Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33403 Publications

Uranium speciation after contact with plant cells

Geipel, G.; Viehweger, K.; Bernhard, G.
Uranium is an ubiqutous element. Besides this depleted uranium amunition as well as uranium mining and milling and manifold other use of uranium leads to an increase of uranium contamination in the environment.
Application of laser-induced and time-resolved methods allow the direct determination of uranium speciation at extremely low concentrations. This behaviour can be directly observed due to the properties extraorbitant luminescence properties of uranium-(VI). Contact of dissolved uranium with living cells at ambient conditions changes dramatically the uranium speciation.
Some examples fluorescence properties of uranium species relevant to the environment are shown. The change of this speciation can be observed then due to a change in luminescence properties. Besides of several organic phosphate binding forms although other uranium species were found as uranium bond to phenolic and thiol groups. Some of them do not emit any luminescence at room temperature. Nevertheless low temperature measurements allow the assignment of species not fluorescing at room temperature, due to strong dynamic quench effects of H2O molecules and COO- groups.
Keywords: Uranium, speciation, plants
  • Contribution to proceedings
    BioMetals 2008, 14.-18.7.2008, Santiago de Compostela, Spain
  • Lecture (Conference)
    BioMetals 2008, 14.-18.07.2008, Santiago de Compostela, Spain
  • Contribution to proceedings
    The 48th Annual American Society for Cell Biology Annual Meeting, 13.-17.12.2008, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-11179
Publ.-Id: 11179


Extracellular defence reactions of rape cells caused by uranium exposure

Viehweger, K.; Geipel, G.
Uranium is a widespread radioactive toxic heavy metal, released into the biosphere mostly by military purposes and nuclear industry. It is taken up by plant root systems and its chemical toxicity is much more dangerous than the radiological. Thus cell suspensions of rape (Brassica napus) revealed specific extracellular defence reactions after uranium exposure. These include characteristic pH-shifts of the culture medium caused by contact with the heavy metal. At the same time a transient release of fluorescent compounds from the cells occurred. These phytoalexins probably belong to the widespread group of flavonoids detected by HPLC and thin layer chromatography (TLC). They are able to interact with uranium and hence can protect the cell against heavy metal poisoning. To gain an insight in these interactions time-resolved laser-induced fluorescence spectroscopy (TRLFS) was performed. Further investigations are under way to identify intracellular defence mechanisms, e.g. spatial patterns of a possible cytoplasmic pH-shift, the formation of proteins possessing thiol groups (phytochelatins), respectively.
Keywords: Plant cells, uranium
  • Contribution to proceedings
    Biometals 2008, 14.-18.7.2008, Santiago de Compostela, Spain
  • Lecture (Conference)
    5th International Conference Uranium Mining and Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 691-691

Permalink: https://www.hzdr.de/publications/Publ-11178
Publ.-Id: 11178


Excitation spectrum and magnetic properties of the new Haldane-gap material NENB

Zvyagin, S.; Cizmar, E.; Ozerov, M.; Ignatchik, O.; Papageorgiou, T.; Wosnitza, J.; Krzystek, J.; Zhou, Z.; Wikaira, J. L.; Landee, C. P.; Thurnbull, M. M.
Results of high-field ESR and magnetization studies of the new spin-1 Haldane-chain material [Ni(C2H8N2)2NO2](BF4) (NENB) are reported. A definite signature of the Haldane state in NENB was obtained. From the analysis of the frequency-field dependence of magnetic excitations in NENB, the spin-Hamiltonian parameters were calculated, yielding Δ/kB = 17.4 K, gk = 2.14, D/kB = 7.5 K, and |E/kB| = 0.7 K for the Haldane gap, g factor and the crystal-field anisotropy constants, respectively. The presence of fractional S = 1/2 chain-end states, revealed by ESR and magnetization measurements, is found to be responsible for spin-glass freezing effects. In addition, extra states in the excitation spectrum of NENB have been observed in the vicinity of the Haldane gap, which
origin is discussed.
  • Lecture (Conference)
    APS March Meeting, 08.-14.03.2008, New Orleans, USA

Permalink: https://www.hzdr.de/publications/Publ-11177
Publ.-Id: 11177


Growth and study of LuNi2B2C single crystals

Köhler, A.; Behr, G.; Bergk, B.; Fuchs, G.; Nenkov, K.; Wosnitza, J.
Rare earth-nickel-borocarbides have attracted much interest in the last years because the compounds show the interplay of superconductivity and magnetic ordering. LuNi2B2C can be considered as non-magnetic reference system of such magnetic borocarbides as HoNi2B2C in which superconducting and antiferromagnetic ordering temperatures, Tc and TN, are similar.
So far, LuNi2B2C crystals were only prepared by a flux method. For growing larger crystals we used an optical floating zone (FZ) technique, which already was successful in crystal growth of other RNi2B2C (R = Y,Tb,Ho,Tm,Er) compounds. In the case of LuNi2B2C, the primary crystallization field is far from the stoichiometric composition, and adjacent to the properitectic LuB2C2 phase field an extended region of LuNiBC occurs. Systematic studies of polycrystalline samples revealed that samples with nominal compositions LuNi5B3.5C and LuNi5B3C0.5 are free of the properitectic LuB2C2 and LuNiBC phases.
Thus in the FZ crystal growth experiments we used a molten zone which corresponds to these compositions. From the grown LuNi2B2C rods single crystalline pieces have been prepared to investigate Fermi surface peculiarities by magnetoresistance measurements and to study the electronic band structure.
  • Lecture (Conference)
    Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 25.-29.02.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11176
Publ.-Id: 11176


Evidence for an Fulde-Ferrell-Larkin-Ovchinnikov state in a layered organic superconductor

Bergk, B.; Böttger, P. H. M.; Lortz, R.; Wang, Y.; Demuer, A.; Sheikin, I.; Zwicknagl, G.; Nakazawa, Y.; Wosnitza, J.
We present specific heat and torque-magnetization data of the layered organic superconductor κ-(BEDT-TTF)2Cu(NCS)2 in high magnetic fields up to 28 T and at low temperatures down to 1.5 K. The magnetic field was aligned perfectly parallel to the superconducting planes of the sample. In that orientation and at low temperatures the upper critical field, Bc2, gets close to the Pauli limit which is about 21 T. But instead of the expected saturation at this field value we observe an upturn of Bc2 towards low temperatures. This comes along with a change of the order of the phase transition from second order to first order. In addition, another first-order phase transition appears below Bc2 in the superconducting state. These features strongly point to the formation of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase in the state above the Pauli limit. Our results are in line with the behaviour predicted for FFLO states in two-dimensional systems.
  • Lecture (Conference)
    Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 25.-29.02.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11175
Publ.-Id: 11175


Anomalous critical behavior at the antiferromagnetic phase of YbRh2Si2

Krellner, C.; Hartmann, S.; Pikul, A.; Oeschler, N.; Geibel, C.; Wosnitza, J.; Steglich, F.
Quantum phase transitions are one of the important topics in the understanding of condensed matter. These transitions are driven by quantum fluctuations in contrast to classical phase transitions which are accompanied by thermal fluctuations. Recently, the heavy fermion system YbRh2Si2 was intensively studied, because it is a clean and stoichiometric metal situated on the magnetic side (TN = 72 mK), but very close to a quantum critical point, which can be crossed by applying a tiny magnetic field. Therefore, this system presents both an antiferromagnetic phase transition driven by thermal fluctuations as well as pronounced quantum fluctuations due to the vicinity to the quantum phase transition. In this contribution, we show accurate measurements of the specific heat C around TN on a single crystal of highest quality (RRR ~ 150). We observe a very sharp peak at TN with absolute values as high as C/T = 8 J/molK2. A detailed analysis of the critical exponent α around TN reveals α = 0.37 which differs significantly from those of the conventional universality classes in the Landau theory α < 0.11. We will discuss in detail the analysis and possible mechanism.
  • Lecture (Conference)
    Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 25.-29.02.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11174
Publ.-Id: 11174


Observation of two-magnon bound states in the spin-1 anisotropic Heisenberg antiferromagnetic chain system NiCl2-4SC(NH2)2

Zvyagin, S. A.; Batista, C. D.; Krzystek, J.; Zapf, V. S.; Jaime, M.; Paduan-Filho, A.; Wosnitza, J.
Results of systematic tunable-frequency ESR studies of the spin dynamics in NiCl2-4SC(NH2)2 (known as DTN), a gapped S = 1 chain system with easy-plane anisotropy dominating over the exchange coupling (large-D chain), are presented. We have obtained direct evidence for two-magnon bound states, predicted for S = 1 large-D spin chains in the fully spin-polarized (FSP) phase. The frequency–field dependence of the corresponding excitations was calculated using the set of parameters obtained earlier [S.A. Zvyagin, et al., Phys. Rev. Lett. 98 (2007) 047205]. Very good agreement between the calculations and the experiment was obtained. It is argued that the observation of transitions from the ground to two-magnon bound states might indicate a more complex picture of magnetic interactions in DTN, involving a finite in-plane anisotropy.
  • Physica B 403(2008), 1497-1499

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Permalink: https://www.hzdr.de/publications/Publ-11173
Publ.-Id: 11173


Possible magnetic-field-induced Lifshitz transition in CeBiPt

Wosnitza, J.; Goll, G.; Bartkowiak, M.; Bergk, B.; Bianchi, A. D.; von Löhneysen, H.; Yoshino, T.; Takabatake, T.
We report on resistance and Hall-effect measurements of the half-Heusler compound CeBiPt in pulsed magnetic fields up to 70 T. The band structure of the semimetal CeBiPt depends highly sensitively on temperature, magnetic field, and stoichiometry. This is reflected by the observed sample-dependent threshold fields above which the Shubnikov–de Haas signal disappears and at which clear changes of the Hall coefficient occur.
  • Physica B 403(2008), 1219-1221

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Permalink: https://www.hzdr.de/publications/Publ-11172
Publ.-Id: 11172


Magnetic properties of the Haldane-gap material [Ni(C2H8N2)2NO2](BF4)

Cizmár, E.; Ozerov, M.; Ignatchik, O.; Papageorgiou, T. P.; Wosnitza, J.; Zvyagin, S. A.; Krzystek, J.; Zhou, Z.; Landee, C. P.; Landry, B. R.; Turnbull, M. M.; Wikaira, J. L.
Abstract. Results of magnetization and high-field electron spin resonance (ESR) studies of the new spin-1 Haldane-chain material [Ni(C2H8N2)2NO2] (BF4) (NENB) are reported. A definite signature of the Haldane state in NENB was obtained. From the analysis of the frequency–field dependence of magnetic excitations in NENB, the spin-Hamiltonian parameters were calculated, yielding ∆/kB = 17.4 K, g = 2.14, D/kB = 7.5K and |E/kB| = 0.7K for the Haldane gap, g factor and the crystal-field anisotropy constants, respectively. The presence of fractional S = 1/2 chain-end states, revealed by ESR and magnetization measurements, is found to be responsible for spin-glass freezing effects. In addition, extra states in the excitation spectrum of NENB have been observed in the vicinity of the Haldane gap; their origin is discussed.
  • Open Access Logo New Journal of Physics 10(2008), 033008

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Permalink: https://www.hzdr.de/publications/Publ-11171
Publ.-Id: 11171


Sources for ferromagnetism in ion implanted ZnO

Potzger, K.; Zhou, S.
The combination of magnetic and semiconducting properties in oxides is currently one of most popular fields in materials research. Besides the expected gain of knowledge about basic physics, such materials have a large application potential in spin electronics. We present a summary of our results on transition metal doping of ZnO single crystals and thin films by means of ion implantation. We found that none of the samples investigated represents a diluted magnetic semiconductor as predicted by theory [1]. The observed ferromagnetism mainly originates from secondary phase formation (metals or inverted spinel ferrites). We highlight the suppression of secondary phase formation by means of deliberately lowering the crystalline quality prior to the doping. Moreover, bombardment with transition metal ions leads to defects which create weak ferromagnetism without participation of the transition metal implanted. We discuss the possibility that such defects are also responsible for ferromagnetism observed in transition metal doped ZnO thin films. Thus, interpretations of ferromagnetic DMS reported in the past are often misleading.

[1] K. Sato and H. Katayama-Yoshida, Physica E 10, 251 (2001).
Keywords: ion implantation, zno, DMS
  • Lecture (Conference)
    IBMM 08 - 16th International Conference on Ion Beam Modification of Materials, 31.08.-5.9.2008, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-11170
Publ.-Id: 11170


Design of non-destructive pulsed magnets at the Dresden High Magnetic Field Laboratory

Zherlitsyn, S.
The Dresden High Magnetic Field Laboratory (HLD) is a user facility which provides external users with the possibility of performing diverse experiments in pulsed magnetic field. Various experimental techniques, such as electrical transport, magnetization, ultrasound and magnetic-resonance measurements are available or are under installation at the HLD. A particular feature of the laboratory is a nearby free-electron laser facility which enables high-field infrared spectroscopy in pulsed magnetic fields [1].
A 50 MJ modular capacitor bank with a maximum charging voltage of 24 kV is in operation at the HLD. This capacitor bank allows to energize independently up to four sub-coils in multi-coil configurations and the energy pulses can be switched to five experimental cells. A program of the non-destructive pulsed magnets for the HLD includes a wide spectrum of coils designed for energies between 1 and 46 MJ, magnetic fields of 60 – 100 T, pulse durations of 10 - 1000 ms, and magnet bores in the range from 20 to 40 mm. In order to fulfill this program the necessary infrastructure accounting for the technical and technological aspects of pulsed-magnet design and fabrication has been established at the HLD. A pulsed-magnet core design has been developed [2]. In spite of the strong external mechanical support, our magnets are designed in a compact way which is suitable both for a mono-coil and a multi-coil configuration. With this design we are trying to achieve higher fields with longer pulse duration and high field homogeneity as well as to provide adequate space inside the magnet for the experimental installations. Important issues of the pulsed-magnet design are numerical simulations of the magnet performance. Both analytical approaches and finite-element analysis are used for these simulations.
Currently a number of 60 T /1.44 MJ and 70 T /8.5 MJ pulsed-magnets are available for external users and for in-house research [3]. A fabrication of a 60 T /43 MJ “long pulse” mono-coil is near to completion. A few double-coil prototypes have been designed, constructed and tested in frame of our 100 T project. Using the test results some improvements have been implemented in the multi-coil configuration. New double-coil prototypes targeting magnetic field above 90 T are under construction now.
  • Invited lecture (Conferences)
    Pioneering High Fields Symposium, 18.-19.03.2008, Tallahassee, USA

Permalink: https://www.hzdr.de/publications/Publ-11169
Publ.-Id: 11169


Simulation study on electron beam X-ray CT arrangements for two-phase flow measurements

Bieberle, M.; Schleicher, E.; Hampel, U.
Recently, we presented a limited-angle computed tomography approach that utilises a scanned electron beam X-ray source to produce multiple projections of an object. From these projections cross sectional images of the object are reconstructed by application of iterative reconstruction algorithms. Experiments with different kinds of two-phase flows proved that this approach is capable to recover the in-plane phase structure of the flow at scan rates of up to 10,000 frames per second and to reach an in-plane resolution of 1 mm. However, there are also some problems associated with this approach. One is the occurrence of limited-angle artefacts due to the limited number of views. Another problem is that no information about the volumetric structure of a multiphase flow can be obtained without knowing phase velocities. Both problems are addressed in this article. By means of a simulation study on software phantoms we evaluated different limited-angle scanning geometries with respect to their capability to suppress limited-angle artefacts. Secondly, we propose and evaluate a multi-slice limited-angle technique which allows to recover phase velocities and reconstruction of volumetric flow data. For the studies we employed a software phantom modelling bubbly two-phase flow in a pipe.
Keywords: electron beam x-ray CT
  • Measurement Science and Technology 19(2008)9, 094003

