized terahertz pulses to induce intersublevel transitions.

The sample studied was an ensemble of n-doped InGaAs/GaAs QDs with an average doping of one electron per dot. The s-p intersublevel energy was tuned to about 20 meV (5 THz) by thermal annealing. A circularly polarized Ti:sapphire laser was used for interband excitation, where the wavelength was adjusted to enable excitation in the barrier, the wetting layer (WL) or the QDs. Terahertz pulses from a free-electron laser (FEL), synchronized to the Ti:sapphire laser, were used to excite intersublevel transitions (~ 20 meV, i.e. 5 THz) in the QDs. A streak-camera coupled to a CCD enabled time and wavelength resolved PL detection.

Time-resolved photoluminescence measurements at ~10 K, for cross-circular (s+s+), i.e. excitation s+ and detection s+, and cross-circular (s+s-) polarizations showed weak negative spin polarization for the QD ground state transition (Figure 1(a)). When excited by long wavelengths, the PL spectrum showed multiple peaks due to selective excitation of the QD ensemble. Some of these features were associated with phonon mediated transitions and exhibited strong positive circular polarization anisotropy (Figure 1(b)). The effect of the FEL pulses on the spin polarization was found to depend on the excitation wavelength. While the strong positive spin polarization for excitation below the wetting layer was drastically reduced by the FEL pulse (as shown by the solid lines in Figure 1 (b)), the weak negative polarization was found to persist. This suggests different mechanisms involved in the generation of spin polarization for different excitation energies. We will discuss the origins of these spin polarizations associated with different transitions in the QD ensemble and their dynamical behaviour. By varying the time-delay of the FEL pulses with respect to the Ti:sapphire laser pulses for interband excitation in the barrier or the WL, we confirmed the existence of trapped carriers. Trapped carriers have been reported to have considerable effect on the PL response of QDs. The FEL pulses induced two competitive phenomena that affect the spin polarization, i.e. (i) diffusion of trapped carriers resulting in increased PL and (ii) intersublevel transitions resulting in a quenching of the PL signal. To summarize, this work investigates the influence of the intradot transitions and interdot diffusion of the trapped carriers on the spin polarization of the QD ensemble.
Keywords: Time-resolved Photoluminescence, Spin polarization, PL quenching
  • Poster
    The 6th International Conference on the Physics and Applications of Spin Related Phenomena in Semiconductors (PASPS-VI), 01.10.2010, Tokyo, Japan

Publ.-Id: 14751 - Permalink


Accessible silanol sites - beneficial for the RP-HPLC separation of constitutional and diastereomeric azaspirovesamicol isomers
Wenzel, B.; Fischer, S.; Brust, P.; Steinbach, J.;
Different RP-HPLC columns (phenyl, conventional ODS, cross-linked C18 and special end-capped C8 and C18 phases) were used to investigate the separation of four basic ionizable isomers. Using ACN/20 mM NH4OAc aq., a separation was observed exclusively on RP columns with higher silanol activity at unusual high ACN concentration, indicating cation-exchange as main retention mechanism. Using MeOH/20 mM NH4OAc aq., another separation at low MeOH concentrations was observed on both, RP columns with higher as well as RP columns with lower silanol activity, which is mainly based on hydrophobic interactions. The isomers were also separated on a bare silica column at higher MeOH content using NH4OAc as buffer. Since cation-exchange governs this retention, the elution order was different compared to the RP phases. A strong retention on the silica column was observed in ACN, which could be attributed to partition processes as additional retention mechanism.
Keywords: azaspirovesamicol isomers, silanol sites, cation-exchange, silica column, retention mechanism, basic analytes, VAChT

Publ.-Id: 14750 - Permalink


Molecular imaging of σ receptors: synthesis and evaluation of the potent σ1 selective radioligand [18F]fluspidine
Fischer, S.; Wiese, C.; Grosse Maestrup, E.; Hiller, A.; Deuther-Conrad, W.; Scheunemann, M.; Schepmann, D.; Steinbach, J.; Wünsch, B.; Brust, P.;
Purpose Neuroimaging of σ1 receptors in the human brain has been proposed for the investigation of the pathophysiology of neurodegenerative and psychiatric diseases. However, there is a lack of suitable 18F-labelled PET radioligands for that purpose.

Methods The selective σ1 receptor ligand [18F]fluspidine (1'-Benzyl-3-(2-[18F]fluoroethyl)-3Hspiro[[2]benzofuran-1,4'-piperidine]) was synthesised by nucleophilic 18F- substitution of the tosyl precursor. In vitro receptor binding affinity and selectivity were assessed by radioligand competition in tissue homogenate and autoradiographic approaches. In female CD-1 mice, in vivo properties of [18F]fluspidine were evaluated by ex vivo brain section imaging and organ distribution of intravenously administered radiotracer. Target specificity was validated by organ distribution of [18F]fluspidine after treatment with 1 mg/kg, i.p. of the σ receptor antagonist haloperidol or the emopamil binding protein (EBP) inhibitor tamoxifen. In vitro metabolic stability and in vivo
metabolism were investigated by LC-MSn and radio-HPLC analysis.

Results [18F]Fluspidine was obtained with a radiochemical yield of 35-45%, a radiochemical purity of ≥99.6%, and a specific activity of 150-350 GBq/μmol (n=6) within a total synthesis time of 90-120 min. In vitro, fluspidine bound specifically and with high affinity to σ1 receptors (Ki = 0.59 nM). In mice, [18F]fluspidine rapidly accumulated in brain with uptake values of 3.9 and 4.7 %ID/g and brain to blood ratios of 7 and 13 at 5 and 30 min after intravenous application of the radiotracer, respectively. By ex vivo autoradiography of brain slices, resemblance between binding site occupancy of [18F]fluspidine and the expression of σ1 receptors was shown. The radiotracer uptake in the brain as well as in peripheral σ1 receptor expressing organs was significantly inhibited by haloperidol but not by tamoxifen. Incubation with rat liver microsomes led to a fast biotransformation of fluspidine. After an incubation period of 30 min only 13 % of the parent compound was left. Seven metabolites were identified by HPLC-UV and LC-MSn techniques. However, [18F]fluspidine showed a higher metabolic stability in vivo. In plasma samples ~94% of parent compound remained at 30 min and ~ 67% at 60min p.i. Only one major radiometabolite was detected. None of the radiometabolites did cross the blood-brain-barrier.
Conclusion [18F]Fluspidine demonstrated favourable target affinity and specificity as well as metabolic stability both in vitro and in animal experiments. The in vivo properties of [18F]fluspidine offer a high potential of this radiotracer for neuroimaging and quantitation of σ1 receptors in vivo.
  • European Journal of Nuclear Medicine and Molecular Imaging 38(2011)3, 540-551

Publ.-Id: 14749 - Permalink


X-Ray Diffraction from Periodically Patterned GaAs Nanorods Grown onto GaAs[111]B
Davydok, A.; Biermanns, A.; Pietsch, U.; Grenzer, J.; Paetzelt, H.; Gottschalch, V.;
We present a high-resolution X-ray diffraction pattern of periodic GaAs nanorod (NR) ensembles and individual GaAs NRs grown catalyst-free throughout a prepatterned amorphous SiN x mask onto GaAs[111]B surfaces. The experiments were performed at a home laboratory using synchrotron radiation in combination with a micron-sized beam prepared by compound refractive lenses. The structural properties were probed by measuring RSMs (q x , q z ) in the vicinity of GaAs(111) and (222) reflections. Besides the GaAs substrate peak, we found a second peak referring to NRs with lattice mismatch of 0.23 pct with respect to the substrate, probably caused by structural defects. The lateral periodicity of NRs was probed by q x scans, and the NR height obtained from the width of the diffraction curve along q z . Grazing-incidence in-plane diffraction revealed the appearance of small crystallites of cubic γ-Si3N4 caused by recrystallization of SiN x during NR growth. Whereas measurements at the home diffractometer provided average structure parameters, the micron-sized X-ray beam experiment was used to probe the parameters at individual NRs.

Publ.-Id: 14748 - Permalink


First In-Human Data of Fluorine-18 Labelled Fluoromethyl-McN5652 for In-Vivo imaging of Brain Serotonin Transporters (SERT) with PET
Hesse, S.; Brust, P.; Mäding, P.; Zessin, J.; Becker, G.; Patt, M.; Seese, A.; Sorger, D.; Habermann, B.; Meyer, P.; Luthardt, J.; Bresch, A.; Steinbach, J.; Sabri, O.;
Aim: DASB is currently the most frequently applied highly selective radiotracer for visualisation and quantification of central SERT. Its use, however, is hampered by the short half‐life of carbon‐11, the moderate cortical test retest reliability, and the lack for quantifying endogenous serotonin. The aim of our study was to first apply in human the new highly SERT‐selective fluorine‐18 labelled fluoromethyl analogue of (+)‐McN5652 ([18F]FMe‐McN).
Methods: The synthesis of [18F]FMe‐McN was performed according to Zessin et al. with some modifications. Briefly, the demethylated (+)‐McN5652 was reacted with bromo‐[18F]fluoromethane to yield [18F]FMe‐McN, which was purified by reversed‐phase HPLC. For in vivo human studies, five healthy volunteers (2 female, age 39±10 years) underwent dynamic PET over 120 minutes after intravenuous injection of a 90 s bolus of 298±57 MBq [18F]FMe‐McN and a static acquisition over 30 minutes 3 h p.i.. PET data were coregistered with individual MRI data set using PMOD and VOI analysis was performed. Target‐to‐background‐ratios (TB‐R, cerebellum as background structure) were compared with those of a reference data set assessed by [11C]DASB‐PET in 21 healthy subjects (11 female, 38±8 years).
Results: TB‐R ([18F]FMe‐McN) displays no hemispheric differences. The values are for the frontal cortex (FC) 1.02±0.04 (right‐hand side) and 1.01±0.03 (left), for the head of caudate region (caud) 1.46±0.16 (right) and 1.50±0.15 (left) and for the raphé region 2.04±0.11. Corresponding TB‐R ([11C]DASB) are 1.10±0.07 (FC right, ANOVA p=0.05), 1.08±0.78 (FC left, 0.06), 2.14±0.21 (caud right, 0.02), 2.06±0.19 (caud left, 0.04) und 2.23±0.39 (raphé, 0.04). Visually, image quality of [11C]DASB‐PET is superior to [18F]FMe‐McN .
Conclusion: Cerebral radiotracer uptake fits well with the known SERT distribution also in humans. Hence, [18F]FMe‐McN might be suitable for in vivo quantification of SERT. Despite a tendency to lower TB‐R compared to [11C]DASB, the lower standard deviation of [18F]FMe‐McN TB‐R can be advantageous with regard to test‐retest estimations in larger study cohorts. Also, labelling with fluorine‐18 allows (1) later data acquisition times, which is useful for the investigation of the
tracer kinetics in brain tissue (modelling), and (2) a widespread application within a satellite concept e.g. in multicenter trials.
References Zessin J, Eskola O, Brust P et al. Nucl Med Biol 2001; 28: 857‐863.
  • Poster
    23rd Annual Congress of the European Association of Nuclear Medicine (EANM), 09.-13.10.2010, Wien, Österreich
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 37(2010)2, S387

