Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
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Only approved publications

31839 Publications
Thin silicon films - texture and grain size improvement
Endler, R.; Voelskow, M.; Mücklich, A.; Schumann, T.; Skorupa, W.;
The structural optimization of polycrystalline silicon films is important to improve the electronic properties of microelectronic devices and photovoltaic solar cells, based on thin film silicon. The enlargement of the grain size is of big interest since the fabrication of silicon based thin film devices started. In this work we present results on the lateral dendritic growth in 100nm thin silicon layers which leads to lateral grain sizes in the range of 100µm. The second topic in this field is the manipulation of the grain lattice orientation within the layer which can lead to a uniformly oriented polycrystalline material.
  • Lecture (Conference)
    31. Deutsches Nutzertreffen RTP und Heißprozesse, 21.03.2012, Erlangen, Deutschland

Publ.-Id: 17322 - Permalink

Focused ion beam induced structural modifications in thin magnetic films.
Roshchupkina, O. D.; Grenzer, J.; Strache, T.; McCord, J.; Fritzsche, M.; Mücklich, A.; Baehtz, C.; Fassbender, J.ORC
Focused ion beam techniques are one way to modify locally the properties of magnetic thin films. We report on structural investigations of 50 nm thick non-ordered nano-crystalline Permalloy (Ni81Fe19) films modified by 30 keV Ga+ focused ion beam (FIB) irradiation. From the X-ray diffraction (XRD) measurements a considerable crystallite growth and a material texturing towards (111)-direction with a linearly increasing lattice constant was observed. In addition cross-sectional transmission electron microscope (XTEM) images show that crystallites are growing through the entire film at high irradiation fluences.
Extended X-ray absorption fine structure (EXAFS) analysis shows a perfect near-order coordination corresponding to a face-centered (fcc) unit cell for both FeNi and Ga atom surrounding. The structural changes are accompanied by a decrease of saturation polarization with increasing ion fluence. Such behavior is attributed to a simple incorporation of non-magnetic Ga atoms in the Permalloy film.

Publ.-Id: 17321 - Permalink

Iron assisted ion beam patterning of Si(001) in the crystalline regime
Macko, S.; Grenzer, J.; Frost, F.; Engler, M.; Hirsch, D.; Fritzsche, M.; Mücklich, A.; Michely, T.;
We present ion beam erosion experiments on Si(001) with simultaneous sputter co-deposition of steel at 660 K. At this temperature the sample remains remains within the crystalline regime during ion exposure and pattern formation takes place by phase separation of Si and iron-silicide. After an ion fluence of F ≈ 5.9 × 1021 ions m−2 investigations by atomic force microscopy and scanning electron microscopy identify sponge, segmented wall and pillar patterns with high aspect ratios and heights of up to 200 nm. Grazing incidence X-ray diffraction and transmission electron microscopy reveal the structures to be composed of polycrystalline iron-silicide. The observed pattern formation is compared to the one in the range from 140 K to 440 K under otherwise identical conditions, where a thin amorphous layer forms due to the ion bombardment.

Publ.-Id: 17320 - Permalink

Das Hochfeld-Magnetlabor Dresden: Rossendorfer Rekorde
Uhlarz, M.;
es hat kein Abstract vorgelegen.
  • Lecture (others)
    Berufsschulzentrum Radebeul, 20.06.2012, Radebeul, Deutschland

Publ.-Id: 17319 - Permalink

Investigation of metal binding by cell wall components of Gram-positive bacteria studied by QCM-D
Suhr, M.; Fischer, S.; Günther, T.; Raff, J.; Pollmann, K.;
Investigation of the interaction of metals with the biosphere is important not only from an ecological point of view but also from an application oriented one. Biosorption of metals by bacteria was intensively studied. Furthermore, bacterial cell wall components itself e.g. surface layer (S-layer) proteins, lipids and peptidoglycan were intensively studied. Nevertheless, the investigation of their interaction with metals both as molecules and as intact layers on a molecular level remains challenging.
Parts of our investigations concentrated on S-layers. These are the outermost cell envelope of many eubacteria and archaea, forming highly ordered paracrystalline lattices not only on the cell, but also after isolation on various technical surfaces by self-assembling processes. These proteins show remarkable high metal binding capacities.
In our work we used the quartz crystal microbalance with dissipation monitoring (QCM-D) in order to study the layer formation of single cell wall compounds and interaction processes on the nano scale range. This method gives a detailed understanding of biological structure formation and the amount of metal deposition. Within the experiments the influence of surface modification with adhesive promoters e.g. polyelectrolytes was studied in order to make exact statements regarding coating kinetics, layer stability and metal interaction. Subsequent atomic force microscopy (AFM) studies enable the imaging of bio nanostructures and reveal complex information of structural properties.
Aim of these investigations is the assembly of a simplified biological cell wall based on Gram-positive bacteria in order to clarify sorption processes in a complex system.
Keywords: biotechnology, S-layer, lipids, QCM-D, AFM, biosorption, proteins, layer formation, metal deposit, polyelectrolytes
  • Poster
    5th International Symposium on Biosorption and Bioremediation, 24.-28.06.2012, Prag, Tschechische Republik

Publ.-Id: 17318 - Permalink

Ge quantum dot lattices in Al2O3: a material with excellent mechanical and size-tuneable optical properties
Buljan, M.; Radić, N.; Ivanda, M.; Bogdanović-Radović, I.; Karlušić, M.; Grenzer, J.; Prucnal, S.; Dražić, G.; Pletikapić, G.; Svetličić, V.; Jerčinović, M.; Bernstorff, S.; Holy, V.;
In this article we show how to produce materials consisting of regularly ordered Ge quantum dots in amorphous alumina matrix with the controllable Ge quantum dot size, shape, spacing, crystalline structure and degree of regularity in the Ge quantum dot ordering. The production of such materials is achievable already at room temperature by magnetron sputtering deposition of a (Ge+Al2O3)/Al2O3 multilayer. The materials show large, size-dependent blueshift of the photoluminescence peak and enhancement in the oscillator strength caused by confinement effects. The materials also show advanced mechanical properties due to alumina matrix, and their internal structure is shown to be highly resistive to irradiation with energetic particles for a large range of the irradiation parameters. The reported materials have excellent potential for application in demanding environments for light harvesting.
Keywords: nano cluster, GISAXS

Publ.-Id: 17317 - Permalink

Ga(1−x)Mn(x)N epitaxial films with high magnetization
Kunert, G.; Dobkowska, S.; Li, T.; Reuther, H.; Kruse, C.; Figge, S.; Jakiela, R.; Bonanni, A.; Grenzer, J.; von Borany, J.; Stefanowicz, W.; Sawicki, M.; Dietel, T.; Hommel, D.;
We report on the fabrication of pseudomorphic wurtzite Gax Mnx N grown on GaN with Mn concentrations up to 10 % using molecular beam epitaxy. According to Rutherford backscattering the Mn ions are mainly at the Ga-substitutional positions, and they are homogeneously distributed according to depth-resolved Auger-electron spectroscopy and secondary-ion mass-spectroscopy measurements. A random Mn distribution is indicated by transmission electron microscopy, no Mn-rich clusters are present for optimized growth conditions. A linear increase of the c-lattice parameter with increasing Mn concentration is found using x-ray diffraction. The ferromagnetic behavior is confirmed by superconducting quantum-interference measurements showing saturation magnetizations of up to 150 emu/cm3 .
Keywords: GaN, GaMnN, DMS

Publ.-Id: 17316 - Permalink

TCOs auf Basis Tantal-dotierter TiO2 Schichten
Neubert, M.; Vinnichenko, M.; Cornelius, S.; Kolitsch, A.;
Die vielfältigen Anwendungen transparenter leitfähiger Oxide (TCO), wie zum Beispiel in Flachbildschirmen, Solarzellen und der Beleuchtungstechnik erfordern die Entwicklung neuartiger TCO-Materialien. Darüber hinaus ist der Einsatz der etablierten TCOs, wie Indiumzinnoxid (ITO) oder Fluor dotiertes Zinnoxid (FTO) zukünftig nur bedingt fortzuführen. Die Verwendung von ITO ist aufgrund des kontinuierlich steigenden Indiumpreises sehr kostenintensiv, während der Einsatz von FTO-Dünnschichten aufgrund des hochgradig toxischen Herstellungsprozesses weltweit umstritten ist. Es konnte gezeigt werden, dass Titandioxid dotiert mit Tantal (TTO) vergleichbare elektrische und optische Eigenschaften, verglichen mit den etablierten TCOs aufweist. Eine wesentliche Herausforderung besteht allerdings darin, TTO-Dünnschichten mittels eines industrienahen kostengünstigen Prozess abzuscheiden. Diese Problemstellung wurde gelöst, indem TTO-Schichten mittels eines 2-stufigen Prozesses bestehend aus Sputtern und anschließender thermischer Nachbehandlung abgeschieden wurden. Die dabei erreichten spezifischen Widerstände im Bereich von 0,001 Ohmcm sind für zahlreiche Anwendung ausreichend. Darüber hinaus wurde gezeigt, dass die Kurzzeittemperprozesse eine mögliche Alternative zur konventionellen Nachtemperung sind.
Keywords: transparent conductive oxide,TCO, TiO2, Ta, tantalum, thin film
  • Lecture (Conference)
    Workshop „Transparente leitfähige Oxide - Festkörperphysikalische Grundlagen und Technologie", 21.-22.05.2012, Dresden, Deutschland

Publ.-Id: 17315 - Permalink

CNT growth from C:Ni nanocomposites
Krause, M.; Haluska, M.; Wenisch, R.; Kunze, T.; Abrasonis, G.; Gemming, S.;
Precise control of single walled carbon nanotube (SWCNT) diameter, chirality, alignment, and intertube arrangement are still remaining challenges in the catalytic chemical vapour deposition (CCVD) synthesis. In this context it has still to be clarified whether a predefined size and shape of the nanoparticles can be stabilized by a suitable matrix material while preserving the catalytic activity of the metal.
For this study Ni nanoparticles were encapsulated in an amorphous carbon matrix by physical vapour deposition. As prepared Ni catalysts were used for CNT fabrication by laser assisted CVD applying either no external carbon source or C2H4 gas, and by low pressure CVD applying C2H2 or CH4 as carbon source. The broad range of CNT synthesis conditions indicates the robustness of the embedded Ni particles as a catalyst for carbon nanotube formation. SEM and laser wavelength dependent Raman spectroscopy were used for CNT characterisation. The nickel-SWCNT-interaction was modelled by density functional calculations with the projector augmented plane wave method, utilizing the generalized gradient approximation for the exchange-correlation functional.
Keywords: Nanocomposites, Carbon Nanotubes, Synthesis
  • Poster
    International winterschool on electronic properties of novel materials, 03.-10.03.2012, Kirchberg, Österreich

Publ.-Id: 17314 - Permalink

Fabrication of Si(1-x)Ge(x) Alloy on Silicon by Ge-ion-implantation and Short-Time-Annealing
Gao, K.; Prucnal, S.; Mücklich, A.; Skorupa, W.; Zhou, S.;
Silicon-Germanium is commonly used as a semiconductor material in integrated circuits (ICs) for heterojunction bipolar transistors or as a strain-inducing layer for CMOS transistors. Normally epitaxial methods (e.g., CVD, MBE) are applied to the synthesis of Si1-xGex alloys.
In our contribution we present the fabrication of Si1-xGex alloy by ion-implantation and short-time-annealing. The Ge ions in the fluence range of 3×1016 - 10×1016 cm2 were implanted into monocrystalline (100)-oriented Si wafers covered by 50 nm thermal oxide at an energy of 100 keV. As the consequence, the 50 nm amorphous Ge rich Si layers were obtained. The recrystallization of the implanted layers and the Si1-xGex alloying were carried out by flash lamp annealing or scanning continuous laser annealing in the time scale of 20 ms or 1 s, respectively. Both flash lamp treatment and laser annealing at high energy densities lead to local melting of the germanium rich silicon layer. The recrystallization of the Si1-xGex layer takes place due to millisecond range liquid phase epitaxy. Formation of the high quality monocrystalline Si1-xGex layer was confirmed by μ-Raman spectroscopy, RBS channeling and cross-section TEM investigation. The μ-Raman spectra reveal tree phonon modes located at around 293, 404 and 432 cm-1 corresponding to the Ge-Ge, Si-Ge and Si-Si in the Si1-xGex alloy vibrational modes, respectively. Due to much higher carrier mobility in SiGe layer than in silicon such system can be used for the fabrication of advanced devices.
Keywords: Silicon Germanium, ion-implantation, flash lamp annealing, continuous laser annealing
  • Lecture (Conference)
    IX-th International Conference Ion Implantation and other Applications of Ions and Electrons, 25.-28.06.2012, Kazimierz Dolny, Poland

Publ.-Id: 17312 - Permalink

Ressourcenanalytik - Spuren finden mit (Sp-)Ionen
Merchel, S.; Renno, A. D.; Rugel, G.;
Die Ionenstrahlanalytik nutzt hochenergetische Ionen zur Material-, Struktur- und Radionuklidanalyse. Sie wird im Rahmen der Ressourcenanalytik eingesetzt, um neue Technologien zur Erkundung, Gewinnung, Nutzung und Recycling von Rohstoffen entlang der Wertschöpfungskette zu entwickeln. Die Projektgruppe Ionenstrahlanalytik am Helmholtz-Institut Freiberg für Ressourcentechnologie (HIF) ist stark methodisch orientiert und entwickelt in interdisziplinären Forschungsprojekten nahezu unikale Analysemethoden unter Einsatz bzw. Eigenbau neuester Technologien. Diese Methoden eröffnen neue und interessante Möglichkeiten der (Ultra-)Spurenelementanalyse. Das HIF ist eine gemeinsame Einrichtung des Helmholtz-Zentrums Dresden-Rossendorf und der TU Bergakademie Freiberg.
Keywords: accelerator mass spectrometry, resource analytics, ion beam analysis, Super-SIMS
  • Lecture (others)
    Dresdner Seniorenakademie, TU Dresden, WS 2012/2013, 30.01.2013, Dresden, Deutschland

Publ.-Id: 17311 - Permalink

ADRIANA Project: identification of research infrastructures for the SFR, within the frame of European Industrial for substainable Nuclear Fission
Latge, O.; Gastaldi, O.; Vala, L.; Gerbeth, G.; Homann, C.; Benoir, P.; Papin, J.; Girault, N.; Roelofs, F.; Buceniecks, I.; Paffumi, E.; Ciampichetti, A.;
Fast neutron reactors have a large potential as sustainable energy source. In particular, Sodium Fast Reactors (SFR) with al closed fuel cycle and potential for minor actinide burning may allow minimization of volume and heat load of high level waste and provide improved use of natural resources (as compared to only 1 % energy recovery in the current once-through fuel cycle, with Thermal Reactors, such as EPR).
Keywords: SFR, sodium, experimental facilities, ADRIANA
  • Contribution to proceedings
    2012 International Congress on the Advances in Nuclear Power Plants (ICAPP'12), 24.-28.06.2012, Chicago, USA
  • Lecture (Conference)
    2012 International Congress on the Advances in Nuclear Power Plants (ICAPP'12), 24.-28.06.2012, Chicago, USA

