Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf
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43543 Publications
Diffusion suppression etc. during electrical activation in implanted Ge and Si-SOI
Skorupa, W.
Abstract
Recent results on diffusion suppression, electrical activation and related problems in implanted Ge and Si-SOI were reported. A prospect regarding millisecond thermal processing of high k dielectrics was given.
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Invited lecture (Conferences)
24. Nutzertreffen Kurzzeittemperung, 23.10.2008, Dortmund, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-12202
Rare Earth Ion Beam Processing for Silicon Photonics
Skorupa, W.; Rebohle, L.; Prucnal, S.; Cherkouk, C.; Helm, M.
Abstract
Combining silicon-based electronic circuits with optoelectronic functionality is one of the key challenges for the future semiconductor technology. Such work must not only be devoted to the telecommunication wavelength of 1.54 µm because there are much more applications requiring light sources from the UV to IR wavelength range. In our work we employed ion beam processing to embed different rare earth (RE) luminescent centers (Gd, Ce, Tm, Tb, Eu, Er) into the silicon dioxide layer of purpose-designed Metal-Oxide-Silicon-based Light Emitting Devices (MOSLEDs) with advanced electrical performance. Efficient electroluminescence was obtained from UV to infrared with a transparent top electrode made of indium-tin oxide. Several developments for improving the device stability will be proposed related to charge compensation and the elimination of defects in SiO2. The electrical and electroluminescence properties of these devices are discussed and evaluated in respect of possible applications for biosensing applications. As an example our recent effort to detect estrogens in drinking water will be discussed.
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Invited lecture (Conferences)
2008 MRS Fall Meeting, Symposium D: Rare-Earth Doping of Advanced Materials for Photonic Applications, 01.-05.12.2008, Boston MA, USA
Permalink: https://www.hzdr.de/publications/Publ-12201
Casting experiments and materials studies for restoring lead pipes in historical organs
Skorupa, W.; Rossner, M.; Werner, H.; Eule, A.-C.; Schucknecht, T.; Rafaja, D.; Hausmann, U.; Wegscheider, K.
Abstract
We will report on a new casting technique basing on old recipes from the 17. and 18. century to produce new pipes approaching the quality of the old ones. Materials studies of old and new metal probes were performed by metallography and other methods. Different casting variants as well as the influence of hammering the casted metal plates onto the microstructure were investigated. In the course of these studies special consideration was devoted to the restoration projects at Borgentreich/Westfalen (Eule) and Stralsund/Vorpommern (Wegscheider).
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Invited lecture (Conferences)
25. Congress of the International Society of Organbuilders (ISO), 21.-26.09.2008, Danzig-Stralsund, Polen-Deutschland
Permalink: https://www.hzdr.de/publications/Publ-12200
A short review on Flash Lamp Annealing
Skorupa, W.
Abstract
A short review on Flash Lamp Annealing
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Invited lecture (Conferences)
Industrie-Projekttreffen mit BASF und Zentrum für Sonnenenergie-& Wasserstoff-Forschung Baden-Württemberg (ZSW), 18.11.2008, Stuttgart, Germany
Permalink: https://www.hzdr.de/publications/Publ-12199
Old Physics for Modern Nanotechnologies - Studies of Nano-Scale Ordering by Simulations and Experiments
Heinig, K.-H.
Abstract
Shaping and ordering of nanostructures is mandatory for many applications. However, top-down approaches like electron lithography have their limits and are expensive. Here, we present some bottom-up approaches like self-ordering and alignment at interfaces, which are driven by well-known thermodynamic processes like phase separation and surface energy minimization. The reaction pathways are studied by atomistic computer simulations and verified by experiments. The relevance for some applications, e.g. FLASH memories and Si-based light emitters, will be demonstrated.
Keywords: nanostructure formation; nanostructure shaping; ion irradiation; self-organisation; kinetic Monte Carlo simulation
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Invited lecture (Conferences)
Fizikai és Anyagtudományi Kutatóintézet Tanácstermében, 21.05.2008, Budapest, Hungary
Permalink: https://www.hzdr.de/publications/Publ-12198
Spontaneous formation of regular nanopattern on surfaces during thin film deposion and ion beam erosion
Heinig, K.-H.
Abstract
Ion erosion of surface results under specific conditions to formation of dot-like or ripple-like nanopattern. These self-organized nanopattern are promising for different nanotechnologies. The presentation gives an overview of experimental techniques and results as well theoretical models and simulation work.
Keywords: ion erosion; nanopattern; experiments; theory; kinteic Monte Carlo simulations
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Invited lecture (Conferences)
Winter School on Nanoelectronic and Nanophotonics, 19.-25.01.2009, Ankara, Turkey
Permalink: https://www.hzdr.de/publications/Publ-12197
Formation of nanodots, nanowires, wormholes etc. driven by capillary forces-reaction pathways predicted by atomistic simulations.
Heinig, K.-H.
Abstract
The use of ion irradiation methods for bulk nanostructure formation will be presented. The focus will be on the help of cappilary forces to find controllable reaction pathways for nanostructure formation. These pathways are demonstrated by kinetic Monte Carlo simulations
Keywords: nanostructure formation; ion implantation; nanodots; nanowires; kinetic Monte Carlo simulation
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Invited lecture (Conferences)
Winter School on Nanoelectronic and Nanophotonics, 19.-25.01.2009, Ankara, Turkey
Permalink: https://www.hzdr.de/publications/Publ-12196
Fundamentals of Ion Beam Synthesis of Nanostructures
Heinig, K.-H.
Abstract
Fundamentals of ion-beam-solid-interactions will be presented. An overview over ion implantation techniques will be given. Range profile calculations, defect creation processes as well as annealing method will be treated. Finally, methods of ion beam synthesis based on phase separation of implanted species will be discussed.
Keywords: ion implantation; ion beam synthesis; kinetic Monte Carlo simulation; TRIM; lecture
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Invited lecture (Conferences)
Winter School on Nanoelectronic and Nanophotonics, 19.-25.01.2009, Ankara, Turkey
Permalink: https://www.hzdr.de/publications/Publ-12195
Novel LEFET with two self-aligned Si nanocrystal layers
Heinig, K.-H.; Beyer, V.; Schmidt, B.; Stegemann, K.-H.
Abstract
A light emitting feld-effect transistor (LEFET) which is based on self-aligned silicon nanocrystal delta-layers in the gate oxide of a nMOSFET device with an active gate area of 20x20 µm2 is demonstrated. Two layers of Si NCs were prepared in the gate oxide close to both Si/SiO2 interfaces by ion irradiation through the 50 nm poly-Si/15 nm SiO2/(001)Si substrate LEFET stack and subsequent annealing. An AC voltage was applied to the gate in order to inject charges of both polarities in the Si NCs. AC voltage and frequency dependent electroluminescence spectra were recorded as a function of the annealing conditions.
Keywords: nanotechnology; ion irradiation; electroluminescence; field effect transistor; modelling; kinetic Monte Carlo simulation
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Invited lecture (Conferences)
Workshop on Nanoelectronics and Nanophotoniocs, 26.-28.01.2009, Ankara, Turkey
Permalink: https://www.hzdr.de/publications/Publ-12194
Mapping of two-plus-one-dimensional KPZ growth onto driven lattice gas model of dimers
Ódor, G.; Liedke, B.; Heinig, K.-H.
Abstract
We show that a 2+1 dimensional discrete surface growth model exhibiting KPZ class scaling can be mapped onto a two dimensional conserved lattice gas model of directed dimers. In case of KPZ height anisotropy the dimers follow driven diffusive motion. We confirm by numerical simulations that the scaling exponents of the dimer model are in agreement with those of the 2+1 dimensional KPZ class. This opens up the possibility of analyzing growth models via reaction-diffusion models, which allow much more efficient computer simulations.