Publ.-Id: 14747 - Permalink


Growth of spatially ordered Ge nanoclusters in an amorphous matrix on rippled substrates
Buljan, M.; Grenzer, J.; Keller, A.; Radic, N.; Vales, V.; Bernstorff, S.; Cornelius, T.; Metzger, H.; Holy, V.;
So far, the growth of spatially ordered nanoclusters by multilayer deposition has been reported and explained satisfactorily only in crystalline materials. Here we demonstrate a method for the growth of spatially ordered nanoclusters in amorphous matrices, where the ordering is achieved in the single large domain. The regular ordering is induced by the deposition of a multilayer on a periodically rippled substrate at an elevated substrate temperature. During the deposition, the nanoclusters self-arrange, following the morphology of the substrate.

Publ.-Id: 14746 - Permalink


Synthesis and first radiopharmaceutical investigation of 5-[125I]Iodo-SU11248, a potential radiotracer for imaging VEGFR
Kniess, T.; Oliveira, C.; Kuchar, M.; Gano, L.; Santos, I.; Steinbach, J.;
Aim: Due to the fact that receptor tyrosine kinases (RTKs) are overexpressed in some tumour entities, they might be a suitable target for PET or SPECT imaging. Then, tyrosine kinase inhibitors labeled with a radioisotope could represent a useful tool for monitoring levels of RTKs in tumour tissue giving valuable information for anti‐angiogenic therapy. SU11248 (Sunitinib®) is a novel highly potent RTK inhibitor targeting vascular endothelial growth factor receptor (VEGFR)
(IC50=0.08μM) [1]. We report here the synthesis of a 125I‐labeled derivative of SU11248 and its first radiopharmaceutical characterization.
Materials and methods: 5‐[125I]lodo‐SU11248 was obtained via destannylation of the corresponding tributylstannyl precursor with [125I]NaI in the presence of H2O2. The radioiodinated compound has been purified by RP‐HPLC with UV and radioactivity detection using methanol/0.1% TFA (85:15) as eluent. Determination of human plasma protein binding at time intervals of 0; 1; 2; 4 and 24h was accomplished by incubation of the radiotracer in fresh human serum at 37°C. Preliminary biodistribution studies were carried out in healthy CD‐1 mice and in vivo stability was assessed by HPLC analysis of urine samples collected at sacrifice time.
Results: 5‐[125I]Iodo‐SU11248 could be obtained in high radiochemical yield (>95%). After HPLC purification the radiochemical purity exceeded 98%. The identity of the radiotracer was confirmed by co‐elution with 5‐Iodo‐SU11248 as reference compound [2]. Lipophilicity of 5‐[125I]Iodo‐SU11248 has been assessed using the octanol/PBS partition coefficients (logPo/w) and was found to be 2.25. Determination of human plasma protein binding suggested a low non‐specific binding of 5‐10%. Biodistribution studies showed a relatively high uptake in VEGFR‐2 rich tissues like kidney and lung, followed by rapid washout (9.6 and 9.7; 4.5 and 3.8% ID/g kidney and lung at 1 and 4 h, respectively).
Conclusion: The new 5‐[125I]Iodo‐SU11248 was synthesized in high radiochemical yield and purity. The high stability in human serum and urine samples, suggests that the tracer is not significantly metabolized. The ability of 5‐Iodo‐SU11248 to inhibit tyrosine kinase activity, a mandatory prerequisite for further studies on RTK expressing cells, is underway, to disclose whether this radiotracer would be a useful tool for monitoring VEGFR expression. Ultimately, the radiochemical profile of 5‐[125I]Iodo‐SU11248 associated to a low non‐specific binding and rapid clearance from most tissues encourages further radiolabeling with other radioisotopes, such as 123I for SPECT or 124I for PET.
[1] Sun L., Liang C. et al., J. Med. Chem., 46, (2003), 1116 [2] Kniess T., Oliveira C. et al., unpublished results
  • Poster
    23rd Annual Congress of the European Association of Nuclear Medicine (EANM), 09.-13.10.2010, Wien, Österreich
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 37(2010)2, S364

Publ.-Id: 14745 - Permalink


Generation of an ordered Ge quantum dot array in an amorphous silica matrix by ion beam irradiation: Modeling and structural characterization
Buljan, M.; Bogdanovic-Radovic, I.; Karlusic, M.; Desnica, U.; Radic, N.; Skukan, N.; Drazic, G.; Ivanda, M.; Gamulin, O.; Matej, Z.; Vales, V.; Grenzer, J.; Cornelius, T.; Metzger, H.; Holy, V.;
We studied the generation of an ordered Ge quantum dot array in an amorphous silica matrix by ion beam irradiation. In particular we investigated the influence of the irradiation process on the nucleation of Ge clusters, on the correlations in their positions and on the crystalline quality of Ge quantum dots formed after subsequent annealing. We have developed a method for the description of the intensity of grazing-incidence x-ray small-angle scattering from irradiated multilayers, which enables a precise determination of the arrangement of quantum dots as well as their position correlation and size distribution. The analysis shows that the irradiation causes an ordering of Ge clusters along the irradiation direction, which substantially improves the correlations of the Ge dot locations in their three-dimensional array. The observed phenomena are explained and simulated by a Monte Carlo model based on the modification of local Ge density induced by ion tracks in the irradia!
ted multilayers.

Publ.-Id: 14744 - Permalink


Comparison of Ga-68 labelled RGD-peptides for imaging integrin alpha(v)beta3 expression
Knetsch, P.; Seidel, G.; Petrik, M.; Rangger, C.; Helbok, A.; Griessinger, C.; Fani, M.; von Guggenberg, E.; Wester, H.; Pichler, B.; Pietzsch, H.-J.; Decristoforo, C.; Haubner, R.;
Aim: An promising therapeutic approach to treat cancer focus on the inhibition of tumourinduced angiogenesis. One target structure involved is integrin alpha(v)beta3. Imaging modalities allowing monitoring of alpha(v)beta3 may provide insights into corresponding molecular process. Labelling techniques becoming more and more interesting for molecular imaging with PET are based on Ga‐68. Especially, due to the straightforward labelling protocols this is an interesting alternative to F‐18 labelling of peptides. Here the imaging properties of c(RGDfK) conjugated to different chelating systems are compared.
Methods: Peptide synthesis follows standard SPPS protocols. The cyclised and selectively deprotected peptides were conjugated with the chelating moieties via the side chain amino function of the lysine. The chelating systems include 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐acetic acid (DOTA), 1,4,7‐triaazacyclononane‐4,7‐acetic acid‐1‐2‐glutaric acid (NODAGA), and a tris(2‐mercaptoethyl)amine derivative (NS3). Labelling was carried out using the fractionated elution method in sodium acetate (DOTA; NODAGA) or phosphate buffer (NS3). In vitro evaluation included log D determination, protein binding assays, plasma stability studies, isolated receptor binding assays, and cell uptake studies. In vivo evaluation was carried out using M21 (alpha(v)beta3 positive) and M21L (alpha(v)beta3 negative) bearing nude mice. For all tracer biodistribution data were collected. For DOTA‐RGD and NODAGA‐RGD also small animal PET imaging was carried out. Results: NODAGA‐RGD and NS3‐RGD could be labelled at room temperature, whereas labelling of DOTA‐RGD has to be carried out at elevated temperature. NODAGA‐RGD and DOTA‐RGD could be labelled in high radiochemical purity without further purification. For NS3‐RGD a subsequent Seppak separation was necessary to obtain the product in high radiochemical purity. The compounds showed comparable log D (‐2.9 ‐ ‐3.9) and IC(50) values (~5 nM) as well as receptor specific uptake. In contrast, great differences were found in the protein binding properties. The found protein bound activity after 1 h incubation was 18.6% (DOTA‐RGD), 42,4% (NS3‐RGD), and 1.4% (NODAGA‐RGD). This performance is reflected in the biodistribution data. Lowest activity concentration in blood (%ID/g 1h p.i.: NODAGA‐RGD=0.12±0.06 ; DOTA‐RGD=0.72±0.07; NS3‐RGD=3.33±1.9) and best tumour/background ratios were found for NODAGA‐RGD. Small animal imaging confirmed these findings and indicated that NODAGA‐RGD might have similar imaging properties as found for F‐18‐Galacto‐RGD. Conclusions: In this series NODAGA‐RGD revealed most promising properties for imaging alpha(v)beta3 expression. Easy radiolabelling at room temperature, low amount of protein bound activity and the resulting lower activity concentration found in blood compared to the other compounds makes it to an attractive alternative to F‐18‐Galacto‐RGD, worth to be tested in clinical studies.
  • Lecture (Conference)
    23rd Annual Congress of the European Association of Nuclear Medicine (EANM), 09.-13.10.2010, Wien, Österreich
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 37(2010)2, S252