Publ.-Id: 17310 - Permalink

Positron emission tomography in pebble beds. Part 1: Liquid particle deposition
Barth, T.; Ludwig, M.; Kulenkampff, J.; Gründig, M.; Franke, K.; Lippmann-Pipke, J.; Hampel, U.;
Accidental scenarios such as the depressurisation of the primary circuit of high temperature gas cooled pebble bed reactors may lead to the release of fission products via the discharge of radioactive graphite dust. For a detailed source term assessment in such accident scenarios knowledge of the flow mechanics of dust transport in complex coolant circuit components, like pebble beds, recuperator structures and pipe systems is necessary. In this article an experimental study of aerosol deposition in a pebble bed is described. We investigated the deposition of radiolabelled liquid aerosol particles in a scaled pebble bed in an air-driven small-scale aerosol flow test facility under isothermal ambient conditions. The aerosol particles were generated by means of a condensational aerosol generator with potassium-fluoride (KF) condensation nuclei. Particle concentration measurements upstream and downstream of the pebble bed were performed by isokinetic sampling and particle counting. The results agree with typical deposition curves for turbulent and inertia driven particle deposition. Furthermore, positron emission tomography (PET) was performed to visualize and measure particle deposition distributions in the pebble bed. Results of a selected deposition experiment with moderately large particles (daero = 3.5 μm, Re′pb=2200) show that the deposited particles are located in the vicinity of the upstream stagnation points of the pebbles. These findings support the thesis that inertia driven particle deposition is predominating.
Keywords: Aerosol deposition, Positron emission tomography, High Temperature Reactor

Publ.-Id: 17309 - Permalink

Experimental setup for in vivo irradiation with laser accelerated electrons
Schürer, M.; Brüchner, K.; Karsch, L.; Nicolai, M.; Oppelt, M.; Pawelke, J.;
  • Poster
    Oncoray Retreat, 07.-08.03.2012, Dresden, Deutschland

Publ.-Id: 17308 - Permalink

First in vivo experiments with laser accelerated electrons
Oppelt, M.; Laschinsky, L.; Beyreuther, E.; Brüchner, K.; Kaluza, M.; Karsch, L.; Krause, M.; Leßmann, E.; Nicolai, M.; Reuter, M.; Säbert, A.; Schnell, M.; Schürer, M.; Pawelke, J.;
  • Poster
    OncoRay Retreat, 07.-08.03.2012, Dresden, Deutschland

Publ.-Id: 17307 - Permalink

Dosimetry for in vivo experiments with laser accelerated electrons
Karsch, L.; Schürer, M.; Woithe, J.; Pawelke, J.;
  • Poster
    OncoRay Retreat, 07.-08.03.2012, Dresden, Deutschland

Publ.-Id: 17306 - Permalink

Establishment of a tumor model on the ear of mice
Brüchner, K.; Oppelt, M.; Pfitzmann, D.; Krause, M.; Pawelke, J.; Baumann, M.;
  • Poster
    OncoRay Retreat, 07.-08.03.2012, Dresden, Deutschland

Publ.-Id: 17305 - Permalink

First Approximation Concept Design for Achromatic Particle Beamline for Laser Accelerated Protons
Masood, U.; Bussmann, M.; Enghardt, W.; Karsch, L.; Pawelke, J.;
  • Poster
    OncoRay Retreat, 07.-08.03.2012, Dresden, Deutschland

Publ.-Id: 17304 - Permalink

Radiobiological consequences of ultra-short electron pulses
Beyreuther, E.; Karsch, L.; Kroll, F.; Laschinsky, L.; Leßmann, E.; Oppelt, M.; Richter, C.; Schürer, M.; Woithe, J.; Pawelke, J.;
  • Poster
    OncoRay Retreat, 07.-08.03.2012, Dresden, Deutschland

Publ.-Id: 17303 - Permalink

Towards the medical application of laser driven particle beams: In vitro dose response studies as the first translational step
Beyreuther, E.; Baumann, M.; Burris-Mog, T.; Enghardt, W.; Kaluza, M.; Karsch, L.; Kraft, S.; Laschinsky, L.; Leßmann, E.; Metzkes, J.; Nicolai, M.; Oppelt, M.; Richter, C.; Schlenvoigt, H.-P.; Schramm, U.; Schürer, M.; Zeil, K.; Pawelke, J.;
  • Poster
    2012 Conference of the Association of Radiation Research, 25.-27.06.2012, London, Great Britain

Publ.-Id: 17302 - Permalink

Laserbeschleunigte Ionen für die Strahlentherapie
Pawelke, J.;
  • Invited lecture (Conferences)
    18. Jahreskongress der Deutschen Gesellschaft für Radioonkologie, 07.-10.06.2012, Wiesbaden, Deutschland

Publ.-Id: 17301 - Permalink

Eigenschaften eines schnellen, szintillatorbasierten 3D-Dosimeters
Karsch, L.; Kroll, F.; Pawelke, J.;
  • Abstract in refereed journal
    Strahlentherapie und Onkologie 188(2012)Suppl. 1, 13
  • Lecture (Conference)
    18. Jahreskongress der Deutschen Gesellschaft für Radioonkologie, 07.-10.06.2012, Wiesbaden, Deutschland

Publ.-Id: 17300 - Permalink

Towards laser driven proton therapy: results of the first translational step
Laschinsky, L.; Baumann, M.; Beyreuther, E.; Burris-Mog, T.; Cowan, T.; Enghardt, W.; Kaluza, M.; Karsch, L.; Kraft, S.; Leßmann, E.; Metzkes, J.; Nicolai, M.; Oppelt, M.; Richter, C.; Schlenvoigt, H.-P.; Schramm, U.; Schürer, M.; Zeil, K.; Pawelke, J.;
  • Abstract in refereed journal
    Radiotherapy and Oncology 102(2012)Suppl. 1, S76
  • Lecture (Conference)
    International Conference on Translational Research in Radiation Oncology / Physics for Health in Europe, 27.02.-02.03.2012, Geneva, Switzerland

Publ.-Id: 17299 - Permalink

Biologische Wirksamkeit laserbeschleunigter Protonen im Vergleich zu konventionell beschleunigten Protonen
Oppelt, M.; Baumann, M.; Beyreuther, E.; Burris-Mog, T.; Dammene, Y.; Enghardt, W.; Karsch, L.; Kraft, S.; Laschinsky, L.; Leßmann, E.; Metzkes, J.; Naumburger, D.; Richter, C.; Schramm, U.; Schürer, M.; Woithe, J.; Zeil, K.; Pawelke, J.;
  • Contribution to proceedings
    20. Symposium Experimentelle Strahlentherapie und Klinische Strahlenbiologie, 10.-12.02.2011, Dresden, Deutschland
    Experimentelle Strahlentherapie und Klinische Strahlenbiologie 20, 73-77
  • Lecture (Conference)
    20. Symposium Experimentelle Strahlentherapie und Klinische Strahlenbiologie, 10.-12.02.2011, Dresden, Deutschland

Publ.-Id: 17298 - Permalink

Influence of pulse length and high pulse dose on saturation correction of ionization chamber
Karsch, L.; Richter, C.; Pawelke, J.;
  • Contribution to proceedings
    International Symposium on Standards, Applications and Quality Assurance in Medical Radiation Dosimetry (IDOS), 09.-12.11.2010, Wien, Austria
    Book of Extended Synopsis International Atomic Energy Agency IAEA-CN-182 (2010), 273-274
  • Poster
    International Symposium on Standards, Applications and Quality Assurance in Medical Radiation Dosimetry (IDOS), 09.-12.11.2010, Wien, Austria

Publ.-Id: 17297 - Permalink

Towards laser-plasma ion accelerators for cancer therapy
Pawelke, J.;
  • Invited lecture (Conferences)
    13th Workshop on Ion Beams in Biology and Medicine (IBIBAM), 26.-29.10.2010, Berkeley/CA, USA

Publ.-Id: 17296 - Permalink

Biologische Wirksamkeit von laserbeschleunigten Elektronen im Vergleich zu konventionell beschleunigten Elektronen
Laschinsky, L.; Beyreuther, E.; Enghardt, W.; Kaluza, M.; Karsch, L.; Leßmann, E.; Naumburger, D.; Nicolai, M.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H.-P.; Baumann, M.;
  • Contribution to proceedings
    19. Symposium Experimentelle Strahlentherapie und Klinische Strahlenbiologie, 04.-06.03.2010, Dresden, Germany
    Experimentelle Strahlentherapie und klinische Strahlenbiologie 19, 109-111
  • Poster
    19. Symposium Experimentelle Strahlentherapie und Klinische Strahlenbiologie, 04.-06.03.2010, Dresden, Deutschland

Publ.-Id: 17295 - Permalink

The project onCOOPtics: High-intensity lasers for radiooncology
Enghardt, W.; Baumann, M.; Cowan, T.; Kaluza, M.; Pawelke, J.; Sauerbrey, R.; Schramm, U.; Tünnermann, A.;
Background: The present technology for proton and ion therapy requires large devices for accelerating and delivering the beams with accordingly high investment costs. Therefore, the potential of several technologies for developing compact and cost effective sources of therapeutic proton or ion beams is intensively studied. One feasible solution may be the interaction of ultra-short, high-intensity laser pulses with matter.

Material and methods: Combining their competences in laser physics and technology as well as in radiation physics and biology the centers ultra optics in Jena and OncoRay in Dresden, respectively, initiated in 2007 the research project onCOOPtics being focused on the long-term goal of developing laser driven particle irradiation devices. The work in Jena is concentrated onto the physics of laser-matter-interaction, the technology of high-power lasers and the development of optimal radiator targets. The research in Dresden comprises the real-time physical characterization of laser driven particle pulses, the investigation of the biological efficiency of this new radiation modality and the development of dedicated therapeutic irradiation equipment. For experiments three high-intensity laser systems are available: JeTi (pulse power: 15 TW, pulse duration: 80 fs) and POLARIS (150 TW, 170 fs) in Jena as well as DRACO (150 TW, 25 fs) in Dresden all equipped with real-time dosimetry and setups for in-vitro cell radiobiology.

Results: The main scientific results of onCOOPtics are (i) the optimization of laser based ion beam generation, in particular the development of novel and highly reliable techniques for direct manipulation of the ion energy spectrum and spatial distribution; (ii) the development of devices for a real-time physical characterization of laser accelerated charged particle pulses; (iii) the first systematic in-vitro studies of the RBE of laser driven electron beams, (iv) the production of proton beams with energies up to 12 MeV; (v) the prediction of an enhancement of proton energies by targets consisting of stacked ultrathin (~100 nm) foils.

Conclusions: If a clinical laser based accelerator for protons or ions will be feasible at all, the development of this technology is expected to require intensive research in the upcoming 10 years. Among other groups worldwide the the partners in the onCOOPtics project have taken the first successful steps on this risky way.
  • Lecture (Conference)
    48th Particle Therapy Cooperative Group (PTCOG) Meeting, 28.09.-03.10.2009, Heidelberg, Germany
  • Contribution to proceedings
    48th Particle Therapy Cooperative Group (PTCOG) Meeting, 28.09.-03.10.2009, Heidelberg, Germany
    Abstract Book (2009) 49 DOI: 10.3205/09ptcog162

Publ.-Id: 17294 - Permalink

Radiobiology with laser accelerated particle pulses
Pawelke, J.;
  • Invited lecture (Conferences)
    440th Heraeus Seminar on Laser Driven Particle and X-ray Sources for Medical Applications, 13.-17.09.2009, Frauenwörth, Germany

Publ.-Id: 17293 - Permalink

Laser-Teilchen Beschleuniger für die Strahlentherapie: Zellexperimente mit Laser beschleunigten Elektronen
Pawelke, J.;
  • Lecture (others)
    Fortbildungsvortrag, 23.03.2009, Dresden, Deutschland

Publ.-Id: 17292 - Permalink

Dosis-Effekt-Kurven für in vitro Zellbestrahlungen mit laserbeschleunigten Elektronen
Laschinsky, L.; Beyreuther, E.; Enghardt, W.; Kaluza, M.; Karsch, L.; Leßmann, E.; Naumburger, D.; Nicolai, M.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H.-P.; Baumann, M.;
  • Lecture (Conference)
    18. Symposium für Experimentelle Strahlentherapie und Klinische Strahlenbiologie, 13.-14.02.2009, Dresden, Germany
  • Contribution to proceedings
    18. Symposium Experimentelle Strahlentherapie und Klinische Strahlenbiologie, 13.-14.02.2009, Dresden, Germany
    Experimentelle Strahlentherapie und klinische Strahlenbiologie, Vol. 18, Dresden, 139

Publ.-Id: 17291 - Permalink

Laser particle accelerators for radiotherapy: cell response to laser-accelerated electron beams
Pawelke, J.;
  • Lecture (Conference)
    2nd Symposium on Laser-Driven Relativistic Plasmas Applied to Science, Industry and Medicine, 19.-23.01.2009, Kizugawa/Kyoto, Japan

Publ.-Id: 17290 - Permalink

Methods and equipment for in vitro cell experiments at laser particle accelerators
Leßmann, E.; Beyreuther, E.; Laschinsky, L.; Naumburger, D.; Pawelke, J.;
  • Poster
    OncoRay Retreat, 14.-15.01.2009, Bautzen, Germany

Publ.-Id: 17289 - Permalink

Biological effectiveness of laser-accelerated electron beams: in vitro cell studies
Laschinsky, L.; Beyreuther, E.; Enghardt, W.; Karsch, L.; Leßmann, E.; Naumburger, D.; Nicolai, M.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H.-P.; Baumann, M.;
  • Poster
    OncoRay Retreat, 14.-15.01.2009, Bautzen, Germany

Publ.-Id: 17288 - Permalink

Dosimetric characterization of a laser-accelerated electron beam for precise cell irradiation experiments.
Karsch, L.; Beyreuther, E.; Enghardt, W.; Laschinsky, L.; Leßmann, E.; Nicolai, M.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H.-P.; Woithe, J.; Baumann, M.;
No abstract.
Dosimetric characterization of a laser-accelerated electron beam for precise cell irradiation experiments
  • Poster
    OncoRay Retreat, 14.-15.01.2009, Bautzen, Germany

Publ.-Id: 17287 - Permalink

Intersubband dynamics in two-photon quantum well infrared photodetectors
Franke, C.; Schneider, H.; Faist, J.; Liu, H. C.;
Two-photon quantum well infrared photodetectors (QWIPs) are interesting nonlinear devices for autocorrelation measurements in the mid-infrared and THz-regime. Here we investigate two-photon QWIPs in the mid-infrared with absorption wavelengths at around six microns, based on the material systems InGaAs/AlGaAs on GaAs and GaInAs/AlInAs on InP. We study the intersubband relaxation dynamics by interferometric autocorrelation. To create the necessary mid infrared sub-picosecond pulses, we use a regenerative amplifier system with subsequent wavelength conversion by optical parametric amplification and difference frequency generation. With this we can create mid-infrared laser pulses shorter than 200 fs tunable from 3 to 10 µm. For the intersubband relaxation time we determined values between 590 and 730 fs.
Keywords: QWIP, Interferometric Autocorrelation
  • Poster
    DPG-Frühjahrstagung 2012, 25.-30.03.2012, Berlin, Deutschland
  • Poster
    ICSNN 2012, 22.-27.07.2012, Dresden, Deutschland

Publ.-Id: 17286 - Permalink

Sensitization of the blue-green electroluminescence by gadolinium coupled to Si nanocluster embedded in a SiO2 matrix
Prucnal, S.; Rebohle, L.; Sun, J. M.; Skorupa, W.; Drozdziel, A.; Pyszniak, K.; Turek, M.; Zuk, J.;
In this work an enhancement of the blue and green electroluminescence (EL) related to silicon inclusions into SiO2 layer by gadolinium co-doping was investigated. The blue (460 nm) and green (550 nm) EL corresponds to the oxygen-deficient-centres (ODC) and Si nanoclusters with average diameter below 1 nm, respectively. After gadolinium co-doping a fourfold increase of the total EL intensity was observed. It was found that the increase of the blue and green EL is due to the energy transfer from Gd3+ ions to the ODC defects and amorphous silicon nanoclusters. Moreover, the gadolinium co-doping increases the concentration of the small silicon nanoclusters.
Keywords: electroluminescence, Gd, Si-nc, MOSLED, energy transfer
  • Poster
  • Open Access LogoMaterials Science - Medziagotyra 19(2013)2, 125-128
    DOI: 10.5755/