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Permalink: https://www.hzdr.de/publications/Publ-11168
Publ.-Id: 11168


Keynote lecture: Biogeochemistry of iron and interacting metals in soils

Scheinost, A. C.; Charlet, L.
Iron is the 4th most abundant element in the Earth’s crust and in soils; its bioavailability is often limited, however, because the Fe(III) oxides and hydroxides forming at oxic, non-acidic conditions are characterized by a very low solubility. Due to their nanoparticulate size and surface properties, the vividly colored soil Fe oxides and oxihydroxides strongly sorb oxyanions as well as metal cations, hence also limit the bioavailability of other nutrients, micronutrients and toxic metals.
In contrast, microbial reduction of Fe(III) to Fe(II) drastically increases Fe solubility and bioavailability, and may release associated nutrients and toxic metals. The Fe-mediated electron cycles are often driving the redox cycles of other redox-sensitive metals, among them micronutrients and toxic metals like Se and U.
Processes like seasonal fluctuations of ground water levels, enhanced O2 diffusion along soil macropores, rhizosphere biochemistry or mineral surface-catalyzed redox processes may produce redox fronts at various spatial and temporal scales, which in turn produce complex spatial and temporal patterns of nutrient and toxin bioavailabilities.
Keywords: Iron, geochemistry, redox
  • Invited lecture (Conferences)
    13th International Symposium on Iron Nutrition and Interactions in Plants, 03.-07.07.2006, Montpellier, France

Permalink: https://www.hzdr.de/publications/Publ-11167
Publ.-Id: 11167


XAS study of Am2Zr2O7 pyrochlore - Evolution under alpha self-irradiation

Martin, P.; Belin, R.; Valenza, P.; Scheinost, A. C.
Management of long-lived nuclear wastes is, after safety, the main issue of nuclear industry, both in terms of scientific challenge as well as public acceptance. Among the different options that have been envisioned and explored for minor actinides over the past thirty years, two alternatives currently remain: long term disposal in a safe repository or “burning” of nuclear wastes in a so-called transmutation process. Materials selected for such applications have to meet the following criteria: high incorporation of actinides, good structural and chemical stability, low thermal dilatation, and resistance to radiation.
Among the various ceramics envisaged, zirconia based pyrochlore oxides of composition An2Zr2O7 (An=actinide) appear to be ideal candidates. Results obtained with lanthanide pyrochlores submitted to ion-beam irradiation show that Zr-based pyrochlores, unlike Ti-based, remain crystalline with a transition from the pyrochlore to a defect fluorite structure [1]. The ordered pyrochlore belongs to the Fd-3m space group and is a superstructure of the ideal defect fluorite structure (Fm-3m) with exactly twice the lattice constant. In the pyrochlore structure, the coordination shell of Am cations (8 (2+6) oxygen atoms) is distinct from that of Zr cations (6 oxygen atoms), whereas the second coordination shell (cation-cation) is the same for both cations (6xAm+6xZr at the same distance). The structural phase transition from pyrochlore to defective fluorite involves the randomization of the oxygen atoms into the anionic and vacant positions of the pyrochlore structure. In the ideal fluorine defect structure, the Am and Zr cations share the same position and thus have the same local environment: a first coordination shell consisting of 7 oxygen atoms at the same distance and the same second coordination shell as observed in the pyrochlore structure.
The objective of this study was to investigate the radiation tolerance of Zr-pyrochlore during a more realistic experiment using alpha emitting 241Am as structural component.
Keywords: Transmutation, XAFS, pyrochlore, Zircon, Americium
  • Lecture (Conference)
    Actinide-XAS 2008, 15.-17.07.2008, Saint Aubin, France

Permalink: https://www.hzdr.de/publications/Publ-11166
Publ.-Id: 11166


On the effect of spatial discretization in LWR calculations with HELIOS 1.9

Merk, B.
The differences arising in the neutron flux distribution due to different spatial discretization are demonstrated. These differences in the flux distribution cause significant changes in the kinf value. An evaluation of the kinf value for the case of infinitely fine discretization is made. The influence of the discretization on the calculation of homogenized few group cross sections which are forwarded to the 3D full core calculations is investigated. The consequences on the calculation time are discussed
Keywords: Spatial Discretization, Neutron Transport, HELIOS, Collision Probabilities, Flat-Flux-Approximation
  • Lecture (others)
    Studsvik User Group Meeting 2008, 09.-11.04.2008, Budapest, Hungary

Permalink: https://www.hzdr.de/publications/Publ-11165
Publ.-Id: 11165


Tidal waves and spatial symmetry

Frauendorf, S.
Tidal waves and spatial symmetry
  • Invited lecture (Conferences)
    Gordon Research Conference on Nuclear Chemistry, 03.-08.06.2007, New London, NH, USA

Permalink: https://www.hzdr.de/publications/Publ-11164
Publ.-Id: 11164


Symmetries and collective nuclear excitations

Frauendorf, S.
Symmetries and collective nuclear excitations
  • Lecture (Conference)
    Workshop on Present and Future Exotics in Nuclear Physics, 28.-29.02.2008, Copenhagen, Danmark

Permalink: https://www.hzdr.de/publications/Publ-11163
Publ.-Id: 11163


Emergence of phases with size

Frauendorf, S.
  • Invited lecture (Conferences)
    Kolloqium, 02.10.2007, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-11162
Publ.-Id: 11162


Role of P2 purinergic receptors in synaptic transmission under normoxic and ischaemic conditions in the CA1 region of rat hippocampal slices

Coppi, E.; Pugliese, A. M.; Stephan, H.; Müller, C. E.; Pedata, F.
The role of ATP and its stable analogue ATPγS [adenosine-5′-o-(3-thio)triphosphate] was studied in rat hippocampal neurotransmission under normoxic conditions and during oxygen and glucose deprivation (OGD). Field excitatory postsynaptic potentials (fEPSPs) from the dendriticlayer or population spikes (PSs) from the soma were extracellularly recorded in the CA1 area of the rat hippocampus. Exogenous application of ATP or ATPγS reduced fEPSP and PS amplitudes. In both cases the inhibitory effect was blocked by the selective A1 adenosine receptor antagonist DPCPX (8-cyclopentyl-1,3-dipropylxanthine) and was potentiated by different ecto-ATPase inhibitors: ARL 67156 (6-N,N-diethyl-D-β,γ-dibromomethylene), BGO 136 (1-hydroxynaphthalene-3,6-disulfonate) and PV4 [hexapotassium dihydrogen monotitanoun-decatungstocobaltate(II) tridecahydrate, K6H2[TiW11CoO40]•13H2O]. ATPγSmediated inhibition was reduced by the P2 antagonist suramin [8-(3-benzamido-4-methylbenzamido)naphthalene-1,3,5-trisulfonate] at the somatic level and by other P2 blockers, PPADS (pyridoxalphosphate-6-azophenyl-2′, 4′-disulfonate) and MRS 2179 (2′-deoxy-N6-methyladenosine 3′,5′-bisphosphate), at the dendritic level. After removal of both P2 agonists, a persistent increase in evoked synaptic responses was recorded both at the dendritic and somatic levels. This effect was prevented in the presence of different P2 antagonists. A 7-min OGD induced tissue anoxic depolarization and was invariably followed by irreversible loss of fEPSP. PPADS, suramin, MRS2179 or BBG (brilliant blue G) significantly prevented the irreversible failure of neurotransmission induced by 7-min OGD. Furthermore, in the presence of these P2 antagonists, the development of anoxic depolarization was blocked or significantly delayed. Our results indicate that P2 receptors modulate CA1 synaptic transmission under normoxic conditions by eliciting both inhibitory and excitatory effects. In the same brain region, P2 receptor stimulation plays a deleterious role during a severe OGD insult.

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Permalink: https://www.hzdr.de/publications/Publ-11161
Publ.-Id: 11161


Heart-shaped nuclei: Condensation of rotational-aligned octupole phonons

Frauendorf, S.
The strong octupole correlations in the mass region A approximate to 226 are interpreted as rotation-induced condensation of octupole phonons having their angular momentum aligned with the rotational axis. Discrete phonon energy and parity conservation generate oscillations of the energy difference between the lowest rotational bands with positive and negative parity. Anharmonicities tend to synchronize the rotation of the condensate and the quadrupole shape of the nucleus forming a rotating heart shape.
  • Physical Review C 77(2008), 021304

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Permalink: https://www.hzdr.de/publications/Publ-11160
Publ.-Id: 11160


Fast Intraband Capture and Relaxation in InAs/GaAs Self-Assembled Quantum Dots

Zibik, E. A.; Menzel, S.; Aivaliotis, P.; Carpenter, B. A.; Cockburn, J. W.; Skolnick, M. S.; Wilson, L. R.; Grange, T.; Ferreira, R.; Bastard, G.; Stehr, D.; Winnerl, S.; Helm, M.; Steer, M. J.; Hopkinson, M.
Electron capture and relaxation processes in n-type InAs/GaAs quantum dots were investigated using mid-infrared degenerated pump-probe spectroscopy. Fast (~4 ps - 10 ps) intraband relaxation/capture times were measured even in the absence of electron-hole scattering.
  • Lecture (Conference)
    Conference on Lasers & Electro-Optics 2007, 06.-11.05.2007, Baltimore, USA
  • Contribution to proceedings
    Conference on Lasers & Electro-Optics 2007, 06.-11.05.2007, Baltimore, USA
    CLEO/QELS & PhAST Technical Digest CD-ROM 2007

Permalink: https://www.hzdr.de/publications/Publ-11159
Publ.-Id: 11159


On the consequences of a lifetime extension on the accumulated Plutonium mass in Germany

Merk, B.
The Plutonium production in the German reactor park under the actual political guidelines is studied. The influence of different options (once-through scenario, single and double MOX recycling scenario) on the residual Plutonium masses are analysed and compared to a close to reality scenario. Additionally an insight into the consequences of a postulated lifetime extension on the residual Plutonium mass is given and the Plutonium reduction and the change of the Plutonium composition due to double recycling are demonstrated. An outlook is given on the consequences of a lifetime extension for 10 years on the UOX fuel, the Plutonium and the Minor Actinide masses and compared to the additional amount of electricity produced due to the lifetime extension.
Keywords: Lifetime Extension, Cycle Studies, Plutonium Management, MOX Fuel
  • Contribution to proceedings
    Actinide and Fission Product Partitioning and Transmutation Tenth Information Exchange Meeting, 06.-10.10.2008, Mito, Japan
  • Poster
    Actinide and Fission Product Partitioning and Transmutation Tenth Information Exchange Meeting, 06.-10.10.2008, Mito, Japan

Permalink: https://www.hzdr.de/publications/Publ-11158
Publ.-Id: 11158


An analytical solution for a simple time dependent neutron transport problem: Shut down of the external source

Merk, B.
An analytical solution for the shut down of an external source in a homogeneous subcritical reactor problem is developed. The problem is described through an approximation of the Boltzmann Transport equation, the Telegrapher's or time dependent P1 equation. The analytical solution to the problem is expressed in terms of a Green's function expansion. The differences between the solution for the Telegrapher's equation and the diffusion equation without separation of space and time are discussed.
Keywords: Telegrapher's equation, Neutron Transport, Space-Time Dependent Transport, Accelerator Driven Systems
  • Contribution to proceedings
    Actinide and Fission Product Partitioning and Transmutation Tenth Information Exchange Meeting, 06.-10.10.2008, Mito, Japan
    Actinide and Fission Product Partitioning and Transmutation: Nuclear Energy Agency
  • Poster
    Actinide and Fission Product Partitioning and Transmutation Tenth Information Exchange Meetin, 06.-10.10.2008, Mito, Japan

Permalink: https://www.hzdr.de/publications/Publ-11157
Publ.-Id: 11157


The dance of the Domains: Excitations in Magnetic Microstructures Studied by X-ray Microscopy

Raabe, J.; Buess, M.; Kuepper, K.; Fassbender, J.ORC; Quitmann, C.
Micron sized magnetic thin film structures have interesting magnetic properties. By adjusting size, shape, and material they can form a multitude of magnetic domain patterns. They consist of homogenously magnetized domains, which are separated by domain walls and magnetic vortices forming at the intersections of the domain walls. We study the static and dynamic magnetic properties of such thin film structures. For this we use synchrotron based Photo Emission Electron Microscopy (PEEM). By combining the naturally pulsed time structure of the synchrotron light with magnetic field pulses to the sample, we are able to study magnetization dynamics with a time resolution of tfwhm<100ps. This allows quantitative analysis of the excitations in such particles which can in turn be compared to simulations based on the Landau-Lifshitz-Gilbert equation. We start with simple discs or squares, where three modes connected to the homogenously magnetized domains, the domain walls and the vortex exist. From there we move to more complex objects. For instance, in a rectangular platelet a configuration containing a stable combination of vortices and an antivortex can be created. Such a single cross-tie wall can be understood as being a coupled micromagnetic system with three static solitons. We report on its magnetization dynamics including the vortex-antivortex interactions. The spectrum of eigenmodes is investigated as well as the effect of different vortex core orientations. We show that the vortex dynamics can be used to identify the core configuration which is not directly accessible to x-ray microscopy because of its limited spatial resolution. In the second part we will briefly show the current capabilities for magnetic imaging of the Scanning Transmission X-ray Microscope (STXM) at the PolLux Beamline of the Swiss Light Source as a complementary x-ray based technique.
Keywords: magnetism, magnetic domains, time-resolved, x-ray microscopy
  • Lecture (Conference)
    MRS Spring Meeting 2008, Symposium: Advances and Applications of Surface Electron Microscopy, 24.-28.03.2008, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-11156
Publ.-Id: 11156


The development of intersubband semiconductor light sources: from MOSFETs to Quantum Cascade Lasers

Helm, M.
I will present a short history of intersubband light emission from semiconductor quantum structures, starting with MOSFETs in 1976 and culminating with the invention of the quantum cascade laser in 1994. I will discuss the underlying physics and present some highlight achievements.
Nowadays these lasers span a wavelength range between 2.8 and 250 microns, which is nearly two spectral decades.
Keywords: intersubband, quantum cascade laser
  • Lecture (others)
    Seminarvortrag am Institute for Laser Engeineering, Osaka University, 17.03.2008, Osaka, Japan

Permalink: https://www.hzdr.de/publications/Publ-11155
Publ.-Id: 11155


THz physics at the Research Center Dresden-Rossendorf: from scalable antennas to free-electron laser based near-field microscopy

Helm, M.
I will discuss two quite different activities, (1) novel scalable THz antennas for time-domain spectroscopy and (2) near field microscopy using a free-electron laser.
We have developed photoconductive antennas based on an interdigitated, scalable design, which combines the advantages of large-aperture emitters and usual antennas, yet without their respective drawbacks. I will discuss their use as THz emitters as well as detectors.
In our institute we have an IR/THz free-electron laser. After describing this facility, I will present some results from using this high-power source for near-field imaging of ferroelectric domains in BaTiO3.

