Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32337 Publications
MicroPET in mice – status and problems
Beuthien-Baumann, B.;
  • Invited lecture (Conferences)
    Pre-Meeting on New Tech and normal toxicity Primer, 11.03.2006, Lugano, Switzerland

Publ.-Id: 9410 - Permalink


Comparison of PET imaging and histology
Beuthien-Baumann, B.;
  • Invited lecture (Conferences)
    Clinical and experimental research in radiation oncology (CERRO), 22.-27.01.2006, Les Menuires, France

Publ.-Id: 9409 - Permalink


Prefrontal Cortex Dysfunction and Depression in Atypical Parkinsonian Syndromes
Herting, B.; Beuthien-Baumann, B.; Pöttrich, K.; Donix, M.; Triemer, A.; Lampe, J. B.; von Kummer, R.; Herholz, K.; Reichmann, H.; Holthoff, V. A.;
Depressive symptoms are common in patients with neurodegenerative disorders. Imaging studies suggest that a
disruption of frontal–subcortical pathways may underlie depression associated with basal ganglia disease. This pilot study tested the hypothesis that frontal dysfunction contributes to depression associated with multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). Depressed patients with MSA (n = 11), PSA (n = 9), and age-matched controls (n = 25) underwent measures of cerebral glucose metabolism applying positron emission tomography with 18F-fluorodeoxyglucose. Regional metabolism in the patient groups was compared
to the normal subjects using the voxel-based statistical parametric mapping. Depressive symptom severity (Hamilton Depression Rating) and degree of locomotor disability (Hoehn & Yahr) were assessed in the patient groups. The association between prefrontal metabolism and the occurrence of depressive symptoms and the degree of locomotor disability was investigated. When compared to controls, MSA patients revealed
significant metabolic decreases in bilateral frontal, parietal, and cerebellar cortex and in the left putamen. In PSP
patients, significant hypometabolism was demonstrated in bilateral frontal cortex, right thalamus, and midbrain. Depression severity but not the patients’ functional condition was significantly associated with dorsolateral prefrontal glucose metabolism in both patient groups. The findings of this pilot study support the hypothesis that depressive symptoms in MSA and PSP are associated with prefrontal dysfunction.
Keywords: multiple system atrophy; progressive supranuclear palsy; depression; tomography; emission-computed; frontal lobe

Publ.-Id: 9408 - Permalink


CFX simulations of ROCOM slug mixing experiments
Moretti, F.; Melideo, D.; D’Auria, F.; Höhne, T.; Kliem, S.;
The present paper documents the CFD code validation activity carried out at the University of Pisa. In particular, the ANSYS CFX-10.0 code has been used to simulate one of the experiments conducted at the ROCOM mixing test facility (FZD, Germany), that reproduced the injection of a de-borated slug in one cold leg of a pressurized water reactor (simulated by a salt tracer) with all circulation pumps at steady-state operation. The calculations were run on several grids obtained through different meshing strategies and having different sizes. The numerical results, in terms ofnormalized concentration of the transported passive scalar in the downcomer and at the core inlet, were compared against corresponding values obtained through experimental measurements of electrical conductivity in the ROCOM facility. Such comparison resulted in a general good qualitative agreement between simulations and experiments, while some discrepancies were evidenced from a quantitative point of view, mainly due to grid coarseness and low order numerical schemes.
Keywords: ROCOM, CFD
  • Contribution to proceedings
    15th International Conference on Nuclear Engineering (ICONE15), 22.-26.04.2007, Nagoya, Japan
    ICONE15-10461
  • Lecture (Conference)
    15th International Conference on Nuclear Engineering (ICONE15), 22.-26.04.2007, Nagoya, Japan
  • Open Access LogoJournal of Power and Energy Systems 2(2008)2, 720-733
    DOI: 10.1299/jpes.2.720

Publ.-Id: 9407 - Permalink


Anisotropy of ion-induced amorphous-crystalline ripples in silicon
Grigorian, S.; Grenzer, J.; Biermanns, A.; Hazra, S.; Datta, D. P.; Chini, T. K.; Sanyal, M. K.; Pietsch, U.;
The morphological evolution of surfaces during ion-beam irradiation has attracted significant interest due to possibility of the evelopment and the controlling of self-organization in nanostructures. Pattering and texture on nanometer length scale at metal and semiconductor surfaces has become a topic of intense research. In particular the surface and subsurface ripple formation under 40Ar+ ion-beam irradiation of Si (100) crystal has been studied recently. Based on transmission electron microscopy (TEM), atomic force microscopy (AFM) and x-ray analysis a dramatic effect of the ripple formation was found at an irradiation energy of 60 keV.
Apart from the crystalline part, the amorphization process is very important for understanding the amorphous-crystalline interface and the ripple formation mechanism. The dose of the ion beam was varied in the range from low 3e16 up to high 7e17 ions/cm^2 at an incident angle of 60° and an energy of 60 keV. Keeping the optimized irradiation parameters constant we have measured the degree of amorphization as a function of Ar+ dose by means of x-ray grazing incidence amorphous scattering (GIAS). For irradiated samples we found two broad peaks indicating a short-range ordering of amorphous material which does what with the penetration depth of probing x-ray. GIAS profiles probed at different azimuthal angles display a strong anisotropy of the amorphous scattering. The strong damage of the crystalline structure takes place along particular crystallographic directions. This is for the directional anisotropy: and strongly reveal for low doses, before it becomes completly amorphous and mostly uniform at high doses of implantation.
Such behavior can be explained taking into account the anisotropy of the crystalline material and orientation of the ion beam with respect crystallographic orientation of the substrate material. This work was supported by the DST-DAAD India-Germany Collaborative Program. We are grateful to ID1 beamline staff for the support at ESRF.
  • Lecture (Conference)
    8th Biennial Conference on High Resolution Diffraction and Imaging, XTOP 2006, 19.-22.09.2006, Baden-Baden/Karlsruhe, Deutschland

Publ.-Id: 9406 - Permalink


Linkage between the intramembrane H-bond network around aspartic acid 83 and the cytosolic environment of helix 8 in photoactivated rhodopsin
Lehmann, N.; Alexiev, U.; Fahmy, K.;
Understanding the coupling between conformational changes in the intramembrane domain and at the membrane-exposed surface of the bovine photoreceptor rhodopsin, a prototypical G protein-coupled receptor (GPCR), is crucial for the elucidation of molecular mechanisms in GPCR activation. Here, we have combined FTIR- and fluorescence spectroscopy to address the coupling between conformational changes in the intramembrane region around the retinal and the environment of helix 8, a putative cytosolic surface switch region in class-I GPCRs. Using FTIR / fluorescence cross-correlation we show specifically that surface alterations monitored by emission changes of fluorescein bound to Cys316 in helix 8 of rhodopsin are highly correlated with (i) H-bonding to Asp83 proximal of the retinal Schiff base but not to Glu122 close to the -ionone and (ii) with a MII-specific 1643 cm-1 IR absorption change, indicative of a partial loss of secondary structure in helix 8 upon MII formation. These correlations are disrupted by limited C-terminal proteolysis but are maintained upon binding of a transducin -subunit (Gt -derived peptide, which stabilizes the MII state. Our results suggest that additional C-terminal cytosolic loop contacts monitored by an amide II absorption at 1557 cm-1 play a functionally crucial role in keeping helix 8 in the position in which its environment is strongly coupled to the retinal-binding site near the Schiff base. In the intramembrane region, this coupling is mediated by the H-bonding network that connects Asp83 to the NPxxY(x)F motif preceding helix 8.
Keywords: long-range coupling in rhodopsin, FTIR spectroscopy, site-directed fluorescence labeling, heterospectral cross correlation, conformational switch, GPCR signaling

Publ.-Id: 9405 - Permalink


[1-11C]Acetate uptake is not increased in renal cell carcinoma
Kotzerke, J.; Linné, C.; Meinhardt, M.; Steinbach, J.; Wirth, M.; Baretton, G.; Abolmaali, N.; Beuthien-Baumann, B.;
Purpose
The purpose of this study was to investigate the potential of [1-11C]acetate (AC) as a metabolic tracer for renal cell cancer in human subjects.
Methods
Twenty-one patients with suspected kidney tumours were investigated with AC and dynamic PET. AC uptake was scored on a five-step scale. Tumour localisation was known from CT/MRI. Histology was available in 18/21 patients. The results in these 18 patients are reported.
Results
AC uptake by the tumour was less than (n=11), equal to (n=5) or higher than (n=2) uptake in the surrounding renal parenchyma. Histological tumour types showed a typical distribution, with a predominance of clear cell carcinomas (n=14) and only a small number of papillary cell carcinomas (n=2) and oncocytomas (n=2). Only the benign oncocytomas were highly positive with AC.
Conclusion
In most kidney tumours the AC accumulation was not higher than in normal kidney parenchyma. Therefore, AC PET cannot be recommend for the characterisation of a renal mass.
Keywords: [1-11C]acetate, Kidney tumour, Positron emission tomography

Publ.-Id: 9404 - Permalink


Detection of neutrons with kinetic energy from 24 keV to 1.2 MeV with long plastic scintillators
Beyer, R.; Grosse, E.; Heidel, K.; Junghans, A. R.; Klug, J.; Légrády, D.; Wagner, A.; Nolte, R.; Röttger, S.;
Proton recoil detectors for neutron time-of-flight measurements have been developed, which have a good time and position resolution and at the same time a relatively high efficiency for neutrons with kinetic energies of about 30 keV.
Keywords: neutron detector, time of flight, ELBE
  • Lecture (Conference)
    Workshop on neutron detectors for FAIR and other facilities, 13.-14.07.2006, Madrid, Spain

Publ.-Id: 9403 - Permalink


Development of Neutron-Time-of-Flight Detectors for the Investigation of Astrophysically Relevant (gamma,n) Reactions
Beyer, R.; Grosse, E.; Heidel, K.; Hutsch, J.; Junghans, A. R.; Klug, J.; Rusev, G.; Schilling, K. D.; Schwengner, R.; Wagner, A.;
Different types of neutron-time-of-flight detectors have been developed and investigated for their applicability for the investigation of astrophysically relevant (gamma,n) reactions.
Keywords: neutron detectors, time of flight, ELBE
  • Poster
    DPG Frühjahrstagung 2006, 20.-24.03.2006, München, Deutschland

Publ.-Id: 9402 - Permalink


Oberflächenmodifikation des Hartmetalls Wolframkarbid-Kobalt durch Bor-Ionenimplantation
Mrotchek, I.;
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-462 2007

Downloads:

Publ.-Id: 9400 - Permalink


Magnetic Excitations in the Spin-1 Anisotropic Heisenberg Antiferromagnetic Chain System NiCl2-4SC(NH2)2
Zvyagin, S. A.; Wosnitza, J.; Batista, C. D.; Tsukamoto, M.; Kawashima, N.; Krzystek, J.; Zapf, V. S.; Jaime, M.; Oliveira, N. F. J.; Paduan-Filho, A.;
NiCl2-4SC(NH2)2 (DTN) is a quantum S = 1 chain system with strong easy-pane anisotropy and a new candidate for the Bose-Einstein condensation of the spin degrees of freedom. ESR studies of magnetic excitations in DTN in fields up to 25 T are presented. Based on analysis of the single-magnon excitation mode in the high-field spin-polarized phase and previous experimental results [Phys. Rev. Lett. 96, 077204 (2006)], a revised set of spin-Hamiltonian parameters is obtained. Our results yield D = 8:9 K, Jc = 2:2 K, and Ja;b = 0:18 K for the anisotropy, intrachain, and interchain exchange interactions, respectively. These values are used to calculate the antiferromagnetic phase boundary, magnetization, and the frequency-field dependence of two-magnon bound-state excitations predicted by theory and observed in DTN for the first time. Excellent quantitative agreement with experimental data is obtained.
  • Physical Review Letters 98(2007), 047205

Publ.-Id: 9399 - Permalink


A new method of improving the acceleration voltage stability of Van de Graaff accelerators
Bürger, W.; Lange, H.; Petr, V.;
The relative energy stability of Van de Graaff type ion accelerators is typically limited to some 10-4. An inexpensive possibility to improve this situation was developed at the Forschungszentrum Dresden-Rossendorf. The method refers to the relatively stable periodic pattern of the acceleration voltage fluctuation in such accelerators. Future values of that fluctuation can be predicted with a high degree of certainty and can taken into account in the belt generator control in spite of the belt convolution caused fundamental reaction delay. The microcontroller based implementation of a ‘‘predictive fluctuation compensation’’ improves the relative acceleration voltage short time stability by a factor of 3–6 to well below 10-4.
Keywords: Van de Graaff; Ion accelerators; Energy stability; Voltage fluctuation compensation; Predictive control
  • Nuclear Instruments and Methods in Physics Research A 586(2008), 160-168

Publ.-Id: 9398 - Permalink


Study of the textural evolution in Ti-rich NiTi using synchrotron radiation
Paula, A. S.; Canejo, J. H. P. G.; Mahesh, K. K.; Silva, R. J. C.; Braz Fernandez, F. M.; Martins, R. M. S.; Cardoso, A. M. A.; Schell, N.;
The aim of the present work is to investigate the textural evolution in high-temperature phase (austenite – B2) of Ti-rich NiTi (Ni–51at%Ti) shape memory alloys (SMA). The alloy was subjected to different thermomechanical treatments involving various heat treatments and cold rollings (10% and 40%). The qualitative texture analysis was performed at BM20 (ROBL-CRG) of the European Synchrotron Research Facility (ESRF) using in-situ high-temperature X-ray diffraction (XRD) with a wavelength of 0.154 nm. In-situ high-temperature texture determination has been carried out for the first time for Ni–Ti alloys, by annealing at different temperatures up to 800 °C under a vacuum better than 1e-4 Pa. The discussion highlights the evolution of texture during annealing at high temperatures and the change in the coherency domain size and microstrain.
Keywords: Ti-rich NiTi; Shape memory alloy; In-situ high-temperature XRD; Texture; Synchrotron radiation