Publ.-Id: 17285 - Permalink

Conductivity type and crystal orientation of GaAs nanocrystals in silicon
Prucnal, S.; Voelskow, M.; Mücklich, A.; Liedke, M. O.; Pyszniak, K.; Drozdziel, A.; Turek, M.; Zuk, J.; Skorupa, W.;
Semiconductors quantum dots of the size in the range of the exciton Bohr radius or smaller are very attractive objects, both for research and application, due to their special optical and electrical properties. In this paper we present investigations of microstructural, electrical and optical properties of GaAs quantum dots (QDs) formed in silicon. The GaAs QDs were obtained by means of sequential ion implantation and flash lamp annealing (FLA). It is shown that the crystallographic orientation of nanocrystals (NCs) and their size can be controlled by varying the annealing parameters. Besides the crystallographic orientation the conductivity type of the GaAs NCs can be controlled as well. The influence of the post implantation millisecond-range annealing on the evolution of the nanoparticles size, shape, crystallographic orientation and doping type of GaAs QDs is discussed.
Keywords: GaAs, ion implantation, flash lamp annealing, silicon, quantum dots
  • Poster

Publ.-Id: 17284 - Permalink

Flash lamp processing of III/V nanostructures in silicon
Turek, M.; Prucnal, S.; Voelskow, M.; Mücklich, A.; Liedke, M. O.; Pyszniak, K.; Drozdziel, A.; Zuk, J.; Skorupa, W.;
Conventionally, the integration of III-V semiconductors with silicon is based on heteroepitaxial growth of multi-layered structures on silicon. But up to now the modification of the optoelectronic properties of silicon in the microelectronic industry is based on the ion implantation method and subsequent thermal annealing. An alternative technique to the epitaxial growth of III-V nanostructures is the high fluence ion implantation followed by milliseconds range annealing. Potentially, with this method any kind of compound semiconductors can be formed in any solid substrate. InP and GaAs with a bulk band gap of 1.34 and 1.42 eV at room temperature, respectively, are most suitable for near infrared light emitters, and InAs (0.35 eV) with an extremely high electron mobility (up to 40000 cm2/Vs) seems to be the most suitable candidate for better electronic devices performance. In this paper formation of the InAs, GaAs and InP nanocrystals in silicon are presented. The optoelectronic and microstructural properties of the compound semiconductors nanostructures were investigated by means of -Raman and temperature dependent photoluminescence spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDS). It is show that conductivity type, size and crystallographic orientation of the III-V nanostructures can be fully controlled by varying implantation and annealing parameters. Finally the heterojunction devices consisting of III-V NCs on a silicon finger realized by selective etching of silicon will be presented.
Keywords: III-V quantum dots, ion implantation, flash lamp annealing, silicon
  • Poster

Publ.-Id: 17283 - Permalink

Flash Lamp Processing of III/V compound semiconductors on silicon and SOI wafers for functional photronic devices
Prucnal, S.; Zuk, J.; Pyszniak, K.; Drozdziel, A.; Facsko, S.; Mücklich, A.; Zhou, S. Q.; Ou, X.; Liedke, M. O.; Liedke, B.; Turek, M.; Skorupa, W.;
One of the solutions enabling performance progress, which can overcome the downsizing limit in silicon technology, is the integration of different functional optoelectronic devices within a single chip. Silicon with its indirect band gap has poor optical properties, which is its main drawback. Therefore, a different material has to be used for the on-chip optical interconnections, e.g. a direct band gap III-V compound semiconductor material. Recently we demonstrated a compact, CMOS compatible and fully integrated solution for the integration of III-V semiconductor nanocrystals with silicon technology for optoelectronic applications. They are synthesized in silicon using combined ion beam implantation and millisecond flash lamp annealing (FLA) techniques [NanoLett. 11, 2814 (2011)]. FLA appears to be the most suitable technique for this purpose. The energy budget introduced to the sample during FLA is sufficient to recrystallize silicon amorphized during the ion implantation and to form III-V nanocrystals (NCs) via the liquid phase. In this talk we will present results of the microstructural, optical and electrical properties of III-V quantum dots (InAs, GaAs and InP) formed in silicon or SOI wafers. An evolution of the III-V nanocrystals growth during FLA and the influence of the annealing parameters on the crystallographic orientation, shape and size will be explored. Moreover, the self-organization of the III-V nano-objects on the SOI wafers after flashing will be presented. A unique nano-swelling effect appearing during ion implantation of the SOI wafers combined with milliseconds range liquid phase epitaxy for the self-organization is responsible. Conventional selective etching was used to form the n-III-V/p-Si heterojunction. Current-voltage measurements confirm the heterojunction diode formation between n-type III-V quantum dots and p-type Si substrate. The main advantage of our method is its integration with large-scale silicon technology, which also allows applying it for Si-based photronic devices.
Keywords: III-V QDs, silicon, ion implantation, SOI, flash lamp annealing, heterojunction
  • Invited lecture (Conferences)
    9th International Conference Ion implantation and other applications of ions and electrons, ION 2012, 25.-28.06.2012, Kazimierz Dolny, Poland

Publ.-Id: 17282 - Permalink

Superconducting layers by Ga implantation and short-term annealing in Si
Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Mücklich, A.; Schmidt, B.; Skorupa, W.; Gobsch, G.; Helm, M.;
Superconductivity in elemental group-IV semiconductors is of great interest because of both, the high potential for new microelectronic applications and its underlying physics.
To observe superconductivity at ambient pressure conditions high doping levels are needed. Sufficient doping concentrations of few at.% were achieved first for boron doped diamond [1]. Suprisingly also silicon, the basic material of todays microelectronic indurstry becomes superconducting below 0.6 K when heavily doped with boron [2]. In our previous work we used ion implantation and short-term annealing to fabricate superconducting Ga doped Ge layers with critical temperatures below 1 K [3]. The solid solubility is exceeded by far and therefore the presence of Ga clusters has to be excluded [4].
However the question arises, how superconducting precipitates influence the low- temperature transport properties. We demonstrate the possibility of embedding extrinsic superconducting nanolayers in commercial microelectronic Si wafers. Ga implantation (4x1016cm-2) through a 30 nm SiO2 cover layer is used because Ga itself is a superconducting element. Sturctural investigations by means of RBS/C and TEM reveal the stabilization of a Ga-rich layer at the SiO2/Si interfae after rapid thermal annealing (RTA). At defined RTA temperatures of 600 – 700°C this interface layer becomes superconducting [5,6]. Amorphous Ga has a critical temperature of 7 K which is comparable to the value of our Ga-rich interface layers. High critical magnetic fields up to 14 T and critical current densities as high as 50 kA/cm2 make the Si:Ga layers interesting for applications.
These results in combination with investigations on similar prepared Ga-rich layers at SiO2/Ge interfaces imply that superconductivity driven by Ga clusters occurs at temperatures of 6 – 7K [7]. If in Ge the onset of superconductivity is below 1 K, it can clearly be attributed to a doping effect.

Financial support by DFG (HE 2604/7-1) is gratefully acknowledged.
[1] E. A. Ekimov et al., Nature 2004;428:542.
[2] E. Bustarret et al., Nature 2006;444:465.
[3] T. Herrmannsdörfer et al., Phys, Rev. Lett. 2009;102:217003.
[4] V. Heera et al., J. Appl. Phys. 2010;107:053508.
[5] R. Skrotzki et al., Appl. Phys. Lett. 2010;97:192505.
[6] J. Fiedler et al., Phys. Rev. B 2011;83:214504.
[7] J. Fiedler et al., Phys. Rev. B 2012;85:134530.
  • Lecture (Conference)
    IX-th International Conference ION IMPLANTATION AND OTHER APPLICATIONS OF IONS AND ELECTRONS - ION 2012 (Ausgezeichnet mit dem 1. Preis für den besten Vortrag im "Young Scientist Contest".), 25.-28.06.2012, Kazimierz Dolny, Polen

Publ.-Id: 17281 - Permalink

Plasma Immersion Ion Implantation for the doping and texturization of silicon based solar cells
Prucnal, S.; Abendroth, B.; Krockert, K.; König, K.; Kolitsch, A.; Steinert, M.; Möller, H. J.; Skorupa, W.;
Cost reduction is the overall goal in the further development of solar cell technologies. In case of low quality mc-Si containing a relatively high concentration of metal impurities a low temperature process is desirable for solar cell fabrication. In order to avoid diffusion of metal impurities into the space charge region of the p-n junction the temperature of the mc-Si substrate should not exceed 400 oC. Although ion implantation doping got very recently distinct consideration for doping of monocrystalline solar material, efficient doping of multicrystalline solar material remains the main challenge to reduce costs. The influence of different annealing and implantation techniques on the optical and electrical properties of mc-Si solar cells was investigated. Flash Lamp Annealing in the ms-range combined with plasma immersion ion implantation (PIII) is demonstrated here as a very promising techniques for the emitter formation at an overally low thermal budget.
The flat silicon surface has a natural reflectivity in the range of 40 % with a strong spectral dependence. The minimization of the reflection loss is very important for high efficiency solar cells fabrication. In order to reduce the surface reflectivity wet chemical etching is the most widely used method in photovoltaic fabrication. Here we present a novel environment friendly method for silicon texturisation. As the reactive gases the mixture of SF6 and O2 with the ratio of 3:2 was used. After 10 min etching the black needle-like surface was obtained. The black silicon fabricated by PIII etching shows the average reflectance below 2% measured over the range from 200 nm to 1100 nm. Presented technology shows great promise to replace the conventional POCl3 –doping and wet chemical etching texturization for efficient silicon based solar cells fabrication.
Keywords: mc-Si, black silicon, flash lamp annealing, PIII, solar cells
  • Poster
    9th International Conference Ion implantation and other applications of ions and electrons, ION 2012, 25.-28.06.2012, Kazimierz Dolny, Poland

Publ.-Id: 17280 - Permalink

III-V compound semiconductors integrated with silicon for functional photronic devices
Prucnal, S.; Facsko, S.; Mücklich, A.; Zhou, S. Q.; Ou, X.; Liedke, M. O.; Turek, M.; Zuk, J.; Skorupa, W.;
The further downsizing of CMOS devices below 16 nm will need to solve some of the practical limits caused by one of the integration issues, such as chip performance, cost of development and production, power dissipation, reliability, etc. One solution for such a performance progress is the integration of different functional optoelectronic elements within one chip.
Recently we demonstrated a compact, CMOS compatible and fully integrated solution for the integration of III-V semiconductor nanocrystals with silicon technology for optoelectronic applications. They are synthesized in silicon using combined ion beam implantation and millisecond flash lamp annealing (FLA) techniques [NanoLett. 11, 2814 (2011)]. FLA appears to be the most suitable technique for this purpose. The energy budget introduced to the sample during FLA is sufficient to recrystallize silicon amorphized during the ion implantation and to form III-V nanocrystals (NCs) via the liquid phase. In this talk we will present results of the microstructural, optical and electrical properties of III-V quantum dots (InAs, GaAs and InP) formed in silicon. Conventional selective etching was used to form the n-III-V/p-Si heterojunction. Current-voltage measurements confirm the heterojunction diode formation between n-type III-V quantum dots and p-type Si. The main advantage of our method is its integration with large-scale silicon technology, which also allows applying it for Si-based photronic devices.
Keywords: III-V semiconductors, silicon, ion implantation, flash lamp annealing
  • Invited lecture (Conferences)
    E-MRS 2012 SPRING MEETING, 14.-18.05.2012, Strasbourg, France

Publ.-Id: 17279 - Permalink

Improvement of CIGS layer quality by Flash Lamp Annealing
Prucnal, S.; Jiao, F.; Zhao, K.; Skorupa, W.; Helm, M.; Zhou, S.;
Copper Indium Gallium diselenide (CIGS) become more significant for solar cell applications as an alternative to silicon. The quality of the layer has a critical impact on the final efficiency of the solar cell. An influence of the post-deposition millisecond range flash lamp annealing (FLA) on the optical and microstructural properties of the CIGS films was investigated. Based on the Raman and photoluminescence spectroscopy, it is shown that FLA reduces the defect concentration and leads to an increase of the photoluminescence intensity by a factor of six compared to the not annealed sample. Moreover, after FLA the degradation of the photoluminescence is significantly suppressed.
Keywords: CIGS, flash lamp annealing, photoluminescence, solar cells
  • Poster
    E-MRS 2012 SPRING MEETING, 14.-18.05.2012, Strasbourg, France

Publ.-Id: 17278 - Permalink

Gettereing of metal impurities by flash lamp annealing in dirty-silicon solar cells
Prucnal, S.; Abendroth, B.; Krockert, K.; König, K.; Henke, D.; Kolitsch, A.; Möller, H. J.; Skorupa, W.;
Multicrystalline silicon has attracted considerable attention because of its high stability against light soaking. In case of Solar Grade (SoG) mc-Si the rigorous control of metal impurities is desirable for solar cell fabrication. Although ion implantation doping got very recently distinct consideration for doping of monocrystalline solar material, efficient doping of multicrystalline solar material remains the main challenge to reduce costs. To extend the application of the ion implantation technique to SoG mc-Si the diffusion of metal impurities during electrical activation of phosphorous and recrystallization of silicon has to be suppressed. Here an advanced annealing technique will be presented and explored, which allows the electrical activation of implanted elements by short time light pulse annealing. Flash Lamp Annealing in the ms-range is demonstrated here as a very promising technique for the emitter formation at an overally low thermal budget. It could be presented that FLA at 1000oC for 3 ms even without preheating is sufficient to recrystallize implanted silicon. The sheet resistance (SR) of FLA samples shows values of about 50 Ohm/sq. Especially, the minority carrier diffusion length for the FLA samples is in the range of 80 um without surface passivation. This is up to one order of magnitude higher than that observed from RTA or FA samples. This technology shows great promise to replace the conventional POCl3 –doping.
Keywords: solar cells, mc-Si, Flash Lamp Annealing, ion implantation
  • Poster
    E-MRS 2012 SPRING MEETING, 14.-18.05.2012, Strasbourg, France

Publ.-Id: 17277 - Permalink

Superconducting layers by gallium implantation and short-term annealing in semiconductors
Fiedler, J.; Heera, V.; Voelskow, M.; Mücklich, A.; Reuther, H.; Skorupa, W.; Gobsch, G.; Helm, M.;
Superconducting layers in silicon and germanium are fabricated via gallium implantation through a thin SiO2 cover layer and subsequent rapid thermal annealing. Gallium accumulation at the SiO2/Si and SiO2/Ge interfaces is observed but no pure gallium phases were found. In both cases superconducting transition occurs around 6 – 7 K which can be attributed to the metallic conduct-ing, gallium rich interface layer. However, the superconducting as well as the normal-state transport properties in gallium overdoped silicon or germanium are different.