Keywords: Terahertz, antenna, near-field microscopy, free electron laser
  • Lecture (others)
    Seminar am Institute for Laser Engineering, Osaka University, 05.03.2008, Osaka, Japan

Permalink: https://www.hzdr.de/publications/Publ-11154
Publ.-Id: 11154


Pump-probe studies of electron dynamics in quantum wells and superlattices

Helm, M.
After introducing the infrared/THz free-electron laser (FEL) facility at the Research Center Dresden-Rossendorf, I will discuss some pump-probe experiments to study the electron relaxation dynamics in superlattices. Both one-color, but also two-color experiments have been performed using the FEL, and, in addition, THz radiation generated by optical rectification in GaSe as the probe beam. In the second part of my talk I will discuss the intersubband dynamics in thin InGaAs/AlAsSb quantum wells, which are important for short-wavelength quantum cascade lasers. These experiments were performed using a femtosecond OPO system and yield information on the relevance of intervalley scattering.
Keywords: pump-probe, quantum well, superalttice, infrared, free-electron laser
  • Lecture (others)
    Seminarvortrag am Institute of Industrial Science, Tokyo University, 27.02.2008, Tokyo, Japan
  • Lecture (others)
    Seminarvortrag am Research Institute of Electrical Communication (RIEC), Tohoku University, 14.03.2008, Sendai, Japan

Permalink: https://www.hzdr.de/publications/Publ-11153
Publ.-Id: 11153


Reaktivitätsmessungen am WWER-440 des KKW Paks mittels Incore-Rhodiumdetektoren

Maletti, R.; Stein, H.; Hoppe, D.; Beier, M.; Jozsa, I.; Horvath, C.
Im Beitrag wird über die Nutzung von Incore-Signalen für Reaktivitätsmessungen zur Bestimmung wichtiger reaktorphysikalischer Parameter wie differentielle Stabwirksamkeit oder Leistungskoeffizient berichtet. Aus der Diskussion von Mess- und Rechenergebnissen folgt, dass für den Zeitraum der Durchführung der Messungen am Block 3 des KKW Paks der Reaktivitätseffekt bei Störungsmessungen mit den Ionisationskammern offensichtlich deutlich unterschätzt wird.
Keywords: Paks-3 reactor, reactivity measurements, in core instruments, self-powered neutron detectors, control rod worths, power coefficient
  • Kernenergie 34(1991)6, 253-260

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Permalink: https://www.hzdr.de/publications/Publ-11152
Publ.-Id: 11152


Dynamische Reaktivitätsstörungsmessungen an Leistungsreaktoren mittels prompt ansprechender Elektronenemissionsdetektoren

Maletti, R.; Seidenkranz, T.; Stein, H.
Erstmals werden prompt ansprechende Elektronenemissionsdetektoren mit Cobalt- bzw. Platin-Emitter für die Anwendung der Methode der Reaktivitätsstörungsmessungen im Leistungsbereich des Reaktors WWER-70 des KKW Rheinsberg eingesetzt. Dadurch lässt sich der experimentelle Aufwand für die Durchführung der Reaktivitätsmessungen senken und die Genauigkeit der ermittelten Reaktivitätskoeffizienten erhöhen. Störungsmessungen wurden auch bei sehr kleiner Reaktorleistung, d. h. im rückkopplungsfreien Reaktorzustand, durchgeführt. Die experimentellen Resultate bestätigen die theoretischen Modellvorstellungen zur Ortskorrektion bei rückkopplungsfreien Zuständen.
Keywords: Rheinsberg akw1 reactor, reactor kinetics, reactivity coefficients, self-powered neutron detectors, space dependence
  • Kernenergie 32(1989)11, 437-441

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Permalink: https://www.hzdr.de/publications/Publ-11151
Publ.-Id: 11151


Evaluation of Intergrated (F-18)fluoro-DOPA-PET/CT for identification of focal forms of congenital hyperinsulinism (CHI)

Blankenstein, O.; Mohnike, W.; Hussain, K.; Barthlen, W.; Koch, M.; Füchtner, F.; Strom, T.; Mohnike, K.; Grueters, A.
kein Abstract verfügbar
  • Lecture (Conference)
    10th European Congress of Endocrinology, 03.-07.05.2008, Berlin, Germany
  • Abstract in refereed journal
    European Journal of Pediatrics 167(2008)3, 363

Permalink: https://www.hzdr.de/publications/Publ-11150
Publ.-Id: 11150


On the influence of spatial discretization in LWR-burnup calculations with HELIOS 1.9 – part II: mixed oxide (MOX) fuel

Merk, B.
Cell- and burnup calculations are the fundament for all deterministic static and transient 3D full core calculations for different operational states of the reactor. The arising differences in the integral transport solution (neutron flux and kinf) for different discretization strategies over the burnup of mixed oxide (MOX) fuel due to different spatial discretization are demonstrated. The influence of different discretization strategies on the calculation of homogenized few group cross sections which are forwarded to the 3D full core calculations is investigated and on the calculation time is evaluated. The differences between UOX and MOX fuel are discussed.
Keywords: Cell- and Lattice calculation, cross section preparation, HELIOS, Discretization, Brunp calculation, Mixed Oxide Fuel
  • Annals of Nuclear Energy 36(2009), 168-182

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Permalink: https://www.hzdr.de/publications/Publ-11149
Publ.-Id: 11149


On the influence of spatial discretization in LWR-burnup calculations with HELIOS 1.9 – part I: Uranium oxide (UOX) fuel

Merk, B.
Cell- and burnup calculations are the fundament for all deterministic static and transient 3D full core calculations for different operational states of the reactor. The spatial discretization used for the cell- and burnup calculations influences the results for the used integral transport solutions significantly. The arising differences in the neutron flux distribution for different discretization strategies over the burnup of Uranium oxide (UOX) fuel due to different spatial discretization are demonstrated. These differences in the flux distribution cause significant changes in the kinf value. The influence of different discretization strategies on the calculation of homogenized few group cross sections which are forwarded to the 3D full core calculations is investigated The influence of the discretization strategies on the calculation time is evaluated.
Keywords: Cell- and Lattice calculation, cross section preparation, HELIOS, Discretization, Burnup calculation
  • Annals of Nuclear Energy 36(2009), 151-167

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Permalink: https://www.hzdr.de/publications/Publ-11148
Publ.-Id: 11148


Nano Composit Materialien fuer Flugzeit RPC Detektoren

Wuestenfeld, J.
The talk presents recent results from our investigations of new nanocomposite materials for the construction of resistive plate counters. This counters are forseen as timing detectors for the upcomming Compressed Baryonic Matter (CBM) experiment at FAIR. These tests where performed at the electron beam of ELBE.
Keywords: RPC, nano composite materials, ELBE
  • Lecture (Conference)
    DPG Frühjahrstagung des AMOP und der Fachverbände Hadronen und Kerne, Umweltphysik 2008, 10.-14.03.2008, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-11146
Publ.-Id: 11146


Application of CFD codes in nuclear reactor safety analysis

Rohde, U.; Höhne, T.; Krepper, E.; Kliem, S.
The last decade has seen an increasing use of computational fluid dynamics codes (CFD) to predict steady state and transient flows in nuclear reactors. The reason for the increased use of CFD methods is that a number of phenomena important for the assessment of the safety of nuclear reactors such as pressurized thermal shocks, boron mixing, thermal striping and sub-cooled boiling cannot be predicted by traditional one-dimensional system codes with the required accuracy and spatial resolution.

CFD codes are characterized by the fact that the underlying equations are implemented in a clearly more detailed way in comparison to the one-dimensional system codes. Nevertheless, these codes contain empirical models for simulating turbulence, heat transfer, multi-phase flows, and chemical reactions. Such models must be validated before they can be used with sufficient confidence in Nuclear Reactor Safety (NRS) applications.

CFD validation simulations are shown in areas such as: heat transfer, buoyancy, multi-phase flows, natural circulation, turbulent mixing, and complex geometries. These topics are related to the above mentioned NRS-relevant issues.

The following topical issues will be discussed in the presentation:

1. Coolant Mixing (Boron Dilution Transient)
2. Coolant Mixing (Pressurized Thermal Shock)
3. Debris Transport Phenomena in multidimensional water flow
4. Sub-cooled boiling - Application to fuel rod bundle safety assessment

The material presented has been prepared by FZD partly under the sponsorship by the European Commission, the German Government (BMWA) and the VGB PowerTech e.V.
Keywords: CFD, NRS
  • Invited lecture (Conferences)
    TOPSAFE 2008, 01.-03.10.2008, Dubrovnik, Kroatia
  • Contribution to proceedings
    TOPSAFE 2008, 01.-03.10.2008, Dubrovnik, Kroatia
    CD-ROM. paper 099
  • Open Access Logo Science and Technology of Nuclear Installations 2010(2010), Article ID 198758
    DOI: doi:10.1155/2010/198758

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Permalink: https://www.hzdr.de/publications/Publ-11145
Publ.-Id: 11145


CFD simulations of Gidropress mixing facility experiments in the framework of TACIS project R2.02/02

Höhne, T.; Rohde, U.; Melideo, D.; Moretti, F.; D’Auria, F.; Shishov, A.; Lisenkov, E.
The main objective for the quantification of the fluid mixing in the downcomer and the lower plenum is the demonstration of the safety of the nuclear plant during non-symmetrical transients. This concerns two main topics: The risk of fragile brittle of the Reactor Pressure Vessel (RPV) during Pressurized Thermal Shock (PTS) transients and the risk of core reactivity excursion during non-symmetrical transient such as Main Steam Line Breaks (MSLB) or Boron Dilution Transients (BDT). The corresponding fluid mixing scenarios are studied in the 1:5 scaled VVER-1000 reactor model at OKB “Gidropress” in the framework of a TACIS project: “Development of safety analysis capabilities for VVER-1000 transients involving spatial variations of coolant properties (temperature or boron concentration) at core inlet”.

An extensive experimental program was running, studying different flow conditions in the reactor mock up, like the start of the 1st coolant pump or natural circulation conditions with density differences of the primary coolant. Pre and post test CFD simulations were carried out for code validation and for a deeper understanding of the flow and mixing behavior in the VVER-1000 reactor also in the future of the project. The 3-D computational fluid dynamics (CFD) codes provide an effective tool for mixing calculations. The CFD-Code used was ANSYS CFX. The geometric details of the construction internals inside the RPV have a strong influence on the flow field and on the mixing. Therefore, an exact representation of the inlet region, the spacer in the downcomer, the elliptical perforated plate and the complicated structures in the lower plenum was necessary. All parts of the lower plenum structures were modeled in detail. The final computational grid contained 6.5 Million nodes. Results of selected experiments and corresponding CFD calculations will be described and discussed in the paper and conclusions will be drawn.
Keywords: CFD, VVER-1000, Coolant Mixing
  • Contribution to proceedings
    TOPSAFE 2008, 01.-03.10.2008, Dubrovnik, Kroatia
    CD-ROM, paper 063
  • Lecture (Conference)
    TOPSAFE 2008, 01.-03.10.2008, Dubrovnik, Kroatia

Permalink: https://www.hzdr.de/publications/Publ-11144
Publ.-Id: 11144


RPC development for CBM @ FZD

Wuestenfeld, J.
The talk presents recent results from our investigations of new nanocomposite materials for the construction of resistive plate counters. This counters are forseen as timing detectors for the upcomming Compressed Baryonic Matter (CBM) experiment at FAIR. These tests where performed at the electron beam of ELBE.
Keywords: RPC, nano composite materials, ELBE
  • Lecture (Conference)
    11th CBM Collaboration Meeting of the CBM Experiment at FAIR, 26.-29.02.2008, GSI, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11143
Publ.-Id: 11143


Complexation study of europium(III) and curium(III) with urea in aqueous solution investigated by time-resolved laser-induced fluorescence spectroscopy

Heller, A.; Barkleit, A.; Bernhard, G.; Ackermann, J.-U.
The complex formation of europium(III) and curium(III) with urea in aqueous solution has been studied at I = 0.1 M (NaClO4), room temperature and trace metal concentrations in the pH-range of 1 to 8 at various ligand concentrations using time-resolved laser-fluorescence spectroscopy. While for curium(III) the luminescence maximum is red shifted upon complexation, in case of europium(III) emission wavelengths remain unaltered but a significant change in peak splitting occurs. Both heavy metals form weak inner sphere complexes of the formulae ML3+ with urea, which are stable till pH 6 but easily repressed by metal hydroxide formation. Stability constants were determined to be logß110 = -0.10 ± 0.07 for europium(III) and -0.80 ± 0.23 for curium(III).
Keywords: curium(III), europium(III), urea, complexation, TRLFS, heavy metal speciation
  • Inorganica Chimica Acta 362(2009)4, 1215-1222

Permalink: https://www.hzdr.de/publications/Publ-11142
Publ.-Id: 11142


Correlation between self-diffusion in Si and the migration mechanisms of vacancies and self-interstitials: An atomistic study

Posselt, M.; Gao, F.; Bracht, H.
The migration of point defects in silicon and the corresponding atomic mobility are investigated by comprehensive classical molecular dynamics simulations using the Stillinger-Weber potential and the Tersoff potential. In contrast to most of the previous studies both the point defect diffusivity and the self-diffusion coefficient per defect are calculated separately so that the diffusion-correlation factor can be determined. Simulations with both the Stillinger-Weber and the Tersoff potential show that vacancy migration is characterized by the transformation of the tetrahedral vacancy to the split vacancy and vice versa and the diffusion-correlation factor is about 0.5. This value was also derived by the statistical diffusion theory under the assumption of the same migration mechanism. The mechanisms of self-interstitial migration are more complex. The detailed study, including a visual analysis and investigations with the nudged elastic band method, reveals a variety of transformations between different self-interstitial configurations. Molecular dynamics simulations using the Stillinger-Weber potential show, that the self-interstitial migration is dominated by a dumbbell mechanism, whereas in the case of the Tersoff potential the interstitialcy mechanism prevails. The corresponding values of the correlation factor are different, namely 0.59 and 0.69 for the dumbbell and the interstitialcy mechanism, respectively. The latter value is nearly equal to that obtained by the statistical theory which assumes the interstitialcy mechanism. Recent analysis of experimental results demonstrated, that in the framework of state-of-the-art diffusion and reaction models the best interpretation of point defect data can be given by assuming. The comparison with the present atomistic study leads to the conclusion that the self-interstitial migration in Si should be governed by a dumbbell mechanism.
Keywords: point defects, silicon, migration, diffusion

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Permalink: https://www.hzdr.de/publications/Publ-11141
Publ.-Id: 11141


High-resolution oil-gas two-phase flow measurement with a new capacitance wire-mesh tomograph