Keywords: KPZ class scaling; lattice gas model; Monte Carlo simulation
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Poster
International Workshop on Nonequilibrium Nanostructures, 01.-06.12.2008, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-12193
Swift-heavy-ion-induced shaping of spherical nanoparticles into disks and rods
Schmidt, B.; Heinig, K.-H.; Mücklich, A.; Akhmadaliev, C.
Abstract
The swift heavy ion induced deformation of SiO2 and metal nanoparticles were studied intensively in the last years. Recently, we reported on ion beam shaping of Ge nanospheres [1]. Surprisingly, Ge nanospheres in silica form oblate ellipsoids, what is opposite to prolate ellipsoids found for metal spheres.
This presentation reports on the experimental features of the shaping of Ge nanospheres and our theoretical search for the shaping mechanism(s). A stack of alternating Ge and SiO2 layers was sputtered on an oxidized Si wafer. The Ge layer thickness varied from 2.5 to 7.5 nm with 100 nm SiO2 in-between. Heating this layer stack to 950 °C for 300 s transformed each Ge layer into a layer of Ge nanospheres. With growing Ge layer thickness the mean diameter increases from 10 to 40 nm. After irradiation with (1-10)x1014 I7+cm-2 at 38 MeV, cross-section TEM images of as-prepared and irradiated samples showed that the largest Ge nanospheres kept spherical, whereas medium-size Ge spheres became oblates, and smaller ones shaped diamond-like. The different shaping of metal and semiconducting spheres is explained by their differences in thermodynamic properties.
Keywords: swift heavy ions; irradiation; nanostructure; shaping; modelling; simulation
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Lecture (Conference)
16th International conference on Ion Beam Modification of Materials (IBMM 08), 31.08.-05.09.2008, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-12192
Surface modification using Binary Collision Approximation and 3D Lattice Kinetic Monte Carlo simulation
Liedke, B.; Facsko, S.; Heinig, K.-H.; Möller, W.
Abstract
Periodic pattern formation during low energetic ion-beam bombardment has been observed for many different surfaces. Two different kinds of approaches have been used to explain and simulate the pattern formation and evolution in time: (i) continuum theories, which are based on the Bradley and Harper model, and (ii) Kinetic Monte Carlo method (KMC) for surface diffusion coupled with Sigmunds theory to incorporate sputtering. Both of them have been developed in terms of surface processes induced by ion sputtering, although without including microscopic effects, i.e. defect creation and diffusion of vacancies in the bulk.
We present a new approach using Binary Collision Approximation for simulating collision cascades during ion bombardment coupled with 3D Lattice KMC Ising model, to simulate surface and bulk diffusion of defects and vacancies. The combination of these two models gives an advantage on the simple Gaussian approximation of the deposited energy proposed by Sigmund, because it includes detailed collision cascades into the discrete lattice system. In addition, information about the relation between atomistic features, i.e. vacancies and defects creation and annihilation, sputtering yield distribution, bulk and surface diffusion, and pattern formation is obtained. We will present the time evolution of surface morphology for different initial system parameters and compare it with continuum theories. Moreover, the influence of substrate temperature on the pattern evolution is studied.
Keywords: ion irradiation; collision cascade; binary collision approximation; kinetic Monte Carlo; surface pattern; nanostructure
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Poster
16th International Conference on Ion Beam Modification of Materials (IBMM 08), 31.08.-05.09.2008, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-12191
Surface patterning by ion erosion atomistic computer simulations
Heinig, K.-H.; Numazawa, S.
Abstract
Surface ripple formation by low-energy ion erosion is a far-from-equilibrium process for which standard thermodynamics have to be put into question. Thus, an effective negative surface tension can be found under low-energy ion irradiation of surfaces [1] and ion beam mixing of interfaces [2]. This negative surface tension tends to increase the surface by inverse Ostwald ripening or surface patterning [2]. Here, for very low energy ion irradiation of surfaces patterning is predicted to evolve even without sputtering, resulting solely from defect creation and annihilation kinetics. Self-organisation of surface pattern by irradiation with ions in the region of keV-energies is strongly affected by sputtering, but even in that case far-from-equilibrium surface defect kinetic can play a major role. This will be underlined by a theoretical study of the temperature-dependent ripple formation found recently on Ag(110) [3]. In agreement with the experiment, kinetic Monte-Carlo calculations show that under ion irradiation at low temperatures (111) facets become unstable, resulting in a ripple rotation from (111) facets to (100) facets.
Keywords: ion erosion; surface pattern; nanostructure; modelling; kinetic Monte Carlo
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Poster
16th International Conference on Ion Beam Modification of Materials (IBMM 08), 31.08.-05.09.2008, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-12190
Nanocomposite Au-SiO2 thin film deposition by co-sputtering: comparison of experiments with atomistic simulations
Khan, S.; Heinig, K.-H.; Avasthi, D.
Abstract
Fast atom beam co-sputtering has been found to be an excellent technique for producing metal nanoclusters in variety of matrices without the need of any post-deposition annealing. The films thus prepared show homogeneous distribution of nanoclusters having rather narrow size distributions. The average size of these embedded nanoclusters can be effectively controlled by varying the ratio of sputtered metal and matrix species. In this contribution, we present results from the computer simulation of the deposition process to investigate the structural evolution and growth of Au nanoclusters embedded in silica matrix during co-sputtering. A three dimensional kinetic Monte Carlo technique has been used here to study the growth kinetics of nanoparticles taking into consideration the effect of the energetic sputtered species reaching the surface of the film during deposition. Nucleation and subsequent growth of Au nanoclusters has been simulated under different deposition conditions. As a result, the simulation has been shown to be useful for deposition parameters optimization in the process of nanocomposite thin film growth by fast atom beam co-sputtering.
Keywords: layer deposition; co-sputtering; nanostructure; kinetic Monte Carlo
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Poster
16th International Conference on Ion Beam Modification of Materials (IBMM 08), 31.08.-05.09.2008, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-12189
Facetting Morphology of Crystallites under Ion Irradiation a 3D Kinetic Lattice Monte Carlo Study
Heinig, K.-H.; Röntzsch, L.
Abstract
The orientation-dependent surface energies of crystal facets determine the shape of crystallites via Wulffs theorem. Thus, in the framework of a nearest neighbor Ising model, the equilibrium shape of a fcc crystallite is a truncated octahedron. This crystallite shape is found frequently, e.g. for A-type CoSi2 crystallites embedded in silicon.
In this contribution we show that crystallites change their shape under intense ion irradiation. A first indication for a crystallite shape change under ion irradiation was reported several years ago [1]. In a Monte Carlo simulation the continuing vacancy production transformed the equilibrium fcc crystallite shape of a truncated octahedron into the steady-state shape of a cube. Here we present a systematic study of ion-irradiation-induced crystallite shape changes for different crystal structures and different irradiation intensities and temperatures. For the first time, an explanation of the shape changes based on the surface defect kinetics will be given: Whereas in thermodynamics the equilibrium concentration of surface defects is determined by energetics (detailed balance), under ion irradiation its steady-state value is controlled by the geometry of atomic displacements. Consequently, facets with a high atomic area density become unstable. It will be shown that this facet instability might be the reason for temperature dependent pattern formation on metal surfaces under ion erosion [2].
[1] P. Bellon, Phys. Rev. Letters 81, 4176 (1998).
[2] U. Valbusa et al., J. Phys.: Condens. Matter 14, 8153 (2002).