Publ.-Id: 9397 - Permalink


What to expect from next generation liquid metal experiments on dynamo action and magnetorotational instability?
Stefani, F.; Gerbeth, G.;
After a short summary of the achievements made in liquid metal experiment during the last seven years, we try to identify some important points which should be addressed by next generation experiments. These include the role of rotation and precession, the role of large scale and small scale fluctuations on the dynamo threshold, the occurrence of field reversals in highly supercritical states and further studies of the magnetorotational instability in cylindrical, spherical and oblate geometries.
  • Invited lecture (Conferences)
    Experimental dynamo meeting, 22.-23.01.2007, Paris, France

Publ.-Id: 9396 - Permalink


Electronegativity and point defect formation in ion implanted SiO2 layers
Prucnal, S.; Sun, J.; Reuther, H.; Skorupa, W.; Buchal, C.;
The Metal-Oxide-Silicon (MOS) diode structure containing ion implanted electropositive (M+) and electronegative (M-) ions is one of the most promising candidates for a new type of high-efficiency electroluminescence (EL) devices which can be integrated with standard silicon CMOS technology. The implantation process creates defects in the SiO2 layer. After implantation an annealing process leads to the diffusion of the implanted elements and a broadening of the SiO2/Si interface. The influence of the different implanted ions (Gd, F, K) was investigated by electroluminescence measurements and correlated to different defects in the oxide layer. Implanted electronegative ions (such as F) lead defects comprising O2 molecules and peroxy radicals (POR). On the other hand, the electropositive ions (Gd and K) increase the number of the oxygen vacancy defects.
Keywords: ion implantation, electronegativity, electroluminescence
  • Lecture (Conference)
    VI-th International Conference on Ion Implantation and other Applications of Ions and Electrons (ION2006), 26.-29.06.2006, Kazimierz Dolny, Poland

Publ.-Id: 9395 - Permalink


Microphonics Measurements at ELBE
Buechner, A.; Gabriel, F.; Schurig, R.; Staats, G.;
  • Lecture (Conference)
    2nd Annual EUROFEL Workshop 2006, 06.-08.11.2006, Daresbury, UK
  • Poster
    2nd Annual EUROFEL Workshop 2006, 06.-08.11.2006, Daresbury, UK

Publ.-Id: 9394 - Permalink


The mineralogy of Böttger stoneware
Kockelmann, W.; Kirfel, A.; Neelmeijer, C.; Walcha, H.-M.;
In the early eighteenth century Johann Friedrich Böttger produced a remarkable type of red stoneware which is extraordinary hard and suitable for surface polishing. Although of considerable value for museums and collectors, surprisingly little is known of the elemental and mineral compositions of this type of stoneware. We have analysed Böttger objects and other red stoneware pieces from the Porcelain Collection of the State art Collections Dresden by non-destructive neutron-diffraction. The neutron analyses of about 20 intact jugs, vases and plates carried out at the spallation source ISIS provides a quantitative overview of the main mineral phase compositions. The data confirm the fine raw material selection by Böttger for the production of his stoneware. The mineral phase composition of Böttger objects, however, is not unique and similar to the also studied Yixing red stoneware.
Keywords: Böttger stoneware, neutron diffraction, mineral phase analysis, material analysis
  • Contribution to external collection
    Andrea Denker, Annemie Adriaens, Mark Dowsett, Alessandra Giumlia-Mair: COST Action G8: Non-destructive testing and analysis of museum objects, Stuttgart: Fraunhofer IRB Verlag, 2006, 3-8167-7178-5, 120-127

Publ.-Id: 9393 - Permalink


Advantages of the Superconducting 3½ Cell SRF Gun in Rossendorf
Staufenbiel, F.;
This paper describes the features of the 3½ cell SRF gun from Rossendorf and the advantages and challenges of superconductivity. One advanced working regime of the SRF photo injectors is to produce short pulses with high bunch charges and low transverse emittance running in cw-mode. The quality of this electron beam is crucially for future FEL's with very short wave lengths. The main challenge is to compensate the growing transverse and longitudinal emittance with increasing bunch charges. Therefore, some procedures for emittance compensation for the 3½ cell SRF gun will be discussed.
  • Lecture (Conference)
    37th ICFA Advanced Beam Dynamics Workshop on Future Light Sources FLS 2006, 15.-19.05.2006, Hamburg, Germany
  • Contribution to proceedings
    37th ICFA Advanced Beam Dynamics Workshop on Future Light Sources FLS 2006, 15.-19.05.2006, Hamburg, Germany
    FLS 2006 - Proceedings

Publ.-Id: 9391 - Permalink


The missing link: What can dynamo simulation learn from dynamo experiments?
Stefani, F.; Gerbeth, G.; Gundrum, T.; Avalos-Zuniga, R.;
Der homogene Dynamoeffekt in stömenden elektrisch leitfähigen Fluids ist verantwortlich für das Auftreten kosmische Magnetfelder, einschließlich des Erdmagnetfeldes. Nach Jahrzehnten ausschließlich analytisch-numerischer Untersuchungen wird der Dynamoeffekt seit 1999 auch in verschiedenen Laborexperimenten untersucht.
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2007
    FZD\FWS\2007\03

Publ.-Id: 9390 - Permalink


Kerne und Sterne - Vom Urknall, der Entstehung der chemischen Elemente und Experimenten im FZR
Wagner, A.;
Kerne und Sterne - Vom Urknall, der Entstehung der chemischen Elemente und Experimenten im FZR
  • Lecture (others)
    Lehrerfortbildung "Astrophysik", 17.02.2006, Dresden, Deutschland

Publ.-Id: 9389 - Permalink


BNL superconducting RF guns-technology challenges as ERL sources
Burrill, A.; Ben-Zvi, I.; Calaga, R.; Chang, X.; Hahn, H.; Kayran, D.; Kewisch, J.; Litvinenko, V.; Mcintyre, G.; Nicoletti, A.; Pate, D.; Rank, J.; Scaduto, J.; Rao, T.; Wu, K.; Zaltsman, A.; Zhao, Y.; Bluem, H.; Cole, M.; Falletta, M.; Holmes, D.; Peterson, E.; Rathke, J.; Schultheiss, T.; Todd, A.; Wong, R.; Lewellen, J.; Funk, W.; Kneisel, P.; Phillips, L.; Preble, J.; Janssen, D.; Nguyen-Tuong, V.;
The design, fabrication and commissioning of a 703.75 MHz SRF photoinjector with a retractable multi-alkali photocathode designed to deliver 0.5A average current at 100% duty factor is the present undertaking of the electron cooling group in the Collider Accelerator Division of Brookhaven National Labs. This photoinjector represents the state of the art in photoinjector technology, orders of magnitude beyond the presently available technology, and should be commissioned by 2007. The R&D effort presently underway, and the focus of this paper, will address the numerous technological challenges that must be met for this project to succeed. These include the novel physics design of the cavity, the challenges of inserting and operating a multi-alkali photocathode in the photoinjector at these high average currents, and the design and installation of a laser system capable of delivering the required 10s of watts of laser power needed to make this photoinjector operational. (c) 2005 Elsevier B.V. All rights reserved.
Keywords: energy recovery linac; high average current; superconducting RF; photoinjector design; ampere class; photocathode

Publ.-Id: 9387 - Permalink


Uranium as a stress factor in well aerated multispecies biofilms – A microsensor study of the O2 concentrations
Krawczyk-Bärsch, E.; Großmann, K.; Arnold, T.; Diessner, S.; Wobus, A.;
Multispecies biofilms were cultured on glass slides in a standard culture medium (Sifin; TN 117) under air atmosphere in annular rotating reactors [1] for two months to obtain a thickness of approximately 800 µm. The slides with the grown biofilms were removed from one reactor for microsensor studies in a flow cell. Two other reactors were fed with UO2(ClO4)2 to adjust the total uranium concentration in the culture medium to 1x10-5 mol/l and 1x10-6 mol/l, respectively, i.e. the biofilms in these reactors were exposed to uranium for three weeks before they were removed for additional microsensor studies. Concentration profiles of oxygen versus biofilm depths were measured in each biofilm by electrochemical microsensors with a tip diameter of 10µm. A motor-driven micromanipulator was used for moving downwards through the biofilm in 20 or 50µm steps. The microsensor results clearly showed a significant dependence of the O2 concentration on the presence as well as on the concentration of uranium. In the absence of uranium the O2 concentration in the well aerated biofilm decreased slightly due to the aerophile microbes, dominating this biofilm. In contrast, O2 concentrations in the biofilms, which were exposed to different concentrations of uranium, decreased with increasing uranium concentration. Apparently, uranium acted as a stress factor for the microbes. Since metals have a strong effect on oxygen consumption, decreases in oxygen concentration could be due to changes in microbial activities [2] as well as on the activation of microbial communities induced by the addition of uranium [3]. 16S rDNA gene sequence retrieval and FISH are currently in progress to provide information on the changes occurring in the biofilm community and the resulting influence on the O2 concentration profiles.

[1] Lawrence, J. R. et al., (2000) Journal of Microbiological Methods 42, 215-224.
[2] Viret, H. et al., (2006) Sci Total Environ. 367, 302-311.
[3] Geissler, A. et al., (2005) Geobiology 3, 275-285.
  • Poster
    International Symposium on Microbial Adaptation in Stress and Enviroment, 12.-14.04.2007, Marburg, Germany
  • Contribution to proceedings
    International Symposium on Microbial Adaptationin Stress and Enviroment, 12.-14.04.2007, Marburg, Germany, P30

Publ.-Id: 9386 - Permalink


Spectroscopic and microscopic characterization of uranium biomineralization in Myxococcus xanthus
Jroundi, F.; Merroun, M.; Arias, J. M.; Rossberg, A.; Selenska-Pobell, S.; González-Muñoz, M. T.;
In this work, synchrotron-based X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) studies were carried out to elucidate at molecular scale the interaction mechanisms of Myxococcus xanthus with uranium at different pH values. Extended X-ray absorption fine structure (EXAFS) experiments show that there are significant differences in the structural parameters of the U complexes formed by this bacterium at pH 2 and 4.5. At very low acidic pH of 2, the cells accumulated U(VI) as organic phosphate-metal complexes. However, at pH 4.5, the cells of this bacterium precipitated U(VI) as meta-autunite-like phase. TEM indicated that at pH 2 the uranium accumulates are located mainly at the cell surface. Whereas, at pH 4.5 the uranium precipitation takes place on the cell wall and within the extracellular polysaccharides (EPS) characteristic of this bacterium. Dead/live staining studies showed that 30% and 50% of the uranium-cell treated cell populations are alive at pH 2 and 4.5, respectively. The precipitation of uranium as mineral phase is possibly due to the acid phosphatase activity which was detected at both pH values. Precipitation of U as mineral phase may lead to more stable U(VI) sequestration that may be suitable for remediation uses. These observations, combined with the very high uptake capacity of this bacterium, imply that bacterial cells may significantly influence the fate of uranium in soils where these bacterial groups are mainly found.

Publ.-Id: 9385 - Permalink


Geochemical behavior of uranium in mine tailings at Freital, Germany: A μ-XRF, μ-XAFS and μ-XRD study
Scheinost, A.; Hennig, C.; Somogyi, A.; Martinez-Criado, G.; Knappik, R.;
- wird nachgereicht
  • Lecture (Conference)
    16th Annual V.M. Goldschmidt Conference 2006, 27.08.-01.09.2006, Melbourne, Australia
  • Abstract in refereed journal
    Geochimica et Cosmochimica Acta 70(2006)18, A560

Publ.-Id: 9384 - Permalink


Defect profiles in B or P implanted Ge after Flash Lamp Annealing probed by Slow Positron Implantation Spectroscopy
Anwand, W.; Skorupa, W.; Schumann, T.; Posselt, M.; Schmidt, B.; Grötzschel, R.; Brauer, G.;
B+ and P+ ions were implanted into Ge wafers covered with an amorphous surface layer of 150 nm. After this, FLA in Ar atmosphere was used in order to realise three objectives:
- recrystallisation of the amorphous region on top of the Ge wafer
- electrical activation of the implanted ions
- reduction of diffusion processes during the FLA.
The heat treatment with Xenon flash lamps having a spectrum in the visible range of light and a pulse length of 3 or 20 ms allowed an ultra-short heating up of the near surface region. In this way, a modification of the structure of the amorphous layer containing the implanted range was possible. Depth profiles of defects, especially of the vacancy-type, were investigated by SPIS before and after FLA.
It will be shown that the remaining vacancy-type defect structure depends on the parameters of the process of heat treatment, and that these defects could not be completely removed by FLA.
These results will be compared with such from SRIM 2003 calculations (Stopping and Range of Ions in Matter) and Rutherford Backscattering Spectrometry.
Keywords: Ge, ion implantation, flash lamp annealing, vacancy-type defects, slow positron implantation spectroscopy
  • Lecture (Conference)
    3rd CADRES Ge Workshop, 23.01.2007, Gent, Belgium
  • Poster
    11th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces (SLOPOS-11), 09.-13.07.2007, Orleans, France