Thiele, S.; Da Silva, M. J.; Hampel, U.; Abdulkareem, L.; Azzopardi, B. J.
The experimental investigation of flow phenomena plays an important role in many fields of research as well as in industrial applications. Wire-mesh tomography allows the study of flows with high spatial and temporal resolution. This tomography modality was introduced about ten years ago and since then it has been employed to investigate a number of single phase and two-phase flow phenomena. In this paper, a new developed wire-mesh tomograph based on capacitance (permittivity) measurements has been employed on a vertical 67 mm diameter pipe up which air and silicone oil mixtures flow under controlled conditions. The wire-mesh sensor consists of two planes of wires forming an angle of 90° and having a small separation between them. An associated electronics measures the local capacitance between the gaps of all crossing points. Thus, the wire-mesh system yields cross-sectional images of the phase distribution. The present system reaches temporal resolution of up to 5 000 frames per second and has a spatial resolution of 2.8 mm. Two visualization techniques were used to display the measured wire-mesh data: (i) virtual sectional side views and (ii) virtual side projections. In the former one the values of phase fraction of the central electrode are displayed along the time. Such an image obtains the character of a side view to the flow on a vertical plane cut through the pipe along the diameter. The second visualization technique applied is the calculation of virtual side projections using a simplified ray-tracing algorithm. Here the three-dimensional phase fraction distribution is assumed to be illuminated by parallel white light and the light intensity departing in the direction of a virtual observer is calculated. Both visualization techniques complement each other in the visualization of flow structures. Different gas and oil flow rates where investigated thus obtaining a variety of flow patterns. All four major accepted flow patterns bubbly, slug, churn and annular flow are reported here. The high-speed capability and the good spatial resolution of the system enable an examination of the flow to be carried out with a high degree of detail. Thus, the spatial resolution is sufficient to detect individual bubbles. Furthermore, quantitative insights of the flow can be obtained by the calculation of axial and radial gas content profiles which are determined by integration of the measured data over appropriate partial volumes.
Keywords: high-speed measurement, capacitance measurement, flow visualization
  • Contribution to proceedings
    5th International Symposium on Process Tomography, 25.-26.08.2008, Zakopane, Poland
    5th International Symposium on Process Tomography, Lodz, Poland: Technical University of Lodz, 978-83-7283-271-9, PT08_cr7
  • Poster
    5th International Symposium on Process Tomography, 25.-27.08.2008, Zakopane, Poland

Permalink: https://www.hzdr.de/publications/Publ-11140
Publ.-Id: 11140


Defect Mediated Desorption of the KBr(001) Surface Induced by Single Highly Charged Ion Impact

Heller, R.; Facsko, S.; Wilhelm, R.; Möller, W.
The formation of nanometer sized monoatomic deep pits on the KBr (001) surface induced by individual impacts of slow (1keV/amu) highly charged Xe ions has been investigated. The volume of the pits have been determined by atomic force microscopy and show a strong dependence on the ions potential energy. The imaging of single ion impact sites allowed us to determine total potential sputter yields from atomically flat (001) terraces. From the dependence of the pit formation ability on the ions initial charge state and the comparison of low and high fluence irradiations we found evidence that defect agglomeration into complex defect centers plays a major role in the desorption process induced by the potential energy.
Keywords: Highly Charged Ion, Defect Mediated Desorption, DIET, Alkali Halides, Frenkel Defects, Potential Sputtering
  • Physical Review Letters 101(2008)9, 096102

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Permalink: https://www.hzdr.de/publications/Publ-11139
Publ.-Id: 11139


Aqueous Uranium(VI) Hydrolysis Species Characterized by Attenuated Total Reflection Fourier-Transform Infrared Spectroscopy

Müller, K.; Brendler, V.; Foerstendorf, H.
The speciation of uranium(VI) in micromolar aqueous solutions at ambient atmosphere was studied by attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy and by speciation modeling applying the updated NEA thermodynamic data base. It can be shown that reliable infrared spectra of micromolar U(VI) solutions are obtained abolishing the restrictions of previous spectroscopic investigations to millimolar concentrations and, consequently, to the acidic pH range. A significant change of the U(VI) speciation can be derived from the spectral alterations of the absorption band representing the antisymmetric stretching mode (ν3) of the UO22+ ion observed upon lowering the U(VI) concentration from the milli- to the micromolar range at a constant pH value 4. The acquisition of spectra of diluted U(VI) solutions allows the increase of the pH up to 8.5 without the risk of formation of colloidal or solid phases. The infrared spectra are compared to the results of the computed speciation patterns. Although a complete interpretation of the spectra can not be given at this state of knowledge, the spectral data strongly suggest the presence of monomeric U(VI) hydroxo species already showing up at a pH value ≥ 2.5 and dominating the speciation at pH 3. This is in contradiction to the predicted speciation where the fully hydrated UO22+ is expected to represent the main species at pH values below 4. At ambient pH, a more complex speciation is suggested compared to the results of the computational modeling technique. The predicted dominance of the UO2(CO3)34− complex at pH ≥ 8 by was not confirmed by the infrared data. However, the infrared spectra indicate the formation of hydroxo complexes obviously containing carbonate ligands.
Keywords: uranium(VI), speciation, infrared spectroscopy, ATR, modeling

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Permalink: https://www.hzdr.de/publications/Publ-11138
Publ.-Id: 11138


Entwicklung einer Elektret-Ionisationskammer für die Dosimetrie in gemischten Neutronen-Gamma-Feldern.

Pawelke, J.
no abstract available
  • Other report
    Dresden: Diplomarbeit, TU Dresden, Institut für Strahlenschutzphysik, 1990
    85 Seiten

Permalink: https://www.hzdr.de/publications/Publ-11135
Publ.-Id: 11135


Neutron dosimetry using electret detectors.

Seifert, H.; Dörschel, B.; Pawelke, J.
no abstract available
  • Kernenergie 34(1991)7-8, 344-348

Permalink: https://www.hzdr.de/publications/Publ-11134
Publ.-Id: 11134


Comparison of calculated and measured neutron sensitivities of an electret albedo dosemeter.

Seifert, H.; Dörschel, B.; Pawelke, J.; Hahn, T.
no abstract available
  • Radiation Protection Dosimetry 37(1991)1, 13-18

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Permalink: https://www.hzdr.de/publications/Publ-11133
Publ.-Id: 11133


The influence of environmental conditions on charge stability and dosimetric properties of electret ionization chambers.

Stoldt, C.; Prokert, K.; Dörschel, B.; Hanisch, S.; Pawelke, J.
no abstract available
  • Kernenergie 33(1990)1, 37-41

Permalink: https://www.hzdr.de/publications/Publ-11132
Publ.-Id: 11132


Two-color pump-probe studies of intraminiband relaxation in doped GaAs/AlGaAs superlattices

Stehr, D.; Wagner, M.; Schneider, H.; Helm, M.; Andrews, A. M.; Roch, T.; Strasser, G.
The miniband relaxation dynamics of electrons in doped GaAs/AlGaAs superlattices are investigated by two-color infrared pump-probe experiments. By this technique, we are able to separate the different contributions from inter- and intraminiband relaxations to the transient behavior after an ultrafast excitation. In particular, the intraminiband relaxation is studied for different miniband widths below and above the optical phonon energy of GaAs. For minibands wider than this critical value, we find fast relaxation, nearly constant for different excitation intensities, whereas for narrow minibands, a strong temperature and intensity dependence of the relaxation is found. The results are in good agreement with previously published Monte Carlo simulations.
Keywords: superlattice, intraminiband dynamics, miniband relaxation

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Permalink: https://www.hzdr.de/publications/Publ-11131
Publ.-Id: 11131


Synthesis and evaluation in vitro and in vivo of a 11C-labeled cyclooxygenase-2 (COX-2) inhibitor

Wüst, F.; Knieß, T.; Bergmann, R.; Pietzsch, J.
The radiosynthesis and radiopharmacological evaluation of 1-[11C]methoxy-4-(2-(4-(methanesulfonyl) phenyl)cyclopent-1-enyl)-benzene [11C]5 as novel PET radiotracer for imaging of COX-2 expression is described\. The radiotracer was prepared via O-methylation reaction with [11C]methyl iodide in 19% decay-corrected radiochemical yield at a specific activity of 20–25 GBq/lmol at the end-of-synthesis within 35 min. The radiotracer [11C]5 was evaluated in vitro using various pro-inflammatory and tumor cell lines showing high functional expression of COX-2 at baseline or after induction. In vivo biodistribution of compound [11C]5 was characterized in male Wistar rats. Compound [11C]5 was rapidly metabolized in rat plasma, and more pronounced, in mouse plasma. In vivo kinetics and tumor uptake were demonstrated by dynamic small animal PET studies in a mouse tumor xenograft model. Tumor uptake of radioactivity was clearly visible overtime. However, radioactivity uptake in the tumor could not be blocked by the pre-injection of nonradioactive compound 5. Therefore, it can be concluded that radioactivity uptake in the tumor was not COX-2 mediated.
Keywords: Positron emission tomography; Cyclooxygenase; COX-2 inhibitor; Carbon-11; Inflammation; Cancerogenesis

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Permalink: https://www.hzdr.de/publications/Publ-11130
Publ.-Id: 11130


Förderprogramm Immissions- und Klimaschutz, Bilanz 1999

Maletti, R.; Enkelmann, W.
Der Bericht enthält die Ergebnisse des Jahres 1999 zu folgenden Fördermaßnahmen des Sächsischen Staatsministeriums für Umwelt und Landwirtschaft:
- Förderprogramm "Vorhaben des Immissions- und Klimaschutzes einschließlich der Nutzung erneuerbarer Energien"
- Sonderprogramm "Hausbrand im grenznahen Raum"
- Sächsische Solarinitiative 1999/2000
Gesondert werden die geförderten Energie-Projekte dargestellt, mit denen Sachsen zur Weltausstellung EXPO 2000 in Hannover vertreten ist.
Die Bearbeitung der Förderprogramme und -projekte erfolgte durch den im Forschungszentrum Rossendorf ansässigen Projektträger Umwelt und Energie.
Keywords: Förderprogramme, Immissions- und Klimaschutz, erneuerbare Energien, Luftreinhaltung, EXPO 2000
  • Other report
    Dresden: Sächsisches Druck- und Verlagshaus, 2000
    36 Seiten

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Permalink: https://www.hzdr.de/publications/Publ-11129
Publ.-Id: 11129


Pattern competition in homogeneously heated fluid layers

Cartland-Glover, G. M.; Generalis, S. C.
Simulations examining pattern competition have been performed on a horizontal homogeneously heated layer that is bounded by an isothermal plane above an adiabatic plane. Several different circulation patterns arose as the heating regime applied to the horizontal layer was modified. The sequence of the patterns formed as the Grashof number was increased had the following order: laminar, z-axis rolls, squares, hexagons and pentagons, pentagons and then two different square modes of differing orientations. Fourier analysis was used to determine how the key modes interact in the presence of different patterns.
  • Contribution to proceedings
    Proceedings of the 5th European Thermal-Sciences Conference, 18.-22.05.2008, Eindhoven, the Netherlands

Permalink: https://www.hzdr.de/publications/Publ-11128
Publ.-Id: 11128


Solarinitiative 1999/2000 für sächsische Städte und Gemeinden

Maletti, R.; Voigt, P.
Die Solarinitiative 1999/2000 ist eine Aktion des Sächsischen Staatsministeriums für Umwelt und Landwirtschaft. Die Initiative verbindet sich mit der bundesweiten Motivationskampagne "Solar - na klar!" des Bundesdeutschen Arbeitskreises für Umweltbewußtes Management e.V. (B.A.U.M.). Das Ziel der beiden Aktionen ist die verstärkte Nutzung der Solarwärme. In Sachsen wurde der Projektträger Umwelt und Energie des Sächsischen Staatsministeriums für Umwelt und Landwirtschaft im Forschungszentrum Rossendorf e.V. mit der Umsetzung der beiden Kampagnen beauftragt.
Keywords: Solarwärme, Solarinitiative, "Solar - na klar!"
  • Lecture (Conference)
    6. Europäische Konferenz "Solarenergie in Architektur und Stadtplanung", 12.-15.09.2000, Bonn, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-11127
Publ.-Id: 11127


Ergebnisse der staatlichen Förderung von Vorhaben der Errichtung und des Betriebes von kleinen Sonnenkollektoranlagen in Sachsen

Maletti, R.
Im Beitrag wird ein Überblick über die in den Jahren 1991 bis 1998 in Sachsen errichteten und geförderten kleinen Sonnenkollektoranlagen gegeben. Es wird dargelegt, dass bei Errichtung und Förderung seit 1997 erhöhtes Augenmerk auf Qualität und Effizienz der Anlagen gelegt wird. Des Weiteren wird festgestellt, dass zum Zeitpunkt der Berichterstattung die Solarerträge im Allgemeinen zu niedrig und die daraus resultierenden Wärmepreise zu hoch sind.
Keywords: Solarenergie, Sonnenkollektoranlagen, Anlagenkosten, Förderung, Solarinitiative
  • Contribution to proceedings
    Neuntes Symposium "Thermische Solarenergie", 05.-07.05.1999, Kloster Banz, Staffelstein, Deutschland
    Ergebnisse der staatlichen Förderung von Vorhaben der Errichtung und des Betriebes von kleinen Sonnenkollektoranlagen in Sachsen, 334-340

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Publ.-Id: 11126


Fabrication of self-assembled L10 ordered FePt nanoislands by conventional DC magnetron sputtering

von Borany, J.; Cantelli, V.; Christalle, E.; Mücklich, A.; Talut, G.; Grenzer, J.
L10 ordered, c-axis oriented FePt thin films belong to the most promising ferromagnetic materials for future magnetic storage media. The coercivity of such films can be significantly improved if changing from homogeneous to granular films or even to arrays of FePt nanoislands.
This contribution describes the formation of self-assembled FePt nanoislands at single-crystalline Si(001) or amorphous SiO2/Si substrates after conventional DC magnetron sputtering. FePt is sputtered (0.5 Å/s) from an alloy target at a substrate temperature of approx. 300°C to an equivalent film thickness of 10 nm. The island formation and the low-temperatureL10 ordering are stimulated by an ultrathin Ag buffer layer. The well-separated FePt islands exhibit a quite regular size of typical 20 - 30 nm. X-ray diffraction investigations reveal the existence of L10 ordered FePt grains; a preferred orientation of the grains has been found for the islands deposited at the crystalline substrate. However, it is noteworthy that the island formation is obtained both for crystalline and amorphous substrate surfaces which is of significant practical relevance. The enhanced coercivity of patterned FePt films with respect to homogeneous FePt layers has been confirmed by SQUID measurements. The formation of the nanoisland structure is discussed in terms of the adatom surface mobility, the influence of energetic ions and the ratio of surface to stress-energy during thin film deposition.
Keywords: Magnetic thin films, Sputter deposition, Nanoparticle
  • Poster
    E-MRS 2007 Spring Meeting, 28.05.-01.06.2007, Strasbourg, France

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Publ.-Id: 11125


X-ray Absorption Studies of the Interaction between Uranium(VI) and Silica-Gel-Bound Tetraazamacrocycles