Keywords: ion irradiation; surface energy; crystal shape; kinetic Monte Carlo
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Poster
16th International Conference on Ion Beam Modification of Materials (IBMM 08), 31.08.-05.09.2008, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-12188
Mapping of 2 + 1 dimensional KPZ growth onto driven lattice gas model of dimers
Odor, G.; Liedke, B.; Heinig, K.-H.
Abstract
We show that a 2+1 dimensional discrete surface growth model exhibiting KPZ class scaling can be mapped onto a two dimensional conserved lattice gas model of directed dimers. In case of KPZ height anisotropy the dimers follow driven diffusive motion. We confirm by numerical simulations that the scaling exponents of the dimer model are in agreement with those of the 2+1 dimensional KPZ class. This opens up the possibility of analyzing growth models via reaction-diffusion models, which allow much more efficient computer simulations.
Keywords: crystal growth; KPZ equation; Edward-Wilkinson equation; scaling behavior; Monte-Carlo simulation
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Physical Review E 79(2009)2, 021125-021130
DOI: 10.1103/PhysRevE.79.021125
Cited 29 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12187
Ion mass dependence of irradiation-induced local creation of ferromagnetism in Fe60Al40 alloys
Fassbender, J.; Liedke, M. O.; Strache, T.; Moeller, W.; Menendez, E.; Sort, J.; Rao, K. V.; Deevi, S. C.; Nogues, J.
Abstract
Ion irradiation of Fe60Al40 alloys results in the phase transformation from the paramagnetic, chemically ordered B2 phase to the ferromagnetic, chemically disordered A2 phase. The magnetic phase transformation is related to the number of displacements per atom (dpa) during the irradiation. For heavy ions (Ar+, Kr+, and Xe+), a universal curve is observed with a steep increase in the fraction of the ferromagnetic phase that reaches saturation, i.e., a complete phase transformation, at about 0.5 dpa. This proves the purely ballistic nature of the disordering process. If light ions are used (He+ and Ne+), a pronounced deviation from the universal curve is observed. This is attributed to bulk vacancy diffusion from the dilute collision cascades, which leads to a partial recovery of the thermodynamically favored B2 phase. Comparing different noble gas ion irradiation experiments allows us to assess the corresponding counteracting contributions. In addition, the potential to create local ferromagnetic areas embedded in a paramagnetic matrix is demonstrated.
- Physical Review B 77(2008), 174430
Permalink: https://www.hzdr.de/publications/Publ-12186
Application of self-actuated 32 cantilever array in atomic force surface measurements
Gotszalk, T.; Zawierucha, P.; Woszczyna, M.; Zielony, M.; Ivanov, T.; Ivanova, K.; Volland, B. E.; Sarov, Y.; Persaud, A.; Dontzov, D.; Schmidt, B.; Nikolov, N.; Kostic, I.; Engl, W.; Sulzbach, T.; Mielczarski, J.; Kolb, S.; Pedreau, R.; Huq, S. E.; Edinger, K.; Fortagne, O.; Blom, H. O.; Rangelow, I. W.
Abstract
Main industry requirement for applying scanning probe microscopy in surface measurements is the high
scan speed, which allow the microelectronics producers to obtain the information about the technological
process quality in-situ on the semiconductor wafer. Common single topography measurement consume few
minutes for scanning area about 100 μm2 because of limited cantilever dynamic properties. To overcome
this problem one may utilize the cantilever with resonance frequency above 1 MHz but in this case,
cantilever suffer from wear and it requires complicated, large bandwidth measurement system. Different
approach to high speed topography measurement is to apply massive array of cantilevers, where the
surface topography image is taken simultaneously from every probe.
In the contribution present the application of the one dimensional VLSI NEMS-chip (Very Large Scale
Integrated Nano Electro Mechanical System) incorporating 32 proximal probes for high speed atomic force
microscopy measurements will be presented. Each array cantilever integrates a thermal deflection actuator, a
piezoresistor acting as a deflection detector and a microtip with radius of 10 nm.
Keywords: NEMS; proximal AFM probe array; piezoresistive deflection sensing; thermal deflection actuation
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Poster
34th Micro and Nano Engineering Conference MNE08, 15.-18.09.2008, Athens, Greece
Permalink: https://www.hzdr.de/publications/Publ-12183
Acceleration of irradiation hardening of low-copper reactor pressure vessel steel observed by means of SANS and tensile testing
Bergner, F.; Ulbricht, A.; Viehrig, H.-W.
Abstract
Neutron irradiation of low-copper reactor pressure vessel steels containing manganese and nickel gives rise to microstructural changes and a deterioration of mechanical properties apparently progressing slower than in steels containing more than or about 0.1 wt% Cu. An acceleration of this process after accumulation of a threshold fluence caused by so-called late blooming phases is a matter of debate. We report results of small angle neutron scattering (SANS) experiments and tensile tests for two low-Cu model RPV steels irradiated at 255°C. Motivation for the use of the integrated magnetic scattering as a microstructural parameter combining the volume fraction and magnetic contrast of nanometre-sized irradiation-induced features is given. The results indicate one of the rare cases of acceleration of both the change of a microstructural parameter and the yield stress increase. The issues of the nature of the irradiation-induced features, the role of phosphorus, and the observed strong correlation of integrated magnetic scattering and yield stress increase are addressed.
Keywords: neutron irradiation; SANS; tensile testing; pressure vessel steel
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Philosophical Magazine Letters 89(2009)12, 795-805
DOI: 10.1080/09500830903304117
Cited 36 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12182
Investgation of crosstalk in cantilever arrays
Frank, A.; Zöllner, J.-P.; Sarov, Y.; Ivanov, T.; Klett, S.; Gotszalk, T.; Zielony, M.; Zawierucha, P.; Schmidt, B.; Zier, M.; Nikolov, N.; Engl, W.; Sulzbach, T.; Langlotz, E.; Dontsov, D.; Schott, W.; Rangelow, I. W.
Abstract
In this paper a macro model of a cantilever for mixed domain simulation only with SPICE is presented. Based on lumped elements of equivalent circuits a model is developed, which realizes a coupled electro-thermal-mechanical simulation including crosstalk effects. Capacitive crosstalk through the substrate are evaluated and modelled with SPICE. This is verified with measurement and helps to solve the crosstalk effect.
Keywords: Cantilever array; SPICE simulation; MEMS modeling
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Lecture (Conference)
EUROSENSORS XXII, 07.-10.09.2008, Dresden, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-12181
Fabrication of ultra-shallow p-n junctions by ion beam processing
Zier, M.
Abstract
Ultra-shallow p-n junctions in silicon play an important role in semiconductor industry, for example as source-drain extensions in highly integrated MOSFETs. The present talk shows their application as piezo-resistive bending sensors in massively parallel AFM arrays.
Difficulties in fabrication of ultra-shallow p-n junctions will be discussed and potential solutions will be given. To obtain ultra-shallow junctions several methods can be employed: pre-amorphisation, low energy ion implantation or the formation of a region with an enhanced vacancy concentration near the sample surface by high energy Si implantation. The activation of the dopant can be accomplished either by rapid thermal annealing or flash lamp annealing. Finally, the characterisation of the ultra-shallow doped layers using electrical and SIMS measurements will be shown.
Keywords: ion beam modification; ion implantation; ultra-shallow junction
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Lecture (others)
Materials Science Seminar, 29.04.2008, Dresden, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-12180
Fabrication of ultra-shallow p-n junctions in Si using fast and ultra-fast annealing
Zier, M.; Schmidt, B.
Abstract
Ultra-shallow p-n junctions in silicon play an important role in the semiconductor industry, for example as source-drain extensions in highly integrated MOSFETs or in this case as piezo-resistive bending sensors for application in massively parallel AFM arrays.