Publ.-Id: 9383 - Permalink


Organometallic 99mTc(III) ‘4+1’ Bombesin(7-14) Conjugates: Synthesis, Radiolabeling and In Vitro/In Vivo Studies
Künstler, J.-U.; Veerendra, B.; Figueroa, S. D.; Sieckmann, G. L.; Rold, T. L.; Hoffman, T. J.; Smith, C. J.; Pietzsch, H.-J.;
Bombesin (BBN) peptide exhibits high selectivity and affinity for the gastrin releasing peptide receptor (GRPr). The GRPr is over-expressed on many human cancer cell types, thus making BBN a potent delivery vehicle for radionuclide targeting. In this study, the biologically active minimal sequence BBN(7-14) was labeled using the novel Tc ‘4+1’ mixed-ligand system, [Tc(NS3)(CN-R)], in which Tc(III) is co-ordinated by a monodentate isocyanide linker bearing the peptide and the tetradentate, tripodal chelator, 2,2’,2’’-nitrilotriethanethiol (NS3). BBN(7-14) was N-terminally modified with Gly-Gly-Gly, ßAla and Ser-Ser-Ser spacer groups (X) and functionalized with 4-(isocyanomethyl)benzoic acid (L1) or 4-isocyanobutanoic acid (L2) resulting in a series of [M(NS3)(L-X-BBN(7-14))] conjugates (M = 99mTc, Re). The isocyanides ligand frameworks were introduced using novel bifunctional coupling agents. The spacer groups (X), the monodentate isocyanide units, and a tetradentate NS3 chelator bearing a pendant carboxylic acid (NS3COOH) were proposed as pharmacological modifiers. 99mTc-labeling was performed in a two-step procedure by first preparing 99mTc-EDTA/mannitol followed by reactions with the isocyanides and NS3 or NS3COOH ligand frameworks. The 99mTc-complexes were obtained with a radiochemical yield of 30 to 80% depending on the amount of the isocyanide (20 to 100 nmol) used. These new conjugates were purified by reversed-phased high performance liquid chromatography (RP-HPLC) to give a radiochemical purity of ≥ 95 %. The 99mTc-conjugates exhibited high in vitro stability (> 90 %, 24 h). Analogous nonradioactive Re-conjugates were synthesized and characterized by electrospray ionization mass spectrometry (ESI-MS). RP-HPLC analyses of the new Re-conjugates indicated that they exhibited identical retention times to the corresponding 99mTc-conjugates under identical HPLC conditions, demonstrating structural similarity between the two metallated species. The [Re(NS3)(L-X-BBN(7-14))] conjugates exhibited GRPr affinity in the nanomolar range as demonstrated by in vitro competitive binding assays using PC-3 human prostate cancer cells. In vitro internalization/externalization assays indicated that ~ 65% of [99mTc(NS3)(L2-βAla-BBN(7-14))] conjugate was either surface bound or internalized in PC-3 cells. Cell-associated activity for all other 99mTc-conjugates was below 20%. Biodistribution studies of [99mTc(NS3)(L-βAla-BBN(7-14))], L = L1, L2, in normal, CF-1 mice showed minimal accumulation in normal pancreas (a tissue expressing the GRPr in high density in rodent models) and rapid hepatobiliary elimination. Introduction of a carboxyl group onto the NS3 ligand framework had only minimal effects to increase renal excretion. Activity distribution and accumulation was highly dominated by the relatively lipophilic ‘4+1’ complex unit.
  • Bioconjugate Chemistry 18(2007), 1651-1661

Publ.-Id: 9382 - Permalink


Electromagnetic excitations in nuclei: from photon scattering to photodisintegration
Erhard, M.; Nair, C.; Beyer, R.; Grosse, E.; Junghans, A. R.; Klug, J.; Kosev, K.; Nankov, N.; Rusev, G.; Schilling, K. D.; Schwengner, R.; Wagner, A.;
In explosive nucleosynthesis temperatures are high enough for photodisintegration reactions to occur, e.g. leading to the production of p-process nuclei. In order to understand the reaction rates of element production and element disruption we started an experimental program at the new bremsstrahlung facility of the superconducting electron accelerator ELBE of FZ Dresden-Rossendorf. The bremsstrahlung facility and the detector setup are designed such that the scattering of photons from nuclei and the photodisintegration of nuclei around the particle separation energies can be studied under optimized background conditions. In activation measurements with bremsstrahlung at end-point energy from 10.0 to 16.5 MeV (g ,p), (g ,n) and (g ,a) reactions of 92,100Mo have been studied. Our activation yields can be described within a factor 2-3 or better with calculations using the cross sections from recent Hauser-Feshbach models.
  • Contribution to proceedings
    International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos - IX, 25.-30.06.2006, Geneva, Swizerland
    PoS (NIC-IX) 056, Trieste: POS Proceedings of Science, ISSN 1824-8039
  • Lecture (Conference)
    International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos - IX, 25.-30.06.2006, Cern, Schweiz

Publ.-Id: 9381 - Permalink


A new module-assisted synthesis of the versatile, bifunctional labelling agent [18F]SFB: From radiochemistry to applications.
Mäding, P.; Füchtner, F.; Bergmann, R.; Pietzsch, J.; Hultsch, C.; Wüst, F.;
kein Abstract verfügbar
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 49(2006), 223-225
  • Lecture (Conference)
    13th Workshop of the Central European Division e.V. of the International Isotope Society (IIS), 16.-17.06.2005, Bad Soden, Deutschland

Publ.-Id: 9380 - Permalink


Hyperon production in the channel pp -> K+ Lambda p near the reaction threshold
Abd El-Samad, S.; Bilger, R.; Böhm, A.; Brinkmann, K.-T.; Clement, H.; Dshemuchadse, S.; Eyrich, W.; Erhardt, A.; Fanara, C.; Filippi, A.; Freiesleben, H.; Fritsch, M.; Geyer, R.; Hauffe, J.; Hassan, A.; Herrmann, P.; Hesselbarth, D.; Jakob, B.; Kilian, K.; Koch, H.; Kress, J.; Kuhlmann, E.; Marcello, S.; Marwinski, S.; Metzger, A.; Michel, P.; Möller, K.; Morsch, H. P.; Naumann, L.; Roderburg, E.; Schamlott, A.; Schönmeier, P.; Schulte-Wissermann, M.; Schroeder, W.; Steinke, M.; Stinzing, F.; Sun, G. Y.; Wächter, J.; Wagner, G. J.; Wagner, M.; Wilms, A.; Wirth, S.; Zielinski, U.;
Hyperon production in the threshold region was studied in the reaction pp→K+Λp using the time-of-flight spectrometer COSY-TOF. Exclusive data, covering the full phase-space, were taken at three different beam momenta pbeam=2.59, 2.68 and 2.85 GeV/c (corresponding to excess energies of var epsilon=85, 115 and 171 MeV). Total cross-sections were deduced to be 7.4±0.5 μb, 8.6±0.6 μb and 16.5±0.4 μb, respectively. Differential observables including Dalitz plots were obtained. From the investigation of the Dalitz plot at pbeam=2.85 GeV/c a dominant contribution of the N*(1650)-resonance to the reaction mechanism was found. In addition the pΛ-final-state interaction turned out to have a significant influence on the Dalitz plot distribution even 171 MeV above threshold.
Keywords: Associated strangeness production; Total cross-section; Angular distribution; Dalitz plot

Publ.-Id: 9379 - Permalink


Status of the superconducting 3 1/2 cell SRF gun in Rossendorf
Arnold, A.; Staufenbiel, F.;
  • Lecture (Conference)
    CARE Annual Meeting 2006, 15.-17.11.2006, Frascati, Rom, Italy

Publ.-Id: 9378 - Permalink


Simultaneous formation of two ripple modes on ion sputtered silicon
Keller, A.; Roßbach, S.; Facsko, S.; Möller, W.;
The amorphized surface of Si(100) sputtered with low energy ions at moderate temperature was found to develop two perpendicular ripple patterns overlaying each other. The evolution of these patterns was studied over a wide range of fluence. Coarsening of both ripple modes was observed, showing a similar time dependence with a coarsening exponent of 1/z ~ 0.08. In the high fluence regime, the surface enters a steady state with both ripple modes still present.

Publ.-Id: 9377 - Permalink


Equilibrium concentration and diffusivity of vacancies and self-diffusion in Ge: An atomistic study
Geßner, H.; Posselt, M.;
We developed an improved Stillinger-Weber-type potential for Ge by adjusting the three-body parameters in such a manner, that the potential yields the correct lattice constant and the correct cohesive energy, and the melting point and other properties are reproduced satisfactorily. Using this potential, the temperature dependence of equilibrium concentration and diffusivity of vacancies as well as the contribution of vacancies to self-diffusion are investigated by atomistic simulations and thermodynamic considerations. The enthalpies and entropies of formation and migration are calculated. Similar investigations are performed for self-interstitials in order to check whether their contribution to self-diffusion can be neglected, as shown experimentally. Finally, the self-diffusion coefficient and the equilibrium concentration of vacancies determined by the simulations are compared with experimental data from the literature.
Keywords: Ge, vacancy, equilibrium concentration, diffusivity
  • Lecture (Conference)
    CADRES Ge Workshop, 23.01.2007, Ghent, Belgium

Publ.-Id: 9376 - Permalink


N-doping by P implantation into pre-amorphized Ge and subsequent annealing: P diffusion, solid-phase-epitaxial regrowth and P activation
Posselt, M.; Schmidt, B.; Anwand, W.; Grötzschel, R.; Skorupa, W.; Heera, V.; Gennaro, S.; Bersani, M.; Giubertoni, D.;
P and As are considered the most suitable n-dopants in Ge. However, because of diffusion and deactivation effects it is difficult to achieve highly-n-doped Ge by ion implantation and subsequent annealing. We investigated high fluence P implantation into pre-amorphized Ge and subsequent annealing. The thickness of the amorphous layer was varied by implanting Ge at different energies. In all cases the main part of the as-implanted P profiles is located within this layer. Both RTA and flash-lamp annealing were employed. Considering samples with amorphous layers of different thickness enables detailed investigations of P diffusion in amorphous and crystalline Ge and solid-phase epitaxial regrowth during the post-implantation annealing. The thickness of the amorphous layers and the quality of the regrown crystalline Ge were monitored by RBS/C. The chemical depth profiles of P and the donor depth distributions were measured by SIMS and SRP, respectively. The results indicate that P diffuses much faster in amorphous Ge than in crystalline Ge. It is assumed that the P diffusivity in amorphous Ge shows a concentration dependence similar to that in crystalline Ge. The solid-phase epitaxial regrowth occurs already at the lowest thermal budget used in this work. It causes a considerable P redistribution and, presumably, the incorporation of P into crystalline Ge at concentrations above the equilibrium solubility.
Keywords: Ge, n-doping, ion implantation, annealing
  • Lecture (Conference)
    CADRES Ge Workshop, 23.01.2007, Ghent, Belgium

Publ.-Id: 9375 - Permalink


Damage accumulation in nitrogen implanted 6H SiC: Dependence on the direction of ion incidence and on the ion fluence
Zolnai, Z.; Ster, A.; Khanh, N. Q.; Battistig, G.; Lohner, T.; Gyulai, J.; Kotai, E.; Posselt, M.;
The influence of crystallographic orientation and ion fluence on the shape of damage distributions induced by 500 keV N+ implantation at room temperature into 6H SiC is investigated. The irradiation was performed at different tilt angles between 0 and 4 with respect to the 0001 crystallographic axis in order to consider the whole range of beam alignment from channeling to random conditions. The applied implantation fluence range was 2.5 1014 3 1015 cm 2. A special analytical method, 3.55 MeV 4He+ ion backscattering analysis in combination with channeling technique (BS C), was employed to measure the disorder accumulation simultaneously in the Si and C sublattices of SiC with good depth resolution. For correct energy to depth conversion in the BS C spectra, the average electronic energy loss per analyzing He ion for the 0001 axial channeling direction was determined. It was found that the tilt angle of nitrogen implantation has strong influence on the shape of the induc! ed disorder profiles. Significantly lower disorder was found for channeling than for random irradiation. Computer simulation of the measured BS C spectra showed the presence of a simple defect structure in weakly damaged samples and suggested the formation of a complex disorder state for higher disorder levels. Full-cascade atomistic computer simulation of the ion implantation process was performed to explain the differences in disorder accumulation on the Si and C sublattices. The damage buildup mechanism was interpreted with the direct-impact, defect-stimulated amorphization model in order to understand damage formation and to describe the composition of structural disorder versus the ion fluence and the implantation tilt angle.
Keywords: ion implantation, SiC, damage accumulation
  • Journal of Applied Physics 101(2007), 023502

Publ.-Id: 9374 - Permalink


Azaspirovesamicols-Regioselective Synthesis and Crystal Structure Analysis of a Novel Class of Vesamicol Analogues as Potential Ligands for the Vesicular Acetylcholine Transporter
Wenzel, B.; Bats, J. W.; Scheunemann, M.; Steinbach, J.;
This report describes the high regioselectivity of nucleophilic epoxide ring-opening reactions which resulted in two of four possible regioisomers of N-benzoyl- (5a and 5b) and N-fluorobenzoylazaspirovesamicol derivatives (6a and 6b), respectively. Based on structural information obtained from X-ray crystal structure analyses of 5a and 5b the mode of epoxide ring-opening is discussed