Giachini, L.; Faure, S.; Meyer, M.; Nguyen, L. V.; Batifol, B.; Chollet, H.; Guilard, R.; Scheinost, A. C.; Hennig, C.
The development of separation processes aimed at the selective uptake of toxic metal ions from dilute wastewaters and industrial process streams is of paramount importance for preventing environmental contamination but still remains a challenging scientific task. In that viewpoint, solid-liquid extraction using chelating agents grafted on hydrophilic supports is appealing, mainly because the affinity and selectivity of the scavenging material towards the targeted species can be fine-tuned by molecular design.1,2 We have synthesized a series of N-functionalized tetraazamacrocyclic ligands covalently bound on the surface of amorphous silica-gel beads for the selective extraction of actinides.2,3 In collaboration with the CEA Centre of Valduc, one of these materials has been prepared on a semi-industrial scale (Scheme 1) and used in the final decontamination step of real effluents for removing the residual α-emitters (U, Pu, Am) contained at the sub-ng/L level.
Keywords: macrocycles uranium EXAFS nuclear waste reprocessing
  • Lecture (Conference)
    Actinide XAS 2008, 15.-17.07.2008, Saint-Aubin, France

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Publ.-Id: 11124


Spectroscopic Verification of the Mineralogy of an Ultrathin Mineral Film on Depleted Uranium

Baumann, N.; Arnold, T.; Foerstendorf, H.; Read, D.
The alteration of a depleted uranium (DU) disc in contact with a synthetic pore water, as simulant for fertilized agricultural soil, was studied by exposing the DU to a Ca-phosphate solution (2.5 • 10−3 M Ca, 1 • 10−3 M P). Within 12 months this contact resulted in the formation of a thin film of a secondary uranium mineral on the metallic DU. The reaction product was analysed both with time-resolved laser-induced fluorescence spectroscopy (TRLFS) and infrared spectroscopy (IR). The TRLFS spectra obtained were compared with spectra of natural occurring uranium reference minerals which could have formed under the specified experimental conditions. IR was used as a complementary analytical technique for spectroscopic characterization of the natural minerals and of the unknown mineral film on DU. Both techniques identified the reac-tion product on DU as a U(VI) phosphate phase, but only TRLFS provided its unequivo-cal identification as meta-autunite based on the positions of the fluorescence emission maxima at 487.8, 502.0, 523.6, 547.0, 572.1, and 600.6 nm and two fluorescence lifetimes of 410 ± 15 ns and 3300 ± 310 ns. These findings demonstrate the enhanced performance and sensitivity of the TRLFS technique for mineralogical characterization of thin sur-face films.
  • Environmental Science & Technology 42(2008)22, 8266-8269

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Publ.-Id: 11123


Irradiation-induced promigratory phenotype of melanoma cells: role of S100A4-RAGE interaction

Haase, C.; Wolf, S.; Pietzsch, J.
Metastases are a devastating and debilitating complication of melanoma with a poor prognosis for the patient. The treatment of metastases would be either radiation only or surgery combined with adjunctive postoperative radiation therapy. S100A4 (metastasin) is known to play a direct role in these metastatic processes. We hypothesize that RAGE (receptor for advanced glycation endproducts) is a putative receptor for S100A4. However, the role of S100A4-RAGE interaction in melanoma metastasis is still unclear. The purpose of this study was to find out how mouse B16-F10 melanoma cells restrained to irradiation. Furthermore, we examined changes in the S100A4-RAGE interaction and the ability for migration of irradiated melanoma cells in the presence of tumor associated macrophages. B16-F10 cells were exposed to single dose irradiation (5 Gy, 20 Gy) and mouse RAW 264.7 cells were used as a model for tumor-associated macrophages. S100A4 and RAGE expression in these cells was quantified via real-time RT-PCR and Western-blot analysis three and six days after irradiation. Cell migration was investigated with B16-F10 cells six days after irradiation in a 24-transwell chamber for 16 h and 24 h. Furthermore, migration was influenced by seeding RAW cells as a chemoattracant into the lower compartments and recombinant S100A4 as a stimulus to the upper compartments. After labeling the cells with Calcein-AM the migratory cells were quantified in a standard fluorescence microplate reader. The total number of vital irradiated B16-F10 cells is significantly decreased with increasing dose up to 20 Gy and up to six days, thereby altering morphological appearance. Surprisingly, in surviving B16-F10 cells expression of S100A4 and RAGE significantly increased three and six days after 20 Gy (p<0.05). Furthermore, irradiated B16-F10 cells showed higher migratory activity supposed due to enhanced expression of S100A4 and RAGE. In the presence of RAW cells and/or recombinant S100A4 a further increasing migration activity of irradiated cells (20 Gy) was found. Our findings suggest an association of melanoma and macrophages with alterations of their migratory and invasive activity after irradiation due to a perpetual para-/autocrine expression mechanism of extracellular S100A4 and RAGE, and thereby changing functional properties of melanoma cells towards a promigratory phenotype. This study was supported in part by the Deutsche Forschungsgemeinschaft (grant Pi 304/1-1).
  • Poster
    20th Meeting of the European Association for Cancer Research, 05.-08.07.2008, Lyon, France
  • Abstract in refereed journal
    EJC Supplements 6(2008)9, 21

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Publ.-Id: 11122


Characterization of dose-dependent metabolic changes in melanoma cells after irradiation in vitro and in vivo

Mosch, B.; Müller, K.; Pietzsch, J.
Background:
Although irradiation is a powerful tool for the therapy of solid tumors, single cells often elude this treatment and constitute a basis for recurrence of the primary tumor and formation of metastases. This rises the question if irradiation-dependent metabolic changes could be responsible for a predisposition of certain cells to show enhanced survival and migratory activity. The aim of our study was to investigate metabolic properties of irradiated melanoma cells and thus to develop and validate appropriate in vitro and in vivo models to characterize new radiopharmaceuticals for diagnosis and therapy of metastases and solid tumors.

Materials and methods:
We applied different single-dose X-ray irradiation (1, 2, 5, 7, 10, and 20 Gy) to murine B16-F10 melanoma cells. At particular times we analyzed cell viability, growth properties, clonogenic regrowth capability, cellular proliferation, and expression of cell cycle markers. Furthermore, we analyzed the cellular uptake of the radiotracers 2-[18F]Fluor-2-desoxy-D-glucose and 3-O-Methyl-[18F]fluor-L-DOPA, providing information about the glucose and amino acid metabolism before and after irradiation. Additionally, we performed in vivo studies in a syngeneic mouse model to analyze the capability of untreated and irradiated cells to form lung metastases.

Results:
In a dose-dependent manner we detected a decrease in the viability, growth properties and tracer uptake of the melanoma cells. These findings appeared particularly in the period 3 to 6 days after irradiation. In contrast, already one day after irradiation cell cycle analyses showed an increase in the number of G2/M phase cells and the expression of G2-phase markers in irradiated compared to untreated cells. Further we demonstrated an influence of irradiation according to the ability to form lung metastases in the mouse.

Conclusions:
Our results indicate that the combination of different in vitro and in vivo approaches is useful for a detailed characterization of metabolic changes in melanoma cells after irradiation. Additionally, the presented approach gives information about dose-dependent effects. These models enable us to characterize new radiotracers and furthermore, to investigate metabolic effects of applied radiopharmaceuticals in combination with experimental radiation therapy.
  • Poster
    20th Meeting of the European Association for Cancer Research, 05.-08.07.2008, Lyon, France
  • Abstract in refereed journal
    EJC Supplements 6(2008)9, 129

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Publ.-Id: 11121


Laser Teilchenbeschleunigung a) Relativistische Optik b) Hochleistingslaser c) Anwendungen d) Status am FZD

Sauerbrey, R.; Schramm, U.
Tutorial lecture series on laser particle acceleration
  • Invited lecture (Conferences)
    XXXIX Arbeitstreffen Kernphysik, 21.-29.02.2008, Schleching, Germany

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Publ.-Id: 11120


Modification of charge compensation in semi-insulating semiconductors by high energy light ion irradiation

Kabiraj, D.; Grötzschel, R.; Ghosh, S.
High energy light ions have been used to engineer the electrical properties of semi-insulating InP and GaAs by creation and annihilation of native defects. Due to light mass, high energy ions lose most of their energy during flight inside the material by electronic excitation, which also modifies the charge states of the defect. Imbalance in charge compensation caused by irradiation induced defect engineering results in the modification of resistivity of the semi-insulating samples. The activation energies of the defect levels responsible for the modified resistivity have been estimated from the measurement of thermally activated currents. It is shown that the modified charge compensation is due to annihilation and/or creation of native defects depending on the material (GaAs or InP) and the fluence of irradiated ions. It has also been observed that annealing does not have any effect on modified compensation in InP, but in the case of GaAs, compensation recovers after thermal annealing.
Keywords: Semi-insulating semiconductors; High energy ion irradiation

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Publ.-Id: 11119


Zur Bestimmung von Reaktivitätswerten bei Störungsmessungen mit Incore-Detektoren an einem WWER-1000 des KKW Saporoshje

Maletti, R.
Zur systematischen Untersuchung der Ortseffekte bei Reaktivitätsmessungen können die in der Spaltzone von Leistungsreaktoren vorhandenen Elektronen-Emissions-Detektoren mit Rhodium-Emitter genutzt werden. Im vorliegenden Beitrag werden Versuchsdurchführung, Messanordnung und Verfahren der Signalbehandlung vorgestellt, die die gleichzeitige Messung des Neutronenflussdichteverhaltens an nahezu 100 Detektorpositionen gestatten. Im Artikel werden Ergebnisse von erstmalig an einem Reaktor des Typs WWER-1000 vorgenommenen Reaktivitätsstörungsmessungen genannt: Die Ortseffekte äußern sich derart, dass bei ausgeführten Änderungen der Reaktorleistung von etwa 2% die Incore-Detektoren Neutronenflussdichteänderungen bis maximal 20% registrieren, wobei die größten Änderungen in Nähe der Störzentren auftreten. Durch sogenannte Kanalreaktivitätsmessungen kann der Einfluss der Ortseffekte auf eine mit systematischen Fehlern behaftete Ermittlung von Reaktivitätswerten bzw. wichtigen reaktorphysikalischen Kenngrößen weitestgehend eliminiert werden. Die anhand der Messergebnisse getroffenen Aussagen werden durch vergleichende Berechnungen zur dreidimensionalen Reaktordynamik bekräftigt.
Keywords: Reactivity parameters, perturbation measurements, in-core detectors, neutron flux behaviour, space dependence, channel reactivity measurements, VVER-1000, NPP Saporoshje
  • Other report
    ZfK Rossendorf bei Dresden: ZfK-Report 716, 1990
    22 Seiten

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Publ.-Id: 11117


Hydrogen, oxygen and carbon losses during 15N bombardment of PMMA layers

Rudolph, W.; Grambole, D.; Groetzschel, R.; Heiser, C.; Herrmann, F.; Neelmeijer, C.; Knothe, P.
We have studied the behaviour of thin PMMA layers during high energy 15N irradiation. Employing the 1H(15N, αγ)12C and 12C(d, p)13C reactions after 15N preirradiation we determined the total energy loss of 15N ions as well as the hydrogen, carbon, and oxygen contributions in dependence upon the 15N fluence φ. Due to release effects the energy losses of the 15N ions within the PMMA films are reduced to about 0.3 of the initial values at φ = 5 × 1014 cm-2. At fluences φ > 2 × 1014 cm-2 the (oxygen plus carbon) contribution becomes constant and the change of the energy loss can be explained by hydrogen release alone.
  • Nuclear Instruments and Methods in Physics Research B 33(1988), 803-807

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Publ.-Id: 11116


Experimentelle Untersuchungen zur Ortsabhängigkeit bei Reaktivitäts-Störungsmessungen

Maletti, R.; Ziegenbein, D.; Kröger, J.
Mit der vorliegenden Arbeit werden erste systematische experimentelle Untersuchungen zur Ortsabhängigkeit von dynamischen Reaktivitätsmessungen an Leistungsreaktoren des Typs WWER vorgelegt und mit den Ergebnissen theoretischer Untersuchungen verglichen. Es wird gezeigt, dass die durch Simulation mit dem eindimensionalen Programm DYNAMIC erhaltenen theoretischen Ergebnisse das charakteristische Verhalten in Bezug auf die axiale Ortsabhängigkeit der gemessenen Parameter richtig widergeben. Insbesondere wird die These gestützt, dass im Flussmaximum in guter Näherung das dem Einpunktmodel der Neutronenkinetik entsprechende Verhalten gemessen wird.
Keywords: Rheinsberg akw1 reactor, reactor kinetics, disturbances, space dependence, control rod worths, power coefficient, one-dimensional calculations
  • Kernenergie 23(1980)11, 380-383

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Publ.-Id: 11115


Compositional Changes of PMMA Layers during 15N Bombardment

Rudolph, W.; Grambole, D.; Heiser, C.; Herrmann, F.; Neelmeijer, C.
The behaviour is investigated of thin PMMA films during 15N2+ ion bombardment at EN = = 6.50 MeV. Using the 1H(15N, alpha gamma)12C and 12C, 16O(d, p) reactions the hydrogen, carbon, and oxygen contents of the layers are measured in dependence on the 15N2+ ion fluence. Strong losses of all three elements are observed and a dependence of the film composition on the nitrogen ion fluence.
  • Physica Status Solidi (A) 112(1989), 765-768

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Publ.-Id: 11114


Space Dependence of Reactivity Parameters on Reactor Dynamic Perturbation Measurements

Maletti, R.; Ziegenbein, D.
Practical application of reactor-dynamic perturbation measurements for on-power determination of differential reactivity weight of control rods and power coefficient of reactivity has shown a significant dependence of parameters on the position of outcore detectors. The space dependence of neutron flux signal in the core of a VVER-440-type reactor was measured by means of 60 self-powered neutron detectors. The greatest neutron flux alterations are located close to moved control rods and in height of the perturbation position. By means of computations detector positions can be found in the core in which the one-point model is almost valid.
Keywords: Reactor-dynamic measurements, reactivity parameters, neutron flux behaviour, space dependence
  • Contribution to proceedings
    IAEA/NPPCI Specialists' Meeting on "New Instrumentation of Water Cooled Reactors", 23.-25.04.1985, Dresden, DDR
    Space Dependence of Reactivity Parameters on Reactor Dynamic Perturbation Measurements

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Publ.-Id: 11113


The influence of iron, fluorine and boron implantation on the magnetic properties of graphite

Höhne, R.; Esquinazi, P.; Heera, V.; Weishart, H.; Setzer, A.; Spemann, D.
Iron, fluorine and boron ions were implanted into highly oriented pyrolytic graphite (HOPG). The samples were characterized before and after ion implantation as well as after heat treatments in vacuum by measurements of the magnetic moment and element analysis.
Whereas the main magnetic contribution remains diamagnetic the paramagnetic one clearly increases with implantations and correlates with the amount of implanted ions. It is shown that a large part of the paramagnetic contribution is caused by the structural disorder created by particle bombardment using iron, fluorine or boron. All implanted HOPG samples show practically no change of the small ferromagnetic signal observed in their virgin state. No particular influence of iron on the ferromagnetic properties of HOPG is observed, up to 4000 mg/g Fe-concentration in the implanted region. For comparison, ferrous sulphates were added to ultra-clean graphite powder. This iron addition increases the number of paramagnetic spins proportional to the iron content in the untreated samples. In heat-treated samples however, a clear ferromagnetic behaviour is observed due to the formation of a ferromagnetic iron compound.
Keywords: graphite, ion implantation, magnetism

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Publ.-Id: 11112


Entwicklung und Validierung des Druckstoßprogramms DYVRO Mod. 3

Neuhaus, T.; Schaffrath, A.; Ronneberger, R.; Altstadt, E.
Druckstöße in Rohrleitungssystemen entstehen, wenn eine Flüssigkeit oder ein Gas durch das plötzliche Öffnen oder Schließen einer Armatur, die Änderung der Drehzahl einer Pumpe, in Folge von Rohrleitungsbrüchen usw. beschleunigt oder abgebremst wird. Hierbei entstehen Druckwellen, die erhöhte Innendrücke verbunden mit mechanischen Spannungen in den Rohrleitungswänden sowie zeitabhängige axiale Kräfte auf Rohrleitungen und deren Halterungen hervorrufen können. Durch Reflexionen der Druckwellen können Unterdrücke entstehen, die bei Unterschreiten des lokalen Sättigungsdrucks zur Bildung von Dampfblasen (Kavitation) führen können. Bei dem Zusammenfall der Dampfblasen können weitere, sekundäre Druckstöße auftreten, die die primären Druckwellen überlagern. Die Ausbreitungsgeschwindigkeit von Druckwellen hängt zum einen von den Eigenschaften des Fluids (speziell dessen Kompressibilität und Dichte) und zum anderen von den mechanischen Eigenschaften des Rohrleitungssystems (Elastizitätsmodul und Querkontraktionszahl) sowie dessen Geometrie (Durchmesser des Rohrs und Wanddicke) ab. Druckstöße sind oftmals die Ursache für Beschädigungen an Rohrleitungen und Rohrleitungshalterungen und stellen daher für viele verfahrenstechnische Anlagen ein Problem dar.