To obtain ultra-shallow junctions several methods of fabrication have been employed: low energy ion implantation and vacancy enhancement near the sample surface by using high energy Si+ implantation followed by in-diffusion of boron from a solid source. The activation of the dopant was accomplished either by rapid thermal annealing or flash lamp annealing.
I-V measurements of the diode formed by the p-n junction show excellent diode behaviour of the p-doped layers, indicating that all employed fabrication methods result in real p-n junctions. The concentration depth profile of boron in the samples have been measured by SIMS, using O2
- ions of 1500 and 500eV to minimise distortion of the depth profile due to the ion bombardment. Finally, measured sheet resistances of the p-doped layers obtained from dedicated test structures are compared against each other.
Keywords: ion implantation; ultra-shallow junction; RTA; FLA
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Poster
16th International Conference on Ion Beam Modification of Materials 2008, 31.08.-05.09.2008, Dresden, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-12179
[18F]FETA PET - A new method for hot spot imaging of the ischemic penumbra in acute stroke
Barthel, H.; Großmann, U.; Zeisig, V.; Patt, M.; Wagner, D.; Patt, J.; Kluge, M.; Franke, H.; Sorger, D.; Luthardt, J.; Nitzsche, B.; Dreyer, A.; Brust, P.; Steinbach, J.; Boltze, J.; Emmrich, F.; Sabri, O.
Abstract
Objectives:
In acute ischemic stroke, an imaging method to directly visualize the ischemic penumbra - the salvageable part of the affected brain - in positive image contrast would potentially improve therapy stratification and monitoring. This study aimed to test [18F] fluoroetanidazole ([18F]FETA), a second-generation radiolabeled 2-nitroimidazole, for the first time with respect to its suitability to image brain hypoxia with positron emission tomography (PET).
Methods:
Primary embryonal corticoencephalic cells (Wistar rats) and necortical brain slices (Sprague Dawley rats) were ex vivo exposed to nitrogen or air. The cells and brain slices were incubated with 5MBq [18F]FETA up to 120min, respectively. The activities of three nitroreductases - enzymes which mediate the intracellular [18F]FETA accumulation - were determined in the corticoencephalic cells. Further, organ distribution was determined in Sprague
Dawley rats up to 2h after i.v. injection of 20MBq [18F]FETA, and ex vivo brain autoradiography was performed up to 24h after permanent middle cerebral artery occlusion (pMCAO). Target-to background image contrast of [18F]FETA autoradiograms at 3h after pMCAO was compared with that of corresponding [18F]fluoromisonidazole ([18F]FMISO) autoradiograms. At 24h after pMCAO, animals were additionally i.v. injected with 1MBq [14C]iodoantipyrine to determine the local cerebral blood flow (lCBF). Nissl staining of brain slices as well as stroke-specific MRI were carried out at 24h after pMCAO to confirm the existence and localization of ischemic brain tissue damage.
Results:
In vitro, the oxygen concentration in the cell suspension was < 1 mm Hg and ~70 mm Hg under nitrogen and air, respectively. The normoxic [18F]FETA uptake by the cells and the brain slices was low and constant over time (0.3±0.08 %ID.mio cells-1 and 0.04±0.01 %ID.g tissue-1). In contrast, under hypoxia a time-dependent linear increase of the [18F]FETA uptake was found which was 2.0- and 2.5-fold by the cells and 2.0- and 2.4-fold by the brain slices at 60min and 120min (p< 0.05), respectively. The analyses of nitroreductases activities showed that cell oxygenation does not affect the enzyme activities. The biodistribution studies revealed fast blood clearance, a rapid urinary excretion and a constantly low uptake in unaffected brain tissue (0.1±0.02 %ID.g-1). Ex vivo brain autoradiography in the pMCAO rats showed a relevant time-dependent [18F]FETA uptake in ipsilateral brain regions which reached maximum target-to background ratios of 3.3±0.2 at 3h. The corresponding [18F]FMISO uptake ratios were only 1.5±0.3 (p< 0.05). Furthermore, at 24h after pMCAO the lCBF was reduced in the infarction core (as determined by Nissl staining and MRI) and surrounding brain areas by 25% and 10%, respectively.
Conclusions:
These results demonstrate that [18F]FETA has a better potential than [18F]FMIS to serve as a brain hypoxia marker. Further testing of this promising new stroke PET marker is warranted. First results employing a new sheep stroke model developed recently by our group [1] are encouraging.
References:
[1] Boltze et al., J Cereb Blood F Metab 2008
First and second author contributed equally to this study
This research was supported by the Translational Centre for Regenerative Medicine Leipzig/BMBF (PtJ-Bio 0313909)
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Lecture (Conference)
XXIVth International Symposium on Cerebral Blood Flow, Metabolism and Function and the IXth International Conference on Quantification of Brain Function with PET, 29.06.-03.07.2009, Chicago, USA -
Abstract in refereed journal
Journal of Cerebral Blood Flow and Metabolism 29(2009)Suppl. 1, S42-S43
ISSN: 0271-678X
Permalink: https://www.hzdr.de/publications/Publ-12178
Scanning proximal probes for parallel imaging and lithography
Ivanova, K.; Sarov, Y.; Ivanov, T.; Frank, A.; Zöllner, J.; Bitterlich, C.; Wenzel, U.; Volland, B. E.; Klett, S.; Rangelowa, I. W.; Zawierucha, P.; Zielony, M.; Gotszalk, T.; Dontzov, D.; Schott, W.; Nikolov, N.; Zier, M.; Schmidt, B.; Engl, W.; Sulzbach, T.; Kostic, I.
Abstract
Scanning proximity probes are uniquely powerful tools for analysis, manipulation, and bottom-up synthesis. A massively parallel cantilever-probe platform is demonstrated. 128 self-sensing and self-actuated proximal probes are discussed. Readout based on piezoresistive sensors and bending control based on bimorph dc/ac actuations are described in detail.
Keywords: Scanning proximity probes; piezoresistive sensing; bimorph actuations; parallel cantilever-probe platform
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Journal of Vacuum Science & Technology B 26(2008)6, 2367-2373
DOI: 10.1116/1.2990789
Cited 51 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12177
Shaping of nanospheres into disks and rods with swift heavy ions
Schmidt, B.; Heinig, K.-H.; Mücklich, A.; Akhmadaliev, C.
Abstract
The swift heavy ion induced deformation of SiO2 and metal nanoparticles were studied intensively in the last years. Recently, we reported on ion beam shaping of Ge nanospheres. Surprisingly, Ge nanospheres in silica form oblate ellipsoids, what is opposite to prolate ellipsoids found for metal spheres.
This presentation reports on the experimental features of the shaping of Ge nanospheres and our theoretical search for the shaping mechanism(s). A stack of alternating Ge and SiO2 layers was sputtered on an oxidized Si wafer. The Ge layer thickness varied from 2.5 to 7.5 nm with 100 nm SiO2 in-between. Heating this layer stack to 950 °C for 300 s transformed each Ge layer into a layer of Ge nanospheres. With growing Ge layer thickness the mean diameter increases from 10 to 40 nm. After irradiation with (1-10)x1014 I7+cm-2 at 38 MeV, cross-section TEM images of as-prepared and irradiated samples showed that the largest Ge nanospheres kept spherical, whereas medium-size Ge spheres became oblates, and smaller ones shaped diamond-like. The different shaping of metal and semiconducting spheres is explained by their differences in thermodynamic properties.