Publ.-Id: 9373 - Permalink


Photocathode Laser for the Superconducting Photo Injector at the Forschungszentrum Rossendorf
Will, I.; Klemz, G.; Teichert, J.; Staufenbiel, F.;
We report on the design of the photocathode laser for a superconducting RF gun, which is presently under development at the Forschungszentrum (FZ) Rossendorf. This laser is foreseen to drive the RF gun in CW mode with up to 1 nC bunch charge. It generates pulses of 12...14 ps duration with 500 kHz repetition rate and 0.8 μJ pulse energy at 263 nm wavelength. This should provide sufficient pulse energy for generation of bunches with 1 nC charge using caesium telluride photocathodes. Due to two active modelockers in the laser oscillator, the latter operates in tight synchronism to the RF master oscillator of the linac. The laser consists of a short-pulse oscillator, a pulse picking Pockels cell, a regenerative amplifier and a wavelength conversion unit. The latter converts the infrared laser radiation to the ultra-violet (UV). This unit turns out to be a particularly critical element of such a photocathode laser driving a RF gun in CW mode.
  • Contribution to proceedings
    28th International Free Elektron Laser Conference FEL 2006, 27.08.-01.09.2006, Berlin, Germany
    Proceedings of FEL 2006, BESSY, 978-3-9809534-3-6, 564-566
  • Poster
    28th International Free Electron Laser Conference FEL 2006, 27.08.-01.09.2006, Berlin, Germany

Publ.-Id: 9372 - Permalink


3-1/2 Cell Superconducting RF Gun Simulations
Beard, C. D.; Rogers, J. H. P.; Teichert, J.; Staufenbiel, F.;
A 3-1/2 cell superconducting RF photocathode gun is being developed at Forschungszentrum Rossendorf to produce a high peak current, low emittance electron beam. This technology is essential to the realisation of many large scale facilities. The gun is designed for CW operation mode with 1 mA current and 9.5 MeV electron energy, and it will be installed at the ELBE superconducting electron linear accelerator. The gun will have a 3-1/2 cell niobium cavity operating at 1.3 GHz. The cavity consists of three cells with TESLA geometry and a specially designed half-cell in which the photocathode will be placed. Typical ERL-based projects require ~100 mA average current, and therefore suitable upgrade paths are required. Simulations have been carried out to evaluate the design and to determine suitable upgrades for higher current operation. Simulations of alternative cathode surface shapes are presented. Several couplers have been identified that can provide higher power to the cavity, whose integration and suitability has been verified. All the investigations that have identified possible solutions to higher current operation are discussed in this report.
  • Contribution to proceedings
    European Particle Accelerator Conference EPAC 2006, 26.-30.06.2006, Edinburgh, GB
    EPAC 2006 Proceedings, 92-9083-278-9, 2481-2483

Publ.-Id: 9371 - Permalink


Benchmark proposal for stratified horizontal two-phase flow phenomena
Höhne, T.; Vallee, C.;
Two-phase flow in the primary circuit of a PWR:LOCA scenarios Relevant example of stratified two-phase flow regime for Computational Fluid Dynamics validation:
Slug flow regime characterized by:acceleration of the gaseous phase, transition of fast liquid slugs
Aims of the numerical simulations:
feasibility study of numerical prediction of slug flow with multiphase flow models built in a commercial code (ANSYS-CFX) to prove the understanding of the general fluid dynamic mechanism leading to slug flow
Keywords: slug flow, two phase flow, stratified flow, cfd
  • Invited lecture (Conferences)
    German CFD Network, 9th Meeting,, 25.-26.01.2007, Köln, Deutschland

Publ.-Id: 9370 - Permalink


Modelling and regrowth mechanism of flashlamp processing of SiC-on-silicon heterostructures
Smith, M.; Mc Mahon, R.; Voelskow, M.; Skorupa, W.; Stoemenos, J.;
This paper describes the development of a thermal model for flashlamp processing of 3C-SiC on silicon. The model is a numerical solution of the enthalpy equation, using a modified Crank-Nichelson scheme to combine accurate prediction of melt depths with resonable computation times.
Keywords: FLASiC flashlamp annealing thermal modelling 3C-SiC
  • Material Science Forum 457-460(2004), 333-338

Publ.-Id: 9369 - Permalink


Ion beam doping of 6H-SiC for high concentration p-type layers
Panknin, D.; Skorupa, W.; Wirth, H.; Voelskow, M.; Mücklich, A.; Anwand, W.; Brauer, G.; Gonzalez-Verona, O.; Perez-Rodriguez, A.; Morante, J. M.;
Results of an extensive study concerning implantation, annealing and electrical activation of Al and B layers of 6H-SiC are presented. With increasing implantation temperature the implantation induced damage decreased. After annealing dislocation loops are observed in Al implanted layers whereas loops and precepitates are found in B implanted layers. For good electrical properties amorphization must be avoided. Using flash lamp annealing hole concentration is measured for Al doping whereas for B doping a limited hole concentration is observed.
Keywords: ion implantation SiC defects annealing electrical activation
  • Solid State Phenomena 69-70(1999), 391-396

Publ.-Id: 9368 - Permalink


The Radiation Source ELBE at Forschungszentrum Rossendorf
Michel, P.;
The radiation source ELBE (Electron Linac of high Brilliance and low Emittance) at Forschungszentrum Rossendorf is based on a superconducting linac that produces a high power continuous wave (cw) electron beam up to 40 MeV and 1 mA. The linac is used to drive two free-electron lasers producing infrared radiation from 5 to 150 microns wavelength. Additionally, from several conversion targets MeV-bremsstrahlung (< 20 MeV) and X-rays (10-100 keV) from electron channelling are generated. In the future even neutron and positron beams will be available at ELBE. The used superconducting RF accelerator technology and details of the machine instrumentation, in particular the electron beam diagnosis will be described.
  • Lecture (Conference)
    DPG - Tagung, 27.-31.03.2006, Dresden, Germany

Publ.-Id: 9367 - Permalink


Nanoscaled semiconductor heterostructures for CMOS transistors formed by ion implantation and hydrogen transfer
Popov, V.; Tyschenko, I.; Cherkov, A.; Voelskow, M.;
Abstract: Using bulk silicon can be ended for planar 22 nm technological node due to silicon mobility limitation. New type of substrates needs for further scaling in CMOS microelectronics. We speculate that these new type of materials will be semiconductor heterostructure on insulator (HOI) compatible with current silicon planar CMOS technology. In this work an effect of interface mediated endotaxial (IME) growth of thin semiconductor film at Si/SiO2 bonded interface was experimentally observed and investigated for the first time. Joint semiconductor material stack obtained by hydrogen transfer of one layer material (silicon) and second one (germanium or indium antimonide) placed on amorphous silicon dioxide film is presented. First of all thin film dual layer Si-Ge heterostructure properties were considered. Si-Ge HOI structures were obtained using Ge ion implantation in dioxide with followed Ge segregation to the interface between directly bonded silicon and silicon dioxide wafers. The method is also compatible with A3B5 thin film formation, as was shown for InSb film. Thermodynamic, kinetic and lattice mismatch parameter influences on IME process are considered.
Keywords: hydrogen transfer silicon films implanted impurities segregation endotaxy
  • Lecture (Conference)
    NATO ARW Conference "Nanoscaled SOI Structures and Devices", 15.-19.10.2006, Sudak/Krim, Ukraine
  • Contribution to external collection
    in: Nanoscaled Semiconductor-on-Insulator structures and Devices, Dordrecht: Springer Netherlands-Dordrecht, 2007, 9781402063800

Publ.-Id: 9366 - Permalink


Ion beam synthesis of 4H-(Si1-xC1-y)Gex+y solid solutions
Pezoldt, J.; Kups, T.; Voelskow, M.; Skorupa, W.;
4H-(Si1-xC1-y)Gex+y solid solutions with a Ge incorporation on lattice site from 0.7 to 2.5 percent were formed by ion beam synthesis. The concentration was varied from 1 to 20 % by implanting Ge at 600 C. The implanted samples were annealed at 1300 C in a rapid thermal processing equipment.
Keywords: implantation Ge into SiC RTA RBS
  • Lecture (Conference)
    EXMATEC 06, 15.-17.05.2006, Cadiz, Spain

Publ.-Id: 9365 - Permalink


Silicon-Germanium Heterostructure-on-Insulator formed by Ge+ Ion Implantation and Hydrogen Transfer
Popov, V. P.; Tyschenko, I.; Cherkov, A.; Voelskow, M.;
Using bulk silicon can be ended for 32 nm technological nodes. New type of substrates needs for further scaling in CMOS microelectronics. We speculate that these new type of materials will be semiconductor heterostructure on insulator (SHI) compatible with current silicon planar CMOS technology. Joint semiconductor material stack placed on cheap amorphous dioxide is presented. First of all thin film SiGe heterostructure properties is considered. It was obtain using Ge ion implantation in dioxide with followed Ge segregation to the directly bonded interface between silicon and silicon dioxide wafers. The method is also compatible with A3B5 thin film formation.
Keywords: Si-Ge heterostructures ion implantation
  • Lecture (Conference)
    210th Electrochemical Society Meeting, 29.10.-03.11.2006, Cancun, Mexico
  • ECS Transactions 3(2006)7, 303-307

Publ.-Id: 9364 - Permalink


Development of a Superconducting RF Photoinjector
Teichert, J.;
A superconducting rf photo electron injector (SRF gun) is under development at the Forschungszentrum Rossendorf. The project aims at several issues: improvement of the beam quality for the ELBE superconducting electron linac, demonstration of feasibility of this gun type, investigation of critical components, and parameter studies for future application (BESSY-FEL, 4GLS). The design layout of the SRF photo-injector, the parameters of the superconducting cavity and the expected electron beam parameters are presented. The SRF gun has a 3+1/2-cell niobium cavity working at 1.3 MHz and will be operated at 2 K. The three full cells have TESLA-like shapes whereas the half-cell has an special form obtained from numerical optimization. In the half-cell a Cs2Te photocathode is situated which will be cooled by liquid nitrogen. In 2005, the main parts for He cryostat like vacuum vessel, cryogenic and magnetic shields were fabricated. Test benches for the cathode cooling system and the cavity tuner were assembled and the measurements performed. The photo cathode preparation lab has been arranged, and the diagnostic beam line has been designed. After delivery of the Nb cavity, its rf properties were measured. The cavity was tuned and its chemical treatment is started.
  • Lecture (Conference)
    DPG - Tagung, 27.03.2006, Dresden, Germany

Publ.-Id: 9363 - Permalink


Effect of elevated substrate temperature on growth, properties, and structure of indium tin oxide films prepared by reactive magnetron sputtering
Rogozin, A.; Vinnichenko, M.; Shevchenko, N.; Vazquez, L.; Mücklich, A.; Kreissig, U.; Yankov, R. A.; Kolitsch, A.; Möller, W.;
The paper correlates the growth and structure formation with the properties of indium-tin-oxide (ITO) films fabricated by pulsed reactive magnetron deposition onto amorphous substrates held at elevated temperatures ranging from RT to 510 °C. The evolution of the microstructure is consistent with the well-known structure zone model. The temperature dependence of the film texture is described with consideration of the interplay between the shadowing and surface diffusion processes. It is shown that deposition at elevated temperatures lowers the crystallization threshold and is more effective in reducing resistivity than the post-deposition vacuum annealing at comparable temperatures. The films grown at a substrate temperature of 400 and 510 °C have the lowest resistivity of 1.2*10^-4 Ohm•cm, the highest free electron density of 1.2 - 1.0*10^21 cm^-3, and mobility of 35 - 42 cm^2•V^-1•s^-1 while showing the strongest (222) texture with the largest grain size.
Keywords: indium-tin-oxide, reactive pulsed magnetron sputtering, electrical properties, texture
  • Journal of Materials Research 22(2007)8, 2319-2329

Publ.-Id: 9361 - Permalink


Multimodal electronic-vibronic spectra of luminescence in ion-implanted silica layers
Fitting, H.-J.; Salh, R.; Schmidt, B.;
Thermally oxidized SiO2 layers of 100 and 500 nm thickness have been implanted by oxygen and sulfur ions with a dose of 3x1016 and 5x1016 ions/cm2, respectively, leading to an atomic dopant fraction of about 4 at.% at the half depth of the SiO2 layers. The cathodoluminescence spectra of oxygen and sulfur implanted SiO2 layers show besides characteristic bands a sharp and intensive multimodal structure beginning in the green region at 500 nm over the yellow-red region extending to the near IR measured up to 820 nm. The energy step differences of the sublevels amount on average 120 meV and indicate vibration associated electronic states, probably of O2-interstitial molecules, as we could demonstrate by a respective configuration coordinate model.
Keywords: ion implantation, SiO2, CL-luminesence
  • Journal of Luminescence 122(2007)SI JAN-APR, 743-746

Publ.-Id: 9360 - Permalink


Sorption Data Bases ("PA ready"): Proposed next steps towards a data base
Brendler, V.; Kienzler, B.; Lützenkirchen, J.;
- wird nachgereicht
  • Invited lecture (Conferences)
    2nd Annual FUNMIG Workshop, 21.-23.11.2006, Stockholm, Sweden

Publ.-Id: 9358 - Permalink


Mechanistische Sorptionsmodelle - gegenwärtiger Stand und Perspektiven für die Langzeitsicherheitsanalyse
Brendler, V.;
- wird nachgereicht
  • Invited lecture (Conferences)
    Vortrag bei der GRS Braunschweig, 14.07.2006, Braunschweig, Germany

Publ.-Id: 9357 - Permalink


Grundlagen der geochemischen Modellierung
Brendler, V.;
- wird nachgereicht
  • Invited lecture (Conferences)
    Seminar am Dresdner Grundwasserforschungszentrum (DGFZ) e.V., 15.09.2006, Dresden, Germany