Publ.-Id: 17276 - Permalink

Free radical kinetics in a plasma immersion ion implanted polystyrene: Theory and experiment
Kosobrodova, E. A.; Kondyurin, A. V.; Fisher, K.; Moeller, W.; Mckenzie, D. R.; Bilek, M.;
The kinetics of free radicals in polystyrene (PS) treated by plasma immersion ion implantation (PIII) in nitrogen plasma are investigated by means of electron paramagnetic resonance (EPR). EPR spectra are recorded for PS samples with various PIII treatment times ranging from 40 to 1600 s (corresponding to ion fluences of 5 x 10(14)-2 x 10(16) ions/cm(2)) after storage times ranging from 45 min to 3 weeks (room temperature). An unexpected, non-linear behaviour at short treatment times is observed. As treatment time increased, the EPR signal first remains constant then shows a sharp increase and a subsequent saturation at long treatment times. An analytical model for the processes of formation and decay of free radicals in PIII treated polymers is proposed. The model describes the kinetics of short-lived and long-lived radicals using a system of linear differential equations. The model is in good agreement with experimental data.
Keywords: Ion implantation; Polystyrene; Radical kinetics

Publ.-Id: 17275 - Permalink

Enhanced Subthreshold e+e- Production in Short Laser Pulses
Titov, A. I.; Takabe, H.; Kämpfer, B.; Hosaka, A.;
The emission of e+e- pairs off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g., laser) wave field is analyzed. A significant increase of the total cross section of pair production in the subthreshold region is found for decreasing laser pulse duration even in the case of moderate laser pulse intensities.

Publ.-Id: 17274 - Permalink

Experimental realization of dynamo action: present status and prospects
Giesecke, A.; Stefani, F.; Gundrum, T.; Gerbeth, G.; Nore, C.; Leorat, J.;
Cosmic magnetic fields are an ubiquitous phenomenon arising in and around many astrophysical objects like planets, stars, or galaxies. There is a common consensus that these fields are generated by (mostly) turbulent flows of conducting liquids or plasmas. Whereas dynamo action in the astrophysical context seems to be quite simple, essentially because of the large scales of the involved flows, the experimental realization of dynamo action on typical laboratory scales is a demanding task. So far only three facilities have been able to demonstrate fluid flow driven self-generation of magnetic fields. The first dynamos in Riga and in Karlsruhe were characterized by non-axisymmetric geometries of the eigenfield which can be well explained utilizing a laminar flow structure or a mean-field model, respectively. More dynamical effects like bursts, oscillations or sudden field reversals have been observed in the von-Karman-Sodium (VKS) dynamo experiment conducted at Cadarache in France. In that experiment a flow of liquid sodium is driven by two opposing impellers located close to the lids of a cylindrical container. However, dynamo action is obtained only when at least one of the flow driving impellers is made of soft iron with a relative permeability around ~65. In contrast to the previous experiments the observed magnetic field geometry is dominated by an axisymmetric mode which is in contradiction with the expectations from simulations as well as with the restrictions from Cowling's anti-dynamo theorem. Our kinematic simulations of an axisymmetric model of the Cadarache dynamo show a close linkage between the exclusive occurrence of dynamo action in the presence of soft iron impellers and the axisymmetry of the magnetic field. We observe two distinct classes of axisymmetric eigenmodes, a purely toroidal mode that is amplified by paramagnetic pumping at the fluid-impeller interface, and a mixed mode consisting of a poloidal and a toroidal contribution that is rather insensitive to the impeller permeability. In the limit of large permeability, the purely toroidal mode is close to the onset of dynamo action with a slightly negative growth-rate that is rather independent of the flow field. However, since in our axisymmetric configuration the purely toroidal mode is decoupled from any poloidal field component no dynamo action can be expected from this mode alone. Thus, a satisfying explanation of the observed axisymmetric dynamo mode requires mean field effects like the alpha-effect. Since the flow is considerably turbulent such effects are undoubtedly operative, however, so far their properties (e.g. spatial distribution or amplitude) are only speculative. Further progress in the experimental examination of dynamo action is expected from the planned liquid sodium facility DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies). Within this framework, a homogeneous dynamo, driven exclusively by precession, will represent the most ambitious compound. We present recent results of preparatory water experiements and design studies, and delineate the scientific prospects for the final set-up.
Keywords: dynamo
  • Lecture (Conference)
    IAU 18 General Assembly, 20.-31.08.2012, Beijing, China
  • Contribution to proceedings
    IAU 18 General Assembly, 19.-31.08.2012, Beijing, China
    Proceedings of the International Astronomical Union Volume 8 - Symposium S294 (Solar and Astrophysical Dynamos and Magnetic Activity) Experimental realization of dynamo action: present status and prospects: Cambridge University Press, 411-416
    DOI: 10.1017/S1743921313002846

Publ.-Id: 17273 - Permalink

The ELBE 1.6-mA-upgrade and status of the new SRF gun
Teichert, J.; Arnold, A.; Büttig, H.; Lehnert, U.; Michel, P.; Murcek, P.; Staats, G.; Xiang, R.; Kamps, T.; Rudolph, J.; Will, I.; Kneisel, P.;
Kein Abstract vorhanden.
Keywords: superconducting radio-frequency, electron accelerator, solid state amplifier, electron source
  • Lecture (Conference)
    PITZ Collaboration Meeting, 12.-13.06.2012, Zeuthen, Germany

Publ.-Id: 17272 - Permalink

Unwanted beam observations at ELBE
Teichert, J.; Arnold, A.; Michel, P.; Murcek, P.; Xiang, R.; Barday, R.; Kamps, T.; Schubert, S.;
Unwanted beam can cause beam losses and may produce acute or chronic damages of the accelerator. Furthermore it can considerably disturb experiments or increase its back-ground. The operation of the superconducting RF photo gun at the ELBE accelerator has delivered the first experimental information on that topic. It was found, that dark current is an important issue, similar to normal conducting RF photo injectors.
Keywords: superconducting radio-frequency, electron source, photo-electron injector, electron accelerator, dark current, beam loss
  • Lecture (Conference)
    FLS 2012– ICFA Beam Dynamic Workshop, 05.-09.03.2012, Newport News, USA

Publ.-Id: 17270 - Permalink

Status and future plans for the SRF gun at ELBE
Teichert, J.; Arnold, A.; Lehnert, U.; Michel, P.; Murcek, P.; Xiang, R.; Kamps, T.; Rudolph, J.; Will, I.; Kneisel, P.;
At the ELBE radiation facility a superconducting RF photo injector has been developed and operated during the last years. The gun has a 3 ½ cell niobium cavity for 1.3 GHz and uses normal-conducting photo cathodes. Since 2010 the electron beam of the gun has been injected into the ELBE linac. In 2011 beam was delivered for the first sophisticated experiment producing x-rays by Compton backscattering of photons of the high-power laser DRACO. The successful operation of the SRF gun confirms the general design with an elliptical cavity, superconducting RF choke filter, and normal-conducting photocathodes as well as the proper design of most of the subsystems like couplers and tuners. At present, the main draw-back is the low acceleration gradient of the cavity. Therefore two new cavities have been designed, built and tested in collaboration with Jlab. This work is in its final stage now, and we expect assembly of the new cavity in an improved cryomodule and its installation at ELBE for 2012.
Keywords: superconducting radio-frequency, electron source, photo injector, niobium cavity, electron accelerator, electron beam, photocathode
  • Lecture (Conference)
    FLS 2012 – ICFA Beam Dynamic Workshop, 05.-09.03.2012, Newport News, USA

Publ.-Id: 17269 - Permalink

Research activities of photocathodes for HZDR SRF gun
Xiang, R.; Arnold, A.; Freitag, M.; Michel, P.; Murcek, P.; Teichert, J.;
Since 2005 the photocathode laboratory has been in operation at HZDR. The main goal is to prepare Cs2Te photocathodes for the SRF gun. A vacuum transport system with UHV is used to move the cathodes from preparation lab to accelerator hall. Up to now 34 Cs2Te photocathodes have been deposited and eight of them have been used in the SRF gun. Quantum efficiency (QE) of 1% and life time of months can be maintained during the gun operation. At the same time activities are directed towards new photocathode materials with high Q.E. for high current electron sources. Cs3Sb and GaN(Cs) photocathodes have been tested as new candidates, and the design of a preparation system for GaAs(Cs, O) is ongoing
Keywords: SRF-gun, Photocathode, Quantum efficiency
  • Open Access LogoContribution to proceedings
    International Particle Accelerator Conference 2012 (IPAC2012), 20.-25.05.2012, New Orleans, USA
    Proceedings of IPAC2012, 978-3-95450-115-1, 1524
  • Poster
    International Particle Accelerator Conference 2012 (IPAC2012), 20.-25.05.2012, New Orleans, USA

Publ.-Id: 17268 - Permalink

Coupling Schemes and Measurements for Multiple Eigenmode Application in Superconducting RF Guns
Arnold, A.; Murcek, P.; Teichert, J.; Xiang, R.;
Superconducting electron sources are a promising candidate to meet the challenges of future electron accelerator, such as high average beam current and high peak brilliance at the same time. Compared to their normal conducting rf equivalent and due to the Meissner-Ochsenfeld effect, the solenoid for emittance compensation has to be placed far in front of the cathode. To solve this problem the use of transverse electric (TE) modes in parallel to the accelerating mode was proposed*. This contribution presents two suitable coupling schemes and first rf measurements at the warm and cold HZDR SRF gun cavity.
* V. Volkov, D. Janssen, Phys. Rev. ST Accel. Beams 11, 061302 (2008)
Keywords: TE mode, emittance compensation, SRF gun, coupling scheme
  • Poster
    International Particle Accelerator Conference IPAC12, 20.-25.05.2012, New Orleans, LA, USA

Publ.-Id: 17267 - Permalink

Monopol HOM Analysis for the 3.5 Cell SRF Gun Cavity
Arnold, A.; Murcek, P.; Teichert, J.; Xiang, R.;
Superconducting radio frequency photoinjectors (SRF gun) seems to be a promising candidate to achieve the required brightness and the high average current for future light sources. In contrast to normal conducting DC and RF guns, higher order modes (HOM) and their influence on beam quality are of particular interest. For this reason, a method is presented that considers the accelerated motion of nonrelativistic electrons to calculate the longitudinal coupling impedances. The results are compared with first beam-based measurements and used to determine the required HOM damping. Additionally, a selective detuning of the eigenmode spectra is discussed.
Keywords: higher order mode, HOM, SRF gun
  • Invited lecture (Conferences)
    EuCARD SRF Annual Review, 29.-30.03.2012, Berlin, Deutschland

Publ.-Id: 17266 - Permalink

RF power upgrade at the superconducting 1.3 GHz CW LINAC “ELBE” with solid state amplifiers
Büttig, H.; Arnold, A.; Büchner, A.; Justus, M.; Kuntzsch, M.; Lehnert, U.; Michel, P.; Schurig, R.; Staats, G.; Teichert, J.;
The RF power for the superconducting CW LINAC has been doubled from 10 to 20 kW per cavity. In January 2012 the four 10 kW klystrons used to drive the four superconducting cavities of the LINAC have been replaced by a pair of 10 kW solid state power amplifiers. ELBE is now worldwide the first 1.3 GHz CW LINAC equipped with Solid State RF Power Amplifiers. This technical note details on this project.
Keywords: Solid state RF power amplifiers, Superconducting CW RF, 1.3 GHz Solid state RF-power amplifiers, ELBE-RF, Superconducting LINAC RF.

Publ.-Id: 17265 - Permalink

Core-core interaction in spin-torque double-vortex oscillators
Sluka, V.; Kákay, A.; Deac, A. M.; Bürgler, D. E.; Hertel, R.; Schneider, C. M.;
Owing to their ability of narrow bandwidth operation, magnetic vortex based spin-torque nano-oscillators (STNOs) are promising candidates for future on-chip microwave sources. Typically, these oscillators are nanopillars containing two stacked ferromagnetic disks, one in a vortex state, the other with quasi-homogeneous magnetization. Devices of that kind have been investigated extensively over the past years [1-3]. Only recently, a different type of vortex oscillators has attracted much interest. In these “double vortex oscillators”, both ferromagnetic disks are in a vortex state. Depending on the relative vorticity, the local alignment of the magnetic layers can be either parallel or antiparallel. Thus, the system constitutes an analogue to single domain spin valves, while also retaining the good oscillator properties of magnetic vortices, which makes this type of STNO particularly interesting for studying fundamental aspects of spin-transfer torque. However, only few studies of double-vortex oscillators exist to-date [5,6].
Here we present our results on Fe/Ag/Fe double vortex oscillators. Combining experimental and numerical methods, we address the yet open question of how the magnetostatic interaction of the vortices – their separation is typically in the order of a few nanometers –affects the spin-torque induced dynamics. Our samples are all-metallic nanopillars 150 nm in diameter, containing a Fe(30)/Ag(6)/Fe(15) pseudo spin valve (layer thicknesses given in nm). By applying d.c. currents perpendicular to the plane of the layers, we excite magnetization dynamics corresponding to gyrotropic vortex motion. The sample geometry stabilizes the magnetic vortex state in each Fe disk even if the strong Oersted fields and the vortex magnetization have opposite sense of rotations. This high degree of stability provides a yet unprecedented opportunity to investigate a more exotic class of double vortex states – those with opposed vorticities – under the high current densities necessary to enter the spin-torque precession regime.
Figure 1 displays a typical combined magnetoresistance and high frequency measurement. The magnetic field, which has an angle of 30° with the sample plane, is swept from positive values to negative saturation. For each field value, in addition to the d.c. voltage, a spectrum is also recorded. In a field interval about 100 mT wide, the sample is in a double vortex state where the vorticities of the top and bottom vortices are opposed to each other. According to the top panel of Fig. 1, this state exhibits magnetization dynamics. We vary our state preparation procedure in order to create the various vorticity and core polarity combinations. The obtained states are characterized with respect to their d.c. and high frequency behavior using the above described measuring technique where in all measurements, the electron flow is directed from the bottom to the top Fe disk. We obtain a fine structure in the modes, where the frequency splittings are in the order of hundreds of MHz.
The micromagnetic simulations are performed with our code TetraMag [7]. The simulations include the Oersted field corresponding to a sample current of 10 mA in magnitude. For a given vorticity and core polarity combination, we find the eigenmodes and frequencies of the system. Comparing the experimentally found set of frequencies to the simulated cases, we find that each measured peak matches the lowest mode of a corresponding computed spectrum in frequency. This suggests that the observed fine structure is caused by two effects. First, the Oersted field lifts the degeneracy of states with the top vortex vorticity parallel or antiparallel to the field’s sense of rotation. On top of this Zeemann-type frequency alteration, the resulting modes are split further depending on the relative alignment of the top and bottom vortex cores. This suggests that the second splitting is due to the magnetostatic interaction of the vortex cores. This remarkable result sheds light on the subtle interplay of forces governing the dynamics of double vortex oscillators, while on the other hand it allows measuring changes in relative core alignment.
[1] V. S. Pribiag et al., Nature Phys. 3, 498 (2007).
[2] A. Dussaux et al., Nat. Commun. 1:8 DOI:10.1038 / ncomms1006 (2010).
[3] X. W. Yu et al., Phys. Rev. Lett. 106, 167202 (2011).
[5] A. V. Khvalkovskiy et al., Appl. Phys. Lett. 96, 212507 (2010).
[6] N. Locatelli et al., Appl. Phys. Lett. 98, 062501 (2011).
[7] A. Kákay, E. Westphal, R. Hertel, IEEE Trans. Magn. 46, 2303 (2010).
Keywords: magnetic vortex, magnetization dynamics, spin-transfer torque, spin-torque nano-oscillators
  • Lecture (Conference)
    Intermag 2012, 07.05.2012, Vancouver, Canada