Keywords: Ge nanoparticles; ion beam shaping
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Lecture (Conference)
Workshop "Ionenstrahlphysik und Nanotechnologie", 11.-12.04.2008, Darmstadt-Wixhausen, Germany
Permalink: https://www.hzdr.de/publications/Publ-12176
Electroluminescence in silicon nanocrystals fabricated by ion beam mixing and annealing of gate oxide/silicon interfaces
Schmidt, B.; Heinig, K.-H.; Beyer, V.; Stegemann, K.-H.
Abstract
A light emitting field-effect transistor (LEFET) which is based on silicon nanocrystals in the gate oxide is demonstrated. The Si nanocrystals in the gate oxide were optimized for a multi-dot floating-gate nonvolatile memory operation [1]. For this aim, ion irradiation through the MOSFET stack of 50 nm poly-Si/15 nm SiO2/Si substrate was performed with 50 keV Si+ ions. The ion beam mixing of the upper poly-Si/SiO2 interface and the lower SiO2/(001)Si interface leads to Si excess in the gate oxide. Subsequent rapid thermal annealing reforms sharp interfaces and separates the excess Si from SiO2. Adjacent to the recovered interfaces, 3-4 nm thick SiO2 zones denuded completely of excess Si have been found, whereas the more distant tails of excess Si form well-aligned narrow layers of nanocrystals with 2-3 nm diameter. LEFETs with an active gate area of 20x20 µm2 were fabricated as nMOSFET devices in a standard 0.6 µm CMOS process line. An AC voltage was applied to the gate in order to inject charges of both polarities into the lower and upper Si nanocrystal layer from the channel and the poly-Si gate of the transistor, respectively. AC voltage and frequency dependent electroluminescence spectra were recorded in the wavelength region of 400-1000 nm as a function of the annealing conditions. The performance of the LEFETs and further possibilities of optimization of efficient light emission will be discussed.
[1] B. Schmidt, et al. Nucl. Instr. and Meth. B 242 (2006) 146.
Keywords: Silicon nanocrystals; electroluminescence; light emitting field-effect transistor
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Lecture (Conference)
E-MRS Spring Meeting, 26.-30.05.2008, Strasbourg, France
Permalink: https://www.hzdr.de/publications/Publ-12175
Nanomagnets - created and tailored by ions
Abstract
Report on the activities in the field of ion beam modification of magnetic materials.
Keywords: magnetism; ion irradiation; focused ion beam; binary alloys; nanostructures
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Invited lecture (Conferences)
Physik von Nanostrukturen, 19.12.2008, Dresden, Deutschland -
Lecture (Conference)
International Seminar and Workshop on Magnonics: From Fundamentals to Applications, 02.-07.08.2009, Dresden, Deutschland -
Lecture (others)
Forschungsseminar, 13.05.2009, Berlin, Deutschland -
Invited lecture (Conferences)
Kolloquiumsvortrag Universität Paderborn, 02.07.2009, Paderborn, Deutschland -
Lecture (others)
SFB 668 - Kolloquium Magnetismus vom Einzelatom zur Nanostruktur, 16.06.2009, Hamburg, Deutschland -
Invited lecture (Conferences)
Nanoscale Modification of Surfaces and Thin Films, 30.08.-03.09.2009, Rathen, Deutschland -
Invited lecture (Conferences)
Kolloquium, Institute of Physics, 21.02.2014, Bhupaneshwar, Indien -
Invited lecture (Conferences)
Kolloquium, Universität Kiel, 27.01.2014, Kiel, Deutschland -
Invited lecture (Conferences)
Kolloquium Institute of Physics, Polish Academy of Sciences, 07.10.2014, Warschau, Polen -
Invited lecture (Conferences)
Eigth International Meeting on Recent Developments in the Study of Radiation Effects in Matter, 20.-23.09.2015, Kerteminde, Dänemark -
Invited lecture (Conferences)
Physikalisches Kolloquium, 13.10.2015, Leipzig, Deutschland -
Invited lecture (Conferences)
Colloquium, 17.05.2016, Krakow, Polen -
Invited lecture (Conferences)
Kolloquium, 07.07.2016, Leipzig, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-12174
Fundamentals and Modelling of Reactive Magnetron Sputtering
Moeller, W.
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Invited lecture (Conferences)
Tutorial "Fundamentals and Trends of Plasma Surface Processing", 14.09.2008, Garmisch-Partenkirchen, Germany
Permalink: https://www.hzdr.de/publications/Publ-12173
Reactive Magnetron Sputtering of Nitrides and Oxides: Understanding the Process and Optimizing the Film Quality
Moeller, W.
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Invited lecture (Conferences)
Plasmas, Surfaces, and Thin Films, 11.06.2008, London, United Kingdom
Permalink: https://www.hzdr.de/publications/Publ-12172
Nanostructures by Ion-Driven Self-Organisation: Can Ions Induce Order?
Moeller, W.
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Lecture (others)
VERA-Seminar, 05.06.2008, Wien, Austria
Permalink: https://www.hzdr.de/publications/Publ-12171
Nanostructures by Ion-Driven Self-Organisation
Moeller, W.
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Lecture (others)
Kolloquium des Max-Planck-Institutes für Plasmaphysik, 18.04.2008, Garching/ Muenchen, Germany
Permalink: https://www.hzdr.de/publications/Publ-12170
Forschung und Entwicklung für die Verfahrenstechnik
Kryk, H.
Abstract
In einem Übersichtsvortrag werden die Aktivitäten des Institutes für Sicherheitsforschung auf den Gebieten der Verfahrens-, Prozess- und Messtechnik vorgestellt. Dies umfasst sowohl die Arbeiten zur Prozessaufklärung und Reaktionskalorimetrie zur Erhöhung der Sicherheit und Effektivität chemischer Prozesse als auch die Entwicklung und Anwendung von Spezialmesstechnik zur Untersuchung von Mehrphasenströmungen in verfahrenstechnischen Apparaten und Anlagen einschließlich der Modellierung und Simulation unter Nutzung von CFD-Methoden.
Einen Schwerpunkt der Präsentation bilden die Möglichkeiten und Perspektiven des Einsatzes von Praktikanten, Diplomanden und Doktoranden chemisch-technischer Studienrichtungen am Institut für Sicherheitsforschung des FZD.
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Lecture (others)
Hochschul-Informationstag, 10.01.2008, Freiberg, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-12169
A rotating cell for in situ Raman spectroelectrochemical studies of photosensitive redox systems
Kavan, L.; Janda, P.; Krause, M.; Ziegs, F.; Dunsch, L.
Abstract
A recently developed rotating spectroelectrochemical cell for in situ Raman spectroscopic studies of photoreactive compounds without marked decomposition of the sample is presented. Photochemically unstable compounds like fullerenes are difficult to be studied under stationary conditions by in situ spectroelectrochemistry using laser excitation as in Raman spectroscopy. Therefore, a rotating spectroelectrochemical was developed to avoid these difficulties. The cell can be used for any type of a planar electrode and of electrode materials in contact with aqueous or non-aqueous solutions as well as ionic liquids under appropriate laser power and accumulation times. The innovative advantage consists in the precession movement of the spectroelectrochemical cell with an eccentric drive. This precession movement allows a fixed electrical connection to be applied for interfacing the electrochemical cell to a potentiostat. Hence, any electrical imperfections and noise, which would be produced by sliding contacts, are removed. Further advantage of the rotating cell is a dramatic decrease of the thermal load of the electrochemical system. The size of the spectroelectrochemical cell is variable and dependent on the thickness of the cuvettes used ranging up to ca. 10 mm. The larger measuring area causes a higher sensitivity in the spectroscopic studies using this cell. The as constructed spectroelectrochemical cell is easy to be handled. The application of the cell is demonstrated for ordered fullerene C60 layers and the spectroelectrochemical behavior of nanostructured fullerenes. Here the charge transfer at highly ordered fullerene C60 films was studied by in situ Raman spectroelectrochemistry under appropriate laser power and accumulation time without marked photodecomposition of the sample.