Publ.-Id: 9356 - Permalink


Verlässliche Daten, Modelle und Codes für die Geochemie
Brendler, V.;
- wird nachgereicht
  • Invited lecture (Conferences)
    Festkolloquium für PD Dr. M. Richter, 20.10.2006, Leipzig, Germany

Publ.-Id: 9355 - Permalink


Thermodynamische Datenbasis für das Nahfeld: aktueller Stand
Brendler, V.;
- wird nachgereicht
  • Invited lecture (Conferences)
    2. Fachgespräch zur Radionuklidmigration bei PTKA, 25.-26.10.2006, Karlsruhe, Germany

Publ.-Id: 9354 - Permalink


Overview of Current Thermodynamic Databases
Brendler, V.;
- wird nachgereicht
  • Invited lecture (Conferences)
    12th ISSP - International Symposium on Solubility Phenomena and Related Equilibrium Processes, 23.-28.07.2006, Freiberg, Germany

Publ.-Id: 9353 - Permalink


SiGe heterostructures-on-insulator produced by Ge+-ion implantation and subsequent hydrogen transfer
Tyschenko, I. E.; Cherkov, A. G.; Voelskow, M.; Popov, V. P.;
Strong decrease in the carrier mobility of the nanometer-thick silicon films imposes a limitation on the application of silicon-on-insulator (SOI) structures in the current silicon planar CMOS technology. The formation of SiGe-heterostructures-on-insulator (HOI) is a way to increase the carrier mobility in the nanometer-scale layers. In this work, we present the results on the interface mediated endotaxial (IME) growth of thin Ge film from the Ge+-ion implanted SiO2 layer of the SOI structure.
Keywords: SOI, implantation
  • Lecture (Conference)
    XII Gadest Conference 2007, 14.-19.10.2007, Erice, Italy
  • Solid State Phenomena 131-133(2008), 143-147

Publ.-Id: 9352 - Permalink


Crystallization of InSb phase near the bonding interface of silicon-on-insulator structure
Tyschenko, I. E.; Cherkov, A. G.; Voelskow, M.; Popov, V. P.;
Bonding interface of SOI structure may be an effective sink for impurity atoms because of higher concentration of vacancies and microvoids on the cleavage planes. The behaviour of ion-implanted Sb and In atoms near the bonding interface of SOI structures was investigated as a function of annealing temperature.
Keywords: SOI, implantation, Sb, In
  • Lecture (Conference)
    XII Gadest Conference 2007, 14.-19.10.2007, Erice, Italy
  • Solid State Phenomena 131-133(2007), 137-142

Publ.-Id: 9350 - Permalink


Process control and melt depth homogenization for SiC-on-Si structures during flash lamp annealing by carbon implantation
Smith, M. P.; Mcmahon, R. A.; Voelskow, M.; Skorupa, W.; Stoemenos, J.; Ferro, G.;
Flash lamp annealing in the millisecond regime of heteroepitaxial silicon carbide on silicon structures involves melting the silicon below the SiC layer, but the deep faceted nature of the liquid-solid interface leads to unacceptable surface roughness. This paper describes a method of controlling melting by implanting a high dose of carbon at a controlled depth below the Si/SiC interface, which significantly alters the melting characteristics of the silicon. This technology has also been applied to SiC and Si multilayer heterostructures. Results confirm the effectiveness of this approach for increasing surface uniformity, making liquid phase processing compatible with standard device fabrication techniques. A thermal model has also been developed to describe this process and results indicate that the theoretical work is consistent with the experimental evidence. The model is a valuable tool for predicting the onset of melting, maximum temperatures, and process windows for controlled liquid phase epitaxy.
Keywords: silicon carbide, ion implantation, flash lamp processing, liquid phase processing, modelling

Publ.-Id: 9349 - Permalink


Charge trapping phenomena in high efficiency Metal-Oxide-Silicon light-emitting diodes with ion-implanted oxide
Nazarov, A.; Osiyuk, I.; Tyagulskii, I.; Lysenko, V.; Prucnal, S.; Sun, J. M.; Skorupa, W.;
This work is a comparative study of the processes of charge trapping in silicon dioxide layers doped with different rare-earth impurities (Gd, Tb, Er) as well as with Ge. Diode structures incorporating such oxide layers exhibit efficient electroluminescence (EL) in the spectral range from UV to IR.
Ion implantation was performed over a wide dose range using doses chosen to provide impurity concentrations of 0.1 to 3 at. % with the implant profiles peaking in the middle of the oxide. Post-implantation anneals were carried out at different temperatures. An ITO layer was employed as the transparent gate electrode for the implanted SiO2/Si light emitting diodes (LEDs).
Charge trapping was studied using an electron injection technique at constant current regime in the range of 1013 to 1021 e/cm2 with simultaneous measurements of the EL intensity. High-frequency C/V characteristics were used to control the net charge in the oxides. The I/V characteristics and the EL intensity vs. applied voltage were also measured.
Analysis of the charge trapping and the variation of the EL intensity during electron injection shows that the current density range can be conveniently divided in three portions: (i) low injection level, where electron/hole capture at traps with a large capture cross-sections and low EL intensity occurs; (ii) medium injection level corresponding to the main operation mode of the LEDs (odd hole trapping depending on the injected current level is observed); and (iii) high injection level (electrical quenching of the EL, which correlates with electron capture at traps of extremely small capture cross-sections of about 10-21 cm2 takes place). The parameters of the hole and electron traps are determined.
The nature of specific electron hole trapping at the medium injection level in RE doped MOSLEDs is discussed. Mechanisms of EL quenching at the high injection level are proposed.
Keywords: chare trapping, electroluminescence, ion implantation, light emitting diodes, rare earths, germanium
  • Lecture (Conference)
    European Materials Research Society (EMRS) Spring Meeting, 29.05.-02.06.2006, Nizza, France

Publ.-Id: 9348 - Permalink


The effect of potassium and fluorine implantation on the electroluminescence stability in Gd and Tb implanted SiO2 layers
Prucnal, S.; Sun, J. M.; Reuther, H.; Skorupa, W.;
Metal-Oxide-Silicon-based light emitting diodes (MOSLEDs) with Gd and Tb implanted SiO2 layers exhibit strong ultra violet and green electroluminescence (EL) at 316 nm and 541 nm, respectively. If amorphous SiO2 is bombarded with energetic ions, various types of defects are created as a consequence of ion-solid interaction and annealing processes (oxygen deficiency centres (ODC), non-bridging oxygen hole centres (NBOHC), E’-centres, etc.) leading to charge trapping effects during electrical excitation. Elimination or neutralisation of such defects is very important from the viewpoint of electrical stability of MOSLEDs. It will be demonstrated that (i) an additional fluorine implant into SiO2:Gd and SiO2:Tb layers leads to a decrease of E’-centres and ODC´s improving the efficiency of the MOSLEDs; and (ii), an additional potassium implant produces positive ions leading to a compensation effect for the negatively charged electron traps and, hence, to an reduced quenching of the EL efficiency and increased MOSLED lifetime .
Keywords: MOSLEDs, rare earths, electroluminescence, ion implantation, fluorine, potassium, nonbridging oxygen hole center, oxygen deficiency center, E'-center
  • Poster
    European Materials Research Society (EMRS) Spring Meeting, 29.05.-02.06.2006, Nizza, Frankreich

Publ.-Id: 9347 - Permalink


Recent progress in efficient electroluminescence from silicon-based light emitting devices made by ion beam processing
Sun, J. M.; Prucnal, S.; Potfajova, J.; Skorupa, W.; Schmidt, B.; Mücklich, A.; Helm, M.; Rebohle, L.; Gebel, T.;
This report reviews our recent progress on efficient electroluminescence (EL) from silicon pn junctions and rare earth doped metal-oxide-semiconductor light emitting devices (MOSLEDs) in the infrared to ultraviolet range [1-3]. Silicon pn diodes prepared by boron implantation have shown efficient band edge EL with a high efficiency above 0.15% at room temperature. A detailed study has shown that the anomalous increase of the EL intensity with increasing temperature comes from the release of free carriers by thermal ionization of bound excitons. They are trapped around locally enhanced p-type doping spikes formed by boron clustering at dislocations or fabricated by selective diffusion of boron through a patterned SiO2 mask layer.
Efficient EL from Er, Tb, Gd doped MOSLEDs at 1535, 541 and 316 nm with an high quantum efficiency of 14, 16.5, and 5 %, respectively, has been demonstrated in our MOSLEDs, which is comparable to that of III-V semiconductor devices. The EL properties of efficiency, decay time, and excitation cross-section were studied concerning cross relaxation at concentrations from 0.25 to 9% and clustering of rare earth dopants at annealing temperatures from 800 to 1100°C. Improving of the device stability is achieved by using double-stacked gate oxide layers, charge compensation and elimination of defects in SiO2 layers.
[1] J. M. Sun, W. Skorupa, T. Dekorsy , and M. Helm, J. Appl. Phys. 97, 123513 (2005)
[2] J. M. Sun, W. Skorupa, T. Dekorsy, and M. Helm, Appl. Phys. Lett. 85, 3387 (2004).
[3] J. M. Sun, T. Dekorsy, W. Skorupa, B. Schmidt, A. Mücklich, and M. Helm, Phys. Rev. B 70, 155316 (2004).
Keywords: electroluminescence, ion implantation, MOSLED, pn junction,rare earths, doping spike, boron clustering, decay time
  • Invited lecture (Conferences)
    European Material Research Society(EMRS) Spring Meeting 2006, 29.05.-02.06.2006, Nizza, France

Publ.-Id: 9346 - Permalink


Electrical activation of implantation-induced defects in ZnO by flash-annealing
Børseth, T. M.; Christensen, J. S.; Anwand, W.; Skorupa, W.; Svensson, B. G.; Kuznetsov, A. Y.;
In this project we study diffusion and electrical activation in lithium and helium implanted ZnO single crystal wafers with high resistivity using secondary ion mass spectrometry (SIMS), scanning spreading resistance microscopy (SSRM) and scanning capacitance microscopy (SCM), respectively. Li+ ions were implanted with an energy of 837 keV at a dose of 2x1015 cm-2, and He+ were implanted with an energy of 683 keV at a dose of 6x1015 cm-2 to ensure similar implantation depths and damage productions. The samples were then annealed using short 20 ms light flashes corresponding to temperatures of 900°C, 1200°C and 1400°C. After each annealing step the samples were characterized with SSRM/SCM and SIMS. In as-implanted samples, no changes in the initially high resistivity are observed in neither the Li- nor the He-implanted samples but after the thermal treatments a substantial decrease is observed in both sets of samples. This resistivity drop is most likely related to electrical activation of shallow implantation-induced defects or deactivation of compensating defects/impurities, as He in principle should be electrically inactive in any solid state material. No significant redistribution of the implanted ions is observed.
Keywords: zinc oxide. ion implantation, flash lamp annealing, electrical activation, SIMS, scanning spreading resistance microscopy, scanning capacitance microscopy
  • Lecture (Conference)
    15, Int. Conf. on Ion Beam Modification of Materials, 18.-22.09.2006, Catania, Italy

Publ.-Id: 9345 - Permalink


Formation of germanium shallow junction by Flash annealing
Satta, A.; D’Amore, A.; Simoen, E.; Anwand, W.; Skorupa, W.; Clarysse, T.; van Daele, B.; Janssens, T.;
We have investigated flash-lamp annealing (FLA) of germanium wafers doped with phosphorous and boron introduced in the crystal by ion implantation. Annealing was performed by using pre-heating at 400-450 oC in a conventional rapid thermal processing (RTP) unit and a fast (3-20 ms) FLA annealing at 800 oC or 900 oC. Diffusion of P is suppressed during the 800oC-20 ms FLA annealing, while concentration-enhanced diffusion occurs upon 900oC FLA anneals. At this higher temperature the FLA pulse time becomes a fundamental parameter, since the shortest FLA pulse (3 ms) causes less junction deepening and less P dose loss as compared to the longest (20 ms) pulse. Importantly, P activation seems to be enhanced by the FLA process.
The FLA process applied to B-doped pre-amorphized Ge layers does not show advantages as compared to a RTP conventional annealing. B diffusion and activation behavior are indeed similar for the millisecond annealing approach and for a conventional RTP combined with a solid phase epitaxial regrowth of the doped Ge layer.
In summary, the FLA technique holds a potential for the development of P shallow junctions in germanium wafers. However, junction stability following the FLA process is a concern and needs to be further investigated.
Keywords: ion implantation, germanium, flash lamp annealing, diffusion, activation, RTP

Publ.-Id: 9344 - Permalink


Germanium shallow junction formation by flash annealing
Satta, A.; D'Amore, A.; Simoen, E.; Janssens, T.; Clarysse, T.; Anwand, W.; Skorupa, W.;
We have investigated flash-lamp annealing (FLA) of germanium wafers doped with phosphorous and boron introduced in the Ge crystal by ion implantation. Annealing was performed by using pre-heating at 400-450 oC in a conventional rapid thermal processing (RTP) unit and a fast (3-20 ms) FLA annealing at 800 oC or 900 oC. Diffusion of P is suppressed during the 800oC-20 ms FLA annealing, while concentration-enhanced diffusion occurs upon 900oC FLA anneals. At this higher temperature the FLA pulse time becomes a fundamental parameter, since the shortest FLA pulse (3 ms) causes less junction deepening and less P dose loss as compared to the longest (20 ms) pulse. Importantly, P activation seems to be enhanced by the FLA process. The FLA process applied to B-doped pre-amorphized Ge layers does not show advantages as compared to a RTP conventional annealing. B diffusion and activation behavior are indeed similar for the millisecond annealing approach and for a conventional RTP combined with a solid phase epitaxial regrowth of the doped Ge layer.
In summary, the FLA technique holds a potential for the development of P shallow junctions in germanium wafers. However, junction stability following the FLA process is a concern and needs to be further investigated.
Keywords: germanium, ion implantation, flash lamp annealing, RTP, diffusion, electrical activation
  • Lecture (Conference)
    15. International Conference on Ion Beam Modification of Materials, 18.-22.09.2006, Catania, Italy