Publ.-Id: 14742 - Permalink


Biodistribution and metabolism of a Ga-68 labeled tris(salicylaldimine) derivative - a myocard perfusion tracer
Bergmann, R.; Jeong, J. M.; Pietzsch, J.; Steinbach, J.; Baum, R. P.;
Aim: The lipophilic cationic Ga‐68‐complex (Tsang B.W. et al. J Nucl Med 1993; 34; 1127) of Tris(4,6‐dimethoxysalicylaldimine)‐N,N′‐bis(3‐aminopropyl)‐N,N′‐ethylenediamine (BAPEN), showed high accumulation in mice hearts (Nucl Med Biol 2010; 37; 149). To reevaluate the radiopharmacological profile in rats the Ga‐68‐BAPEN was produced by a kit formulation and the biodistribution, kinetics and metabolism were studied with small animal PET.
Materials & methods: The BAPEN was labeled with 0.1 M HCl Ga‐68‐Cl3 (generator eluate 1 M HCl) in a one step procedure. Before application human serum albumin was added to a final concentration of 1%, and the solution filtrated (22 μm pore size). The biodistribution at 5 and 60 min p.i. (each time point 8 rats) after single intravenous injection, arterial blood clearance over 1 h (n=2), and the in vivo metabolism in Wistar rats were investigated in combination with small animal PET, and the main biokinetic parameters of Ga‐68‐BAPEN were estimated.
Results: Ga‐68‐BAPEN was prepared with purity >91% within 20 min. The activity was fast accumulated in the rat heart (values in SUV; 5 min p.i., 1.56 ± 0.19; 60 min, 1.42 ± 0.35) with the following heart‐to‐tissue ratios at 5 min p.i.: blood 4.2, lung 2.2, liver 0.4, kidneys 0.3, and brain 109.6. No clearance of Ga‐68‐activity from the heart was observed over 1 hour. The arterial blood clearance of the original compound was biphasic with half lifes of 2 min and 23 min respectively; it was metabolized with a half‐life of 1.6 min. The Ga‐68‐activity was rapidly excreted into the intestine (5 min p.i. 34.9 ± 4.0%ID; 60 min p.i. 56.7 ± 7.0%ID).
Conclusion: Ga‐68‐BAPEN showed a typical perfusion dependent biodistribution pattern in rats, with high accumulation in heart, kidneys, liver, adrenals, and pancreas. The heart was clearly delineated with low background. The increasing liver uptake could complicate the quantitative imaging of the heart apex at late time points. Ga‐68‐BAPEN was fast distributed followed by a slow blood clearance on a low activity level. The fast in vivo metabolism of the Ga‐68‐BAPEN in rats prevented a more distinct perfusion dependent biodistribution pattern. No transport through the blood‐brain‐barrier into the brain was observed. The Ga‐68‐BAPEN may be useful as radiopharmaceutical for perfusion imaging, particularly, for the heart.
  • Lecture (Conference)
    23rd Annual Congress of the European Association of Nuclear Medicine (EANM), 09.-13.10.2010, Wien, Österreich
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 37(2010)2, S251
  • Poster
    2010 World Molecular Imaging Congress, 08.-11.09.2010, Kyoto, Japan

Publ.-Id: 14741 - Permalink


Preclinical radiation dose assessment of (-)-[F18]NCFHEB, a new PET tracer for imaging of cerebral alpha4beta2 nicotinic acetylcholine receptors
Sattler, B.; Deuther-Conrad, W.; Fischer, S.; Hiller, A.; Patt, M.; Kendziorra, K.; Hesse, S.; Smits, R.; Hoepping, A.; Steinbach, J.; Sabri, O.;
Aim: (‐)‐[F‐18] Norchloro‐fluoro‐homoepibatidine ((‐)‐NCFHEB) is a new and promising tracer for neuroimaging of alpha4beta2 nicotinic acetylcholine receptors with PET. To assess the radiation risk to humans caused by systemic application of the tracer, CD1 mice were injected with (‐)‐NCFHEB. The biodistribution of the tracer and, thereby, resulting organ doses (OD) and the effective dose (ED) were calculated.
Methods: 27 female CD1 mice (weight: 28.2 ± 2.1g) were injected i.v. with 0.75± 0.334MBq of (‐)‐[F18]NCFHEB (specific activity >100GBq/μmol) through the V. caudata lateralis. At 5, 15, 30, 45, 60, 90, 120, 180 and 240 min. p.i. the animals were sacrificed (n=3 per time). The organs (brain, heart, lung, stomach, small intestine, large intestine, liver, kidneys, urinary bladder, spleen, thymus, pancreas, adrenals, ovaries, blood, skin, muscle, skeleton) were isolated, weighed and counted in a γ‐counter to determine mass and radioactivity. The masses of the skeleton and the muscle were extrapolated from tissue samples [1]. Time and mass scales were adapted to the respective human scales [2]. The fractions of activity in source organs were displayed as %ID/g, and %ID/organ for both scales. Time‐activity curves were derived by trapezoidal and exponential fits. The numbers of disintegrations in the source organs were calculated and ODs and the ED was calculatedusing OLINDA.
Results: The urinary bladder receives the highest OD of 104.0 μSv/MBq, followed by the kidneys (24.2 μSv/MBq), uterus (14.1 μSv/MBq), liver (14.0 μSv/MBq), pancreas (14.0 μSv/MBq) and small intestine (14.0 μSv/MBq) The highest contribution to the ED was by urinary bladder (5.2μSv/MBq) followed by the ovaries (2.1μSv/MBq), lower large intestine (1.5μSv/MBq) and red marrow (1.3 μSv/MBq). According to these data, the ED by i.v. application of (‐)‐[F18]NCFHEB
results in an ED of 14.2 μSv/MBq.
Conclusion: The ED as a measure of the overall radiation risk upon i.v. application of about 370 MBq (‐)‐[F‐18] NCFHEB to humans would be 5.3 mSv. This is well within the range of the application of other [F18]‐labeled compounds to humans. This risk assessment encourages to transfer (‐)‐[F‐18]NCFHEB from preclinical to clinical study phases and to further develop as a clinical tool for PET brain imaging.
References: [1] Lindstedt SL, Schaeffer PJ.: Use of allometry in predicting anatomical and physiological parameters of mammals Laboratory Animals (2002) 36, 1‐19 [2] Stabin MJ: Fundamentals of Nuclear Medicine Dosimetry, Springer 2008, ISBN 978‐0‐387‐74578‐7, 237P The trial is granted by the German Federal Ministry of Education and Research (Nr. 01EZ0820)
  • Lecture (Conference)
    23rd Annual Congress of the European Association of Nuclear Medicine (EANM), 09.-13.10.2010, Wien, Österreich
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 37(2010)2, S205

Publ.-Id: 14740 - Permalink


Reduced myocardial glucose utilization after fasting and heparin injection in rats
Bergmann, R.; Pietzsch, J.;
kein Abstract verfügbar
  • Poster
    78th European Atherosclerosis Society Congress (EAS), 20.-23.06.2010, Hamburg, D
  • Abstract in refereed journal
    Atherosclerosis 11(2010)2, 192

Publ.-Id: 14739 - Permalink


Observation of the intraexciton Autler-Townes effect in GaAs/AlGaAs semiconductor quantum wells
Wagner, M.; Schneider, H.; Stehr, D.; Winnerl, S.; Andrews, A. M.; Schartner, S.; Strasser, G.; Helm, M.;
The near-infrared transmission of a semiconductor multiple quantum well is probed under intense terahertz illumination. We observe clear evidence of the intraexcitonic Autler-Townes effect when the terahertz beam is tuned near the 1s-2p transition of the heavy-hole exciton. The strongly coupled effective two-level system has been driven with terahertz field strengths of up to 10  kV/cm resulting in a Rabi energy of ≈0.6 times the transition energy. The induced near-infrared spectral changes at low intensities are qualitatively explained using a basic two-level model.
Keywords: Autler-Townes effect, AC Stark, intraexciton, free-electron laser

Publ.-Id: 14738 - Permalink


Terawatt Yb:CaF2 laser
Siebold, M.; Uecker, R.; Hornung, M.; Hein, J.; Sauerbrey, R.;
We present a terawatt diode-pumped laser employing single-crystalline Yb:CaF2 as the amplifying medium. A pulse energy of 197 mJ and a duration of 192 fs were obtained, corresponding to a peak power of 1 TW.
  • Invited lecture (Conferences)
    6th International Conference on Crystal Growth ICCG-16, 08.-13.08.2010, Beijing, China

Publ.-Id: 14737 - Permalink


Copper binding to S100A12: Suggested role in oxidative modification of human LDL
Pietzsch, J.; Walther, M.; Bergmann, R.; Hoppmann, S.;
kein Abstract verfügbar
  • Poster
    78th European Atherosclerosis Society Congress (EAS), 20.-23.06.2010, Hamburg, D
  • Abstract in refereed journal
    Atherosclerosis 11(2010)2, 118

Publ.-Id: 14736 - Permalink


Native and glycooxidized high density lipoprotein (HDL) modulate adrenal steroidogenesis via scavenger receptor class B, type I (SR-Bi)
Kopprasch, S.; Saha, S.; Graessler, J.; Pietzsch, J.; Bornstein, S. R.;
kein Abstract verfügbar
  • Poster
    78th European Atherosclerosis Society Congress (EAS), 20.-23.06.2010, Hamburg, D
  • Abstract in refereed journal
    Atherosclerosis 11(2010)2, 113

Publ.-Id: 14735 - Permalink


Influence of novel selective cyclooxygenase-2 (COX-2) inhibitors on copper-mediated oxidation of human LDL
Pietzsch, J.; Pietzsch, F.-J.; Laube, M.; Wuest, F.; Steinbach, J.; Kniess, T.;
kein Abstract verfügbar
  • Poster
    78th European Atherosclerosis Society Congress (EAS), 20.-23.06.2010, Hamburg, D
  • Abstract in refereed journal
    Atherosclerosis 11(2010)2, 76