Keywords: spectroelectrochemistry; Raman spectroelectrochemical cell; in situ measurements; fullerenes; fullerene layers
- Analytical Chemistry 81(2009), 2017-2021
Permalink: https://www.hzdr.de/publications/Publ-12168
An anisotropic Heisenberg model on the trigonal lattice for multiferroic oxides
Kunze, T.; Gemming, S.; Olbrich, C.; Chaplygin, I.; Schmidt, P.; Schreiber, M.
Abstract
Hexagonal manganites are oxides, in which structural, electronic, and magnetic degrees of freedom are coupled in a complex manner. Therefore, such materials have the potential for novel, nanoscale sensing and switching applications. Manganites are composed of dense-packed hexagonal manganese oxide layers with strong in-plane and weak interlayer coupling, thus the possible spin configurations may be studied with the help of a two-dimensional model Hamiltonian. For this purpose a two-dimensionally periodic trigonal spin system is qualitatively studied with the help of an extended multiparameter Heisenberg model. The temperature dependence of the magnetisation is investigated with the help of a Metropolis-Monte-Carlo algorithm as a function of the anisotropy term and of an external magnetic field. Thermodynamic quantities such as the total energy, the heat capacity and the magnetization are determined by statistical evaluation.
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Poster
DPG Frühjahrstagung, 25.-29.02.2008, Berlin, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-12167
Nanoschreiben mit fokussierten Ionen
Bischoff, L.
Abstract
Fokussierte Ionenstrahlsysteme (FIB) sind ein modernes Werkzeug für die Strukturerzeugung sowie deren Analyse im µm bis in den nm- Bereich hinein. Ein Ionenstrahl, der aus einer Flüssigmetall-Ionenquelle (Liquid Metal Ion Source - LMIS) kommt wird mittels einer Ionenpotik beschleunigt und in einen Spot von bis zu wenigen nm fokussiert und dann Computergesteuert über die Probe geführt. Eine Auflösung von kleiner 10 nm bei Stromdichten von mehr als 10 Acm-2 können erreicht werden.
Der Einsatz von FIB Systemen ist spezialisiert auf die Präparation von Proben in der Analytik der Halbleiterindustrie sowie der nm - Strukturerzeugung in der Forschung. Die pixelweise Abarbeitung des Ionenstrahlschreibens ist für eine Massenproduktion nicht geeignet aber umso mehr für die Erzeugung von Prototypen neuer Bauelemente. Besonders effektiv ist die Kopplung des FIB mit einem Rasterelektronenmikroskop zu einem Zweistrahlsystem. Die Erweiterung auf neue Ionenarten durch den Einsatz spezieller Legierungen in der Ionenquelle eröffnet ein breites Spektrum neuer Anwendungsfelder.
Ausgewählte Applikationen aus dem FZD werden demonstriert und erläutert.
Keywords: Fokussierte Ionenstrahlsysteme; Strukturerzeugung; Analyse; nm- Bereich; Anwendungen
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Lecture (others)
Lange Nacht der Wissenschaften Dresden, 04.07.2008, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-12166
Application of mass-separated focused ion beams
Bischoff, L.; Akhmadaliev, C.; Pilz, W.; Schmidt, B.
Abstract
During the last decades, focused ion beams (FIB) became a very useful and versatile tool in microelectronics industry, as well as in the field of basic and applied research and derived an exceedingly importance within the nanotechnology. For special purposes like ion milling, ion beam writing for doping or patterning from the µm- to the nm-range without any lithographic steps using Gallium and also other ion species which are of increasing interest. An introduction in design and operation of mass separated FIB systems, equipped with alloy liquid metal ion sources and the development and characterization of suited alloy liquid metal ion sources is given and their preparation and characterisation is discussed.
Keywords: focused ion beams; alloy liquid metal ion source; preparation; characterisation
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Lecture (others)
Seminar at Carl Zeiss NTS, 07.05.2008, Oberkochen, Germany
Permalink: https://www.hzdr.de/publications/Publ-12165
Application of Focused Ion Beams
Bischoff, L.
Abstract
During the last decades, focused ion beams (FIB) became a very useful and versatile tool in microelectronics industry, as well as in the field of basic and applied research and derived an exceedingly importance within the nanotechnology. For special purposes like ion milling, ion beam writing for doping or patterning from the µm- to the nm-range without any lithographic steps using Gallium and also other ion species which are of increasing interest. An introduction in design and operation of mass separated FIB systems, equipped with alloy liquid metal ion sources and the development and characterization of suited ion sources is given.
Examples, like ion beam synthesis of CoSi2 nano-structures, sputtering investigations and applications, the formation of ripples under FIB irradiation or the fabrication of NEMS structures on SOI substrates should demonstrate the manifold utilization of the microbeam technology.
Finally an outlook to prospective work with FIB in FZD is presented.
Keywords: focused ion beam; nanotechnology; liquid metal ion source
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Lecture (others)
Seminar Materials Science at FZD, 28.10.2008, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-12164
Si+ implantation induced photoluminescence enhancement in PMMA
Tsvetkova, T.; Balabanov, S.; Avramov, L.; Borisova, E.; Bischoff, L.
Abstract
Si+ ion implantation effects on the photoluminescence (PL) properties of polymethyl-methacrylate (PMMA) have been studied. Low-energy ion implantation (E=30÷50 keV) was carried out over a range of different ion doses (D=1013÷1017 cm-2). The observed effect of PL enhancement (PLE) is essentially dependent on the ion dose. For certain doses, the overall amplitude of the PL emission has a several times (~ 5 times) increase. Electron microscopy results and surface elemental analysis reveal implanted Si atoms clustering which could be related to the observed PLE effects.
Keywords: ion implanted polymers; polymethyl-methacrylate; photoluminescence
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Przeglad elektrotechniczny 84(2008)3, 72-74
ISSN: 0033-2097
Permalink: https://www.hzdr.de/publications/Publ-12162
Ultrasound Doppler array used for vortex investigations in liquid metals
Franke, S.; Büttner, L.; Czarske, J.; Räbiger, D.; Eckert, S.
Abstract
An Ultrasound Doppler system for measuring the flow velocity field of magnetically-driven metal is introduced: Two orthogonally arranged sensor line arrays facilitate a two-dimensional measurement of two velocity components (2d/2c) in an area of 70 x 70 mm2. First measurement results of liquid metal flows driven by a rotating magnetic field are presented.
Keywords: Ultrasound Doppler method; sensor array; liquid metal; rotating magnetic field
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Lecture (Conference)
Sensor 2009, 26.-28.05.2009, Nürnberg, Germany
Permalink: https://www.hzdr.de/publications/Publ-12161
NEMS structures on SOI by writing FIB implantation and subsequent anisotropic wet chemical etching
Bischoff, L.; Schmidt, B.; Lange, H.
Abstract
The further miniaturization of silicon nanomechanical structures in combination with the highly developed microelectronic technology at the micro- and nanometer level will lead to a new generation of nano-electro-mechanical systems (NEMS). A modern technique to fabricate such three-dimensional structures is the combination of high-concentration p-type doping of silicon by high resolution writing implantation using a focused ion beam (FIB) and subsequent anisotropic and selective wet chemical etching. FIB-patterned and chemically etched 3D Si structures with nanoscale thickness and width have been fabricated using 30 keV Ga+ ion implantation and subsequent anisotropic etching in KOH/H2O solution on Silicon-On-Insulator (SOI) substrates. Design and fabrication considerations to achieve freestanding Si structures, like nanowires and -bridges are discussed and some typical structures are shown. Electrical measurements are demonstrated which reveal a broad spectrum in the field of sensor applications.