Publ.-Id: 9343 - Permalink


Flash lamp processing in the millisecond-range for Metal-Oxide-Silicon-based light emitting diodes
Prucnal, S.; Sun, J. M.; Muecklich, A.; Skorupa, W.;
The influence of different annealing processes (furnace annealing FA, rapid thermal annealing RTA and flash lamp annealing FLA) on the electroluminescence intensity, electric stability and point defect creation in SiO2 layers containing Gd atoms was investigated. The samples were annealed at different temperatures (from 800 to 10000C with the step 1000C for FA and from 10000C to 12000C with the step 500C for RTA and FLA). In the case of the peak at 316 nm which corresponds to Gd3+ the strongest EL intensity was observed from the sample annealed at 11000C after FLA. Increasing of the annealing temperature leads to a decreasing of the luminescence for each of annealing methods. The same effect was observed after increasing of the annealing time. In the case of defect formation under different annealing conditions an inverse situation was observed. Increasing of the annealing temperature and annealing time leads to an increase of the EL from oxygen deficiency centers (ODCs) An increase of the luminescence from defects at a simultaneous decrease of the luminescence from Gd at 316 nm can be explained by Gd-nanocluster creation in a-SiO2 during the annealing process.
Keywords: flash lamp annealing, silicon-based light emission, electroluminescence, ion implantation
  • Lecture (Conference)
    MRS Spring Meeting 2006, 17.-21.04.2006, San Francisco, USA

Publ.-Id: 9342 - Permalink


Energy Transfer by Gd to ion Implanted Ce and Er Atoms in Metal-Oxide-Silicon-based Light Emitting Diodes
Prucnal, S.; Sun, J. M.; Reuther, H.; Skorupa, W.;
The excitation mechanism of electroluminescence (EL) of cerium and erbium ions co-implanted with gadolinium into the SiO2 layer of MOSLEDs was investigated. Ce and Er ions were implanted into SiO2 with a concentration of 1% and 2%, respectively, subsequently implanted by gadolinium ions with concentrations of 0.5, 1.5 and 3%. Silicon dioxide containing cerium co-implanted with Gd exhibits two different excitation mechanisms: direct Ce3+ ion excitation by hot electrons and transfer of energy from 6PJ energy level of Gd to 5d energy state of Ce leading to an increase of the EL of Ce in the blue region. The EL observed from the sample containing 3% of Gd was 5 times higher in comparison with samples implanted only by Ce. The Er implanted SiO2 exhibits the typical peak at 1540 nm and weak luminescence in the green and blue region. Two green peaks correspond to the transitions from 2H11/2 and 4S3/2 to 4I15/2 and blue peaks to those from 2H9/2 and 4F5/2 to 4I15/2. The additional implantation of Gd leads to an increase of luminescence from Er3+ lines in the visible region caused by the energy relaxation from the Gd excited level 6PJ to the higher energy levels of erbium, whereas it has no influence on the infrared luminescence at 1.54 mm.
Keywords: Gd sensitization, Cer, Erbium, energy transfer, silicon-based light emission, ion implantation, electroluminescence
  • Lecture (Conference)
    MRS Spring Meeting 2006, 17.-21.04.2006, San Francisco, USA

Publ.-Id: 9341 - Permalink


Optical activation and electrical stabilization of the EL from SiO2:Gd gate oxide layers by fluorine and potassium co-implantations
Prucnal, S.; Sun, J. M.; Reuther, H.; Skorupa, W.;
When amorphous silica is bombarded with energetic ions, various types of defects are created as consequence of ion-solid interaction (oxygen deficient centres ODC, non-bridging oxygen hole centres NBOHC, E’-centres, etc.). Metal-oxide-silicon (MOS) structure contains gadolinium implanted SiO2 layer exhibit strong ultra violet (UV) electroluminescence (EL) at 316 nm from Gd3+ ions and enhancement of luminescence from defects (465 nm, 520 nm and 650 nm corresponds to ODC, Ed’-centre and NBOHC, respectively). Creation and transformation of point defects in bulk SiO2 contains Gd and F atom during constant current injection was investigated. Elimination of such defects is very important from viewpoint of electrical stability of MOS devices. Additional implantation of fluorine in to SiO2:Gd layer leads to decreasing of number of E’-centres and ODC, improves the stability of EL from Gd3+ at 316 nm and lengths working time of MOS structure.
Keywords: defects, silicon dioxide, ion implantation, silicon-based light emitter, electroluminescence
  • Lecture (Conference)
    MRS Spring Meeting 2006, 17.-21.04.2006, San Francisco, USA

Publ.-Id: 9340 - Permalink


Issues In Flash Lamp Annealing
Smith, M. P.; Seffen, K. A.; Mcmahon, R. A.; Skorupa, W.;
Review of recent work presented at the MRS Spring Meeting at San Francisco
Keywords: Flash lamp annealing, simulation
  • Lecture (others)
    Seminar bei der Fa. Mattson, 21.04.2006, Fremont, Ca, USA

Publ.-Id: 9339 - Permalink


Flash Lamp Processing for Conductive ITO Layers
Skorupa, W.; Anwand, W.; Schumann, T.; Voelskow, M.; Luethge, T.; Adam, D.;
Vortrag anlässlich eines vertraulichen Projekttreffens bei der Creavis-Degussa AG
Keywords: ITO layers, Flash lamp annealing
  • Lecture (Conference)
    Summer School Nanotronics 2006, 11.-13.09.2006, Marl, Deutschland

Publ.-Id: 9338 - Permalink


Advanced Thermal Processing of Semiconductor Materials in the msec-Range
Skorupa, W.;
Vortrag anlässlich der Begutachtung eines japanischen Grossprpojektes
Keywords: Flash lamp annealing, silicon carbide, silicon
  • Lecture (others)
    Projekttreffen OSTEC Advanced Quantum Beam Project, 27.09.2006, FZ Dresden-Rossendorf, Deutschland

Publ.-Id: 9337 - Permalink


Efficiency and Stability Issues of MOSLED´s made by RE Ion Implantation
Skorupa, W.; Prucnal, S.; Sun, J. M.; Helm, M.; Rebohle, L.; Gebel, T.; Nazarov, A.; Osiyuk, I.; Tjagulski, I.; Zuk, J.;
Combining silicon-based electronic circuits with optoelectronic functionality is one of the key challenges for the future semiconductor technology. Such work must not only be devoted to the wavelength of 1.54 µm because there are more applications needing light sources from all the UV to IR wavelength range. In our work we employed ion beam processing to embed different rare earth (RE) luminescent centers (Gd3+, Ce3+, Tm3+, Tb3+, Eu3+, Er3+) into the silicon dioxide layer of a purpose-designed Metal-Oxide-Silicon-based Light Emitting Diodes (MOSLEDs) with advanced electrical performance. Efficient electroluminescence was obtained from UV to infrared with a transparent top electrode made of indium-tin oxide. The distinct differences in efficiency of the various rare earth atoms will be discussed as well as problems of electrical stability of such devices due to hot electron injection and charge trapping phenomena. Several developments for improving the device stability will be proposed related to charge compensation and elimination of the defects in SiO2.
Keywords: Silicon-based light emitter, ion implantation, rare earths, electroluminescence, Metal-Oxide-Silicon-based Light Emitting Diodes (MOSLEDs), hot electron injection, charge trapping
  • Invited lecture (Conferences)
    MRS Spring Meeting 2006, 17.-21.04.2006, San Francisco, USA

Publ.-Id: 9336 - Permalink


Thermally Induced Deformation and Stresses During Millisecond Flash Lamp Annealing
Smith, M. P.; Seffen, K. A.; Mcmahon, R. A.; Anwand, W.; Skorupa, W.;
A flash lamp has been proposed for annealing wafers with diameters approaching 100 mm.
The equipment applies a pulse, with duration 0.5 ms to 20 ms, resulting in large transient thermal
gradients in the wafer. In this paper, we present a model for the thermal reaction of this process
and its effect upon the mechanical behaviour, in order to predict stresses, shape changes and to
capture practical phenomenon, such as bifurcation of deformation modes. We then use the
model to follow changes in the expected response consequent on altering process conditions, as
well as exploring important issues associated with scaling to large wafer sizes. The model is
further used to predict material yielding leading to permanent deformations. This work presents
the first description of the thermo-mechanical response of wafers to flash lamp annealing in the
millisecond time regime and is therefore fundamental to the use of this technique in the
fabrication of semiconductor devices.
Keywords: Stress, Wafer, Flash lamp annealing
  • Contribution to proceedings
    MRS Spring Meeting 2006, 17.-21.04.2006, San Francisco, USA
    Materials Research Society Symposium Proceedings 912, 912-C04-08
  • Lecture (Conference)
    MRS Spring Meeting 2006, 17.-21.04.2006, San Francisco, USA

Publ.-Id: 9335 - Permalink


Process Control During Liquid Phase Rerowth of 3C-SiC on Si Substrates
Smith, M. P.; Voelskow, M.; Mcmahon, R. A.; Muecklich, A.; Anwand, W.; Skorupa, W.;
Flash lamp annealing in the millisecond regime of heteroepitaxial silicon carbide on silicon structures involves melting the Si below the SiC layer, but the deep facetted nature of the solid-liquid interface leads to unacceptable surface roughness. This paper describes a method of controlling melting by implanting a high dose of carbon or germanium at a controlled depth below the Si/SiC interface, which significantly alters the melting characteristics of the silicon. Results confirm the effectiveness of these approaches for increasing surface uniformity, making liquid phase processing compatible with standard device fabrication techniques. A thermal model has also been developed to describe this process and results indicate that the theoretical work is consistent with the experimental evidence. The model is a valuable tool for predicting onset of melting, maximum temperatures and process windows for liquid phase epitaxy.
Keywords: Silicon carbide, Silicon, Heteroepitaxy, Liquid phase epitaxy, Flash lamp annealing
  • Contribution to proceedings
    MRS Spring Meeting 2006, 17.-21.04.2006, San Francisco, USA
    Materials Research Society Symposium Proceedings 911, 0911-B08-0
  • Lecture (Conference)
    MRS Spring Meeting 2006, 17.-21.04.2006, San Francisco, USA

Publ.-Id: 9334 - Permalink


Thermal and Stress Modeling for the Flash Lamp Crystallization of Amorphous Silicon Films
Smith, M. P.; Mcmahon, R. A.; Seffen, K. A.; Panknin, D.; Voelskow, M.; Skorupa, W.;
Thin poly-crystalline silicon films are attractive for the fabrication of active matrix liquid crystal displays. We investigate the use of flash lamp annealing to crystallize amorphous silicon layers on glass substrates as a low cost manufacturing route. In this process amorphous silicon (a-Si) can be crystallized by solid phase crystallization (SPC) or in the super lateral growth (SLG) regime. We present a thermal model incorporating the phase transitions during annealing; providing a valuable tool for optimizing the process conditions. Another consideration is the evolution of stress resulting from the transient thermal loading of the substrate material. Results are presented for various substrate geometries and important scalability issues are addressed.
Keywords: polycrystalline silicon, flash lamp annealing, amorphous silicon on glass, active matrix liquid crystal displays
  • Contribution to proceedings
    MRS Spring Meeting 2006, 17.-21.04.2006, San Francisco, USA
    Materials Research Society Symposium Proceedings 910, A 21-15
  • Lecture (Conference)
    MRS Spring Meeting 2006, 17.-21.04.2006, San Francisco, USA

Publ.-Id: 9333 - Permalink


Deactivation of Li by vacancy clusters in ion-implanted and flash-annealed ZnO
Borseth, T. M.; Tuomisto, F.; Cristensen, J. S.; Skorupa, W.; Monakhov, E.; Svensson, B. G.; Kuznetsov, A.;
Li is present in hydrothermally grown ZnO at high concentrations and is known to compensate both n- and p-type doping due to its amphoteric nature. However, Li can be manipulated by annealing and ion implantation in ZnO. Fast, 20 ms flash anneals in the 900–1400 °C range result in vacancy cluster formation and, simultaneously, a low-resistive layer in the implanted part of the He- and Li-implanted ZnO. The vacancy clusters, involving 3-4 Zn vacancies, trap and deactivate Li, leaving other in-grown donors to determine the electrical properties. Such clusters are not present in sufficient concentrations after longer (1 h) anneals because of a relatively low dissociation barrier ~2.6±0.3 eV, so ZnO remains compensated until Li diffuses out after 1250 °C anneals.
Keywords: flash annealing, ion implantation, zinc oxide, lithium, vacancy cluster
  • Physical Review B 74(2006), 161202(R)