Publ.-Id: 14734 - Permalink


Multiple bandgap solar cells based on confined Ge nanocrystals in an oxide matrix
Zschintzsch, M.; Jeutter, N.; von Borany, J.; Mücklich, A.; Sahle, C.;
Si and Ge nanocrystals are supposed to be a promising material for high efficient 3rd generation multiple bandgap thin film solar cells. Photoluminescence studies of the quantum confinement effect in Si and Ge nanocrystals showed the feasibility of this approach [1, 2]. We propose the design sketched in Fig. 1 using a stack of well separated, mono-dispersed Ge nanoclusters of different size which allows bandgap tuning for light absorption from the blue to the infrared region.
In this contribution investigations on Ge nanocrystals formation in GeOx-SiO2 multilayer structures will be presented. The nanocrystals growth during annealing is vertically limited by the SiO2 separation layer while the phase separation of the GeOx layer during annealing leads to laterally GeO2 separated Ge nanocrystals. The goal is to achieve well confined, graded, equally sized and dense nano¬crystal superlattices only by the variation of the layer thicknesses and the GeOx composition. The GeOx-SiO2 stacks were deposited via reactive DC magnetron sputtering. A process window for the oxygen partial pressure in the O2/Ar sputtering gas mixture allows both, SiO2 formation for the separation layers as well as GeOx films with tuneable stoichiometry in the range of x = 0.2 - 2 [4].
Very smooth interfaces of the multilayers with roughness’s below 1 nm and a SiO2 separation layer thickness < 2 nm could be revealed with XRR and TEM – fig. 2 shows an annealed sample with Ge nanocrystals with a size of 2 nm. XANES synchrotron measurements (fig. 3) show that the phase separation of GeOx~1 is already finished at 400°C. The crystallisation occurs at 550°C which was monitored by GIXRD and Raman scattering. The Ge nanocrystal size was determined to be 2, 3 or 6 nm for different samples by GIXRD, TEM and Raman. Ellipsometry and absorbance measurements showed additional information’s about the structural and optical parameters of the multilayers. The stochiometry of the stack was always controlled with RBS.
Ge nanoclusters of 2 … 6 nm in size could be formed by phase separation at a temperature of about 400°C and crystallised at 550°C into nanocrystals which allows a broad variety of substrate materials. The very thin and smooth SiO2 separation layer enable interesting possibilities for charge transport via tunnelling.
[1] G. Conibeer et al. TSF 511-512, 654 (2006)
[2] Y. M. Niquet et al. APL 77, 1182 (2000)
[3] F. Dimroth et al. MRS Bulletin 32,230 (2007)
[4] M. Zschintzsch et al. JAP, in print (2010)
  • Poster
    25th European Phtotvoltaic Solar Energy conference, 5th World Conference on Photovoltaic Energy Conversion, Symposium: Advanced Photovoltaics: New Concepts and Ultra-High Efficiency, 06.-10.09.2010, Valencia, Spain

Publ.-Id: 14733 - Permalink


Confined Ge nanocrystals in an oxide matrix for multiple bandgap solar cells
Zschintzsch, M.; Jeutter, N.; von Borany, J.; Mücklich, A.; Sahle, C.;
Si and Ge nanocrystals are believed to be a promising material for high efficient 3rd generation multiple bandgap thin film solar cells. Photoluminescence studies of the quantum confinement effect in Si and Ge nanocrystals showed the feasibility of this approach [1, 2].
Our design is sketched in Fig. 1 which uses a stack of well separated, mono-dispersed Ge nanoclusters of different size on an absorbing Ge layer which allows bandgap tuning for light absorption from the blue to the infrared region. In this conference contribution investigations on Ge nanocrystals formation in GeOx-SiO2 multilayer structures will be reported. The goal is to achieve well separated, equally sized and dense nanocrystal superlattices only by the variation of the layer thicknesses and the GeOx composition. The GeOx-SiO2 multilayers were deposited via reactive DC magnetron sputtering. A process window for the oxygen partial pressure in the O2/Ar sputtering gas mixture allows both, SiO2 formation for the separation layers as well as GeOx films with tuneable stoichiometry in the range of x = 0.2 - 2 [4]. The films stoichiometry were always controlled with RBS. The nanocrystals growth during annealing is vertically limited by the SiO2 separation layer while the phase separation of the GeOx layer during annealing leads to laterally GeO2 separated Ge nanocrystals.
Very smooth interfaces of the multilayers with roughness’s below 1 nm and a SiO2 separation layer thickness < 2 nm could be revealed with XRR and TEM – fig. 2 shows an annealed sample with Ge nanocrystals of 3 nm size. XANES synchrotron measurements (fig. 3) show that the phase separation of GeOx~1 -> Ge + GeO2 is already completed at 400°C. GIXRD and Raman scattering confirme a crystallisation temperature of about 550°C. Ge nanocrystals with well defined sizes between 2 and 10 nm have be fabricated by the variation of the GeOx sublayer thickness. As derived from RAMAN measure¬ments, the degree of crystallinity decreases with reduced layer thickness. The energy dependent optical parameters were determined by means of photoluminescence, ellipsometry and absorbance mea¬surements. The very thin and smooth SiO2 separation layer enables interesting possibilities for charge transport via direct tunnelling.
References:
[1] G. Conibeer et al. Thin Solid Films 511-512, 654 (2006)
[2] Y. M. Niquet et al. Applied Physics Letters 77, 1182 (2000)
[3] F. Dimroth et al. Materials Research Society Bulletin 32, 230 (2007)
[4] M. Zschintzsch et al. Journal Applied Physics 107, 0343061-8 (2010
  • Poster
    Nanofair conference, Symposium: Energy, 06.-07.07.2010, Dresden, Deutschland

Publ.-Id: 14732 - Permalink


Self-Organized Formation of Ge nanocrystals out of (GeOx-SiO2) superlattice structures
Zschintzsch, M.; Jeutter, N.; Mücklich, A.; von Borany, J.; Sahle, C.;
Bandgap engineered Si and Ge nanocrystal solar cells are supposed to be a candidate for high effective 3rd generation thin film solar cells. Photoluminescence studies of the quantum confinement effect in Si and Ge nanocrystals showed the feasibility of this approach [1,2]. However the design and the fabrication of a high density of well separated, monodispersed nanoclusters remains a great challenge.
We want to present our investigations [3] on Ge nanocrystals formation in GeOx-SiO2 multilayer structures based on the phase separation of GeOx during annealing. The size of the laterally self-ordered Ge nanocrystals is vertically limited by the SiO2 separation layer. The final goal is to achieve well confined, graded, equally sized and dense nanocrystal superlattices only by the variation of the layer thicknesses and the oxygen content in the GeOx layer.
The GeOx-SiO2 stacks were deposited via reactive DC magnetron sputtering. A process window for the oxygen partial pressure in the O2/Ar sputtering gas mixture can be defined which allows both, SiO2 formation for the separation layers as well as GeOx films with tunable stoichiometry in the range of x = 0.2 … 2.
In-situ X-ray studies at synchrotron beamlines were performed to monitor the phase separation (XANES) of GeOx and the Ge nanocrystal formation (GIXRD, XRR, GISAXS) which was proofed in addition via TEM, Raman scattering and Absorbance.
Separated Ge nanocrystals of 2 … 6 nm in size can be formed at temperatures < 600°C. Very smooth interfaces with roughnesses below 1 nm allowed the separation of the Ge nanocrystal layers by SiO2 films < 2 nm which enables interesting possibilities for charge transport via tunnelling.
[1] G. Conibeer et al. TSF 511-512, 654 (2006)
[2] Y. M. Niquet et al. APL 77, 1182 (2000)
[3] M. Zschintzsch et al. JAP, 107, 0343061 - 8 (2010)
  • Poster
    MRS Spring Meeting, Symposium: Photovoltaics and Optoelectronics from Nanoparticles, 05.-09.04.2010, San Francisco, California, USA

Publ.-Id: 14731 - Permalink


Quantitative determination of the charge carrier concentration of sub-surface implanted silicon by IR-near-field spectroscopy
Jacob, R.; Winnerl, S.; Schneider, H.; Helm, M.; Wenzel, M. T.; von Ribbeck, H.-G.; Eng, L. M.; Kehr, S. C.;
We use a combination of a scattering-type near-field infrared microscope with a free-electron laser as an intense, tunable radiation source to spatially and spectrally resolve buried doped layers in silicon. To this end, boron implanted stripes in silicon are raster scanned at different wavelengths in the range from 10 to 14 μm. An analysis based on a simple Drude model for the dielectric function of the sample yields quantitatively correct values for the concentration of the activated carriers. In a control experiment at the fixed wavelength of 10.6 μm, interferometric near-field signals are recorded. The phase information gained in this experiment is fully consistent with the carrier concentration obtained in the spectrally resolved experiments.
Keywords: Spectroscopy, Near-field microscopy, Infrared, Semiconductor materials

Publ.-Id: 14730 - Permalink


The CBM time-of-fligth wall
Deppner, I.; Herrmann, N.; Gonzalez-Diaz, D.; Ammosov, V.; Cheng, J.; Ciobanu, M.; Gapienko, V.; Hildenbrand, K. D.; Kiselieva, A.; Kis, M.; Kresan, D.; Kotte, R.; Huangshan, C.; Leifels, Y.; Li, C.; Li, Y.; Loizeau, P. A.; Naumann, L.; Petrovici, M.; Petris, M.; Semak, A.; Simion, V.; Stach, D.; Sun, Y.; Sviridov, Y.; Tang, Z.; Usenko, E.; Wang, J.; Wang, Y.; Wisnieswki, K.; Wüstenfeld, J.; Xu, L.; Zaets, V.; Zhang, Y.; Zhu, X.;
The key element providing hadron identification in the future Compressed Baryonic Matter spectrometer at FAIR is a time-of-flight wall placed at 10 m distance from the target. The most promising technological option for such a task consists on a 150 m² carpet based on Resistive Plate Chambers. Due to the fixed-target geometry, the conceptual design foresees two extreme regions: an outermost region (low rate/low multiplicity) covered by float glass RPCs in multi-strip fashion, and a central region (high rate/high multiplicity) consisting of densely packed read-out cells made with low resistive electrodes. The status of the ongoing R&D efforts in both regions is presented.