Keywords: nano-electro-mechanical systems; focused ion beam; anisotropic etching; sensor applications
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Lecture (Conference)
Ionenstrahlphysik und Nanotechnologie, 11.-12.04.2008, Darmstadt, Germany
Permalink: https://www.hzdr.de/publications/Publ-12160
Comparative study of gas-oil and gas-water two-phase flow in a vertical pipe
Szalinski, L.; Da Silva, M. J.; Thiele, S.; Beyer, M.; Lucas, D.; Hampel, U.; Hernandez Perez, V.; Abdulkareem, L. A.; Azzopardi, B. J.
Abstract
A wire-mesh sensor has been employed in a vertical pipe of 67 mm diameter and 6 m length to investigate two-phase flows of two different two-phase mixtures. Conductivity-based measuring electronics was used to measure water-air flow and permittivity-based one for silicone oil-air flow. This experimental setup enables a direct comparison of both two-phase flow systems. Thus, wire-mesh sensor data of both gas-liquid systems were analysed with regard to radial gas volume fraction profiles and bubble size distributions. Furthermore wire-mesh sensor images were evaluated to determine the occurring flow pattern. A flow pattern map was created which contains all experimental measurement points denoted with observed flow pattern.
Keywords: gas-liquid flow; flow visualization; wire-mesh sensor; capacitance; permittivity; conductivity
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Contribution to proceedings
3rd International Workshop on Process Tomography, 17.-19.04.2009, Tokyo, Japan
Proceedings of 3rd International Workshop on Process Tomography -
Lecture (Conference)
3rd International Workshop on Process Tomography (IWPT-3), 17.-19.04.2009, Tokyo, Japan -
Chemical Engineering Science 65(2010)12, 3836-3848
DOI: 10.1016/j.ces.2010.03.024
Cited 105 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12159
Nano-Structures made by Swift Heavy Ions
Bolse, W.; Paulus, H.; Bolse, T.; Bischoff, L.
Abstract
Recently we have discovered that the irradiation of thin oxide films with swift heavy ions (SHI) at small incident angles results in an instability of the film against periodic cracking and subsequent reorganisation on a sub-micron level due to ion hammering. Varying the conditions during irradiation (ion species, rotating the target) we were able to generate a wide range of nano-structures and patterns, the most interesting of which was an array of NiO-nanopillars with a diameter of the order of 100 nm and a height of about 2000 nm. Unfortunately, the arrangement of these nanotowers was not regular. [1] To overcome this problem, we have prestructured the films by means of a focused ion beam with an array of perpendicular cuts of about 100 nm width and 1000 nm distance. In fact, the subsequent irradiation with SHI under grazing incidence and permanent target rotation results in an ordered array of the NiO nanotowers. To our surprise, the same treatment of TiO-films lead to an ordered pattern of holes.
[1] W. Bolse, T. Bolse, C. Dais, D. Etissa-Debissa, A. Elsanousi, A. Feyh, M. Kalafat, H. Paulus, Surf. Coat. Technol. 200 (2005) 1430
Keywords: swift heavy ions; nano-structures; prestructured; focused ion beam; TiO-film
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Lecture (Conference)
72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.02.2008, Berlin, Germany
Permalink: https://www.hzdr.de/publications/Publ-12158
Spin-state transition and spin-polaron physics in cobalt oxide perovskites: ab initio approach based on quantum chemical methods
Hozoi, L.; Birkenheuer, U.; Stoll, H.; Fulde, P.
Abstract
A fully ab initio scheme based on quantum chemical wavefunction methods is used to investigate the correlated multiorbital electronic structure of a 3d-metal compound, LaCoO3. The strong short-range electron correlations, involving both Co and O orbitals, are treated by multireference techniques. The use of effective parameters like the Hubbard U and interorbital U′, J terms and the problems associated with their explicit calculation are avoided with this approach. We provide new insight into the spin-state transition at about 90 K and the nature of charge carriers in the doped material. Our results indicate the formation of a t2g
4eg
2 high-spin state in LaCoO3 for T > 90K. Additionally, we explain the paramagnetic phase in the low-temperature lightly doped compound through the formation of Zhang-Rice-like O hole states and ferromagnetic clusters.
Keywords: heavy fermions; electron correlation; local correlation methods; high-Tc superconductors
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New Journal of Physics 11(2009), 023023
DOI: 10.1088/1367-2630/11/2/023023
Cited 31 times in Scopus
Downloads
Permalink: https://www.hzdr.de/publications/Publ-12157
Ultrasound Doppler array system for flow field investigations in liquid metals
Franke, S.; Büttner, L.; Czarske, J.; Räbiger, D.; Eckert, S.
Abstract
An Ultrasound Doppler system for measuring the flow velocity field of magnetically-driven metal is introduced: Two orthogonally arranged sensor line arrays facilitate a two-dimensional measurement of two velocity components (2d/2c) in an area of 70 x 70 mm2. First measurement results of liquid metal flows driven by a rotating magnetic field are presented.
Keywords: Ultrasound Doppler method; sensor array; liquid metal; rotating magnetic field
- Flow Measurement and Instrumentation 21(2010)3, 402-409
Permalink: https://www.hzdr.de/publications/Publ-12156
Application of rate theory modeling to cluster evolution in binary Fe-Cu alloys
Birkenheuer, U.; Bergner, F.; Ulbricht, A.; Gokhman, A.; Almazouzi, A.
Abstract
A rate theory model for the simulation of the irradiation-induced time-evolution of Cu-rich precipitates in Fe-Cu model alloys is presented which takes into account that precipitate clusters are mixed Cu-vacancy aggregates by explicitly allowing the defect clusters to absorb vacancies. The resulting Vacancy-Coupled Copper Clustering (V3C) model is calibrated on a series of SANS experiments on two different Fe-Cu model alloys neutron-irradiated at four different doses. Quantitative agreement with the SANS experiments could be achieved by introducing a dependence of the Fe-Cu interface energy on the amount of vacancies in the mixed precipitate clusters. This energy is a function of the weight-percentage of Cu in the iron matrix. An analytic expression for this dependence is suggested.
Keywords: rate theory; percipitation; Fe-Cu model alloys; SANS experiments; neutron irradiation; irradiation damage; ageing of steels
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Contribution to HZDR-Annual report
Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZD-501 Dezember 2008, 70-76
ISSN: 1437-322X
Downloads
Permalink: https://www.hzdr.de/publications/Publ-12155
Fabrication of light-emitting Si quantum dots by pulsed annealing of Si-rich SiO2 layers
Kachurin, G. A.; Yankov, R. A.; Cherkova, S. G.; Marin, D. V.