Die TÜV NORD SysTec GmbH & Co. KG beschäftigt das Druckstoßprogramm DYVRO entwickelt und qualifiziert. Der vorliegende Beitrag beschreibt die nun hinsichtlich des verwendeten partiellen Differentialgleichungssystems und der eingesetzten Numerik überarbeitete Programmversion DYVRO Mod. 3 und deren Validierung anhand repräsentativer Experimente (u.a. anhand des Simpson-Experiments sowie anhand eines Versuches an der Cold Water Hammer Test Facility). Die Ergebnisse der Validierungsrechnungen werden anschließend mit eigenen oder fremden Rechnungen mit Systemcodes (hier ATHLET und RELAP ) sowie dem Druckstoßprogramm WAHA verglichen. Bei diesen Vergleichen werden u.a. die Ergebnisse des im 5. EU-Rahmenprogramm geförderten Forschungsvorhabens WAHALOADS mit einbezogen. Die Vergleiche zeigen eine sehr gute Übereinstimmung der Rechenergebnisse von DYVRO mit den Experimenten sowie den Ergebnissen des WAHA-Codes. Die Ergebnisse der Druckstoßcodes WAHA und DYVRO sind – sowohl im einphasigen als auch im zweiphasigen Bereich - deutlich besser als die der Systemcodes.
Keywords: Water hammer, pressure wave, pipe systems
  • atw - International Journal for Nuclear Power (2008)2

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Publ.-Id: 11111


Atomistic simulation of amorphous germanium

Gabriel, A.; Posselt, M.
Electrical doping of Ge is usually performed by ion implantation and subsequent annealing. In many cases ion bombardment leads to formation of an amorphous layer. During annealing the layer recrystallizes by solid-phase epitaxial regrowth. In order to investigate this process by classical molecular dynamics simulations, first of all amorphous Ge with realistic properties must be prepared. This is the subject of the present work. The atomistic simulations use the Stillinger-Weber interatomic potential with a parameter set that yields correct or reasonable structural, thermodynamic and defect properties of diamond-structure Ge. In the first simulation step liquid Ge is prepared. Then, the system is cooled down slowly to 300 K using the method of Luedtke and Landman which was applied to simulate amorphous silicon. Finally, an equilibration at 300 K and zero pressure is performed. The characterization of amorphous Ge obtained in this manner includes density and cohesive energy, radial distribution function and static structure factor, coordination number, bond-angle distribution, distribution of interatomic distances as well as melting temperature and heat of fusion. The simulation results show very good agreement with experimental data and are consistent with previous theoretical investigations.
Keywords: Computer simulation, amorphous Germanium
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11110
Publ.-Id: 11110


Discontinuity of capacitance at the onset of surface superconductivity

Morawetz, K.; Lipavsky, P.; Mares, J. J.
The effect of the magnetic field on a capacitor with a superconducting electrode is studied within the Ginzburg-Landau (GL) approach. It is shown that the capacitance has a discontinuity at the onset of the surface superconductivity B_{\rm c3} which is expressed as a discontinuity in the penetration depth of the electric field into metals. Estimates show that this discontinuity is observable with recent bridges for both conventional and high-T_{\rm c} superconductors of the type-II.
  • Open Access Logo New Journal of Physics 11(2009)023032, 1-8

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Publ.-Id: 11109


THz detection with scalable photoconductive antennas

Peter, F.; Winnerl, S.; Nitsche, S.; Dreyhaupt, A.; Schneider, H.; Helm, M.; Köhler, K.
We present studies on nonresonant photoconductive THz detectors and emitters. Our system consists of a large-area terahertz detector based on an interdigitated electrode structure and an emitter with similar electrode geometry [1]. Emitters based on this concept stand out due to their high efficiency for conversion of near-infrared radiation into far-infrared radiation. The main advantage of the scalable antennas as compared to conventional photoconductive antennas is that they do not require tight focusing of the THz and gating beams. While the emitter is fabricated on semi-insulating GaAs, we compare different detection antennas based on ion-implanted and low temperature grown (LT) GaAs, respectively. We discuss which material properties affect the performance and noise level of our system and discuss the role of the carrier lifetime upon the measured THz signal. The best signal-tonoise ratios are found for N+ dual energy implantations (0.4 MeV and 0.9 MeV) with doses in the 1013 cm−2 range and for (LT) GaAs.
[1] F.Peter, S.Winnerl, S. Nitsche, A. Dreyhaupt, H. Schneider, M.Helm, Appl. Phys. Lett. 91, 081109 (2007)
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik mit anderen Fachverbänden und den Arbeitskreisen der DPG, 24.-29.02.2008, Berlin, Germany

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Publ.-Id: 11108


Fe-implantation for rear-facet coatings of InP-based quantum cascade lasers

Wienold, M.; Semtsiv, M. P.; Dressler, S.; Masselink, W. T.; Potzger, K.; Winnerl, S.; Helm, M.
Fe-implantation is used to create a high-resistivity layer at the rear facet of an InP-based quantum cascade laser (lambda = 3.9 mu m), subsequently coated with a metallisation of Cr (5 nm) and Au (200 nm). The coatings lead to a 3.7-fold increase of front-facet power and a 20–30% reduction in threshold current density compared to uncoated lasers.
Keywords: quantum cascade laser, ion implantation
  • Electronics Letters 44(2008), 293-284

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Publ.-Id: 11107


Two-color pump-probe spectroscopy of electron dynamics in superlattices

Wagner, M.; Stehr, D.; Schneider, H.; Winnerl, S.; Helm, M.; Andrews, M.; Roch, T.; Strasser, G.
We report on two-color pump-probe measurements to investigate the intraminiband dynamics of doped GaAs/AlGaAs SLs with different miniband widths smaller or larger than the optical phonon energy. We have analyzed the cooling behaviour at low temperature. We employed infrared pulses from a free-electron laser to excite electrons to the upper miniband at the center of the SL mini-Brillouin zone and the interminiband transition was probed at the zone edge with broadband THz pulses. After relaxation to the ground miniband the electronic distribution is heated up which results in more absorption at the zone edge. When the distribution cools down this induced absorption signal decays, leading to decay times of 40-50 ps for a miniband width smaller and 3.5 ps for a width larger than the optical phonon energy. This difference in time constants can be explained by the new relaxation channel through polar optical phonons. Additionally we performed measurements at room temperature where the lower miniband is already occupied at the zone edge. Thus no induced absorption and fast decay times are observed.
Keywords: pump-probe, intraminiband dynamics, superlattice, cooling
  • Lecture (Conference)
    72. Jahrestagung der Deutschen Physikalischen Gesellschaft und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.08, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11106
Publ.-Id: 11106


Effect of isothermal annealing on electrical and optical properties of Al-doped ZnO films

Vinnichenko, M.; Rogozin, A.; Shevchenko, N.; Kolitsch, A.; Möller, W.
The aim of present work is to investigate mechanisms of Al incorporation and its effects on electrical and optical properties of ZnO
films. Highly c-axis textured polycrystalline thin films of insulating ZnO were implanted by 110 keV Al+ ions and then annealed at 520 °C. The films were characterized by Hall effect, four-point probe, spectroscopic ellipsometry and x-ray diffraction techniques. The films are
nanocrystalline in as-implanted state. Their dielectric function shows broadened features near the band gap energy and increased, compared
to unimplanted films, absorption in the near IR and visible spectral range. If the implantation dose is below 2x10^16 cm−2, the free electron
density, Ne, increases after annealing and the film resistivity decreases monotonously during annealing. If the dose is above 2x10^16 cm−2, Ne
decreases after annealing while film resistivity reaches minimum and then increases during the treatment. The annealing decreases optical
absorption in the near IR and visible and improves film crystallinity. The behavior of the film electrical properties may be explained by the
interplay between oxygen vacancies formation and Al donor activation.
Keywords: Al-doped ZnO, ion implantation, reactive pulsed magnetron sputtering, spectroscopic ellipsometry
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik mit anderen Fachverbänden und den Arbeitskreisen der DPG, 25.-29.02.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11105
Publ.-Id: 11105


Gültigkeitsprüfung von Prozeßinformationen mittels analytischer Redundanz und Paritätsraumdarstellung

Maletti, R.; Stein, H.
Ständig steigende Anforderungen bezüglich optimaler Prozeßführung und Gewährleistung hoher Anlagensicherheit erfordern in zunehmendem Maße den erweiterten Einsatz rechnergestützter Beratungs- und Diagnosesysteme. Mit dem Beitrag wird der internationale Stand auf dem Gebiet der Gültigkeitsprüfung von Sensorsignalen mittels analytischer Redundanz und Parity-space-Darstellung aufgearbeitet, insbesondere wird das Parity-space-Verfahren in geschlossener mathematischer Form dargeboten.
Keywords: Signaldiagnose, Gültigkeitsprüfung von Sensorsignalen, Sensorvalidierung, Parity-space-Verfahren; sensor validation, parity space technique
  • Messen, Steuern, Regeln 32(1989)9, msr 8855

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Permalink: https://www.hzdr.de/publications/Publ-11104
Publ.-Id: 11104


Die Benutzung eines modifizierten Simplex-Algorithmus zur Verfahrensoptimierung in der Mikroelektronik

Maletti, R.
Im Artikel werden Anwendungsmöglichkeiten eines Simplex-Verfahrens zur Prozessoptimierung bei der Herstellung mikroelektronischer Bauelemente gezeigt. Anhand ausgewählter Beispiele der Plasmaätztechnologie wird die Einsatzbreite für die optimale Versuchsplanung, die Bestimmung von Modellgrößen für Simulationsrechnungen und die Ermittlung von Parametern der in situ Prozesskontrolle angedeutet.
Keywords: Simplexmethode, Versuchsplanung, Optimierung, Simulation, Modellierung, Mikroelektronik, Dünnschichttechnik, Plasmaätzen, Substratgrabenätzen, Laserinterferometer; simplex-method, experimental planning, optimization, simulation, modelling, microelectronics, thin-film technique, plasma etching, trench etching, laser interferometer
  • Wissenschaftliche Zeitschrift der Technischen Universität Dresden 37(1988)1, 279-282

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Permalink: https://www.hzdr.de/publications/Publ-11103
Publ.-Id: 11103


Surface deformation caused by the Abrikosov vortex lattice

Lipavský, P.; Morawetz, K.; Kolavcek, J.; Brandt, E. H.
In superconductors penetrated by Abrikosov vortices the magnetic pressure and the inhomogeneous condensate density induce a deformation of the ionic lattice. We calculate how this deformation corrugates the surface of a semi-infinite sample. The effect of the surface dipole is included.
  • Physical Review B 77(2008), 184509-1-184509-7

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Permalink: https://www.hzdr.de/publications/Publ-11102
Publ.-Id: 11102


Thermal decomposition and new luminescence bands in wet, dry, and additional oxygen implanted silica layers

Fitting, H.-J.; Salh, R.; Schmidt, B.
Wet and dry silica oxide layers have been treated thermally up to Ta = 1300 °C and were investigated by cathodoluminescence (CL) spectroscopy. Whereas the dry oxides after high temperature treatment show an increase of the yellow–red spectra region, contrary, in wet oxides the UV–blue region is enhanced. Even a new strong band in the near-UV region (NV) at 330 nm (3.76 eV) is found for wet oxides at liquid nitrogen temperature (LNT), but much broader and with lower intensity for room temperature (RT) in a triple band structure UV: 290 nm, NV: 330 nm, and V: 400 nm. These violet bands should be associated with a thermally decomposed and rapidly cooled-down silica network in presence of OH groups or even dissociated oxygen. Additional oxygen implantation into dry silica with high doses up to 1017 ions/cm2 and high thermal treatment T > 1100 °C leads as well to enhanced UV–NV–V luminescence emission bands supporting the fact that oxygen and structural decomposition play a decisive role in formation of near-UV luminescent defects in silica.
Keywords: Glass formation; Glass transition; Hydrogen in glass; Radiation effects; SEM S100; Optical properties; Luminescence; Silica; Defects; Short-range order; Thermal properties; Viscosity and relaxation; Structural relaxation

Permalink: https://www.hzdr.de/publications/Publ-11101
Publ.-Id: 11101


Room temperature photoluminescence from the amorphous Si structure generated under keV Ar-ion- induced surface rippling condition

Chini, T. K.; Datta, P. D.; Facsko, S.; Mücklich, A.
We observe room temperature (RT) visible and infrared (IR) photoluminescence (PL) bands peaked around 680 and 1020 nm, respectively, from a silicon (Si) surface amorphized and patterned with ripples by 60 keV Ar+ bombardment at 60 degrees angle of ion incidence. However, the Si surface amorphized but not patterned under normal bombardment (0 degrees angle of ion incidence) condition shows a drastic reduction in the intensity of the visible PL along with the complete suppression of IR emission. The present work demonstrates that Ar ion irradiation at rippling condition may yield a porouslike light emitting amorphous silicon (a-Si) nanostructure.
Keywords: Si, Photoluminescence, Ion irradiation
  • Applied Physics Letters 92(2008)10, 101919

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Publ.-Id: 11100


Aligned Silver Nanoparticles on Rippled Silicon Templates Exhibiting Anisotropic Plasmon Absorption

Oates, T. W. H.; Keller, A.; Facsko, S.; Mücklich, A.
Aligned silver nanoparticles, grown by combining two simple bottom-up techniques, are reported. Physical vapor-deposited silver adatoms are shown to form nanoparticles preferentially in the valleys of rippled silicon templates prepared by low-energy ion bombardment. A 35-nm ripple periodicity produced highly aligned structures with a 0.21 eV polarization-dependent shift in the plasmon resonance peak. The speed and simplicity of the method is viable for cost-effective, large-scale production of mesoscale aligned nanostructures with adjustable periodicity.
Keywords: Self-organization, Self-alignment , Plasmon coupling, SERS, Island films

Permalink: https://www.hzdr.de/publications/Publ-11099
Publ.-Id: 11099


Investigation of planar channeling radiation on diamond and quartz crystals at electron energies between 14 and 34 MeV and probing the influence of ultrasonic waves on channeling radiation

Azadegan, B.
Theoretical investigations and measurements of planar channeling radiation out off different crystallografic planes of diamond and quartz single crystalls at electron energies between 14 and 34 MeV have been performed. Based upon the obtained results a novel intense X-ray source has been designed and came into operation at ELBE. First experimental investigations of the influence of ultrasonic waves on the channeling radiation properties have been carried out on quartz crystalls.
Keywords: channeling radiation, diamond, quartz, ultrasound
  • Doctoral thesis
    Technische Universität Dresden, 2007
    110 Seiten

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Publ.-Id: 11098


Comparative small-angle neutron scattering study of neutron-irradiated Fe, Fe-Cu, Fe-Ni-Mn and Fe-Ni-Mn-Cu

Bergner, F.; Lambrecht, M.; Ulbricht, A.; Almazouzi, A.
Irradiation-induced damage in reactor pressure vessel steels covers a multitude of different features at the nanometer size scale. The nature, formation kinetics and relative importance of these features are not yet well understood in detail. It also turned out that there is no single experimental technique capable of closing all the remaining gaps. The present approach is based on the idea that significant progress can be achieved by investigating the same set of neutron irradiated model alloys of increasing complexity with several experimental techniques including transmission electron microscopy (TEM), atom probe tomography (APT), positron annihilation spectroscopy (PAS) and small-angle neutron scattering (SANS). The aim is to explore both complementarity and overlaps of the information gained from individual techniques and to close gaps by introducing proper models. In the present paper the results obtained by means of SANS are reported, self-consistent interpretation is given and the results are qualified for the discussion in combination with the other experimental techniques to be given in separate papers.