Publ.-Id: 14729 - Permalink


Electrical and Magnetic Properties of Polycrystalline Mn-Doped BaTiO3 Thin Films Grown on Pt/Sapphire Substrates by Pulsed Laser Deposition
Shuai, Y.; Zhou, S. Q.; Schmidt, H.;
5 at.% Mn-doped and undoped, 200 nm thick BaTiO3 thin films have been grown under different oxygen partial pressures by pulsed laser deposition on Pt/sapphire substrates. X-ray diffraction (XRD) measurements reveal the same polycrystalline single-phase perovskite structure for all the thin films despite the different oxygen partial pressure, while their preferred orientation strongly depends on the oxygen partial pressure. The 5 at. % Mn-doping decreases the dielectric loss of the Mn-doped BaTiO3 thin films, however, their relative permittivity is also decreased. Ferroelectricity has been probed on the Mn-doped and undoped BaTiO3 thin films grown under relatively high oxygen partial pressure. A ferromagnetic coupling of the Mn dopant ions has been probed at room tempetature on the Mn-doped BaTiO3 thin films prepared under low oxygen partial pressure and is understood in terms of the bound magnetic polaron model.
Keywords: multiferroics, ferroelectricity, magnetism, barium titanate, bound magnetic polarons
  • Contribution to proceedings
    12th INTERNATIONAL CERAMICS CONGRESS, 06.-11.06.2010, Montecatini Terme, Tuscany, Italy
    Electrical and Magnetic Properties of Polycrystalline Mn-Doped BaTiO3 Thin Films Grown on Pt/Sapphire Substrates by Pulsed Laser Deposition

Publ.-Id: 14728 - Permalink


CFD-Analyses on the behaviour of mineral wool in the reactor sump
Krepper, E.; Grahn, A.; Cartland-Glover, G.; Weiss, F.-P.; Alt, S.; Kratzsch, A.; Renger, S.; Kästner, W.;
The investigation of insulation debris generation, transport and sedimentation becomes important with regard to reactor safety research for PWR and BWR, when considering the long-term behaviour of emergency core cooling systems during all types of loss of coolant accidents. A joint research project on such questions is being performed in cooperation between the University of Applied Sciences Zittau/Görlitz and the Forschungszentrum Dresden-Rossendorf. The project deals with the experimental investigation of particle transport phenomena in coolant flow and the development of CFD models for its description. While the experiments are performed at the University at Zittau/Görlitz, the theoretical modelling efforts are concentrated at Forschungszentrum Dresden-Rossendorf. In the current presentation the basic concepts for CFD modelling are described and feasibility studies are presented. On the example of a complex flow situation at plunging jet conditions the model capabilities are demonstrated.
Keywords: Insulation material transport, CFD, plunging jet
  • Contribution to proceedings
    Fachtagung der KTG-Fachgruppen, 07.-08.10.2010, Rossendorf, Deutschland
    Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland
  • Invited lecture (Conferences)
    Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland Fachtagung der KTG-Fachgruppen, 07.-08.10.2010, Rossendorf, Deutschland

Publ.-Id: 14727 - Permalink


Development of Multi-Physics Code Systems based on the Reactor Dynamics Code DYN3D
Kliem, S.; Gommlich, A.; Grahn, A.; Rohde, U.; Schütze, J.; Frank, T.; Gomez, A.; Sanchez, V.;
In the presentation the recent developments of the coupling of the reactor dynamics code DYN3D with the coarse-mesh CFD code FLICA-4 and the CFD code ANSYS CFX are presented. First results of verification calculations for small-size test problems confirm the correctness of the implementation of the coupling.
  • Invited lecture (Conferences)
    Fachtag der KTG: "Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland", 07.-08.10.2010, Dresden, Deutschland
  • Contribution to proceedings
    Fachtag der KTG: "Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland", 07.-08.10.2010, Dresden, Deutschland
    Tagungsband des Fachtages der KTG: "Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland", CDROM: FZ Dresden-Rossendorf
  • Kerntechnik 76(2011)3, KT100569

Publ.-Id: 14726 - Permalink


Medical Impact of Polynuclear Cluster Compounds
Stephan, H.; Müller, C. E.;
Polynuclear metal compounds may have considerable potential as metallic drugs. The most prominent representatives are polyoxometalates which have been investigated since the last third of the 19th century. In addition to applications in catalysis, separation, analysis, and as electron-dense imaging agents, some of these substances have been shown to exhibit biological activity in vitro as well as in vivo ranging from anti-cancer, antibiotic, and antiviral to anti-diabetic effects.1
Polymetalates represent a diverse ensemble of nanostructures with an almost infinite variability of chemical, physical and biological properties. The size of typical covalent bridged cluster compounds is in the range from 1 to 3 nm. The attachment of special surface groups on the periphery of cluster compounds may result in self-assembled non-covalent organized structures larger than 5 nm which are characteristic for bio-molecules, such as enzymes. Cells of mammalian organisms are typically 10 to 30 µm. However, sub-cellular organelle dimensions are smaller and range in sub-µm sizes. This comparison of size dimension illustrates that polymetalates are small enough to allow the cell membrane to be penetrated without too much interference. Evidently, some types of polymetalates are able to be transported into cells, particularly into mitochondria. Our aim is focused on the development of novel cluster compounds with improved chemical and metabolic stability. Furthermore, increased recognition of target biomolecules - such as enzymes - shall be achieved.
On the way to explore the biological activity of polynuclear cluster compounds, we recently recognised polyoxometalates as a new class of potent enzyme inhibitors.2 Certain polymetalates are able to inhibit E-NTPDases (ecto-nucleoside triphosphate diphosphohydrolases) that are surface-located nucleotide-hydrolyzing enzymes involved in the regulation of signaling cascades by activating P2 (nucleotide) receptors. The most potent compound - described to date – is K6H2[TiW11CoO40] I exhibiting IC50 values which are significantly lower than those of known standard inhibitors. Some compounds are also able to directly interact with P2 receptors. A further promising new class of cluster compounds to permit selective inhibition of E-NTPDases are hexanuclear rhenium complexes with bridging sulfur, selenium and/or tellurium atoms. In this perspective, a broad ensemble of water-soluble octahedral rhenium cluster compounds II becomes available by ligand exchange reactions.3
The paper will give a brief overview about the potential of inorganic cluster compounds in medicine as well as a survey of recent progress that was achieved on E-NTPDase inhibition and P2 receptor antagonism with polymetalates.

[1] J. T. Rhule, C. L. Hill, D. A. Judd, R. F. Schinazi, Chem. Rev.1998, 98, 327-357.
[2] C. E. Müller, J. Iqbal, Y. Baqi, H. Zimmermann, A. Röllich, H. Stephan, Bioorg. Med. Chem. Lett. 2006, 16, 5943-5947.
[3] K. A. Brylev, Y. V. Mironov, S. Kozlova, V. E. Fedorov, S.-J. Kim, H.-J. Pietzsch,
H. Stephan, A. Ito, S. Ishizaka, N. Kitamura, Inorg. Chem. 2009, 48, 2309-2315.
  • Lecture (Conference)
    IWTMC-II International Workshop on Transition Metal Clusters-II, 30.09.-02.10.2010, Rostock, D

Publ.-Id: 14725 - Permalink


A novel Dibenzoazacyclooctyne precursor in regioselective Copper-free click chemistry. An innovative 3-step synthesis.
Starke, F.; Walther, M.; Pietzsch, H.-J.;
A novel carboxylic acid substituted dibenzoazacyclooctyne precursor has been synthesized using a fast and innovative three-step synthesis. It can be easily converted into the corresponding alkyne through UV-irradiation. Due to its fast and regioselective reaction with azides, the alkyne is a promising agent for copper-free "click chemistry". The second order reaction rate constant was determined by 1H-NMR.
  • Open Access LogoARKIVOC (2010), 350-359

Publ.-Id: 14724 - Permalink


Nanotribology of lubricated carbon-based nanocoatings
Kunze, T.; Posselt, M.; Gemming, S.; Seifert, G.;
Nanocoatings have the potential to improve the surface properties of various materials. They are of extreme importance for surfaces in sliding lubricated contact such as highly stressed automotive engine parts. Here, nanocoatings have to be optimized with respect to low friction properties and a high wear resistance to enhance the energetic and environmental efficiency. An additional variation of the tribological characteristics arises due to the presence of the fuel as the lubricant.
The present study employs atomic-scale simulations in order to assist the manufacturing and optimization of functional nanocoatings. Our investigations focus on two basic functional film species - tetrahedral amorphous carbon (ta-C) and transition metal enriched carbon (TM:C) coatings. These films are modeled and studied with the help of bond-order potentials such as the reactive empirical bond-order (REBO) potential [1] for carbon-carbon interaction and the Shibuta potential [2] for TM-carbon interaction. Our simulations also incorporate an adaptive cutoff scheme, which is able to enhance the REBO potential characteristics [3]. Since the tribological properties of lubricated engine parts depend not only on the properties of the nanocoatings but also on the lubricant, the hydrocarbon dodecan is selected as a representative of the fuel in the automotive engines. Preliminary results on the ta-C film morphology and its tribological properties such as friction coefficients with and without lubrication are presented.

[1] D. W. Brenner et al., J. Phys.: Condens. Matter 14 (2002) 783
[2] Y. Shibuta et al., Chem. Phys. Lett. 472 (2009) 200
[3] L. Pastewka et al., Phys. Rev. B 78 (2008) 161402
Keywords: nanotribology, diamond-like carbon, atomistic simulations
  • Poster
    5th Int. Conf. Multiscale Materials Modeling (MMM2010), Symposium Tribology, 04.-08.10.2010, Freiburg, Deutschland
  • Contribution to proceedings
    5th Int. Conf. Multiscale Materials Modeling (MMM2010), 04.-08.10.2010, Freiburg, Deutschland
    Conference Proceedings MMM2010, Stuttgart: Fraunhofer Verlag, 978-3-8396-0166-2, 858

Publ.-Id: 14723 - Permalink


Status of atomic-level simulations of solid phase epitaxial recrystallization of amorphous Si
Posselt, M.;
In semiconductor technology amorphous Si layers are formed by ion implantation, and during subsequent annealing the solid phase epitaxial recrystallization (SPER) of the amorphous material takes place. In order to simulate the SPER process and to understand its atomic-level mechanisms, classical molecular dynamics calculations are employed since they allow the consideration of several thousand atoms and a time scale up to some hundreds of nanoseconds. In the last decade different authors investigated SPER in Si by this type of simulations, but the critical review shows that their results are not consistent with the experimental data. In most cases the SPER rate was strongly overestimated. Moreover, the results obtained by different groups under virtually equal conditions do not agree. This may be due to the different approaches used to prepare the initial state consisting of an atomic system with a nearly planar amorphous-crystalline interface. The main cause for the disagreement with experimental data is the inaccuracy of the interatomic potentials used in the different studies. The improvements considered in the present work are based on a better description of the amorphous phase using a modified potential without changing the established potential for the single-crystalline material. It is found that amorphous Si with realistic structural and thermodynamic properties can be obtained by certain modifications of known interatomic potentials, but these modifications do not yield the correct SPER rate. However, it is shown that the value of the SPER rate is strongly correlated with the melting temperature of amorphous silicon obtained by the corresponding modified potential. Obviously, this dependence can be explained by the fact that both melting and SPER are essentially determined by the flexibility of atomic bonds. The atomic mechanism of SPER consists in sequential local arrangements of atomic bonds and positions, preferentially along {111} facets or terraces.
Keywords: epitaxial recrystallization, Si, atomistic computer simulations
  • Lecture (Conference)
    5th Int. Conf. Multiscale Materials Modeling (MMM2010), Symposium Microstructure Modeling, 04.-08.10.2010, Freiburg, Deutschland
  • Contribution to proceedings
    5th Int. Conf. Multiscale Materials Modeling (MMM2010), 04.-08.10.2010, Freiburg, Deutschland
    Conference Proceedings MMM2010, Stuttgart: Fraunhofer Verlag, 978-3-8396-0166-2, 509