Publ.-Id: 17264 - Permalink

Quenched Slonczewski-windmill in spin-torque vortex-oscillators
Sluka, V.; Kákay, A.; Deac, A. M.; Bürgler, D. E.; Hertel, R.; Schneider, C. M.;
Spin-torque nano-oscillators (STNOs) typically consist of two single domain ferromagnetic layers separated by a metallic spacer or a tunnel barrier, one with its magnetization fixed (polarizing layer), the other one susceptible to torques (free layer). An electric current traversing the system perpendicular to the layers becomes spin-polarized and exerts torques on the magnetic moments [1-3], thereby inducing switching or steady-state dynamics. The pinning of the polarizing layer can be achieved by exchange coupling to an antiferromagnet [4] or by extending its thickness and lateral dimension [5]. In the absence of pinning, both ferromagnetic layers can be excited. For increasingly symmetric STNOs, this can lead to a dynamic equilibrium state called the Slonczewski-windmill [1,6], with the magnetic moments of both layers rotating in the same direction with a constant relative angle, resulting in a vanishing magnetoresistance (MR) time-dependence.
Here we investigate STNOs containing two stacked magnetic vortices, i.e., a system consisting of two ferromagnetic disks, each in a vortex state and separated by a metallic, nonmagnetic spacer. Employing analytical and numerical methods, we study the coupled spin torque-driven motion of the magnetizations in the two disks, which are not pinned by any of the above mentioned mechanisms. The theoretical findings are supported by our experimental data obtained from double-vortex Fe/Ag/Fe STNOs.
The motion of the magnetic vortex in each of the disks is governed by the Thiele equation [7] with an additional force expression arising from the transfer of spin angular momentum from the polarised current to the vortex. Assuming that in the double vortex system, each vortex is free to move while at the same time it serves as a polarizing layer for the other, we solve the system of Thiele equations coupled by the spin-polarized current. We use parabolic approximations to the magnetostatic potentials for each vortex, which are chosen to represent our Fe/Ag/Fe nanopillars with ferromagnetic layers with a thickness ratio of 5/3; the uncoupled top and bottom vortices’ eigenfrequencies are set to 1.0 and 1.7 GHz, respectively.
The solutions are obtained numerically using Maple's rkf45 implementation. The results can be summarized as follows: While the spin torque induces large orbit vortex gyration in one of the layers, the vortex motion in the other disk is strongly reduced, resulting in a quenching of the Slonczewski-windmill mode. Which of the two layers contributes dominantly to the magnetization dynamics is determined by the direction of the applied current. This effect results from an adaption of the motion of the constricted vortex according to the dominant one. The former acquires a stable phase to the dominant vortex, while the latter determines the frequency and sense of gyration of the whole system: If its core polarity is positive (negative), the system gyrates in the counterclockwise (clockwise) direction. If the dominating vortex is in the top disk, the gyration frequency is 1.0 GHz while for large orbit gyration in the bottom disk, we obtain 1.7 GHz. Figure 1 displays the relations between the phase, frequency and gyration radius of the bottom vortex in the case, where the top vortex is dominant. For an experimental confirmation of the frequency and phase adaption mechanism and the related quenching of the windmill modes, we study the current-induced magnetization dynamics of a Fe/Ag/Fe nanopillar with a Fe layer thickness ratio of 5/3. We apply current densities of 6.1x107 A/cm2 and investigate the resulting double vortex dynamics depending on the current polarity. At low external field, the ratio between the obtained frequencies is close to the ratio of the disk aspect ratios, which strongly supports our numerical findings.

[1] J. C. Slonczewski, J. Magn. Magn. Mater. 159, L1 (1996).
[2] L. Berger, Phys. Rev. B 54, 9353 (1996).
[3] J. C. Slonczewski, J. Magn. Magn. Mater. 247, 324 (2002).
[4] I. N. Krivorotov et al., Science 307, 228 (2005).
[5] I. Kiselev et al., Nature 425, 380 (2003).
[6] Y. B. Bazaliy, D. Olaosebikan, and B. A. Jones, J. Nanosci. Nanotechnol. 8, 2891 (2008).
[7] A. A. Thiele, Phys. Rev. Lett. 30, 230 (1973).
Keywords: Spin-transfer torque, spin-torque nano-oscillators, magnetic vortex, magnetization dynamics
  • Poster
    Intermag 2012, 07.-11.05.2012, Vancouver, Canada

Publ.-Id: 17263 - Permalink

Use of cold liquid metal models for investigations of the fluid flow in the continuous casting process
Timmel, K.; Wondrak, T.; Röder, M.; Stefani, F.; Eckert, S.; Gerbeth, G.;
Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications. Water model experiments are of limited value, particularly in the cases of strong temperature gradients, two-phase flows or flows exposed to electromagnetic fields. We present the new experimental facility LIMMCAST for modelling the continuous casting process of steel using the alloy SnBi at temperatures of 200-400°C. The parameters of the facility and the dimensions of the test sections will be given, and the possibilities for flow investigations in tundish, submerged entry nozzle and mould will be discussed. In addition, the smaller set-up mini-LIMMCAST will be presented, which works with the room-temperature liquid alloy GaInSn. The main value of cold metal laboratory experiments consists in the capabilities to obtain quantitative flow measurements with a reasonable spatial and temporal resolution. New ultrasonic and electromagnetic techniques for measuring the velocity in liquid metal flows came up during the last decade allowing for a satisfying characterisation of flow quantities in the considered temperature range up to 400°C. A selection of results from LIMMCAST and mini-LIMMCAST will be presented in this paper covering various phenomena occurring in single-phase and two-phase flows.
Main emphasis of the experimental programme is put on the effect of diverse magnetic fields on the fluid flow in the mould. Although magnetic fields have already been adopted for industrial use since more than 20 years, the impact of electromagnetic brakes or stirrers on complex and highly turbulent flows appears to be very complex and has not been fully understood until now. The flow measurements performed at the liquid metal model experiments deliver a valuable experimental data base being suitable for validation of numerical simulations.
Keywords: continuous casting, liquid metal models, electromagnetic brake, ultrasonic flow measurement, contactless inductive flow tomography
  • Lecture (Conference)
    5th International Congress on the Science and Technology of Steelmaking, 01.-03.10.2012, Dresden, Deutschland
  • Contribution to proceedings
    5th International Congress on the Science and Technology of Steelmaking, 01.-03.10.2012, Dresden, Deutschland
  • Steel Research International 85(2014)8, 1283-1290
    DOI: 10.1002/srin.201300034

Publ.-Id: 17262 - Permalink

Ultrafast electron beam X-ray computed tomography for 2D and 3D two-phase flow imaging
Bieberle, M.; Barthel, F.; Hoppe, D.; Banowski, M.; Wagner, M.; Lucas, D.; Stürzel, T.; Hampel, U.;
Imaging of complex and dynamic processes such as two- or multiphase flows with high structural as well as temporal resolution has always been a challenging task. In recent years, the electron beam X-ray computed tomography technique has been developed towards a powerful imaging tool, which reaches frame rates of 8000 fps in 2D and 1000 fps in 3D. In this paper, the latest developments as well as selected applications of ultrafast electron beam X-ray CT are presented.
Keywords: X-ray; computed tomography; two-phase flow; measurement; electron beam
  • Lecture (Conference)
    2012 IEEE International Conference on Imaging Systems and Techniques, 16.-17.07.2012, Manchester, United Kingdom
  • Contribution to proceedings
    2012 IEEE International Conference on Imaging Systems and Techniques, 16.-17.07.2012, Manchester, United Kingdom
    Proceedings 2012 IEEE International Conference on Imaging Systems and Techniques: IEEE, 978-4577-1774-1, 1569596631

Publ.-Id: 17261 - Permalink

Grundlagen und Anwendungen der kontaktlosen induktiven Strömungstomographie
Stefani, F.; Gerbeth, G.; Gundrum, T.; Wondrak, T.;
The contactless inductive flow tomography (CIFT) aims at the determination of flow structures in metal and semiconductor melts. It relies on the induction of electric currents in moving conductors exposed to magnetic fields. The flow induced deformations of the magnetic fields can be measured in the exteriour of the melt and utilized for the reconstruction of the velocity field. After a presentation of the principles, first applications and possible extensions of the method are discussed.

Publ.-Id: 17260 - Permalink

Combining contactless inductive flow tomography and mutual inductance tomography for two-phase flow measurements at a continuous casting model
Stefani, F.; Eckert, S.; Gerbeth, G.; Klotsche, K.; Timmel, K.; Wondrak, T.; Peyton, A. J.; Terzija, N.; Yin, W.;
The flow structure in the mould of a continuous caster is of key importance for the quality of the final product. The use of most conventional flow measurement techniques is prevented by the high temperature of the liquid steel. For a downscaled physical model of the continuous casting process, we present combined measurements of the flow in the mould by Contactless Inductive Flow Tomography (CIFT), and of the conductivity distribution in the submerged entry nozzle by Mutual Inductance Tomography (MIT). In addition, we summarize an experiment with a magnetic stirrer around the submerged entry nozzle and its effects on the flow in the mould. Some new developments towards a robust implementation of CIFT at a real caster, including the use of pickup coils and gradiometric probes, are also discussed.
  • Lecture (Conference)
    7th International Conference on Electromagnetic Processing of Materials (EPM2012), 22.10.-26.12.2012, Bejing, China
  • Journal of Iron and Steel Research International 19(2012)Suppl. 1-1, 479-482

Publ.-Id: 17259 - Permalink

Temperature impact on the sorption of selenium(VI) onto anatase
Jordan, N.; Müller, K.; Franzen, C.; Brendler, V.;
The impact of temperature (298 K, 313 K and 333 K) on the sorption of selenium(VI) onto anatase was investigated for the first time. At a macroscopic level, batch experiments showed a decrease of selenium(VI) retention with both increasing pH (3.5-7.0) and temperature. The thermodynamic parameters of the sorption reaction, i.e. the enthalpy ΔRH, entropy ΔRS and the Gibbs free energy ΔRG were determined from the temperature dependence sorption data using the van´t Hoff equation. The sorption process was found to be exothermic. Neither significant phase transformation nor a significant increase of anatase solubility could be detected with increasing temperature by XRD and ICP-MS. However, electrophoretic mobility measurements showed that both the zeta potential as well as the isoelectric point (pHIEP) of anatase were shifted to lower values with increasing temperature, decreasing selenium(VI) sorption. At a microscopic level, the sorption mechanism of selenium(VI) onto anatase was elucidated at the three investigated temperatures by means of in situ Attenuated Total Reflection Fourier-Transform Infrared spectroscopy (ATR FT-IR). Results evidenced the formation of outer-sphere surface complexes, with no significant structural changes within the investigated temperature range.
Keywords: selenate, titanium dioxide, anatase, infrared spectroscopy, ATR FT-IR

Publ.-Id: 17258 - Permalink

Superconducting layers in semiconductors – Ready for the quantum interference?
Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Skorupa, W.; Gobsch, G.; Helm, M.;
Superconductivity is a fascinating ground state of matter and has been discovered one century ago. A new debate about the fundamental physical background and technological potential of superconducting group-IV semiconductors occurred, since superconductivity at ambient pressure conditions was shown for boron doped diamond [1] and silicon [2]. These unusual superconductors open the way towards new microelectronic devices and applications.
In our previous work, we used Ga-ion implantation and subsequent short-time annealing for creating highly Ga doped layers in Ge. [3] These layers show an intrinsic superconducting transition at temperatures below 1 K because of the high doping level. [4] In a next step we could show the feasibility to stabilize Ga-rich layers at SiO2/Si [5,6] and SiO2/Ge [7] interfaces by using a 30 nm SiO2 cover layer during implantation and annealing.
The presented structural investigations by means of Rutherford Backscattering Spectrometry (RBS) and cross-sectional Transmission Electron Microscopy (XTEM) reveal the presence of a 10 nm thin, superconducting layer at the interfaces containing Ga-rich precipitates. In both cases the critical temperature increases to 7 K which is comparable to amorphous Ga and therefore enables the detailed investigation of the influence of superconducting precipitates on the superconducting properties of doped semiconductor layers.
However, the previous investigations were done on 1 x 1 cm2 size samples. The possibility of fabricating superconducting microstructures in Si with standard microelectronic lithography will be shown. Theses microstructures still undergo a superconducting transition below 7 K. High critical magnetic fields in the range of 10 T and high critical current densities of 50 kA/cm2 were achieved. For applications in superconducting microelectronics a Josephson-Junction has to be implemented. [8] We plan to use a Focused Ion Beam (FIB) for this task. Details about the sample processing, layer microstructure and processing of superconducting microstructures will be presented.

[1] E. A. Ekimov et al., Nature (London) 428 (2004) 542.
[2] E. Bustarret et al., Nature 444 (2006) 465.
[3] V. Heera et al., J. Appl. Phys. 107 (2010) 053508.
[4] T. Herrmannsdörfer et al., Phys, Rev. Lett. 102 (2009) 217003.
[5] R. Skrotzki et al., Appl. Phys. Lett. 97 (2010) 192505.
[6] J. Fiedler et al., Phys. Rev. B 83 (2011) 214504.
[7] J. Fiedler et al., Phys. Rev. B 85 (2012) 134530.
[8] J. Q. You et al., Nature 474 (2011) 589.
  • Poster
    18th International Conference on Ion Beam Modifications of Materials (IBMM 2012) - Ausgezeichnet mit einem "Best Poster Award", 02.-07.09.2012, Qingdao, China

Publ.-Id: 17257 - Permalink

Superconductivity in Ga-implanted group-IV semiconductors
Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Mücklich, A.; Facsko, S.; Reuther, H.; Perego, M.; Schmidt, B.; Skorupa, W.; Gobsch, G.; Helm, M.;
Beginning in 2004, the interest in superconductivity of elemental group-IV semiconductors has been renewed because Ekimov et al. [1] showed that boron doped diamond could become superconducting at ambient pressure conditions. Besides fundamental physical background of driving a semiconductor into a superconducting state, the high potential for applications in new microelectronic devices is in the main focus.
High doping levels are needed to observe superconductivity at ambient pressure conditions in elemental group-IV semiconductors. Gas immersion laser doping is used to fabricate superconducting boron doped silicon [2]. The possibility to use Ga-ion implantation and short-time annealing for creating superconducting Ga-doped Ge layers was shown in our previous work [3, 4]. These highly doped Ge-layers show an onset of superconductivity below 1 K. All doping techniques mentioned above exceed the equilibrium solid solubility limit by far and the question arises, whether the observed superconductivity is a doping effect or related to dopant clusters [5].
Especially if the doping element itself is a superconductor, like Ga in Ge, it was not clear how superconducting precipitates influence the low-temperature transport properties. To investigate these effects, we stabilized superconducting Ga-rich layers at SiO2/Si interfaces [6, 7]. Again, we have used ion implantation through a 30 nm thick SiO2 cover layer and rapid thermal annealing. The critical temperature of 7 K is comparable to the values obtained for amorphous Ga. Furthermore, high critical magnetic fields of 14 T and critical current densities of 50 kA/cm2 were achieved.
With the results of the investigations discussed above, we could go one step further and fabricate similar Ga-rich layers at SiO2/Ge interfaces. Now it is possible to investigate selectively the influence of superconducting Ga-rich areas on the normal- and superconducting properties of Ga-doped Ge. It will be shown that the critical temperature changes dramatically while the critical magnetic field stays rather constant. The results of detailed microstructural investigations by means of XTEM and time-of-flight SIMS will be correlated with electrical properties. Finally, the presented results indicate that superconductivity with critical temperatures around 1 K can clearly be attributed to a doping effect.