Publ.-Id: 9332 - Permalink


Engineering of radiation defects and Li by flash anneals in ion-implanted ZnO
Borseth, T. M.; Cristensen, J. S.; Monakhov, E.; Svensson, B. G.; Kuznetsov, A.; Tuomisto, F.; Skorupa, W.;
Li is present in hydrothermally grown ZnO at high concentrations and is known to compensate both n- and p-type doping due to its amphoteric nature. However, Li can be manipulated by annealing and ion implantation in ZnO. Fast, 20 ms flash anneals in the 900–1400 °C range result in vacancy cluster formation and, simultaneously, a low-resistive layer in the implanted part of the He- and Li-implanted ZnO. The vacancy clusters, involving 3-4 Zn vacancies, trap and deactivate Li, leaving other in-grown donors to determine the electrical properties. Such clusters are not present in sufficient concentrations after longer (1 h) anneals because of a relatively low dissociation barrier ~2.6±0.3 eV, so ZnO remains compensated until Li diffuses out after 1250 °C anneals.
Keywords: zinc oxide, lithium, flash annealing, ion implantation, vacancy cluster, doping
  • Lecture (Conference)
    4th International Workshop on ZnO and Related Materials, 03.-06.10.2006, Gießen, Deutschland

Publ.-Id: 9331 - Permalink


Blitzlampen-Prozessieren: Stress und Oberflächen-Schmelzen bei Silizium
Skorupa, W.;
Überblick zu Stress und Oberflächen-Schmelzen bei Silizium infolge Blitzlampen-Prozessierens
Keywords: Flash lamp annealing, silicon, ion implantation
  • Invited lecture (Conferences)
    Deutsches Nutzertreffen Kurzzeitausheilung, 23.11.2006, Villach, Österreich

Publ.-Id: 9330 - Permalink


Silicon MOS light emitters by rare earth doping
Skorupa, W.;
Review of recent results regarding Silicon MOS light emitters using rare earth doping
Keywords: Silicon-based light emitter, rare earth, doping
  • Invited lecture (Conferences)
    1st Optence workshop on silicon photonics, 10.11.2006, Mainz, Germany

Publ.-Id: 9329 - Permalink


High dose high temperature ion implantation of Ge into 4H-SiC
Kups, T.; Weih, P.; Voelskow, M.; Skorupa, W.; Pezoldt, J.;
A box like Ge distribution was formed by ion implantation at 600 C. The Ge concentration was varied from 1 to 20 %. The TEM investigations revealed an increasing damage formation with increasing implantation dose. No polytype inclusions were observed in the implanted regions.
Keywords: 4H-SiC, Ge, solid solution, ion implantation, transmission electron microscopy
  • Materials Science Forum 527(2006), 851-854
  • Lecture (Conference)
    ICSCRM 2005, 18.-23.09.2005, Pittsburgh, USA

Publ.-Id: 9328 - Permalink


Millisecond annealing with flash lamps: tool and process challenges
Gebel, T.; Rebohle, L.; Fendler, R.; Hentsch, W.; Skorupa, W.; Voelskow, M.; Anwand, W.; Yankov, R.;
Sub-second annealing is one of the key issues to meet the requirements of the 45 nm technology node according to the ITRS roadmap. Therefore, over the past decade there has been great interest in techniques such as laser and flash lamp annealing (FLA). In addition, advanced ultra-fast annealing shows promise for technologies that are not directly related to Si device processing. The main reason for using FLA in alternative applications is the reduced thermal budget because of the short annealing time, which enables one to achieve high temperatures (> 500°C) in the near-surface region while keeping the substrate bulk relatively cold. This is of particularly high importance for the development of novel polymer-based electronics and flexible solar cell technologies, where the substrates cannot withstand temperatures in excess of 150°C. An overview of theoretical simulations and related results from FLA experiments for a variety of layered systems is given. The influence of the flash duration and intensity on the heat distribution and the resulting physical properties is considered. Design and performance issues of the FLA tools depending on the specific uses and technical requirements are addressed. Furthermore, topics covered include high-throughput applications e.g. for roll-to-roll production of polymer substrates. Results of a prototype tool for multi-flash processing up to a frequency of 1 Hz using a pulse duration of 1 ms are also discussed.
Keywords: Flash lamp annealing, Silicon device processing, roll-to-roll production, polymer substrates, sub-second annealing
  • Contribution to proceedings
    14. International Conference on Advanced Thermal Processing of Semiconductors (RTP 2006), 10.-13.10.2006, Kyoto, Japan
    Proceedings, RTP 2006, Piscataway, New York, USA: Institut of Eletrical and Electronics Engineers, 1-4244-0648-X
  • Invited lecture (Conferences)
    14. Int. Conf. on Advanced Thermal Processing of Semiconductors, 10.10.2006, Kyoto, Japan

Publ.-Id: 9327 - Permalink


Thermische Prozesse im msec-Bereich für Elektronik und Photonik
Skorupa, W.;
Vortrag über die jüngsten Entwicklungen und Experimente am FZD zur Blitzlampentemperung
Keywords: Blitzlampen-Temperung, Silizium, ITO, Siliziumkarbid
  • Lecture (others)
    Seminar am Institut für Bio- und Nanosysteme des Forschungszentrums Jülich, 16.10.2006, Jülich, Deutschland

Publ.-Id: 9326 - Permalink


Mikro-Nano-Piko: Elektronik und Photonik erobern das Nichts
Skorupa, W.;
Es wird über Entwicklungen in der Elektronik und deren Übergang in Photonikanwendungen berichtet.
Keywords: Lichtemitter, Blitzlampen-Temperung
  • Lecture (others)
    Technologietag der FDP-Fraktion am Sächsischen Landtag, 18.05.2006, Dresden, Deutschland

Publ.-Id: 9325 - Permalink


Ausgründung einer GmbH aus dem FZD aus der Perspektive eines Wissenschaftlers
Skorupa, W.;
Vortrag zu den Arbeiten am FZD sowie zu den Erfahrungen mit der Ausgründung einer GmbH aus dem FZD
Keywords: Lichtemitter, Blitzlampenausheilung
  • Lecture (others)
    Treffen mit Mittelstandsvereinigung Saxonia der sächsischen FDP, 09.06.2006, Dresden-Rossendorf, Deutschland

Publ.-Id: 9324 - Permalink


Advanced Thermal Processing of Semiconductor Materials in the msec-Range
Skorupa, W.;
Sub-second annealing is one of the key issues to meet the requirements of the 45 nm technology node according to the ITRS roadmap. Therefore, over the past decade there has been great interest in techniques such as laser and flash lamp annealing (FLA). In addition, advanced ultra-fast annealing shows promise for technologies that are not directly related to Si device processing. The main reason for using FLA in alternative applications is the reduced thermal budget because of the short annealing time, which enables one to achieve high temperatures (> 500°C) in the near-surface region while keeping the substrate bulk relatively cold. This is of particularly high importance for the development of novel polymer-based electronics and flexible solar cell technologies, where the substrates cannot withstand temperatures in excess of 150°C. An overview of theoretical simulations and related results from FLA experiments for a variety of layered systems is given. The influence of the flash duration and intensity on the heat distribution and the resulting physical properties is considered. Design and performance issues of the FLA tools depending on the specific uses and technical requirements are addressed. Furthermore, topics covered include high-throughput applications e.g. for roll-to-roll production of polymer substrates. Results of a prototype tool for multi-flash processing up to a frequency of 1 Hz using a pulse duration of 1 ms are also discussed.
Keywords: silicon, flash lamp annealing
  • Lecture (others)
    Institutsseminar, 07.06.2006, Freiberg, Deutschland

Publ.-Id: 9323 - Permalink


Visokotemperaturnaja implantazia ionov N+ i Al+ v 6H-SiC pri visokich dosach
in Russian
Yankov, R.; Voelskow, M.; Kreissig, U.; Kulikov, D. V.; Pezoldt, J.; Skorupa, W.; Truschin, Y. V.; Charlamov, V. S.; Zigankov, D. N.;
the effect of high temperature high dose nitrogen and aluminium implantation into 6H-SiC is investigated
Keywords: implantation high dose
  • Pisma v Zhurnal Tekhnicheskoi Fiziki 23(1997)16, 6

Publ.-Id: 9322 - Permalink


Industrial Application of Gamma Ray CT
Hampel, U.; Bieberle, A.; Schleicher, E.; Hoppe, D.; Zippe, C.;
Gamma ray CT is a powerful tool for the measurement of phase fraction distributions in thermal hydraulic systems and process diagnostics applications. Challenging process and plant conditions, such as high pressures and temperatures, opaque metallic vessels or machine parts as well as thermally unsteady and electromagnetically noisy environments limit the range of applicable measurement techniques in real processes. Gamma ray CT is a non-invasive technique and can be applied without major modification of the process facility. The tomography equipment is still not too bulky and complex to enable industrial measurements outside the laboratory. Recently our group has developed a high resolution gamma ray CT system that comprises a Cs-137 isotopic source (165 GBq activity, 622 keV photon energy) and a 320 channel scintillation detector that employs highly compact and robust avalanche photo detector technology in combination with fast LYSO scintillation crystals. The detector is operated in gamma photon counting mode. The spatial resolution of the detector is 2 mm. For measurements at industrial facilities we further devised a tomograph gantry that consists of a vertical translational and a rotational motor driven unit for tomographic scans at different axial planes of an object. The vertical operating range is approximately 1800 mm and objects of up to 900 mm diameter can be scanned.
Keywords: gamma ray CT, computed tomography
  • Contribution to proceedings
    International Conference on Multiphase Flow ICMF 2007, 09.-13.07.2007, Leipzig, Germany
    Proceedings of the International Conference on Multiphase Flow 2007, Paper No. PS/_10
  • Lecture (Conference)
    International Conference on Multiphase Flow ICMF 2007, 09.-13.07.2007, Leipzig, Germany

Publ.-Id: 9321 - Permalink


Anwendung der Elektronenstrahltechnik zur ultraschnellen Tomographie von Mehrphasenströmungen
Hampel, U.; Fischer, F.; Mattausch, G.;
Computertomographie (CT) auf der Basis von Röntgen- und Gammastrahlung stellt ein attraktives Messverfahren zur Untersuchung von Mehrphasenströmungen dar. Die Messung erfolgt dabei berührungslos und hat somit keine Rückwirkung auf die Strömung. Die Strahlung ermöglicht einen Blick in undurchsichtige Gefäße und durchdringt trübe oder intransparente Fluide, Supensionen, Emulsionen und Feststoffschichten ohne Probleme. Da die Strahlungsausbreitung geradlinig erfolgt, sind scharfe Abbildungen verborgener Strukturen möglich. Bisher wird die Computertomographie als bildgebendes Messverfahren hauptsächlich in der Medizin aber auch in der zerstörungsfreien Werkstoffprüfung eingesetzt. Seit einiger Zeit gibt es vielfältige internationale Bestrebungen, computertomographische Messverfahren für die Untersuchung von Mehrphasenströmungen verfügbar zu machen.
Das Prinzip der Elektronenstrahltomographie eignet sich für die Untersuchung schneller Strömungsvorgänge. Dabei ist es allerdings erforderlich, die Bildrate eines derartigen CT-Scanners über die in der Kardiobildgebung üblichen 50 Bilder pro Sekunde hinaus auf mindestens 1000 Bilder pro Sekunde zu steigern. Am Institut für Sicherheitsforschung am Forschungszentrum Dresden-Rossendorf wird derzeit daran gearbeitet, die Elektronenstrahltomographie als messtechnisches Tool für die Untersuchung von Zweiphasenströmungen im Forschungsschwerpunkt Sicherheit und Betriebsverhalten nuklearer Anlagen bzw. zu Zwecken der Entwicklung und Validierung von Zweiphasen-CFD-Codes verfügbar zu machen. Mit der Entwicklung eines optimierten ultraschnellen Elektronenstrahl-CT-Scanners mit eigenem Elektronenstrahlerzeuger und halbkreisförmiger Targetgeometrie wurde nunmehr am Forschungszentrum Dresden-Rossendorf ein nächster wichtiger Schritt in Richtung einer universell einsetzbaren Elektronenstrahl-CT für Strömungsuntersuchungen beschritten. In naher Zukunft wird dieses Messverfahren Anwendung bei der Untersuchung von Wasser-Wasserdampf-Strömungen in einer Rohrleitung mit 50 mm Innendurchmesser finden. Die Untersuchungen werden an der am Forschungszentrum Dresden-Rossendorf betriebenen Mehrzweck-Thermohydraulik-Versuchsanlage TOPFLOW durchgeführt.
Keywords: electron beam tomography
  • Contribution to external collection
    in: Jahresbericht 2006, Fraunhofer Institut für Elektronenstrahl- und Plasmatechnik, München: Fraunhofer, 2007, 57-58

Publ.-Id: 9320 - Permalink


Positron and deuteron depth profiling in He-3-implanted electrum-like alloy
Grynszpan, R. I.; Baclet, N.; Darque, A.; Flament, J. L.; Zielinski, F.; Anwand, W.; Brauer, G.;
In spite of previous extensive studies, the helium behavior in metals still remains an issue in microelectronics as well as in nuclear technology. A gold–silver solid solution (Au60Ag40: synthetic gold-rich electrum) was chosen as a relevant model to study helium irradiation of heavy metals. After helium-3 ion implantation at an energy ranging from 4.2 to 5.6 MeV, nuclear reaction analysis (NRA) based on the 3He(d,p)4He reaction, was performed in order to study the thermal diffusion of helium atoms. At room temperature, NRA data reveal that a single Gaussian can fit the He-distribution, which remains unchanged after annealing at temperatures below 0.45 of the melting point. Slow positron implantation spectroscopy, used to monitor the fluence dependence of induced defects unveils a positron saturation trapping, which occurs for He contents of the order of 50–100 appm, whereas concentrations larger than 500 appm seem to favor an increase in the S-parameter of Doppler broadening. Moreover, at high temperature, NRA results clearly show that helium long range diffusion occurs, though, without following a simple Fick law.
  • Applied Surface Science 252(2006), 3252-3255