Publ.-Id: 14722 - Permalink


Applications of 100TW class ultrashort-pulse lasers
Schramm, U.;
first steps to laser driven radiation oncology
and the future of the Dresden laser lab
  • Lecture (Conference)
    Superstrong fields in plasmas, 03.-08.10.2010, Varenna, Italien

Publ.-Id: 14721 - Permalink


Nano-Biotechnologie für den Umweltschutz: Neue photokatalytisch aktive Verbundmaterialien zur Eliminierung von pharmazeutischen Reststoffen (NanoPharm)
Pollmann, K.; Raff, J.;
Vorstellung des BMBF-geförderten "NanoPharm"-Projekts
  • Lecture (others)
    4. MITTELDEUTSCHES NETZWERKTREFFEN, 30.11.2010, Magdeburg, Deutschland

Publ.-Id: 14720 - Permalink


Bioinspired nanomaterials
Raff, J.;
Protecting the environment and saving resources are two of the society’s challenges of the 21th century. Therefore interesting insights coming also from nature. As many bacteria and archaea live in extreme habitats, they developed early in evolution so called surface layers (S-layers), which function as intelligent interface between cells and their environment. One function of such S-layers is the binding of toxic metals and metalloids and thusly the protection of the cells from being damaged by these elements and their compounds. This makes, together with their self-assembling properties, S-layer very interesting building blocks for the construction of new bioinspired nanomaterials for different technical applications. Currently under development are materials for the selective metal-binding for the removal of toxic metals and metalloids or the recovery of precious metals, highly efficient (photo)catalysts for the elimination of organic pollutants or organic synthesis and new biosensors for chemicals or pharmaceuticals.
Keywords: S-layer, nanomaterials
  • Lecture (others)
    nanoSeminar des Instituts für Werkstoffwissenschaft, TU Dresden, 11.11.2010, Dresden, Deutschland

Publ.-Id: 14719 - Permalink


Domains and Dynamics in NiMnGa
Neudert, A.; Schäfer, R.; McCord, J.;
Magnetic domains in the shape memory alloy NiMnGa are investigated using magneto-optical indicator film technique. Depending on whether the twin boundary is moved by applying mechanical stress or magnetic fields a different domain state is found after twin boundary motion.
  • Lecture (Conference)
    SPP Convention Tutzing, 29.09.2010, Tutzing, Germany

Publ.-Id: 14718 - Permalink


Local patterning of damping by ion-irradiation In ferromagnetic-antiferromagnetic thin films
McCord, J.; Mönch, I.; Strache, T.; Fassbender, J.ORC; Mattheis, R.
The control of the effective magnetic anisotropy, saturation magnetization as well as the dynamic magnetic properties in ferromagnetic thin films is of significant importance for most applications in spin electronics. The two materials’ parameters which control the dynamic response of soft magnetic thin films are the precessional frequency f_res and the effective damping parameter alpha. Whereas anisotropy and saturation magnetization together determine the precessional frequency of the films, the magnetic damping parameter cannot be varied easily. However it was shown that exchange coupled ferromagnetic/antiferromagnetic (F/AF) systems exhibit strong changes in f_res and alpha independent of the occurrence of exchange bias [1, 2]. On the other hand, ion irradiation of magnetic thin films [3] has been shown to provide an alternative method to alter soft magnetic properties of magnetic multilayer films due to ion induced changes in the interfacial structure. Here we use Ni-ion irradiation to control the dynamic magnetic properties in Ni81Fe19/IrMn/Ni81Fe19 structures in a controlled way. We show that for very thin AF layers alpha can be increased significantly [4]. Selecting an IrMn thickness below the onset of exchange bias, it is possible to solely alter alpha. This effect is reversible by low fluence Ni ion irradiation without changing the composition of the ferromagnetic alloy and thus can be used to adjust alpha over a wide range. As a consequence, the method can be used to laterally pattern samples only by the damping parameter. As shown in Fig. 1 the overall integral damping parameter then is determined by the relative fraction of materials with high and low damping parameter. alpha is thereby varied linearly without any significant change in f_res. The demonstrated paths of film alteration by ion irradiation provide an additional degree of freedom for the tailoring of dynamic magnetic properties of softmagnetic thin films. The method not only allows for general adjustment of magnetic properties, but also for a local setting of dynamic magnetic properties.
This work was supported by the German Science Foundation DFG under grant no. MC9-8/2.

[1] J. McCord et al., Phys. Rev. B 70, 094420 (2004)
[2] J. McCord et al., Phys. Rev. B 75, 134418 (2007).
[3] J. Fassbender and J. McCord, J. Magn. Magn. Mater. 320, 579 (2008).
[4] J. McCord, et al., Appl. Phys. Lett. 92 162506 (2008).
  • Lecture (Conference)
    IEEE 7th International Symposium on Metallic Multilayers (MML2010), 20.-24.09.2010, Berkeley, USA

Publ.-Id: 14717 - Permalink


Domain width effects on the magneto-dynamic response of CoFeB element arrays
Patschureck, C.; McCord, J.; Schäfer, R.; Mattheis, R.; Schultz, L.;
Understanding the role of the magnetic domain structure on the magneto-dynamic properties of patterned magnetic thin film structures is crucial for the optimization of devices, e.g. recording heads and integrated inductors. Arrays of rectangular amorphous Co40Fe40B20 elements of micron size, a separation to width ratio of 1.5 and a thickness of 60 nm have been fabricated. Magneto-optical Kerr microscopy was used to study the domain structure. At zero field closure domain patterns are present whereas the domain width was systematically altered by varying the magnetic field history. The magneto dynamic response of different domain patterns with adjusted domain width was measured using pulsed inductive microwave magnetometry. We show that the resonance frequency is the lowest for broad closure domain structures and increases when the domain width is decreased.
  • Lecture (Conference)
    Joint European Magnetic Symposia JEMS 2010, 25.08.2010, Krakow, Poland

Publ.-Id: 14716 - Permalink


Spatially controlled manipulation of damping in ferromagnetic thin films
McCord, J.; Strache, T.; Mönch, I.; Fassbender, J.ORC; Mattheis, R.
The control of dynamic magnetic properties in ferromagnetic thin films is of significant importance for applications in spin electronics. We demonstrate the use of low fluence Ni-ion irradiation to locally and solely tailor the magnetic damping parameter e in ferromagnetic-antiferromagnetic Ni81Fe19/IrMn/Ni81Fe19 sandwich structures. The overall relaxation time then depends on the relative fraction of the phases with different e , which thereby can be controlled without changing the precessional frequency. The superposition of alpha is confirmed by modeling of the dynamic response. The demonstrated path of film engineering by local ion irradiation [J. Fassbender, J. McCord, JMMM 320 (2008) 579] provides an additional degree of freedom for the local tailoring of dynamic magnetic properties of soft-magnetic thin films.
  • Lecture (Conference)
    Joint European Magnetic Symposia JEMS 2010, 27.08.2010, Krakow, Poland

Publ.-Id: 14715 - Permalink


P0806 Verfahren und Anordnung zum Nachweis von Östrogen in wässrigen Lösungen
Cherkouk, C.; Rebohle, L.; Skorupa, W.;
Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zum schnellen Nachweis von Östrogen in wässrigen Lösungen vor Ort zu realisieren. Der Nachweis basiert auf einer Fluoreszenzanalyse, wobei eine integrierte Lichtquelle mit einer bioaktiven Schicht auf deren Oberfläche verwendet wird. Die bioaktive Schicht wird durch ein spezielles Hybridisierungs- und Silanisierungsverfahren erzeugt. Die Messung erfolgt durch die optische Detektion farbstoffmarkierter Hormonmoleküle, die nach einem bestimmten Messprotokoll die Rezeptoren belegen, die noch nicht durch Hormone aus der Messprobe gesättigt worden sind.
  • Patent
    Anmeldung: DE102008024526 A1 2009/12/03

Publ.-Id: 14714 - Permalink


Optical and microstructural properties of self-assembled InAs quantum structures in silicon
Prucnal, S.; Turek, M.; Drozdziel, A.; Pyszniak, K.; Wójtowicz, A.; Zhou, S. Q.; Kanjilal, A.; Shalimov, A.; Skorupa, W.; Zuk, J.;
The InAs quantum structures were formed in silicon by sequential ion implantation and subsequent thermal annealing. Samples were characterized by micro-Raman spectroscopy, Rutherford backscattering spectrometry (RBS), low temperature photoluminescence (PL), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Two kinds of crystalline InAs nanostructures were successfully synthesized:quantum dots (QDs) and nanopyramides (NPs). The Raman spectrum shows two peaks at 215 and 235 cm-1 corresponding to the transverse optic (TO) and longitudinal optic (LO) InAs single-phonon modes, respectively. The narrow PL band at around 1.3 mm due to the excitation of InAs QDs with an average diameter 7.5 ± 0.5 nm was observed. The InAs NPs were found only in samples annealed for 20 ms at temperatures ranging from 1000 up to 1200 oC. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by HRTEM and XRD techniques. The average size of the NPs is 50 nm base and 50 nm high and they are oriented parallel to the Si (001) planes. The lattice constant of the NPs increases from 6.051 to 6.055 Ǻ with the annealing temperature increasing from 1100 to 1200 oC due to network relaxation. Energy dispersive spectroscopy (EDS) shows almost stoichiometric composition of the InAs NPs.
Keywords: InAs, nanopyramid, quantum dots, flash lamp annealing, ion implantation
  • Poster
    E-MRS 2010 Spring Meeting, 07.-11.06.2010, Strasbourg, France

Publ.-Id: 14713 - Permalink


Electro-Optical Properties of Solar Cell Emitters Fabricated by Plasma Immersion Ion Implantation and Flash Lamp Millisecond Annealing
Prucnal, S.; Skorupa, W.; Abendroth, B.; Krockert, K.; Möller, H. J.;
Both mono- and multicrystalline p-type silicon wafers were used for the phosphorous ion implantation. After ion implantation the silicon is strongly disordered or amorphous within the ion range. Therefore subsequent annealing is required to remove the implantation damage and to activate the doping element. During FLA, only the wafer surface is heated homogeneously to very high temperatures at ms time scales, resulting in the annealing of the implantation damage and an electrical activation of the phosphorous. It is demonstrated that FLA at 800 oC for 20 ms even without preheating is sufficient to recrystallized implanted silicon. The highest recrystallization and the lowest resistivity were obtained after annealing at 1200 oC for 20 ms both for mono- and multicrystalline silicon wafers. Photoluminescence results point towards P - cluster formation at high annealing temperatures which effects on metal impurity gettering within the emitter.
Keywords: c-Si, mc-Si, ion implantation, FLA, solar cells
  • Poster
    26th European Photovoltaic Solar Energy Conference and Exhibition (26th EU PVSEC), 05.-09.09.2010, Valencia, Spain