[1] E. A. Ekimov et al., Nature (London) 428 (2004) 542.
[2] E. Bustarret et al., Nature 444 (2006) 465.
[3] T. Herrmannsdörfer et al., Phys, Rev. Lett. 102 (2009) 217003.
[4] V. Heera et al., J. Appl. Phys. 107 (2010) 053508.
[5] N. Dubrovinskaia et al., PNAS 105 (2008) 11619.
[6] R. Skrotzki et al., Appl. Phys. Lett. 97 (2010) 192505.
[7] J. Fiedler et al., Phys. Rev. B 83 (2011) 214504.
  • Lecture (Conference)
    18th International Conference on Ion Beam Modifications of Materials (IBMM 2012), 02.-07.09.2012, Qingdao, China

Publ.-Id: 17256 - Permalink

Nanoteilchen in biologischen Systemen
Bergmann, R.;
kein Abstract verfügbar
  • Lecture (others)
    Akademisches Donnerstagkolloquium der Dresdner Seniorenakademie, 24.05.2012, Dresden, Deutschland

Publ.-Id: 17255 - Permalink

From sponge to dot arrays on (100) Ge by increasing the energy of ion impacts
Böttger, R.; Bischoff, L.; Heinig, K.-H.; Pilz, W.; Schmidt, B.;
Ge surfaces were subjected to normal incidence Bi+ irradiation with ion energies from 10 to 30 keV. The Ge substrate was irradiated with fluences up to 1 x10^17 / cm² and substrate temperatures up to 780 K. Surface modification was investigated using scanning electron microscopy. While at room temperature porous networks are obtained, increase of temperature during irradiation leads to formation of hexagonal dot arrays at the surface, which vanish at very high temperatures. Extensive experimental studies of energy and temperature ranges and limits for dot formation are presented. Formation of dot arrays is governed by the vacancy diffusion mechanism via different energy densities deposited in the cascade volume, as well as by substrate heating. An energy-temperature phase diagram of the obtained surface morphology is composed with respect to varying order of dot-like patterns.
Keywords: Ge, FIB, sponge, ordered dots, self-organization, vacancy, ion beam

Publ.-Id: 17254 - Permalink

Probing Graded Perpendicular Anisotropy with Polarized Neutron Reflectometry
Greene, P.; Gilbert, D.; Kirby, B.; Borchers, J.; Lau, J.; Shull, R.; Chih-Huang, L.; Osten, J.; Fassbender, J.ORC; Davies, J.; Fitzsimmons, M.; Zimanyi, G.; Liu, K.
Magnetic nanostructures with graded anisotropy offer a solution to both thermal stability and writability challenges in advanced magnetic recording media. The interlayer exchange coupling lowers the overall coercivity, facilitating the writing process, while the magnetically hard layer provides pinning for the media and ensures its thermal stability. However, it is challenging to probe and tune the depth-dependent anisotropy gradient, as conventional magnetometry approaches only give convoluted response from the entire layer. In this work, we have investigated magnetization reversal in Co/Pd and Co/Pt films and patterned structures with perpendicular anisotropy using polarized neutron reflectometry (PNR), along with magnetometry and structural characterizations. Perpendicular magnetic anisotropy is varied by changing the growth conditions during synthesis (Co layer thickness, sputtering pressure, or multilayer deposition order), or post-deposition ion irradiation. PNR directly reveals depth-dependent magnetization profiles along the in-plane magnetic hard axis, which reflect the magnetic anisotropy gradient as different amounts of magnetic moment come into alignment with the in-plane field. Effects of lateral patterning have also been investigated in patterned nanostructures (networks and nanodots). An increase in coercivity and a modified switching field distribution are observed in patterned structures. This is due to the reduced lateral dimensions which limit the domain nucleation and propagation commonly found in unpatterned films. These results demonstrate attractive features of nanostructures with graded anisotropy towards future magnetic recording applications.
Work supported by the US NSF (DMR-1008791 & ECCS-0925626).
  • Invited lecture (Conferences)
    ACNS American Conference on Neutron Scattering, 24.-28.06.2012, Washington, DC, USA

Publ.-Id: 17253 - Permalink

Tuning Perpendicular Anisotropy Gradients in Co/Pd Multilayers by Ar Ion Irradiation
Greene, P.; Osten, J.; Fassbender, J.ORC; Endo, T.; Iwata, N.; Liu, K.
Magnetic nanostructures with graded anisotropy offer a solution to both thermal stability and writability challenges in advanced magnetic recording media. The interlayer exchange coupling lowers the overall coercivity, facilitating the writing process, while the magnetically hard layer provides pinning for the media and ensures its thermal stability. Typically, the anisotropy gradient has been achieved by changing the sample growth conditions [3-5]. In this work we report an alternative approach of using Ar ion irradiation to create an anisotropy gradient in Co/Pd multilayer films.
  • Lecture (Conference)
    INTERMAG 2012, IEEE International Magnetics Conference, 07.-11.05.2012, Vancover, Kanada

Publ.-Id: 17252 - Permalink

Microscopic magnetic structuring of a spin-wave waveguide by ion implantation in a Ni81Fe19 layer
Obry, B.; Meyer, T.; Pirro, P.; Brächer, T.; Lägel, B.; Neb, R.; Osten, J.; Strache, T.; Fassbender, J.ORC; Hillebrands, B.
Ion implantation of ferromagnetic films has proven to be a promising tool for the fabrication of fully planar samples with a microscopic magnetic substructure. A waveguide-like propagation of spin waves in a Ni81Fe19 film which was locally patterned by ion implantation could be observed. The investigations have been performed using Brillouin light scattering microscopy on samples patterned with varying ion fluences. Further investigations on the coupling behavior of two parallel stripes in this fully planar structures have been performed. The presented fabrication technique of spin-wave waveguides provides much lower stray fields and better heat conduction. Especially the latter is a matter of interest when the objects are exposed to intense microwave fields (excitation of spin waves) or investigated by laser spectroscopy like Brillouin light scattering. Financial support by the DFG (GRK 792) is gratefully acknowledged.
  • Poster
    Frühjahrstagung der Sektion Kondensierte Materie (SKM), 25.-30.03.2012, Berlin, Deutschland
  • Poster
    INTERMAG 2012, 07.-11.05.2012, Vancover, Kanada
  • Applied Physics Letters 102(2013)2, 022409
    DOI: 10.1063/1.4775759

Publ.-Id: 17251 - Permalink

Shell model for REOx nanoclusters in amorphous SiO2: charge trapping and electroluminescence quenching
Tiagulskyi, S.; Nazarov, A.; Tyagulskii, I.; Lysenko, V.; Rebohle, L.; Lehmann, J.; Skorupa, W.;
In this work charge trapping and electroluminescence (EL) quenching in rare-earth (RE) implanted SiO2 on Si as a function of injected charge into the dielectric were studied. The blocking of the luminescent REOX nanoclusters from the hot exciting electrons by negative charge trapping in a defect region (shell) located in the vicinity of the REOX nanocluster/SiO2 interface is considered as the main mechanism of EL quenching for small size (up to 10 nm) REOX nanoclusters. It is suggested that the increase of the nanoclusters size results in disordering of the SiO2 matrix but in a decrease of local blocking for excitation of the luminescent centers.
Keywords: MOSLEDs, rare earth implanted oxide, electroluminescence, charge trapping, clustering

Publ.-Id: 17250 - Permalink

Thermal Effect on Electroluminescence Quenching in SiO2 with Ge and ReOX Nanoclusters
Tiagulskyi, S. I.; Tyagulskiy, I. P.; Nazarov, А. N.; Nazarova, T. M.; Rymarenko, N. L.; Lysenko, V. S.; Rebohle, L.; Lehmann, J.; Skorupa, W.;
Thermal quenching and thermal dependences of the electrical quenching of electroluminescence in metal-oxide-silicon lightemitting devices implanted by Ge and Tb ions containing Ge and TbOx nanoclusters after annealing are studied. Light thermal quenching of the main green line (541 nm) in the EL spectrum of Tb implanted structures is observed. The strong temperature dependence of the electrical quenching of EL both for Ge and Tb implanted structures is explained by the participation of mobile ions in negative and positive charge generation in the bulk of SiO2 and near the SiO2-Si interface, correspondingly.
Keywords: MOSLEDs, rare earth implanted oxide, electroluminescence, charge trapping, clustering

Publ.-Id: 17249 - Permalink

Nd-implanted MOS light emitting devices for smart biosensor applications
Rebohle, L.; Wutzler, R.; Germer, S.; Lehmann, J.; Helm, M.; Skorupa, W.;
Electrically driven, Si-based light emitters are of great interest for integrated photonic applications, especially for smart biosensors. Among the possible candidates Nd-implanted MOS devices are of special interest because of the emission wavelength of 900 nm of Nd3+ which have the potential to integrate a complete SPR (surface plasmon resonance) measurement in one chip.
In this study we explore the influence of the Nd-concentration and the annealing parameters on the electrical and optoelectronic properties. The focus is on the electroluminescence and the electrical properties of the devices which will be compared to those of Er-implanted devices.
Keywords: Electroluminescence, Erbium, Neodymium, Rare Earth, Optoelectronic Device, Si-based light emission
  • Poster
    E-MRS 2012 Spring Meeting, 14.-18.05.2012, Strasbourg, France

Publ.-Id: 17248 - Permalink

Er- and Nd-implanted MOS light emitting devices and their use for integrated photonic applications
Rebohle, L.; Wutzler, R.; Germer, S.; Lehmann, J.; Helm, M.; Skorupa, W.;
In the past, the suitability of Er for Si-based light emission was already investigated in detail. However, much less attention has been paid to Nd with its main electroluminescence (EL) line around 900 nm. In this study we compare the electrical and EL properties of Er- and Nd-implanted metal-oxide-semiconductor (MOS) structures where the dielectric stack is composed of the implanted SiO2 layer and a SiON buffer layer. Regarding the EL, the EL spectrum, the EL decay time and the EL efficiency were measured. The electrical characterization comprises current-voltage and capacitance-voltage measurements. Although the EL efficiency of Nd-implanted devices is by a factor of 5 to 10 lower than that of Er-based, the emission wavelength of Nd has some advantages compared to that of Er. Finally, based on these results the suitability of these two types of light emitters for integrated photonic devices is discussed.
Keywords: Electroluminescence, Erbium, Neodymium, Rare Earth, Optoelectronic Device, Si-based light emission
  • Lecture (Conference)
    SPIE Photonics Europe, 16.-19.04.2012, Brussel, Belgium
  • Contribution to proceedings
    SPIE Photonics Europe, 16.-19.04.2012, Brussel, Belgium
    Proceedings of SPIE, 978-0-8194-9123-7, 843116
    DOI: 10.1117/12.921755

Publ.-Id: 17247 - Permalink

Formation of dendritic structures in thin silicon films on amorphous substrates by high intensity flash lamp annealing
Endler, R.; Voelskow, M.; Schumann, T.; Gebel, T.; Liepack, H.; Kolitsch, A.; Skorupa, W.;
Grain enlargement of the poly silicon is a key process to improve the electronic properties of microelectronic and photovoltaic devices. We report on lateral dendritic crystal growth in thin silicon films during liquid phase crystallization (LPC) induced by high intensity flash lamp irradiation (FLA). In a series of experiments first a 140 nm SiO2 film and then amorphous silicon of 100 nm thickness were deposited on 500µm thick (100) Si wafers. After that the top silicon film was ion implanted with carbon, first, with the aim to improve the wetting properties of the underlying silicon dioxide by the liquid silicon film during the LPC process. Secondly, due its different solubility in solid and liquid silicon, carbon is responsible for the formation of a laterally depending melting temperature inducing a lateral dendritic growth process. To prove in particular this influence of carbon on the wetting and crystallization process, the flash lamp irradiated structures were studied using XTEM analysis. The pulse annealing process was carried out using the commercial flash lamp annealing tool FLA-50RD of DTF-Technology. The installed set of standard Xenon flash lamps guarantees irradiation densities up to 150 J/cm2 at a pulse length of 20 ms on preheated substrates. As expected, depending on the carbon implantation conditions and the FLA energy densities, the films show, as a result, up to several hundred micrometers extended grains having the characteristic dendritic shape.
Keywords: Large grain silicon; Silicon layers on SiO2; Flash Lamp Annealing; Pulse melting; Dendritic crystal growth
  • Poster
    E-MRS 2012 SPRING MEETING, 14.-18.05.2012, Strasbourg, France

Publ.-Id: 17246 - Permalink

Evidence for a novel superconducting state in quasi-two-dimensional organic superconductors at high magnetic fields
Wosnitza, J.;
In the so-called FFLO state, named after Fulde, Ferrell, Larkin, and Ovchinnikov, the super-conducting state can survive even at high magnetic fields above the Pauli paramagnetic limit. The quasi-two-dimensional (2D) organic superconductors have been suggested as good can-didates for exhibiting the FFLO state. When applying the magnetic field exactly parallel to the conducting layers the orbital pair breaking is greatly suppressed and the Pauli limit is reached. We performed high-resolution specific-heat and torque-magnetization experiments in magnetic fields up to 32 T for such 2D organic superconductors. Besides an upturn of the upper critical field towards lowest temperatures, we observe a second thermodynamic transition within the superconducting phase signaling the existence of an additional superconducting phase. These features appear only in a very narrow angular region close to parallel-field orientation as evi-denced by comprehensive angular- and field-dependent specific-heat measurements for one organic superconductor. Our results give strong evidence for the realization of the FFLO state in organic superconductors.
  • Invited lecture (Conferences)
    Workshop on "Novel States in Quantum Matter", 03.-04.02.2012, Braunschweig, Deutschland

Publ.-Id: 17245 - Permalink

EPR Study of the Two-Dimensional Quantum System Cu(en)(H2O)2SO4
Tarasenko, R.; Orendácová, A.; Cizmár, E.; Orendác, M.; Zvyagin, S.; Wosnitza, J.;
The angular dependence of electron paramagnetic resonance spectra of Cu(en)(H2O)2SO4 single crystals was studied in the X-band frequency range at temperatures 4 and 300 K. Analysis of the linewidth at 300 K revealed nice agreement with the angular variation of the g-factor. This coincidence is the manifestation of the symmetric and antisymmetric exchange coupling, as main broadening mechanisms in Cu(en)(H2O)2SO4 at high temperatures. The radical change of the angular dependence of the linewidth observed at 4 K can be ascribed to dipolar coupling.
  • Open Access LogoActa Physica Polonica A 121(2012), 1095-1097

Publ.-Id: 17244 - Permalink

Magnetotransport through graphene nanoribbons at high magnetic fields
Minke, S.; Jhang, S. H.; Wurm, J.; Skourski, Y.; Wosnitza, J.; Strunk, C.; Weiss, D.; Richter, K.; Eroms, J.;
We have investigated the magnetoresistance of lithographically prepared single-layer graphene nanoribbons in pulsed, perpendicular magnetic fields up to 60 T and performed corresponding transport simulations using a tight-binding model and several types of disorder. In experiment, at high carrier densitieswe observe Shubnikov-de Haas oscillations and the quantum Hall effect, while at low densities the oscillations disappear and an initially negative magnetoresistance becomes strongly positive at high magnetic fields. The strong resistance increase at very high fields and low-carrier densities is tentatively ascribed to a field-induced insulating state in the bulk graphene leads. Comparing numerical results and experiment, we demonstrate that at least edge disorder andbulk short-range impurities are important in our samples.