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Publ.-Id: 11097


Factfile: S100A12

Pietzsch, J.
S100A12 is a member of the S100 family of EF-hand calcium-binding proteins. Human S100A12 is predominantly expressed and secreted by neutrophil granulocytes and, therefore, has been assigned to the S100 protein subfamily of calgranulins. It is part of the innate immune response and linked to certain autoimmune reactions. Human S100A12 is markedly overexpressed in inflammatory compartments, and elevated serum levels of S100A12 are found in patients suffering from metabolic, neurodegenerative, inflammatory and neoplastic disorders. In this regard, interaction of calcium-activated S100A12 with the receptor for advanced glycation endproducts (RAGE) plays a central pathogenetic role.
  • Open Access Logo Calcium Binding Proteins 3(2008), 18-21

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Publ.-Id: 11096


Correlates of local cerebral blood flow (CBF) in normal pressure hydrocephalus patients before and after shunting—A retrospective analysis of [15O]H2O PET-CBF studies in 65 patients

Klinge, P. M.; Brooks, D. J.; Samii, A.; Weckesser, E.; van den Hoff, J.; Fricke, H.; Brinker, T.; Knapp, W. H.; Berding, G.
Objectives:
Findings in local cerebral blood flow (rCBF) in Normal pressure hydrocephalus (NPH) have always been challenged by the variable and inconsistent relation to clinical symptoms before and after shunt treatment. [15O]H2O PET data from a consecutive cohort of 65 idiopathic NPH patients were retrospectively analyzed questioning whether the functional status before and after shunt treatment might correlate with local blood flow.

Patients and methods
Using statistical parametric mapping (SPM99, Wellcome Department of Cognitive Neurology, London), the [15O]H2O uptake was correlated with the preoperative clinical scores, graded according to a modified Stein and Langfitt score. Furthermore, differences in the uptake in the pre-and post-shunt treatment study after seven to 10 days in patients with and without clinical improvement were studied.

Results
A higher clinical score significantly correlated with a reduced tracer uptake in mesial frontal (k = 1239 voxel, Z = 4.41) and anterior temporal (k = 469, Z = 4.07) areas. In the mesial frontal areas, tracer uptake showed significant reciprocal changes in the clinically improved vs. the unimproved patients.

Conclusion
Matched with the existing literature, the regional blood flow alterations are suggested relevant to the NPH syndrome and to post-treatment functional changes. The present rCBF findings warrant prospective studies on the accuracy of neuroimaging studies as they may provide a more specific insight into disease mechanisms.
Keywords: Hydrocephalus; NPH; PET; Blood flow; Metabolism; Imaging

Permalink: https://www.hzdr.de/publications/Publ-11095
Publ.-Id: 11095


PET und Bestrahlungsplanung - technische Aspekten / PET and Radiation Treatment Planning - Technical Aspects

Wolf, U.; Hofheinz, F.; Oehme, L.; van den Hoff, J.
Zusammenfassung

Die Integration der PET in die Bestrahlungsplanung wirft verschiedene technische Probleme auf, welche zurzeit überwiegend noch nicht zufriedenstellend gelöst sind, gegenwärtig aber intensiv untersucht werden. Erste Lösungen für Teilaspekte wie etwa die geometrisch korrekte ROI-Abgrenzung und die Übersetzung dieser Information in DICOM-RT-Structure-Sets für den Import in die Bestrahlungsplanungssysteme existieren mittlerweile, sind aber noch nicht allgemein verfügbar. Es ist jedoch zu erwarten, dass sich die dynamische technische Entwicklung in den nächsten Jahren fortsetzen und zu einer Lösung der noch bestehenden Probleme führen wird.


Abstract

Integration of PET into radiation treatment planning causes several technical problems, which have not yet been solved satisfactory up to now, but which are currently investigated intensively. First solutions of some aspects such as geometrically correct ROI delineation and the translation of this information into DICOM-RT Structure Sets for import into the radiation treatment planning systems have already been developed, but are not yet generally available. It is to be expected, however, that the dynamic technical development will continue in the next years and lead to solution of the currently persisting problems.
Keywords: PET, CT - radiation treatment planning - DICOM-RT - 3D-ROIs - volumetry

Permalink: https://www.hzdr.de/publications/Publ-11094
Publ.-Id: 11094


PET in der Strahlentherapie: Perspektiven / PET in Radiation Oncology - Perspectives

Baumann, M.; Beuthien-Baumann, B.; Zips, D.
Zusammenfassung
Die Positronen-Emissions-Tomografie (PET) hat einen wichtigen Stellenwert in der modernen Strahlentherapie erlangt. Die Integration der funktionellen PET-Daten in die Bestrahlungsplanung wurde durch die Fusion von CT und PET in einem Gerät wesentlich erleichtert. Entwicklungs- und Optimierungsbedarf besteht jedoch in der Definition der Tumorgrenzen im PET und im Umgang mit Atembewegungen. Neben dem am häufigsten zur Anwendung kommenden Radiopharmakon 18F-Fluordesoxyglukose (FDG) sind die Anwendung von Hypoxiemarkern und Radiotracerentwicklungen für die Visualisierung anderer definierter radiobiologischer Resistenzmechanismen wünschenswert.

Abstract
Positron emission tomography (PET) has evolved as an important tool in modern radiotherapy. Integration of functional PET data into radiation treatment planning is facilitated due to PET-CT scanner, optimizing data fusion. Optimization of definition of tumour borders and reduction of movement artifacts is warranted. Besides the application of 18F-fluorodeoxyglucose (FDG) utilization of tracers visualizing hypoxia and the development of novel tracers depicting other defined biological mechanisms of radioresistance is a promising avenue for future research.
Keywords: PET, CT - FDG - radiation treatment planning - radiation biology - hypoxia - theragnostics

Permalink: https://www.hzdr.de/publications/Publ-11093
Publ.-Id: 11093


Hydrolysis and dimerization of Th4+ ion

Tsushima, S.
Hydrolysis of Th4+ in aqueous solution was studied by density functional theory (DFT) calculations. First, stable coordination numbers (CNs) of Th4+ hydrolysis products were studied systematically, and it was found that the CN significantly decreases as a stepwise hydrolysis reaction proceeds. The fourth hydrolysis product Th(OH)40 has CN 6 with an octahedron coordination. Th(OH)40 can readily form a dimer complex Th2(OH)80 via a Th-OH-Th bridging through an exergonic reaction with a Gibbs energy change of -24.0 kJ/mol. Consequently, dimerization inhibits Th(OH)40 to stay as stable aqueous species. The calculated result is in agreement with the fact that there is no direct evidence to confirm the presence of Th(OH)40 while oligomeric species such as Th4(OH)160 are presumably present. Similar calculations on the Th4+ disulfato complex reveal that the CN and the average Th-O distance of Th(SO4)20 remain almost the same as those in the Th4+ aquo ion, which is also in agreement with experimental data.
Keywords: Hydrolysis, tetravalent, actinide, thorium, quantum chemistry

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Publ.-Id: 11092


Ion-induced nanopatterns on silicon: experiment, theory, and application

Keller, A.; Facsko, S.; Möller, W.
It is well known that oblique low and medium energy (typically 0.1 – 100 keV) ion erosion of solid surfaces can lead to the formation of periodic ripple patterns with wavelengths ranging from 10 to 1000 nm. The ripples produced in this way are oriented either parallel or normal to the projection of the ion beam and their wavelength scales with ion energy. These structures have been found on a large variety of materials, such as semiconductors, metals, and insulating surfaces. The formation and early evolution of the ripple patterns can be qualitatively reproduced by a linear continuum equation derived by Bradley and Harper. At longer times, however, nonlinear terms have to be taken into account, leading to nonlinear models based on the Kuramoto-Sivashinsky equation.
In this talk, recent experimental results on the evolution of ripple morphologies on Si(100) surfaces during high-fluence ion sputtering will be presented and compared to numerical integrations of the damped Kuramoto-Sivashinsky equation. In addition, promising applications of nanorippled substrates as templates in thin film growth will be discussed.
  • Lecture (others)
    Seminar, 15.02.2008, Madrid, Spain
  • Lecture (others)
    Seminar, 27.02.2008, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-11091
Publ.-Id: 11091


Medical Physics Activities in the Integrated EU Project BioCare

Möckel, D.
Presentation of the Medical Physics Activities in the Integrated EU Project BioCare
  • Invited lecture (Conferences)
    3rd Meeting of the Scientific Advisory Board of OncoRay, 28.02.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11090
Publ.-Id: 11090


The interplay of PVD growth parameter and nanostructuring of C:Co and C:V nanocomposites

Berndt, M.; Abrasonis, G.; Krause, M.; Mücklich, A.; Kolitsch, A.; Möller, W.
The growth regimes of C:V and C:Co nanocomposite thin films (metal content of ~15 and 30 at.%) grown by ion beam co-sputtering in the temperature range of RT-500°C are investigated. X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy at two excitation wavelengths (532 nm and 785 nm) have been used to characterize the microstructure of carbon and metal coexisting constituents of the nanocomposites. In order to reveal the influence of the transition metal on the encapsulating matrix, pure carbon films were deposited at the same temperatures.
C:Co and C:V nanocomposites exhibit a fine-grained structure at deposition temperatures below 300°C. At higher temperatures C:Co films tend to form nanocolumns, whereas the globular structure is preserved for C:V. X-ray patterns show low degree of crystallinity of the nanoparticles in C:Co and C:V composites.
Raman spectroscopy results show that the presence of metal significantly enhances the formation of aromatic clusters. This enhancement occurs independently on metal nanoparticle size, shape and phase.
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.2.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11089
Publ.-Id: 11089


Room temperature ferromagnetism in ZnO films due to defects

Xu, Q.; Schmidt, H.; Zhou, S.; Potzger, K.; Helm, M.; Hochmuth, H.; Lorenz, M.; Setzer, A.; Esquinazi, P.; Meinecke, C.; Grundmann, M.
ZnO films were prepared by pulsed laser deposition on a-plane sapphire substrates under N2 atmosphere. Ferromagnetic loops were obtained with the SQUID at room temperature, which indicate a Curie temperature much above room temperature. No clear ferromagnetism was observed in intentionally Cu-doped ZnO films. This excludes that Cu doping into ZnO plays a key role in tuning the ferromagnetism in ZnO. 8.8 % negative magnetoresistance probed at 5 K at 60 kOe on ferromagnetic ZnO proves the lack of s-d exchange interaction. Anomalous Hall effect (AHE) was observed in ferromagnetic ZnO as well as in non-ferromagnetic Cu-doped ZnO films, indicating that AHE does not uniquely prove ferromagnetism. The observed ferromagnetism in ZnO is attributed to intrinsic defects.
Keywords: diluted magnetic semiconductor, ZnO, ferromagnetism, anomalous Hall effect, magnetoresistance

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Publ.-Id: 11088


Enzymatic properties of an ecto-nucleoside triphosphate diphosphohydrolase from Legionella pneumophila; substrate specificity and requirement for virulence

Sansom, F. M.; Riedmaier, P.; Newton, H. J.; Dunstone, M. A.; Müller, C. E.; Stephan, H.; Byres, E.; Beddoe, T.; Rossjohn, J.; Cowan, P. J.; D'Apice, A. J. F.; Robson, S. C.; Hartland, E. L.
Legionella pneumophila is the predominant cause of Legionnaires’ disease, a severe and potentially fatal form of pneumonia. Recently, we identified an ecto-nucleoside triphosphate diphosphohydrolase (NTPDase) from L. pneumophila, termed Lpg1905, which enhances intracellular replication of L. pneumophila in eukaryotic cells. Lpg1905 is the first prokaryotic member of the CD39/NTPDase1 family of enzymes that are characterized by the presence of five apyrase-conserved regions (ACR) and the ability to hydrolyse nucleoside tri- and diphosphates. Here we examined the substrate specificity of Lpg1905 and showed that apart from ATP and ADP, the enzyme catalysed the hydrolysis of GTP and GDP but had limited activity against CTP, CDP, UTP and UDP. Based on amino acid residues conserved in the ACR regions of eukaryotic NTPDases, we generated five site directed mutants, Lpg1905E159A, R122A, N168A, Q193A and W384A. While the mutations, E159A, R122A, Q193A and W384A abrogated activity completely, N168A resulted in decreased activity because of less affinity for nucleotides. When introduced into the lpg1905 mutant strain of L. pneumophila, only N168A (and not the isoforms E159A, R122A, Q193A and W384A) partially restored the ability of L. pneumophila to replicate in THP-1 macrophages. Following intratracheal inoculation of A/J mice, none of the Lpg1905E159A, R122A, Q193A, W384A or N168A isoforms were able to restore virulence to an lpg1905 mutant during lung infection, thereby demonstrating the importance of NTPDase activity to L. pneumophila infection. In addition, the kinetic studies undertaken here demonstrated important differences to mammalian NTPDases, which may be exploited in the design of novel inhibitory compounds to microbial NTPDases for use as anti-infective agents.
  • Journal of Biological Chemistry 283(2008)19, 12909-12918

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Publ.-Id: 11087


Magnetic properties of amorphous, p-type conducting CuCr0.95Mg0.05O2 and CuCr0.93Mg0.05Mn0.02O2