Publ.-Id: 14712 - Permalink


P0801 Anordnung zur dreidimensionalen Elektronenstrahltomographie
Hampel, U.;
Aufgabe der vorliegenden Erfindung ist es, eine Anordnung zur Röntgen-Computertomographie anzugeben, die eine kontinuierliche dreidimensionale Abbildung des Untersuchungsobjektes bzw. eines Teilvolumens des Untersuchungsobjektes bei hoher zeitlicher und räumlicher Auflösung gestattet, wobei mit hoher räumlicher Auflösung sowohl eine hohe Auflösung innerhalb der Schnittebene als auch in axialer Richtung definiert ist.
  • Patent
    Anmeldung: DE 102008005718A1 2009/07/30
  • Patent
    Anmeldung: WO 2009092372A1: Offenlegung-30.07.2009; Nationaliserung in US, EP

Publ.-Id: 14711 - Permalink


Solar cell emitters fabricated by flash lamp millisecond annealing
Prucnal, S.; Shumann, T.; Skorupa, W.; Abendroth, B.; Krockert, K.; Möller, H. J.;
Phosphorous ion implantation was used for the emitter formation in mono- and multicrystalline silicon solar cells. After ion implantation the silicon is strongly disordered or amorphous within the ion range. Therefore subsequent annealing is required to remove the implantation damage and to activate the doping element. Flash-lamp-annealing (FLA) offers here an alternative route for the emitter formation at an overall low thermal budget. During FLA, only the wafer surface is heated homogeneously to very high temperatures at ms time scales, resulting in the annealing of the implantation damage and an electrical activation of the phosphorous. However, variation of the pulse time also allows to modify the degree of annealing of the bulk region to some extent as well, which can have an influence on the gettering behaviour of metallic bulk impurities.
The μ-Raman spectroscopy showed that the silicon surface is amorphous after ion implantation. It could be demonstrated that FLA at 800°C for 20 ms even without preheating is sufficient to recrystallize implanted silicon. The highest carrier concentration and efficiency and the lowest resistivity were obtained after annealing at 1200°C for 20 ms both for mono- and multicrystalline silicon wafers. Photoluminescence results point towards P-cluster formation at high annealing temperatures which effects on metal impurity gettering within the emitter.
Keywords: Solar cells, silicon, Flash Lamp Annealing
  • Open Access LogoActa Physica Polonica A 120(2011)1, 30-34

Publ.-Id: 14710 - Permalink


Optical and microstructural properties of In(As, N) quantum structure made by ion implantation and flash lamp processing
Prucnal, S.; Turek, M.; Drozdziel, A.; Pyszniak, K.; Wójtowicz, A.; Kanjilal, A.; Shalimov, A.; Skorupa, W.; Żuk, J.;
The In(As, N) quantum structures were formed in silicon, SiO2 and Si3N4 films by sequential ion implantation and subsequent thermal annealing. Samples were characterized by -Raman spectroscopy, Rutherford backscattering spectrometry (RBS), low temperature photoluminescence (PL), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Two kinds of crystalline InAs nanostructures were successfully synthesized: quantum dots (QDs) and nanopyramides (NPs). The Raman spectrum shows two peaks at 215 and 235 cm-1 corresponding to the transverse optical (TO) and longitudinal optical (LO) InAs phonon modes, respectively. The narrow PL band at around 1.3 m from the InAs QDs with an average diameter 7.5 ± 0.5 nm was observed.
The InAs NPs were found only in samples annealed for 20 ms at temperature range from 1000 up to 1200 oC. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by high resolution transmission electron microscopy (HRTEM) (see Fig. 1) and X-ray diffraction (XRD). The average size of the NPs is 50 nm base and 50 nm high and they are oriented parallel to the Si (001) planes. The InAs nanopyramids grow in silicon due to liquid phase epitaxy. The InN crystals are formed on the top of silicon nitride layer due to outdiffusion of indium and in Si3N4 film. The PL measurements shows narrow band at around 1.35 m originated from hexagonal InN nanocrystals due to quantum confinement size effect. -Raman scattering study shows two peaks at 495 and 588 cm-1, which correspond to (TO) of E2h and (LO) of A1 phonon modes, respectively.
Keywords: InAs, InN, Quantum dots, photoluminescence, FLA
  • Lecture (Conference)
    VIII-th International Conference Ion Implantation and Other Applications of Ions and Electrons, 14.-17.06.2010, Kazimierz Dolny, Poland

Publ.-Id: 14709 - Permalink


P0808 Verfahren und Anordnung zur Reinigung des Reaktionsgemisches bei der Herstellung von Radiopharmaka
Füchtner, F.; Mäding, P.; Preusche, S.; Zessin, J.;
Die Erfindung betrifft die Herstellung von Radiopharmaka, insbesondere in Verfahren, und eine Anordnung zur Reinigung des Reaktionsgemisches bei der Herstellung von Radiopharmaka, insbesondereF-markierte Radiopharmaka, wie z. B. [F]FDOPA und [F]OMFD sowie [F]FMeMcN. Erfindungsgemäß wird zur Reinigung des Raktionsgemisches eine Vorsäule als Vorreinigungssäule, gefüllt mit RP-Material (Reversed Phase Material), zur Abtrennung des bei der Reaktion verwendeten Lösungsmittels (Matrix) bzw. unerwünschter Nebenprodukte verwendet, während die eigentliche chromatographische Trennung des Reaktionsgemisches auf einer HPLC-Säule, bevorzugt einer RP-HPLC-Säule, durchgeführt wird.
  • Patent
    Anmeldung: DE 102009009344 A1 2010/09/02
  • Patent
    Anmeldung: WO201088901A1 2010/02/05

Publ.-Id: 14708 - Permalink


Magnetic Anisotropy of Thin Magnetic Films on Nanometer Scale Silicon Ripples
Ball, D.; Liedke, M. O.; Lenz, K.; Fritzsche, M.; Yilgin, R.; Keller, A.; Ranjan, M.; Facsko, S.; Fassbender, J.ORC
Ion beam erosion techniques allow for the creation of well-ordered substrate ripples with nanometer periodicity. Moreover, the periodicity can be tuned by changing the ion beam energy over a wide range [1]. The ripple pattern is directly transferred into films grown on these substrates. This offers the possibility of tailoring the magnetic properties by inducing additional magnetic anisotropy due to the structural modifications.
We study the influence of rippled vs. flat Si substrates for 10 nm thin Fe and Co films, as well as technologically relevant Heusler alloys (Fe3Si and Co2FexMn1-xSi). The magnetic anisotropy is measured by frequency and angle dependent vector network analyzer ferromagnetic resonance. The ripple morphology of the magnetic layers induces a strong uniaxial magnetic anisotropy.
Keywords: Vector network analyzer ferromagnetic resonance, Co2FexMn1-xSi, Fe3Si, rippled morphology
  • Poster
    Nanofair, 06.-07.07.2010, Dresden, Germany

Publ.-Id: 14707 - Permalink


P0802 Hochgeordnete Nanostrukturen und Sensor und deren Verwendung
Pollmann, K.; Raff, J.; Fahmy, K.;
Die vorliegende Erfindung betrifft eine hochgeordnete Nanostruktur und Sensor, in der bzw. dem organische Molekülgruppen, die spezifische Bindungseigenschaften für ein Zielmolekül haben, geordnet gebunden sind, und deren Verwendung. Anwendungsgebiet dafür finden sich in der Biotechnologie, Verfahrenstechnik, Umwelttechnik und Pharmazie, insbesondere bei der Herstellung von Biosensoren, in der biomedizinischen Analytik, bei der Beseitigung von Schadstoffen und Pathogenen, in der DNA-Analytik, für die Herstellung von Filtermaterialien, für Separationsverfahren, für Katalysatoren und in der medizinischen Therapie. Die Aufgabe der Erfindung ist es, eine Struktur zur Verfügung zu stellen, in der organische Molekülgruppen, insbesondere Molekülgruppen, die spezifische Bindungseigenschaften haben, geordnet gebunden sind, und dadurch die von den organischen Molekülgruppen gebundenen Substanzen in die Nähe funktioneller Bestandteile zu bringen. Dies wird gelöst durch eine Nanostruktur, die selbstorganisierende Proteine, an die Aptamere oder andere organische Molekülgruppen, die spezifische Bindungseigenschaften für ein Zielmolekül aufweisen, gebunden sind, und an die selbstorganisierenden Proteine gebundene anorganische Nanopartikel enthält.
  • Patent
    Anmeldung: DE 102008014298 A1 2009/09/24
  • Patent
    Anmeldung: EP 2101175 A1 2009/09/16

Publ.-Id: 14706 - Permalink


Solar cell emitters fabricated by plasma immersion ion implantation and flash lamp millisecond annealing
Prucnal, S.; Skorupa, W.; Abendroth, B.; Krockert, K.; Möller, H. J.;
Both mono- and multicrystalline p-type silicon wafers were used for the implantation of phosphorous. After ion implantation the silicon is strongly disordered or amorphous within the ion range. Therefore subsequent annealing is required to remove the implantation damage and to activate the doping element. Flash-lamp-annealing (FLA) offers here an alternative route for the emitter formation at an overall low thermal budget. During FLA, only the wafer surface is heated homogeneously to very high temperatures at ms time scales, resulting in the annealing of the implantation damage and an electrical activation of the phosphorous. However, variation of the pulse time also allows to modify the degree of annealing of the bulk region to some extent as well, which can have an influence on the gettering behaviour of metallic bulk impurities.
The μ-Raman spectroscopy showed that the silicon surface is amorphous after ion implantation. It could be demonstrated that FLA at 800oC for 20 ms even without preheating is sufficient to recrystallize implanted silicon. The highest carrier concentration and efficiency and the lowest resistivity were obtained after annealing at 1200oC for 20 ms both for mono- and multicrystalline silicon wafers. Photoluminescence results point towards P-cluster formation at high annealing temperatures which effects on metal impurity gettering within the emitter.
Keywords: solar cells, FLA,silicon
  • Poster
    VIII-th International Conference Ion Implantation and Other Applications of Ions and Electrons, 14.-17.06.2010, Kazimierz Dolny, Poland