Publ.-Id: 17243 - Permalink

High-field electron spin resonance in a spin-1/2 ladder with strong leg interactions
Ozerov, M.;
es hat kein Abstract vorgelegen.
  • Poster
    International Workshop on Strongly Correlated Electron systems in high magnetic Fields (SCEF), 20.-25.05.2012, Les Houches, France

Publ.-Id: 17242 - Permalink

Magnetic excitations in the distorted diamond chain system Cu3(CO3)2(OH)2
Kamenskyi, D.;
  • Poster
    International Workshop on Strongly Correlated Electron systems in high magnetic Fields (SCEF), 20.-25.05.2012, Les Houches, France

Publ.-Id: 17241 - Permalink

In vitro and in vivo evaluation of yttrium-90 labelled cetuximab in combination with external X-ray irradiation – radiooncology and nuclear medicine shake hands
Heldt, J.-M.; Saki, M.; Saker, J.; Zenker, M.; Koi, L.; Ingargiola, M.; Reichelt, U.; Sommer, D.; Bergmann, R.; Sihver, W.; Mosch, B.; Dikomey, E.; Kunz-Schughardt, L.; Cordes, N.; Pietzsch, H.-J.; Pietzsch, J.; Zips, D.; Henniger, J.; Rodemann, H. P.; Baumann, M.; Steinbach, J.;
Results from preclinical and clinical trials indicate that combination of the Epidermal Growth Factor Receptor (EGFR) specific antibody Cetuximab (C225) with classical radiotherapy improves local tumor control and overall survival of patients with head and neck cancers1-4. First results of Meller et al. showed a synergistic effect of 131I-labelled C225 in combination with external irradiation in vitro5. These data indicate that the combination of internal radiation dose delivered by radiolabelled C225 plus the therapeutic effect of C225 in combination with radiotherapy might significantly lower the overall external dose applied to patients, reducing undesired side effects on healthy tissue. Thus, bimodal cancer therapy seems a promising approach. This encouraged us to investigate the combined effect of 90Y[Y]-CHX-A"-DTPA-Cetuximab (90Y-C225) and radiation dose delivered by external beam irradiation in vitro and in vivo in our joint project.

Materials and Methods
CHX-A´´-DTPA was conjugated to C225 via thiourea bridging. Radiolabelling was performed under mild conditions using [90Y]YCl3. Binding affinity of 90Y-C225 was studied by flow cytometric analysis as well as by competitive binding assays using cells in 2D and 3D culture or cell membrane preparations. Distribution in spheroids (FaDu) was studied in a concentration- and time-dependent manner. Cellular uptake, EGFR binding specificity and kinetics, retention of 90Y-C225 as well as clonogenic activity of 90Y-C225 treated cells in combination with external irradiation were studied. The capacity of 90Y-C225 to induce DNA double-strand breaks (DSBs) was assessed through the Gamma-H2AX/53BP1 foci technique and cell survival by colony formation. Ex vivo autoradiography was performed with 90Y-C225. Biodistribution and in vivo kinetics were measured with PET using 86Y as radiolabel. FaDu tumour bearing nude mice were treated with 90Y-C225 (2.8 MBq 13 μg C225 / mouse, i.v.) and external beam irradiation (20 Gy single dose, 1.1 Gy/min). Experimental endpoints are the tumour growth delay and the local tumour control after 180 d.

Radiolabelling of the conjugate resulted in specific activities up to 9 GBq/mg. For the present study, a labelling protocol to achieve a reproducible specific activity of 1.2 GBq/mg was established.

in vitro: Flow cytometric analysis showed that affinity of 90Y-C225 is not significantly reduced compared to native C225. A Ki of 0.4 nM vs 0.22 nM for native C225 was determined by a competitive binding assay. Saturation of FaDu spheroids with 90Y-C225 was achieved after 24 h of incubation at 5 μg/ml. A saturation test showed that the optimal concentration to block all EGFR (SAS and UT5 cells) by C225 in monolayer culture is about 3-5 nM. No unspecific binding on an EGFR-negative CHO cell line was observed. Binding 90Y-C225 to EGFR in HNSCC cells occurred time dependently with a maximum after 24 h. 24 h after treatment approximately 10% of bound activity was found in the supernatant. Conjugation of CHX-A"-DTPA to C225 does not alter the cellular and biological function of C225. Combination of single doses of 2 or 4 Gy with 90Y-C225 reduced clonogenic survival in the UT5 and SAS cell lines. For UT5 cells the D37 value for non-treated control cells was 3.7 Gy with X-rays. Treatment with C225 reduced D37 of UT5 cells to 2.7 Gy. When 90Y-C225 was combined with X-rays, the D37 of UT5 cells dropped to 1.8 Gy. Thus, in comparison to C225, a decrease of D37 by about 33 % was observed in cells treated with 90Y-C225. D37 of untreated cells was only reduced from 3.9 Gy to 3.7 Gy after incubation with native C225. A D37 of 3.3 Gy resulted upon treatment with 90Y-C225 which reflects only a reduction of about 11%, compared to C225.
Induction of DNA DSBs by 90Y-C225 in cell lines with varying EGFR expression showed that the amount of 90Y-C225 binding and the number of induced DSBs is proportional to the EGFR on the cell membrane and that the cytotoxicity is dependent on the number of residual DSB (clonogenic survival).

in vivo: Autoradiography revealed high tumour accumulation 48 h p.i., also PET showed an increasing accumulation of activity in the tumour, which was abundant after 24 h p.i.
The combined treatment was well tolerated by all mice and no histological alterations in organs were found. A clear dose-dependent effect of the external irradiation was observed. A significant improvement of the local tumour control after X-ray irradiation with 20 Gy was achieved after application of 13 μg of 90Y-C225 compared to native C225 or to the treatment by external irradiation alone.

The results from in depth investigations of the effects of 90Y-C225 on various EGFR expressing cell lines validate it as a powerful tool for in vivo studies. The combined treatment of tumours in our experimental mouse model permits a reduction of the external radiation dose of 12 Gy. Our in-vivo data support the concept that bimodal cancer treatment results in a potentially relevant improvement of local tumour control. This encourages us to follow this promising scientific concept.

Research Support: The Bundesministerium für Bildung und Forschung (grant 02NUK006, framework “Kompetenzverbund Strahlenforschung” (KVSF)) is gratefully acknowledged for the financial support.

1 Bonner JA, Harari PM, Giralt J et al. [2010] Lancet Oncol.; 11: 21-8.
2 Bonner JA, Harari PM, Giralt J et al. [2006] N Engl J Med.; 354: 567-78.
3 Curran D, Giralt J, Harari PM et al. [2007] J Clin Oncol.; 25: 2191-7.
4 Zhang N, Erjala K, Kulmala J et al. [2009] Radiother Oncol.; 92: 388-92.
5 Meller B, Rades D, Wolff C et al. [2009] IJROBP 75: 1226-1231.
  • Lecture (Conference)
    ESRR'12 - 16th European Symposium on Radiopharmacy and Radiopharmaceuticals, 26.-29.04.2012, Nantes, France
  • Abstract in refereed journal
    Quarterly Journal of Nuclear Medicine and Molecular Imaging 56(2012), 7

Publ.-Id: 17240 - Permalink

Ultrasound investigations of spin-ice materials
Erfanifam, S.; Zherlitsyn, S.; Wosnitza, J.; Moessner, R.; Petrenko, O. A.; Balakrishnan, G.; Zvyagin, A. A.;
The elastic properties of spin-ice materials Dy2Ti2O7 and Ho2Ti2O7 have been studied for different longitudinal and transverse acoustic modes in a temperature range from 20 mK to 300 K and magnetic fields applied along various crystallographic directions up to 17.5 T. The sound velocity and the sound attenuation exhibit a number of anomalies versus applied magnetic field at temperatures below the “freezing” temperature. In Dy2Ti2O7 compound, most notable are peaks in the sound velocity, which exhibit two distinct regimes: an intrinsic (extrinsic) one in which the data collapse for different field sweep rates when plotted as function of field strength (time). The intrinsic regime involves the release of Zeeman energy from spins, the extrinsic one, transfer of energy out of the sample. At B = 1.25 T additionally a sharp drop in the sound velocity can be seen. This can indicate a 1st-order phase transition from a low-density monopole state to the highdensity monopole state. We discuss our observations in context of the emergent quasiparticles which govern the low-temperature dynamics of the spin ice.
  • Poster
    International Workshop on Strongly Correlated Electron systems in high magnetic Fields (SCEF), 20.-25.05.2012, Les Houches, France
  • Poster
    Quantum Criticality & Novel Phases 2012 (QNCP12), 26.-29.08.2012, Dresden, Deutschland

Publ.-Id: 17239 - Permalink

Magnetization and magneto-acoustics studies on UCo2Si2 single crystal
Yasin, S.; Andreev, A. V.; Skourski, Y.; Zherlitsyn, S.; Wosnitza, J.;
We report results of magnetization and magneto-acoustic studies on a UCo2Si2 single crystal in high magnetic fields. This compound has a tetragonal crystal structure and orders antiferromagnetically at TN = 83 K. At low temperatures, it shows a first-order metamagnetic transition (MT) at 45 T with very small hysteresis (μ0ΔHcr = 0.16 T) to a ferrimagnetic state. This transition is seen as a sharp jump in the magnetization when the magnetic field is applied along the c direction. The acoustic properties exhibit drastic anomalies in the vicinity of both magnetic phase transitions; the spontaneous and the field-induced one. At TN, a pronounced change in the sound velocity Δv/v accompanied with a peak in the attenuation Δα has been observed. Whereas only Δα shows a very sharp peak at the MT, Δv/v displays a more complicated behavior. In addition the sound-velocity anomaly exhibits a non-monotonous temperature evolution with maximum effects at 30 K, which can be due to the transition change from the first to the second order. Our results enabled us to map the phase diagram of UCo2Si2 in fields applied along the c axis. We discuss our observations in relation to the magnetism on the U site and the magneto-elastic interaction in this material.
  • Poster
    International Workshop on Strongly Correlated Electron systems in high magnetic Fields (SCEF), 20.-25.05.2012, Les Houches, France

Publ.-Id: 17238 - Permalink

Spin Dynamics in Quantum Spin Chains
Zvyagin, S.;
Quantum fluctuations, significantly enhanced in spin systems with reduced dimensionality, give rise to a variety of strongly correlated spin states, making low-dimensional magnets an ideal ground for testing various theoretical concepts. The way a magnetic field changes the ground-state properties and, correspondingly, the low-energy excitation spectrum of such systems is one of the fundamental aspects in quantum magnetism. Here, we report on experimental studies of the spin dynamics in copper pyrimidine dinitrate (hereafter Cu-PM), a spin-1/2 antiferromagnetic chain with alternating g-tensor and Dzyaloshinskii-Moriya interactions, by means of high-field electron spin resonance (ESR) spectroscopy in magnetic fields up to 64 T. Due to the presence of the field-induced staggered moment, this material exhibits a field-induced gap. We show that the spin dynamics of Cu-PM can be effectively described using the quantum-field-theory sine-Gordon formalism (with soliton and breather modes forming the excitation spectrum). Furthermore, we show that in the fully spin-polarized state (Hsat = 48.5 T) the spectrum is formed by ordinary magnons. The soliton-magnon crossover is characterized by a minimum of the spin gap, predicted using DMRG calculations and clearly observed by us. The temperature and field evolution of the ESR parameters approaching the sine-Gordon regime is studied as well. Excellent agreement with the theory in all cases is found.
  • Invited lecture (Conferences)
    III International Conference for Young Scientists, Low Temperauture Physics (ICYS-LTP-2012), 14.-18.05.2012, Kharkov, Ukraine
  • Invited lecture (Conferences)
    International WORKSHOP on Strongly Correlated Electron systems in high magnetic Fields (S C E F), 20.-25.05.2012, Les Houches, France

Publ.-Id: 17237 - Permalink

Dresden High Magnetic Field Laboratory: Towards 100 T and Higher
Zvyagin, S.;
As a high-field user facility, the Dresden High Magnetic Field Laboratory (Hochfeld-Magnetlabor Dresden, hereafter HLD) at the Helmholtz-Zentrum Dresden-Rossendorf is open since 2007. In this presentation I will give some details of the instrumentation and research infrastructure of HLD. The talk will be illustrated by some recent examples of the high-field applications in solid state physics and material science.
  • Invited lecture (Conferences)
    III International Conference for Young Scientists Low Temperature Physics (ICYS-LTP-2012), 14.-18.05.2012, Kharkov, Ukraine

Publ.-Id: 17236 - Permalink

Production of 85Sr at a 18 MeV-cyclotron and purification for geochemical investigations
Mansel, A.; Gruhne, S.; Franke, K.; Fischer, S.;
The production of 85Sr by irradiation of a Rb-target at a cyclotron was investigated. The purification of the radionuclide was performed by a Sr-selective resin. 85Sr was separated in no-carrier-added aqueous solution with a recovery of 98% and a concentration up to 5 MBq in 200 µl.
Keywords: Strontium-85, Rubidium target, Proton induced nuclear reaction, Chemical separation, Sr-SpecTM

Publ.-Id: 17235 - Permalink

Improved anatomic visualization of a glomus caroticum tumour within the carotic bifurcation with combined 68Ga-DOTATATE PET/MRI
Beuthien-Baumann, B.; Platzek, I.; Lauterbach, I.; van den Hoff, J.; Schramm, G.; Zöphel, K.; Laniado, M.; Kotzerke, J.;
kein Abstract verfügbar

Publ.-Id: 17234 - Permalink

Ion beams for application in science and industry: Activities in Germany and the European infrastructure project SPIRIT
Möller, W.;
On the grounds of largely mature methodologies of ion beam modification, ion irradiation and ion beam materials analysis, ion beams have established as a powerful and indispensable tool in front-line research and present-day industrial production, with special impact in fields of high socio-economic relevance such as new functional materials, information technology, health, environment and cultural heritage.
The present lecture will first give an overview of corresponding activities in Germany. The availability of ion facilities is concentrating at a few Universities and public research infrastructures such as the Helmholtz association. Prominent research includes the ion-beam assisted generation and modification of nanostructures at ion energies ranging from eV/amu to MeV/amu, damage of materials in the electronic stopping regime, low-fluence ion implantation for single photon emission, and radiation-biology studies with living cells. A significant amount of device capacity is also available for industrial services. For this purpose, associated transfer companies have been created in some cases.
The second part of the lecture will briefly report on the performance of the European Integrated Infrastructure Activity SPIRIT ( 9 of the 11 beneficiaries of the project offer their ion beam facilities transnational European users, with about 8000 user hours having been delivered so far. The areas of user interest will be discussed at the hand of selected results. Finally, the lecture will address new instrumental and methodological developments within SPIRIT, such as the development and employment of new detectors and the use of ion beams for chemical analysis of solid surfaces.
Keywords: Ion technologies, EU Project SPIRIT
  • Invited lecture (Conferences)
    Ion Beams '12: Multidisciplinary Applications of Nuclear Physics with Ion Beams, 06.-08.06.2012, Legnaro, Italia

Publ.-Id: 17233 - Permalink

Taming Nanostructures: From Sponge to Dot Pattern on Ge Controlled by Heavy-Ion-Deposited Energy
Böttger, R.; Bischoff, L.; Heinig, K.-H.; Schmidt, B.; Anders, C.; Urbassek, H.;
The self-organization of highly ordered patterns on surfaces, induced by ion beam irradiation, has attracted attention as potential nanostructured templates for magnetic and plasmonic applications. The origin of the high spatial order and its dependence on ion irradiation parameters are still under discussion. In agreement with former studies we found that ion irradiation of Ge with heavy ions (here: Bi) leads to a strong change in surface morphology in terms of roughness and formation of amorphous porous layers (sponge) with a thickness of about six times the projected ion range.
Here, we present our finding that the surface morphology on Ge, caused by irradiation with focused Bi monomer and cluster ions, can be controlled by the deposited energy density as well as the substrate temperature. While, at room temperature, the irradiation with Bi cluster ions can lead to highly ordered dot pattern having high aspect ratios, irradiation with Bi monomers results in the well-known porous surface patterns ranging from holes via columns to sponge. At elevated substrate temperatures, highly ordered dot structures can be achieved by monomer irradiation too. The pair correlation of these SEM images reveals that dot formation occurs in a temperature range which depends on the energy density deposited by a single ion. At very high temperatures, surface diffusion leads to smoothing.
A cellular defect structure model based on ion beam induced strong defect creation and high vacancy mobility in Ge explains the formation of holes, columns and sponge-like structures at low atomic energies in the cascade, i.e. Bi monomer irradiation at room temperature. This defect formation is incapacitated by thermal spikes, which form at elevated temperatures or by cluster ion impacts.
The dependence of the observed dot formation on the deposited energy density and the substrate temperature under normal ion beam irradiation cannot be explained by any model published up to now.
Keywords: Germanium, Bi, monomer, cluster, ions, surface patterns, self-organized, void formation
  • Lecture (Conference)
    56th International Conference on Electron, Ion and Photon Beam Technology and Nanofabrication, 29.05.-01.06.2012, Waikoloa, USA

Publ.-Id: 17232 - Permalink

Quasi-temperature Stable Luminescence at 1.3 μm from Flash Lamp Annealed GaAs
Gao, K.; Prucnal, S.; Anwand, W.; Skorupa, W.; Helm, M.; Zhou, S.;
GaAs is being widely used in optical communication devices in virtue of its outstanding luminescent and electronic performances. Many approaches have been applied to GaAs based materials, to realize the luminescence in fiber-optic transmission windows.