Publ.-Id: 9318 - Permalink


Modification of Solid Surfaces by Slow Highly Charged Ions: Effects of Highly Confined Excitation
Heller, R.; Facsko, S.; Kost, D.; Zschornack, G.;
Due to their high amount of potential energy highly charged ions induce various changes in morphology and electronic structure of solid surfaces [1,2]. The potential energy which is the sum of the ionization energies of all removed electrons, is released on a very small localized area of a few nm2 and in very short times of tens of fs. Hence the power density deposited into the surface can reach values of up to 1014 Wcm−2 depending on the ions incident charge state. The changes in surface topology depend strongly on the electronic excitation in the surface and its lateral and longitudinal confinement. Focus of our investigations is the interaction of slow HCIs with surfaces that have a high confinement of excitation. Such surfaces are mainly all kind of insulators, but also samples with an additional confinement due to a layered structure. In this case the electron transfer between different layers is suppressed and the interacting system becomes quasi two dimensional. Investigations were performed at the Rossendorf Two Source Facility, an ion beam facility consisting of two sources: a 14.5 GHz ECR ion source and an Electron Beam Ion Source, the Dresden EBIT [3]. Ions of both sources are decelerated by a common deceleration unit to suppress kinetic effects during ion surface interaction. The combination of these both sources offers ions of various charge states (up to q = 44 for Xe), species (He, Ne, Ar, Xe, C, N, O) and kinetic energies (<q · 100 eV to q · 25 keV). We present scanning probe microscopy studies of surface modifications induced by single ion impacts. HOPG, MICA and ultra thin SiO2 layers were irradiated with ions of argon (charge states q = 1...16) and xenon (charge states q = 1...40). The diameter and the height of created nano structures wer e investigated in dependence on the ion charge state for both ion species. Additional to SPM investigations Raman spectroscopy of HOPG before and after irradiation was performed to get information about structural changes induced by the HCI impact.
Keywords: Highly Charged Ions, Surface Interaction, HOPG, Excitation, STM
  • Poster
    13th International conference on the Physics of Highly Charged Ions (HCI), 28.08.2006, Belfast, Nord Irland

Publ.-Id: 9317 - Permalink


The Rossendorf Two Source Facility – A Device for the Observation of the Interaction of Slow Highly Charged Ions with Surfaces
Heller, R.; Facsko, S.; Kost, D.; Zschornack, G.;
The interaction of slow highly charged ions with solid surfaces is mainly characterized by the high amount of potential energy stored in the ions and discharged on the surface. Thereby the potential energy is the sum of the ionization energies of all removed electrons. While the kinetic energy of an ion scales linearly with the charge state, its potential energy grows rapidly with each removed electron. Figure 1 shows the ionization energy and the resulting potential energy of iron ions of different charge states. The ion bombardment of solid surfaces with HCIs can lead to various changes in surface morphology [1-4]. The Rossendorf Two Source Facility presents a world wide unique ion beam facility consisting of two ion sources and providing ions of adjustable charge state and kinetic energy. These two sources are: a 14.5 GHz-Electron-Cyclotron-Resonance (ECR) ion source (Super Nanogan / Pantechnik) and an Electron Beam Ion Trap (Dresden EBIT / Leybold Vacuum Dresden GmbH) operating at room temperature [5,6,7].
Keywords: highly charged ions, surface interaction, nano dots, STM, HOPG
  • Contribution to proceedings
    International Doctoral Seminar 2006, 23.04.2006, Smolenice, Slowakia

Publ.-Id: 9316 - Permalink


Extraktion hochgeladener Ionen aus der Dresden EBIT im Überlaufregime
Heller, R.; Zschornack, G.;
For the first time the production and the extraction of highly charged ions from the Dresden EBIT using the so-called leaky mode, an operating mode with a continuous ion extraction (DC) at fixed axial trap potantial was investigated. Measurements of the ion output current at a Faraday cup directly behind the source were done with integral ion currents of up to 1.5nA depending on the source parameters. Also the charge state distribution of the extracted ions at leaky mode was investigated. It was shown, that ions of argon gas can be extracted up to a charge state of q=17 with an ion current of 1pA (DC) and xenon ions up to a charge state of q=21 with currents of about 0.5pA (DC).
Keywords: highly charged ions, leaky mode, EBIT
  • Contribution to proceedings
    28. EAS-Tagung - Energiereiche atomare Stöße, 06.-10.02.2006, Dresden, Deutschland

Publ.-Id: 9315 - Permalink


Ioneninduzierte Nanostrukturen
Möller, W.;
  • Lecture (others)
    Festkolloquium, 06.12.2006, Cottbus, D

Publ.-Id: 9314 - Permalink


Mechanisms of target poisoning during reactive sputtering of TiN
Möller, W.;
  • Invited lecture (Conferences)
    BELVAC Symposium on Reactive Sputter Deposition, , Belgium, 30.11.2006, Ghent, Belgium

Publ.-Id: 9313 - Permalink


Ion induced stress release – by thermal or collisional spikes?
Möller, W.;
  • Lecture (others)
    Thin Film Workshop, 17062006, Linköping, Sweden

Publ.-Id: 9312 - Permalink


Ion irradiation for generation and control of nanostructures
Möller, W.;
  • Lecture (others)
    Seminar, 10.01.06, Prag, CZ

Publ.-Id: 9311 - Permalink


Kontinuumsgleichungen zur Beschreibung ionenstrahlinduzierter Nanostrukturen
Facsko, S.;
  • Lecture (Conference)
    Workshop "Ionenstrahlphysik und Nanotechnologie", 16.05.2006, Berlin, Deutschland

Publ.-Id: 9310 - Permalink


Properties of thin films grown on periodically corrugated surfaces
Facsko, S.; Keller, A.; Liedke, O.; Fassbender, J.ORC; Möller, W.
  • Lecture (others)
    Seminar, 30.05.2006, Konstanz, Deutschland

Publ.-Id: 9309 - Permalink


Changing carbon films by highly charged ions
Facsko, S.; Som, T.; Wilhelm, R.; Heller, R.; Möller, W.;
Carbon films exist in a variety of modifications ranging from soft amorphous carbon film (a-C) to hard diamond-like carbon (DLC) films [1]. Due to their diverse proper-ties carbon films are technologically important materials, especially for protective, biomedical, or field emission coatings. In addition, special forms such as fullerene-like films have attracted the scientific interest for their special structure. Many of the properties of the carbon films are intrinsically related to their nanostructure which in turn is strongly related to the existence of sp2 and sp3 hybridized phases.
The nanostructure of the carbon films depends strongly on the preparation conditions but are as well modified by the irradiation with ions. Irradiation with single charged heavy ions at high energy normally turns the films amor-phous reducing the amount of sp3 and sp2 hybridized phases [2]. Here, we present systematic studies of irradia-tion of carbon films by highly charged argon and xenon ions with low kinetic energy.
Keywords: highly charged ions, carbon films
  • Poster
    International Workshop on Inelastic Ion-Surface Collisions (IISC-16), 17.-22.09.2006, Hernstein, Österreich

Publ.-Id: 9308 - Permalink


Periodic surface patterns induced by low energy ion erosion
Facsko, S.; Keller, A.; Rossbach, S.; Möller, W.;
In the series of self-organized processes for the fabrication of nanostructures the pattern forma-tion during ion erosion of surfaces has attracted much interest in the last years. In the continuous sputtering process, induced by the bombardment with low-energy ions, periodic surface patterns appear in form of ripples under off-normal incidence or arrays of hexagonally ordered dots at normal incidence. The dimension of the pattern is related to the size of the typical collision cas-cade and lies in the range of ten to tens of nanometers, depending on ion energy. The self-organization mechanism relies on the interplay between a surface instability caused by the sput-tering, and surface diffusion processes. Regular ripple and dot array morphologies have been produced in this way on very different materials including semiconductors, insulators, and met-als, demonstrating the universality of the mechanism.
Keywords: Nanostructures
  • Lecture (others)
    Seminar, 15.12.2006, Göttingen, Deutschland

Publ.-Id: 9307 - Permalink


Thermal phase transformation and perpendicular exchange coupling of Co nanocrystals embedded in ZnO
Zhou, S.; Potzger, K.; Skorupa, W.; Helm, M.; Fassbender, J.ORC
Recently, due to the potential application in spintronics, ferromagnet-semiconductor hybrid structures have attracted huge research attention [1]. Large magnetoresistance was observed in GaAs consisting MaAs nanocrystals formed by ion implantation [2] and in granular ZnO/Co systems [3]. Very recently, wide-band-gap semiconductors (GaN, ZnO and TiO2) doped with transition metals were reported to be diluted magnetic semiconductors with Curie temperatures above room temperature [4]. However, the origin of the observed ferromagnetism is still controversial, e.g. ferromagnetic clusters, or extrinsic reasons. In this work, Co nanocrystals (NCs) were formed inside ZnO my means of ion beam synthesis. The Co NCs are crystallorgraphically oriented inside ZnO. The magnetic properties, e.g. anisotropy and blocking temperature can be tuned by annealing. In the as-implanted and annealed (823 K) samples, hcp-Co or co-existing of hcp and fcc Co NCs have been found and show superparamagnetism. After annealing at 923 K, the sample exhibits a much higher blocking temperature and shows a perpendicular exchange bias effect, which indicates the formation of a Co/CoO core/shell structure. The system of ZnO semiconductor consisting of crystallorgraphically oriented Co NCs could be a promising hybrid for spin-injection.
1. H. Ohno, Semicond. Sci. Technol. 17, 275 (2002).
2. P. J. Wellmann, et al., Appl. Phys. Lett. 73, 3291 (1998).
3. A. B. Pakhomov, et al., J. Appl. Phys. 95, 7393 (2004).
4. A. H. MacDonald, et al., Nature Materials 4, 195 (2005).
Keywords: ZnO, magnetic semiconductor, Co nanocrystals
  • Lecture (Conference)
    71. Jahrestagung der Deutschen Physikalischen Gesellschaft und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 26.-30.03.2007, Regensburg, Germany

Publ.-Id: 9306 - Permalink


Structural investigations of magnetic nanocrystals embedded in semiconductors using synchrotron radiation x-ray diffraction
Zhou, S.; Potzger, K.; von Borany, J.; Skorupa, W.; Helm, M.; Fassbender, J.ORC
Traditional electronics can be greatly stimulated by a combination of magnetic and semiconducting properties where spins provide an additional freedom degree. Recently theoretical works predict that some semiconductors (e.g. ZnO, GaN, TiO2, and Si) doped with transition metal (TM) are diluted magnetic semiconductors (DMS) [1]. In DMS materials, TM ions are substituted onto cation sites of the host semiconductor and are coupled with free carriers via indirect interaction resulting in ferromagnetism. However most experimental works have only concentrated on reporting high Tc and interpreted the observed ferromagnetism in terms of DMS without detail structural characterization. In this work, we have prepared magnetic ZnO, TiO2 and Si samples doped with TM by implantation, and correlated their magnetic and structural properties [2-5]. By synchrotron radiation x-ray diffraction, Fe, Ni, Co and Mn-silicide nanocrystals are observed in our samples, and are responsible for the magnetism. Depending on their crystalline structure, those nanocrystals are crystallographically oriented with respect to the host matrix. The structural information is well agreeable with the magnetic properties measured by SQUID. Additionally due to their orientation nature (crystallographically oriented or randomly oriented with respect to the host crystal), these nanocrystals in some cases are very difficult to detect by a simple Bragg-Brentano scan. This nature results in the pitfall of using XRD to exclude secondary phase in DMS materials.
References
[1] T. Dietl, et al, Science 287, 1019 (2000).
[2] K. Potzger, Shengqiang Zhou , et al, Appl. Phys. Lett. 88, 052508 (2006).
[3] Shengqiang Zhou, et al., J. Appl. Phys. 100, 114304 (2006).
[4] Shengqiang Zhou, et al., to be published at Phys. Rev. B (2007).
[5] Shengqiang Zhou, et al., to be published at J. Phys. D: Appl. Phys. (2007).
Keywords: synchrotron radiation x-ray diffraction, diluted magnetic semiconductor, magnetic nanocrystals
  • Poster
    The 17th ESRF Users Meeting, 05.-08.02.2007, Grenoble, France
  • Lecture (Conference)
    Nanospintronic design and realization 2007, 21.-25.5.2007, Dresden, Deutschland

Publ.-Id: 9305 - Permalink


Buoyancy driven flow in the VeMix test facility
Vaibar, R.; Sühnel, T.;
Buoyancy driven flow is often presented in many engineering application such as mixing process of fluids with different density. The aim of our study is to simulate mixing processes that are relevant in safety analyses of nuclear reactors. The boron dilution problem is one such safety issue analysis.
Borated and unborated water are of different densities and may be of the diffenrent temperatures, what causes additional density defferences. The degree of mixing of low and high borated coolant is a critical issue with respect to reactivity insertion into the reactor core. As nuclear reactor geometries are complex, the mixing process not widely understood and the influence of the buoyancy is small, a very simple vertical test facility was chosen for validation of numerical models of the mixing process. A new source term, which consists of a sum of the component turbulent density fluxes, is defined for the turbulent model and in this case is based on the definition turbulent kinetic energy.
Keywords: buoyancy driven turbulence, turbulence two-equation model
  • Lecture (Conference)
    Seminar on Numerical Analysis and Tutorial - SNA'07, 22.-26.01.2007, Ostrava, Czech Republic

Publ.-Id: 9304 - Permalink


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