Publ.-Id: 14705 - Permalink


Formation of InAs quantum dots in silicon by sequential ion implantation and flash lamp annealing
Prucnal, S.; Turek, M.; Drozdziel, A.; Pyszniak, K.; Zhou, S. Q.; Kanjilal, A.; Zuk, J.; Skorupa, W.;
InAs quantum dots (QDs) were successfully formed in single-crystalline Si by sequential ion implantation and subsequent milliseconds range flash lamp annealing (FLA). Samples were characterized by μ-Raman spectroscopy, Rutherford Backscattering Spectrometry (RBS) high-resolution transmission electronmicroscopy (HRTEM) and low temperature photoluminescence (PL). The Raman spectrum shows two peaks at 215 and 235 cm−1 corresponding to the transverse optical (TO) and longitudinal optical (LO) InAs phonon modes, respectively. The PL band at around 1.3 μm originates from the InAs QDs with an average diameter 7.5±0.5 nm and corresponds to the increased band gap energy due to the strong quantum confinement size effect. The FLA of 20 ms is sufficient for InAs QDs formation. It also prevents the out-diffusion of implanted elements.
Moreover, the silicon layer amorphized during ion implantation is recrystallized by solid-phase epitaxial regrowth during FLA.
Keywords: InAs, Quantum Dots, Si, photoluminescence, FLA

Publ.-Id: 14704 - Permalink


Comparison of the room temperature 1.53 μm Er photoluminescence from flash lamp and furnace annealed Er-doped Ge-rich SiO2 layers
Kanjilal, A.; Prucnal, S.; Rebohle, L.; Voelskow, M.; Helm, M.; Skorupa, W.;
The furnace and flash-lamp annealing (FLA) temperature dependent variation in the room temperature 1.53 μm Er photoluminescence (PL) from Er-doped Ge-rich SiO2 layers is investigated. The appearance of the 1.53 μm Er PL is discussed in the framework of the phonon-assisted fluorescent resonant energy transfer from Ge-related luminescence-centers (LCs) to the Er3+. Detailed analyses suggest that in case of FLA the decrease in the 1.53 μm Er PL intensity is governed by the temperature dependent recrystallization of Ge nanoclusters, while for furnace-annealing it is associated with the reduction in the LC-Er3+ coupling due to Ge out-diffusion and the formation of Er-rich clusters with increasing temperature.
Keywords: rare earth, electroluminescence, MOSLED, Flash Lamp Annealing

Publ.-Id: 14703 - Permalink


Infrared magneto-spectroscopy using quantum cascade lasers
Drachenko, O.; Winnerl, S.; Schneider, H.; Helm, M.; Leotin, J.;
We present a magneto-transmission experimental set up covering spectral region from 5 to 120 µm. Interchangable quintum cascade lasers are used as an excitation sources. Performance of the setup is illustrated via cyclotron resonance studies of InGaAs/GaAs QWs under magnetic fields up to 60T
Keywords: Cyclotron resonance, quantum cascade laser, high magnetic fields
  • Lecture (Conference)
    The 35th International Conference on Infrared, Millimeter and THz Waves (IRMMW-THz 2010), 05.-10.09.2010, Rome, Italy
  • Contribution to proceedings
    The 35th International Conference on Infrared, Millimeter and THz Waves (IRMMW-THz 2010), 05.-10.09.2010, Rome, Intaly: IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 978-1-4244-6657-3

Publ.-Id: 14702 - Permalink


Nucleation of copper-vacancy clusters in bcc-Fe: An atomistic study
Al-Motasem, A. T.; Posselt, M.; Bergner, F.;
Copper-rich precipitates are assumed to be the main cause of hardening and embrittlement of Cu-bearing reactor pressure vessel steels since they act as obstacles to dislocation motion within the grains of the polycrystalline bcc-Fe. Multiscale modeling contributes to a better understanding of point-defect-enhanced formation of these clusters during reactor operation. Rate theory is an efficient tool to simulate the cluster evolution on realistic time and length scales. However, many parameters used in rate theory, such as the diffusion coefficients of mobile species and the free binding energies of clusters, are not very well known from experimental investigations. Atomic-level computer simulations can provide these data. In the present work the nucleation free energy is determined for pure copper and pure vacancy clusters as well as for mixed clusters up to a maximum cluster size of 200. The energetics of the coherent CunVm clusters in bcc-Fe is obtained using a combination of on-lattice Monte Carlo simulations and off-lattice molecular dynamics. The most recent Fe-Cu interatomic potential by Pasianot and Malerba [1] is employed in the calculations.
[1] R. C. Pasianot and L. Malerba, J. Nucl. Mater. 360, 118 (2007).
Keywords: Lattice Monte Carlo, Nucleation of Cu-vacancy Cluster, free binding energy.
  • Poster
    Nuclear Materials 2010, An international conference in association with Journal of Nuclear Materials, 04.-07.10.2010, Karlsruhe, Germany

Publ.-Id: 14701 - Permalink


Traumatic Brain Injury Elicits Similar Alterations in α7 Nicotinic Receptor Density in Two Different Experimental Models
Hoffmeister, P.-G.; Donat, C. K.; Schuhmann, M. U.; Voigt, C.; Walter, B.; Nieber, K.; Meixensberger, J.; Bauer, R.; Brust, P.;
Traumatic brain injury (TBI) is a major cause of death and disability worldwide, especially in children and young adults. Previous studies have shown alterations in the central cholinergic neurotransmission after TBI. We therefore determined α7 nicotinic acetylcholine receptor (nAChR) densities in newborn piglets and adult rats after experimental TBI. Thirteen newborn piglets (post-TBI survival time: 6 h) underwent fluid percussion (FP) injury
(n = 7) or sham operation (n = 6). Furthermore, adult rats randomized into three groups of post-TBI survival times (2, 24, 72 h) received controlled cortical impact injury (CCI, n = 8) or sham operation (n = 8). Brains were frozen, sagittally cut and incubated with the α7-specific radioligand [125I]a-bungarotoxin for autoradiography. In injured newborn piglets, decreased α7 receptor densities were observed in the hippocampus (-38%), the hippocampus CA1 (-40%), thalamus (-30%) and colliculus superior (-30%). In adult rats, CCI decreased the receptor densities (between -16 and -47%) in almost any brain region within 2 and 24 h. In conclusion, widespread and significantly lowered α7 nAChR densities were demonstrated in
both TBI models. Our results suggest that a nearly similar TBI-induced decrease in the α7 density in the brain of immature and adult animals is found, even with the differences in species, age and experimental procedures. The alterations make the α7 nAChR a suitable target for drug development and neuroimaging after TBI.
Keywords: Traumatic brain injury; α7 nAChR; Autoradiography; Cholinergic system; α-Bungarotoxin

Publ.-Id: 14700 - Permalink


Texture development, microstructure and phase transformation characteristics of sputtered Ni-Ti Shape Memory Alloy films on TiN<111>
Martins, R. M. S.; Schell, N.; Reuther, H.; Pereira, L.; Mahesh, K. K.; Silva, R. J. C.; Fernandes, F. M. B.;
Near equiatomic Ni–Ti films have been deposited by magnetron co-sputtering on TiN films with a topmost layer formed by b111N oriented grains (TiN/SiO2/Si(100) substrate) in a chamber installed at a synchrotron radiation beamline. In-situ X-ray diffraction during Ni–Ti film growth and their complementary ex-situ characterization by Auger electron spectroscopy, scanning electron microscopy and electrical resistivity measurements during temperature cycling have allowed us to establish a relationship between the structure and processing parameters. A preferential development of b110N oriented grains of the B2 phase since the beginning of the deposition has been observed (without and with the application of a substrate bias voltage of −45 and −90 V). The biaxial stress state is considerably influenced by the energy of the bombarding ions, which is dependent on the substrate bias voltage value applied during the growth of the Ni–Ti film. Furthermore, the present work reveals that the control of the energy of the bombarding ions is a promising tool to vary the transformation characteristics of Ni–Ti films, as shown by electrical resistivity measurements during temperature cycling. The in-situ study of the structural evolution of the growing Ni–Ti film as a consequence of changing the Ti:Ni ratio during deposition (on a TiNb111N layer) has also been performed. The preferential growth of b110N oriented grains of the Ni–Ti B2 phase has been as well observed despite the precipitation of Ti2Ni during the deposition of a Ti-rich Ni–Ti film fraction. Functionally graded Ni–Ti films should lead to an intrinsic “twoway” shape memory effect which is a plus for the miniaturization of Ni–Ti films based devices in the field of micro-electro-mechanical systems.

Publ.-Id: 14699 - Permalink


Enantioselective σ1 receptor binding and biotransformation of the spirocyclic PET tracer 1’-Benzyl-3-(3-fluoropropyl)-3H-spiro[[2]benzofuran-1,4’-piperidine]
Wiese, C.; Große Maestrup, E.; Schepmann, D.; Grimme, S.; Humpf, H.-U.; Brust, P.; Wünsch, B.;
It was shown that racemic (±)-2 [1’-benzyl-3-(3-fluoropropyl)-3H-spiro[[2]benzofuran-1,4’-piperidine], WMS-1813] represents a promising positron emission tomography (PET) tracer for the investigation of centrally located σ1 receptors. To study the pharmacological activity of the enantiomers of 2, a preparative HPLC separation of (R)-2 and (S)-2 was performed. The absolute configuration of the enantiomers was determined by CD-spectroscopy together with theoretical calculations of the CD-spectrum of a model compound. In receptor binding studies with the radioligand [3H]-(+)-pentazocine, (S)-2 was thrice more potent than its (R)-configured enantiomer (R)-2. The metabolic degradation of the more potent (S)-enantiomer was considerably slower than the metabolism of (R)-2. The structures of the main metabolites of both enantiomers were elucidated by determination of the exact mass using an Orbitrap-LC-MS system. These experiments showed a stereoselective biotransformation of the enantiomers of 2.
Keywords: σ1 receptor ligands; PET tracer; resolution; CD spectroscopy; enantioselective receptor binding; enantioselective metabolism

Publ.-Id: 14698 - Permalink


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