In this contribution, we present a novel method to achieve the 1.3 μm light emission by defect-induced luminescent centers. N, Bi and Mn were doped into GaAs wafers by ion-implantation and then their incorporation into GaAs lattice was carried out by flash lamp annealing (FLA). The optical and structural properties of the samples were investigated by micro-Raman spectroscopy, temperature dependent photoluminescence and positron annihilation spectroscopy. For the intrinsic and the N or Bi incorporated GaAs, a strong luminescence peak occurs at 1.3 μm. On the other hand, Mn-doping had suppressed this luminescence. Results have shown that for the 1.3 μm emission the donor and acceptor pairs are responsible. Furthermore, it is noticeable that the 1.3 μm light emission exhibited outstanding thermal stability (e.g., 20nm red-shift and 58% intensity decline as temperature rose from 20 K to room temperature). Our investigation suggests that GaAs treated by flash lamp annealing (i.e. a chip-relevant technology) exhibits a promising prospect on applications of light emitters and detectors for optical communication devices.
  • Lecture (Conference)
    European Materials Research Society Spring Meeting, 14.-18.05.2012, Strasbourg, France

Publ.-Id: 17231 - Permalink

Millisecond flash lamp annealed GaAs: a promising light emitter material at 1.3 um
Gao, K.; Prucnal, S.; Jiang, Z.; Skorupa, W.; Helm, M.; Yastrubchak, O.; Gluba, L.; Zhou, S.;
Gallium arsenide based materials have outstanding performances in light-emitting devices and are being widely used in optical communication devices in virtue of their remarkable efficiency and thermal stability.
We present a novel method to achieve the 1.3 um light emitting by defect-induced luminescent centers. Mn-implanted and N-implanted GaAs as well as un-doped GaAs wafers were treated by millisecond flash lamp annealing techniques. The optical properties of the samples were investigated. Results have shown the successful incorporation of Mn and N into GaAs lattice. For the intrinsic and the N-incorporated GaAs, a strong luminescence peak occurs at 1.3 um. On the other hand, Mn-doping has suppressed this luminescence. It is still noticeable that the 1.3 um light emitting only have a slight redshift (about 20 nm) and 58% intensity decline as the temperature rises from 20 K to room temperature. Our investigation suggests that after flash lamp annealing GaAs based materials exhibit a promising prospect on applications of light emitters and detectors for optical communication devices.
Keywords: GaAs, ion-implantation, flash lamp annealing, 1.3 um luminescence
  • Lecture (Conference)
    76. Jahrestagung der DPG und DPG-Frühjahrstagung, 25.-30.03.2012, Berlin, Germany

Publ.-Id: 17230 - Permalink

Ion Beams in Materials Processing and Analysis
Schmidt, B.; Wetzig, K.;
The main purpose of this book is two-fold. On the one hand, it is meant as a compendium for the physical fundamentals of ion-solid interactions, which are important for the understanding of ion implantation, ion beam sputtering, ion channeling, ion-induced damage formation and ion-beam mixing, but also for the comprehension of ion beam synthesis, ion-induced phase transformation and nano-patterning. Therefore, the book addresses both scientists and research engineers. The principles of ion-solid interactions are not only of fundamental importance, but ion beam irradiation of solids is becoming an increasingly important technique for modifying surface and thin film properties. Therefore, this book is also intended to bridge the gap between fundamental phenomena and their technological applications in modern materials research, development and analysis. The book demonstrates the possibilities for optimisation of solid state properties related to modern functional materials such as doped semiconductors and metal based layers for micro- and nanoelectronics, to metal alloys, nanopatterned surfaces and to new ion beam synthesized materials. A thematic rounding of the book is realized by special ion beam applications in selected materials fields. To these belong the use of ion beam analysis in magnetoelectronic layers, in art and archeometry and also in life sciences. The present book is organized into several chapters covering the range from principal aspects and phenomena over actual technological and device concepts to contemporary challenges in materials science. It thereby mainly concentrates on the relevant fields of semiconductors, nanomaterials, metals and polymers, interfaces and thin layers.
  • Book (Authorship)
    Wien, Austria: Springer-Verlag, 2013
    418 Seiten

Publ.-Id: 17229 - Permalink

Synthesis, microstructure, and mechanical properties of YPd3B thin films
Takahashi, T.; Iskandar, R.; Munnik, F.; Music, D.; Mayer, J.; Schneider, J. M.;
Ternary Y-Pd-B thin films have been synthesized by magnetron sputtering from elemental targets to investigate the mechanical properties of the perovskite YPd3B phase. The as-deposited YPd2.73B1.18 film is identified as a single phase fcc-type structure with the measured lattice parameter of 0.415(5) nm. The film microstructure consists of dense columnar grains. The elastic modulus of the YPd2.73B1.18 film is determined to be 137 GPa by nanoindentation, which is in good agreement with ab initio calculations reported previously. The measurement of the critical shear stress for the onset of plasticity suggests that YPd3B can be classified as ductile material.
Keywords: Thin films; Transition metal alloys and compounds; Vapor deposition; Mechanical properties

Publ.-Id: 17228 - Permalink

Electron microscopic imaging of an ion beam mixed SiO2/Si interface correlated with photo- and cathodoluminescence
Fitting, H.-J.; Fitting-Kourkoutis, L.; Schmidt, B.; Liedke, B.; Ivanova, E. V.; Zamoryanskaya, M. V.; Pustovarov, V. A.; Zatsepin, A. F.;
Energy filtered transmission electron microscopy (EFTEM), scanning transmission electron microscopy (STEM) imaging, and electron energy loss spectroscopy (EELS) of a thin 28 nm SiO2 layer on Si substrate implanted by Si+ ions with an energy of 12 keV are reported. The maximum concentration of implanted Si+ ions is located near the SiO2–Si interface region leading there to an ion beam mixed gradual SiOX (2>x>0) buffer region, which is even extended into the Si substrate by atomic collisions (knocking-off and knocking-on processes) during ion implantation. Thus, the width of this SiOX buffer layer amounts to about 30 nm extended from 10 to 40 nm depth. The SiOX profile is demonstrated by the above given electron microscopic and spectroscopic methods. Thermal annealing leads to partial phase separation from SiOX1 to SiOX2 with x2>x1 and silicon precipitates (partially nc-Si) changing the photo- (PL) and cathodoluminescence (CL) spectra especially in the near IR-region, probably, due to the formation of Si nanoclusters and associated quantum confinement effects.
Keywords: cathodoluminescence, energy-filtered TEM, ion beam mixing, silicon suboxides

Publ.-Id: 17227 - Permalink

Update on the laser facility at HZDR
Kraft, S.;
  • Lecture (Conference)
    Ion instrumentation workshop, 07.-08.06.2012, Palaiseau, Frankreich

Publ.-Id: 17226 - Permalink

Scintillator-based online detectors for laser-accelerated protons – Concepts and realizations at the DRACO lab
Metzkes, J.; Zeil, K.; Kraft, S. D.; Stiller, N.; Schramm, U.; Karsch, L.; Richter, C.; Pawelke, J.; Sobiella, M.;
Es werden zwei am HZDR entwickelte Online-Detektoren für laserbeschleunigte Protonen basiert auf Plastikszintillatoren vorgestellt.
Keywords: online detectors for laser-accelerated protons, plastic scintillators
  • Lecture (Conference)
    Instrumentation for Diagnostics and Control of Laser-Accelerated Proton (Ion) Beams: Second Workshop, 07.-08.06.2012, Paris, Frankreich
  • Invited lecture (Conferences)
    NAUUL 2013 - 2nd Workshop Operation of PW-class lasers, 13.-14.06.2013, Dornburg, Deutschland

Publ.-Id: 17225 - Permalink

The impact of climate transitions on the radionuclide transport through a sedimentary aquifer
Flügge, J.; Stockmann, M.; Schneider, A.; Noseck, U.;
In long-term safety assessments for nuclear waste repositories in deep formations, geological time scales have to be considered. Possible future climatic changes are expected to alter the boundary conditions, the flow regime and the geochemical environment in the aquifers. The codes d³f (distributed density-driven flow) and r³t (radionuclides, reaction, retardation, and transport) are being developed to simulate contaminant transport in large heterogeneous areas over long periods in time, considering hydrogeochemical interactions and radioactive decay. A new methodology to use temporally and spatially variant sorption coefficients depending on the geochemical environment is being developed by introducing the transport of relevant components in solution and a pre-computed matrix of sorption coefficients with values being dependent on these components. In Germany, the Gorleben salt dome is being investigated as a potential site for a nuclear waste repository. A sea water inundation will lead to a decrease of the flow velocities and a horizontal salinity-dependent stratification of the groundwater, while permafrost formation in the upper aquifer and an inflow of glacial meltwater into the lower aquifer will lead to low salinities and high flow velocities in unfrozen zones. Transport simulations employing conventional sorption coefficients are the basis for future analyses employing the new methodology.
Keywords: Climate transitions, nuclear waste disposal, radionuclide transport, numerical modeling, smart Kd-concept, Northern Germany
  • Book chapter
    Jude Cobbing; Shafick Adams; Ingrid Dennis; Kornelius Riemann: Assessing and Managing Groundwater in Different Environments, Netherlands: CRC Press, 2013, 9781138001008, Kapitel 11


Publ.-Id: 17224 - Permalink

Approaching physical limits of ZnO:Al film performance for application in photovoltaics
Cornelius, S.; Vinnichenko, M.; Munnik, F.; Heller, R.; Möller, W.;
ZnO:Al films which combine high optical transmittance in the visible, maximum carrier mobility (mu), moderate free electron densities (Ne) and high surface roughness are of special interest for application as transparent front electrode in thin film solar cells.
Present work focuses on systematic investigation of ZnO:Al films grown by reactive magnetron sputtering, a cost-efficient deposition method, using metal Zn-Al alloy targets with a wide range of Al target concentrations (c_Al). The observed dependence of the mobility on Ne is discussed in the framework of ionized impurity scattering and clustering as well as grain boundary limited transport which predicts a fundamental physical limit of mu. Precise control of growth parameters results in high quality polycrystalline and epitaxial ZnO:Al films exhibiting optimum mobility values (>45 and >55 cmK/Vs, respectively) approaching the upper limit set by ionized impurity scattering. A combination of ion beam analysis for Al quantification in the film with Hall effect measurements shows that above a critical Al concentration (~2.5 at.%) further Al enrichment in the films with increasing substrate temperature leads to deterioration of electrical properties. This approach also enables estimation of the fraction of electrically active Al in the ZnO matrix, which is rarely reported in a quantitative and systematic manner. It is shown that the Al donor activation in the ZnO:Al films does not exceed 40%.
Keywords: transparent conductive oxide, zinc oxide, dopant activation, ion beam analysis, mobility
  • Poster
    EMRS Spring Meeting 2012, 14.-18.05.2012, Strasbourg, France

Publ.-Id: 17223 - Permalink

Nature and origin of the protolith succession to the Paleoproterozoic Serra do Navio manganese deposit, Amapa Province, Brazil
Chisonga, B. C.; Gutzmer, J.; Beukes, N. J.; Huizenga, J. M.;
Until its closure in 1997, the Serra do Navio deposit, located in Amapá Province, Brazil, was one of the most important sources of high-grade manganese ore to the North American market. The high-grade manganese oxide ores were derived by lateritic weathering from metasedimentary manganese protoliths of the Serra do Navio Formation. The local geological context and nature of this protolith succession are not well understood, due to poor surface outcrop conditions, and intense deformation. However, based on similar age, regional tectonic setting and lithology the Paleoproterozoic volcanosedimentary succession that includes the Serra do Navio Formation is widely believed to be similar in origin and laterally equivalent to the Birimian Supergroup in West Africa. For the present investigation several diamond drill cores intersecting the protolith succession were studied. Detailed petrographic and whole rock geochemical studies permit distinction of two fundamental lithological groups comprising of a total of five lithotypes. Biotite schist and graphitic schist lithotypes are interpreted as former metapelites. A greywacke or pyroclastic protolith cannot be excluded for the biotite schist, whereas the graphitic schist certainly originated as a sulfide-rich carbonaceous mudstone. Rhodochrosite marble, Mn-calcite marble and Mn-silicate rock are grouped together as manganiferous carbonate rocks. Manganese lutite constitutes the most probable protolith for rhodochrosite marble, whereas Mn-calcite marble was derived from Mn-rich marl and Mn-silicate rock from variable mixtures of Mn-rich marl and chert.

The sedimentary succession at the Serra do Navio deposit is similar to that encountered at many other black shale and chert-hosted Mn carbonate deposits. A metallogenetic model is proposed, predicting deposition of manganese and closely associated chert in intra-arc basins, in environments that were bypassed by distal siliciclastic (carbonaceous mud) and proximal pyroclastic/siliciclastic detritus. Positive Ce anomalies and δ13CVPDB values of − 4.3 to − 9.4 per mill suggest that manganiferous carbonates derived during suboxic diagenesis from sedimentary Mn4+ oxyhydroxide precipitates. Metamorphic alteration of manganese carbonate–chert assemblages resulted in the formation of Mn-silicates, most importantly rhodonite and tephroite; porphyroblastic spessartine formed where Mn-carbonate reacted with aluminous clay minerals. Microthermometric studies of fluid inclusions in spessartine porphyroblasts suggests that peak metamorphic conditions reached the upper greenschist facies (1–2 kbars and 400–500 °C). Retrograde metamorphism is marked by partial re-carbonation, expressed by the formation of small volumes of rhodochrosite, and Mn-calcite that are closely associated with quartz, chlorite and minor amounts of sulfides related to post-metamorphic veinlets. It is this metamorphosed succession that sourced the high-grade manganese oxide ores during prolonged lateritic weathering.
Keywords: Serra do Navio manganese deposit; Brazil; Lithogeochemistry; Metamorphic petrology; Fluid inclusion microthermometry; Metallogenesis

Publ.-Id: 17222 - Permalink

Manganese metallogenesis: Introduction to the special issue
Polgari, M.; Gutzmer, J.;
Research into the origin and distribution of manganese deposits has always occupied a small but important niche in economic geology. Of particular value for the progress achieved in manganese deposit research was a succession of programs funded by the International Geological Correlation Programmes (IGCP). Through six of these IGCP projects international research collaboration was effectively supported from 1975 until 2002 (Table 1). These programs enabled a large number of scientists and postgraduate students from various continents and countries to interact with one another. Manganese ore deposits worldwide were investigated during field workshops and results were presented at numerous international conferences.
Keywords: Manganese, metallogenesis

Publ.-Id: 17221 - Permalink

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