Xu, Q.; Schmidt, H.; Zhou, S.; Potzger, K.; Helm, M.; Hochmuth, H.; Lorenz, M.; Meinecke, C.; Grundmann, M.
CuCr0.95Mg0.05O2 has been reported to be p-type oxide semiconductor with the highest conductivity determined by the Seebeck effect [1]. We prepared conductive, polycrystalline and amorphous CuCr0.95Mg0.05O2 and CuCr0.93Mg0.05Mn0.02O2 films on a-plane sapphire substrates by pulsed laser deposition under different O2 partial pressure and substrate temperature. Hall measurements were performed to study the majority carrier type in these films. The polycrystalline CuCr0.95Mg0.05O2 and CuCr0.93Mg0.05Mn0.02O2 films are n-type conducting up to 290 K, while in amorphous CuCr0.95Mg0.05O2 and CuCr0.93Mg0.05Mn0.02O2 films the type of majority charge carriers changes from n-type to p-type around 270 K. Interestingly, the structure has little influence on the magnetic properties of the films. The well-known antiferromagnetic to paramagnetic transition was observed in both polycrystalline and amorphous CuCr0.95Mg0.05O2 films at 25 K, while the CuCr0.93Mg0.05Mn0.02O2 films revealed no antiferromagnetic ordering below 25 K.
[1] R. Nagarajan et al. J. Appl. Phys. 89, 8022 (2001)
Keywords: diluted magnetic semiconductor, p-type oxide, Hall effect
  • Poster
    72. Annual Meeting of the DPG and DPG Spring Meeting of the Condensed Matter Division, 24.-29.02.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11086
Publ.-Id: 11086


High energy Xe+ ion beam induced ripple structures on silicon

Hanisch, A.; Grenzer, J.; Facsko, S.; Winkler, I.; Biermanns, A.; Grigorian, S.; Pietsch, U.
Ion beam bombardment on semiconductor surfaces leads to welldefined morphological structures in the nanoscale range. Due to the impact of ions a self-organized wave-like surface structure develops. Ion bombardment causes an amorphization of a surface-adjacent layer of several nanometers and creates a periodical structure on the surface as well as at the amorphous-crystalline interface. We investigate the dependence of the periodicity on the crystallography of (100) silicon bombarded with Xe+ ions, the ion beam incidence and the azimutal angle of the sample surface. So far we found that the ripple wavelength scales with the ion energy in a range of 5 to 70 keV. In order to understand the initiation of the ripple formation we also ask the question which role the initial surface structure plays. Therefore we investigate the formation of ripples on pre-structured and rough surfaces such as wafers with an intentional miscut. Therefore, we not only introduce a certain initial roughness but also vary the orientation of the (100) lattice plane in respect to the surface. We try to distinguish between ion beam induced surface defects (sputter erosion) and the influence of the crystalline Si lattice (strain) on the ripple formation.
Keywords: nanostructures ion-beam patterning
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.08, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11085
Publ.-Id: 11085


X-ray scattering and diffraction from Xe-induced ripples in crystalline silicon

Biermanns, A.; Pietsch, U.; Grigorian, S.; Grenzer, J.; Facsko, S.; Hanisch, A.; Carbone, D.; Metzger, H.
The formation of surface-nanostructures with a characteristic size ranging from several nanometer up to microns has attracted significant interest in the last decades in the context of fabrication of novel opto-electronic and storage devices. One kind of those nanostructures are wave-like patterns (ripples) produced by an interplay between a roughening process caused by ion beam erosion (sputtering) of the surface and smoothening processes caused by surface diffusion. In this contribution we report on investigations of patterned Si (001) surfaces after irradiation with Xe+ -ions using ion-energies up to 40keV. During the sputtering, an amorphous surface-layer is formed followed by a rather sharp interface towards crystalline material, showing the same morphology as the surface. The structures of the amorphous layer and the amorphous-crystalline interface were studied by means of grazingincidence - small angle scattering (GISAXS) and diffraction (GID) using synchrotron-radiation. We found that the crystal structure at the interface is expanded along the ripples, caused by the creation of defects inside the surface region, whereas this expansion is strongly reduced across the ripples. This different relaxation may play a driving role in pattern formation at the interface.
Keywords: ion-beam erosion X-ray scattering nanostructures
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.08, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11084
Publ.-Id: 11084


Magnetoresistance in n-type conducting Co-doped ZnO

Xu, Q.; Hartmann, L.; Schmidt, H.; Hochmuth, H.; Lorenz, M.; Spemann, D.; Grundmann, M.
Series of Co-doped Al-codoped ZnO films with electron concentration at 5 K ranging from 8.31017 cm-3 to 9.91019 cm-3 were prepared by pulsed laser deposition under different O2 pressure and substrate temperature. The magnetoresistance (MR) effect was studied between 5 K and 290 K with fields up to 6 T, showing large electron concentration and temperature dependence. A large positive MR of 124 % has been observed in the film with the lowest electron concentration of 8.31017 cm-3, while only negative MR of –1.9 % was observed in the film with an electron concentration of 9.91019 cm-3 at 5 K. The positive MR is attributed to the quantum correction on the conductivity due to the s-d exchange interaction induced spin-splitting of the conduction band [1]. The negative MR is attributed to the magnetic field suppressed weak localization [1]. The modelled superimposed positive and negative MR agrees well with the experimentally observed MR and hints towards the physical origin of MR in Co-doped ZnO [2].
[1] P. A. Lee and T. V. Ramakrishnan, Rev. Mod. Phys. 57, 287 (1985)
[2] Q. Xu, L. Hartmann, H. Schmidt, H. Hochmuth, M. Lorenz, D. Spemann, and M. Grundmann, Phys. Rev. B 76, 134417 (2007)
Keywords: diluted magnetic semiconductors, ZnO, magnetoresistance, exchange interaction, weak localization
  • Lecture (Conference)
    72. Annual Meeting of the DPG and DPG Spring Meeting of the Condensed Matter Division, 24.-29.02.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11083
Publ.-Id: 11083


Polycrystalline Mn-alloyed indium tin oxide films

Scarlat, C.; Schmidt, H.; Xu, Q.; Vinnichenko, M.; Kolitsch, A.; Helm, M.; Iacomi, F.
Magnetic ITO films are interesting for integrating ITO into magnetooptoelectronic devices. We investigated n-conducting indium tin oxide (ITO) films with different Mn doping concentration which have been grown by chemical vapour deposition using targets with the atomic ratio In:Sn:Mn=122:12:0, 114:12:7, and 109:12:13 [1]. The average film roughness ranges between 30 and 50 nm and XRD patterns revealed a polycrystalline structure. Magnetotransport measurements revealed negative magnetoresistance for all the samples, but high field positive MR can be clearly observed at 5 K with increasing Mn doping concentration. Spectroscopic ellipsometry (SE) has been used to prove the existence of midgap states in the Mn-alloyed ITO films revealing a transmittance less than 80%. A reasonable model for the ca. 250 nm thick Mn-alloyed ITO films has been developed to extract optical constants from SE data below 3 eV. Depending on the Mn content, a Lorentz oscillator placed between 1 and 2 eV was used to model optical absorption below the band gap.[1]C. Baban et al. E-MRS 2007, Straßbourg.
  • Poster
    72. Annual Meeting of the DPG and DPG Spring Meeting of the Condensed Matter Division, 25.-29.02.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11081
Publ.-Id: 11081


Empirical pseudopotential calculation of strain induced birefringence in ZnO

Fritsch, D.; Schmidt, H.
One big challenge in the fabrication of ZnO-based heterostructure devices is the lattice mismatch between ZnO films and substrates and the different thermal expansion coefficients inducing biaxial strain. There is currently also much interest in ZnO doped with 3d transition metal ions for spintroncis applications and the detection of ferromagnetic signatures by magneto-optical measurements of ordering induced birefringence being most intense around the critical point structure of the dielectric function. A quantitative understanding of Zeeman splitting far away from the center of Brillouin zone is still an open question and requires a separation of strain and magnetic field induced modifications of electronic band strcucture. We report on the effect of strain on the birefringence in ZnO films grown on Al2O3 or on SiC substrates. The imaginary part of the dielectric function has been calculated b means of the empirical pseudopotential method. Thereby we also accounted for relativistic effects in form of te spin-orbit interaction, for the energy-dependence of the crystal potential through the use of nonlocal model potentials, and for excitonic conrtibutions to the dielectric functiuon fue to discrete excitonic states and Coulomb enhanced band-to-band transitions.
Keywords: ZnO, birefringence
  • Poster
    72. Annual Meeting of the DPG and DPG Spring Meeting of the Condensed Matter Division, 25.-29.02.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11080
Publ.-Id: 11080


Magnetism of the high spin molecules [Mn4L6](BF4)2·2CH3-CN·H2O and [CrIIIMnII3 (PyA)6Cl3]

Prinz, M.; Raekers, M.; Kuepper, K.; Chaudhuri, P.; George, S. J.; Neumann, M.
We have studied the electronic and magnetic structure of high spin molecules by spectroscopic investigations in combination with theoretical calculations. We present results on [MnII4 L6](BF4)2·2CH3CN·H2O (Mn4)and the hetero nuclear, spin frustrated molecule [CrIIIMnII3 (PyA)6Cl3] (CrMn3), which have been studied using X-ray photoelectron spectroscopy (XPS), X-ray absorption and emission spectroscopy (XAS, XES), and X-ray magnetic circular dichroism (XMCD). Magnetic measurements of Mn4 show a magnetization saturation of about 20 μB/f.u. at a magnetic field of B = 7 T and a temperature of T = 2 K. From XMCD measurements of Mn4 at T = 5 K and B = 5 T we obtained a high magnetic moment of 18.5 μB/f.u, whereas a quenching of the Mn orbital moments was observed (morb = 0.4 μB/f.u.). The element selective MnII and CrIII dichroic signals of the CrMn3 complex at B = 5 T and T = 5 K where recorded. For the three MnII ions a magnetic moment of 15 μB was determined. For both complexes we will present a comparison to XAS/XMCD charge transfer multiplet calculations.
Keywords: magnetic high spin molecules, electronic structure, x-ray magnetic circular dichroism
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11079
Publ.-Id: 11079


Manganese implanted GaAs films

Bürger, D.; Schmidt, H.; Xu, Q.; Kolitsch, A.; Winnerl, S.; Schneider, H.; Zhou, S.; Potzger, K.; Helm, M.; Biehne, G.; Gottschalch, V.
Electron spin preservation has been proven in unmagnetic GaAs over several μm by time-resolved luminescence measurements. The synthesis of Mn-alloyed GaAs has introduced a controllable spin degree of freedom in the GaAs device technology. Approx. 1 μm thick n-type (Si) and p-type (Zn) GaAs films have been grown on highly conducting n- and p-GaAs substrates by metalorganic chemical vapour deposition. For magnetotransport measurements reference samples have been grown on insulating substrates. Mn+ ion beam implantation with 300/150 keV at 200°C yielded a boxlike Mn-implantation profile of the 250 nm thick GaAs surface layer with a nominal implantation dose dependent Mn content of 1 and 5 at%. Rapid thermal annealing has been performed at 650°C for 10 s. Magnetic properties have been investigated by means of SQUID-magnetometry. The relation between concentration of free charge carriers, defect formation and magnetoresistance effects in manganese implanted GaAs will be discussed.
Keywords: GaAs, ion implantation, magnetic semiconductor, magnetoresistance, DLTS
  • Poster
    72. Annual Meeting of the DPG and DPG Spring Meeting of the Condensed Matter Division, 25.-29.02.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11078
Publ.-Id: 11078


Charge accumulation in a type-II Ge/Si heterostructure

Henkel, C.; Biehne, G.; Grundmann, M.; Wagner, G.; Stoffel, M.; Schmidt, O. G.; Schmidt, H.
The main motivation for mixing a small amount of Ge into Si for example by the self-organized growth of a stack of Ge dots into Si [1], is the controlled modification of the electronic band structure in strained Si namely charge carrier mobility and optical transition probabilities [2]. We report on charge accumulation in fivefold stacks of Ge quantum dots embedded in the n-region of a p+n-Si diode. By means of thermal admittance spectroscopy, capacitance voltage and deep level transient spectroscopy measurements [3] electron confinement in the type II Ge/Si-heterostructures, barrier effects of the quantum wells and wetting layers and defect states in the n-region of the sample associated with the surrounding Si-matrix have been probed. By relating these results to the self consistently modeled electronic band-structure and capacitance voltage characteristic charge accumulation in quantum confined electron states in the investigated type II Ge/Si-heterostructures is clearly revealed.
[1] A. Malachias, T. H. Metzger, M. Stoffel, O.G. Schmidt and V. Holy, Thin Solid Films 515, 5587 (2007)
[2] O.G. Schmidt and K. Eberl, Phys. Rev. B 61, 20 (2000)
[3] M. Gonschorek, H. Schmidt, J. Bauer, G. Benndorf, G. Wagner, G.E. Cirlin and M. Grundmann, Phys. Rev. B 74, 115312 (2006)
Keywords: Ge/Si, space charge spectroscopy
  • Poster
    72. Annual Meeting of the DPG and DPG Spring Meeting of the Condensed Matter Division, 25.-29.02.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11077
Publ.-Id: 11077


High Resolution Measurement of the Thermal Expansion Coefficient of Semiconductor Multilayer Lateral Nanostructures

Brueser, B.; Pietsch, U.; Grigorian, S.; Panzner, T.; Grenzer, J.; Zeimer, U.
We measured the thermal expansion coefficient of a vertically stacked multi-quantum-well structure buried under a thick GaAs top layer before and after lateral patterning of the GaAs top layer. After patterning the thermal expansion coefficient of the whole multi-quantum-well structure differs from that of the planar structure by about 20%. Based on calculations in terms of methods of finite elements the effect is explained by the influence of the strain field originating from the bottom edges of the etched nanostructure. Due to the long range nature of this strain field the strain release within the individual quantum wells changes as a function from the distance from the valley.
Keywords: nanostructrues, X-ray scattering
  • Poster
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany
  • Physica Status Solidi (A) 205(2008)2, 316-320

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Permalink: https://www.hzdr.de/publications/Publ-11076
Publ.-Id: 11076


X−ray investigations on CoSi2 nano wires manufactured by focused ion beam synthesis

Grenzer, J.; Bischoff, L.; Biermanns, A.
Nanowires and chains of nanoparticles are of emerging interest in nano-electronics, nano-optics and plasmonics as well as for their monolithic integration into microelectronic devices; CoSi2 is a promising material due to its CMOS-compatibility in micro-electronics technology. It shows metallic behaviour with low resistivity and high thermal stability. It is well known that cobalt disilicide films can be formed in silicon by implanting Co in stoichiometric concentration and a subsequent annealing procedure. Ion beam synthesis allows the fabrication of epitaxial buried or surface CoSi2 layers on silicon. Sub-micron patterns with feature dimensions much smaller than 100nm can be directly produced by writing focused ion beam (FIB) cobalt implantation.
We have studied the strain of the Si host lattice in the surrounding area of a single nanostructures depending on their crystallographic orientation using high resolution x-ray diffraction in combination with a highly focused (≈ 3µm) x-ray beam at the beam line ID1 at the ESRF. The pattern measured directly on the wire shows a small peak indicating tensile strain (approx. −1.4%). This feature can be only found if the beam focused on a nano wire whereas its intensity changes
with the layer width.
Keywords: nao wire; x-ray scattering
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany
  • Poster
    9th Biennial Conference on High Resolution X-Ray Diffraction and Imaging, XTOP 2008, 15.-19.09.2008, Linz, Austria

Permalink: https://www.hzdr.de/publications/Publ-11075
Publ.-Id: 11075


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