Abstract
Thin Si-rich SiO2 layers have been prepared by implantation of 100 to 190 keV Si ions in thermally grown oxide films. The ion doses provided the excess Si concentration of about 10-15%. KrF excimer laser pulses, flash lamp annealing and rapid thermal annealing were used for the post-implantation heat treatments to form light-emitting Si quantum dots. The pulse durations were 20 ns, 20 ms and 1 s, respectively. Studies were carried out using a spectroscopy of PL excited at room temperature by a nitrogen laser (λ = 337 nm). The excess Si atoms in SiO2 are not free to migrate, but are rather incorporated into the oxide network. The fabrication of Si-ncs necessitates segregation of the Si atoms, availability of sinks to which these atoms may diffuse, availability of Si-phase nucleation centers, growth of the incipient nanoprecipitates, their crystallization, and, finally, the Ostwald ripening Due to the high temperatures resulting from intense light pulses, the different stages in the formation of light-emitting Si quantum dots may occur quite rapidly. Treatment for times as short as 20 ns is already sufficient for the segregation of the excess Si in the SiO2 atomic network and the formation of quantum dots that luminesce in the visible portion of the spectrum (400-600 nm). For laser pulse duration of 20 ns no formation of nanocrystals occurs, which is evidently associated with the insufficient growth time. However, if one creates in advance amorphous Si precipitates of the right size, it is possible to form quantum-size Si nanocrystals by pulsed laser processing. This process occurs most likely via melting rather than in a solid phase, favored by the release of latent heat and the reduction in temperature of melting of the nanoparticles. Photoluminescence band near 800 nm, typical to quantum-size Si nanocrystals, was found after laser annealing. Formation of the luminesing Si nanocrystals in Si-rich SiO2 layers is feasible under the influence of intense light pulses of 20 ms and 1 s duration. In this case the SiO2 layer has not been heated above the Si melting point. Comparison of the nanocrystals formation rate and the estimates of the diffusion-limited growth yields diffusivity of the excess Si in SiO2 that are substantially larger than the values obtained in experiments using stationary annealing. The discrepancies may be explained by the existence of a transient mechanism of rapid growth at the very beginning of the pulsed annealing.
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Poster
15th International Conference on Semiconductor Dots, 11.-16.05.2008, Gyeongju, Korea
Permalink: https://www.hzdr.de/publications/Publ-12153
Pulsed annealing creation of light-emitting Si nanostructures in SiO2 layers implanted with Si ions
Kachurin, G. A.; Cherkova, S. G.; Yankov, R. A.; Marin, D. V.
Abstract
Implantation of 100-190 keV Si ions in thin SiO2 layers followed by intense light pulse annealing was used to form Si quantum dots. The ion doses provided the excess Si concentrations of ~10-15%. KrF excimer laser pulses, flash lamp annealing and rapid thermal annealing were used for the post-implantation anneals. The pulse durations were 20ns, 20ms and 1s, respectively. Studies were carried out using photoluminescence excited at 20 oC by a N2 laser. Treatments for 20ns are already sufficient for the segregation of Si and formation of low-dimensional clusters, emitting light in the visible range (400-600 nm). For 20ns pulses no formation of Si-ncs occurs, which is associated with the lack of annealing time. However, if one creates in advance amorphous Si nanoprecipitates, it is possible to form Si-ncs by laser pulses. The crystallization occurs most likely via melting. Formation of the Si-ncs is feasible under the 20ms and 1s light pulses. In this case the temperatures never exceeded Si melting point. Comparison of the Si-ncs formation rate and the estimates of the expected diffusion-limited grain growth yields diffusivity of Si in SiO2 that is much higher, than the values obtained for stationary annealing. Possible mechanism of Si-ncs formation is discussed.
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Lecture (Conference)
9th International Conference on Applications of Nuclear Techniques, 08.-14.06.2008, Crete, Greece
Permalink: https://www.hzdr.de/publications/Publ-12152
Luminescing quantum-size Si nanostructures formed in Si rich SiO2 by intense light pulses
Kachurin, G. A.; Cherkova, S. G.; Yankov, R. A.; Marin, D. V.
Abstract
Implantation of Si ions in thin thermally grown SiO2 layers followed by intense light pulse annealing was used to form light-emitting Si nanostructures. The ion doses provided the excess Si concentration of about 10-15%. KrF excimer laser pulses, flash lamp annealing and rapid thermal annealing were used for the post-implantation heat treatments. The pulse durations were 20 ns, 20 ms and 1 s, respectively. Studies were carried out using a spectroscopy of PL excited at room temperature by a nitrogen laser (λ = 337 nm). Due to the high temperatures resulting from intense light pulses, the different stages in the formation of light-emitting Si nanostructures may occur quite rapidly. Treatment for times as short as 20 ns is already sufficient for the segregation of the excess Si in the SiO2 atomic network and the formation of clusters that luminesce in the visible portion of the spectrum (400-600 nm). For laser pulse duration of 20 ns no formation of nanocrystals occurs, which is evidently associated with the insufficient growth time. However, if one creates in advance amorphous Si precipitates of the right size, it is possible to form quantum-size Si nanocrystals by pulsed laser processing. This process occurs most likely via melting rather than in a solid phase, favored by the release of latent heat and the reduction in temperature of melting of the nanoparticles. Photoluminescence band near 800 nm, typical to quantum-size Si nanocrystals, was found after laser annealing. Formation of the luminesing Si nanocrystals in Si-rich SiO2 layers is feasible under the influence of intense light pulses of 20 ms and 1 s duration. In this case the SiO2 layer has not been heated above the Si melting point. Comparison of the nanocrystals formation rate and the estimates of the diffusion-limited growth yields diffusivity of the excess Si in SiO2 that are substantially larger than the values obtained in experiments using stationary annealing. The discrepancies may be explained by the existence of a transient mechanism of rapid growth at the very beginning of the pulsed annealing.
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Poster
The 15th International Conference on Luminescence and Optical Spectroscopy of Condensed Matter (ICL'08), 07.-11.07.2008, Lyon, France
Permalink: https://www.hzdr.de/publications/Publ-12151
Light-emitting Si nanostructures formed in Si-rich SiO2 by pulsed annealing
Kachurin, G. A.; Cherkova, S. G.; Yankov, R. A.; Marin, D. V.
Abstract
Formation of Si-nanocrystals hase been achieved under the influence of intense light pulses of 20 ms and 1 s duration. In this case the Si surface has not been observed to melt, and therefore the SiO2 layer has not been heated above 1400 °C. Comparison of the Si-nc formation rate and the estimates of the diffusion-limited growth yields diffusivity of the excess Si in SiO2 that are substantially larger than the values obtained in experiments using stationary annealing. The discrepancies have been explained by the occurrence of a transient mechanism of rapid growth at the start of the pulsed annealing.
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Poster
16th Annual International Conference on Composites/Nano Engineering (ICCE-16), 20.-26.06.2008, Kunming (City of Eternal Spring), China
Permalink: https://www.hzdr.de/publications/Publ-12150
Light-emitting Si nanostructures formed in Si implanted SiO2 layers by pulsed anneals
Kachurin, G. A.; Cherkova, S. G.; Marin, D. V.; Yankov, R. A.
Abstract
Thin thermally grown SiO2 layers were implanted with 100 to 190 keV Si ions. The ion doses provided the excess Si concentration of about 10-15%. KrF excimer laser pulses, flash lamp annealing and rapid thermal annealing were used for the post-implantation heat treatments to analyze their possibilities to synthesize the light-emitting Si nanocrystals (Si-ncs) and therewith the mechanism of Si-ncs formation . The pulse durations were 20 ns, 20 ms and 1 s, respectively. Studies were carried out using the photoluminescence spectroscopy, excited at 20 oC by a nitrogen laser (λ = 337 nm). The formation of Si-ncs necessitates segregation of the Si atoms from the oxide network, availability of sinks to which these atoms may diffuse, availability of Si-phase nucleation centers, growth of the incipient nanoprecipitates, and, finally, their crystallization. Treatment for times as short as 20 ns is already sufficient for the segregation of the excess Si and for formation of nanostructures that luminesce in the visible range (400-600 nm). For laser pulse duration of 20 ns no formation of Si-ncs occurs. However, if one creates in advance amorphous Si nanoprecipitates, it is possible to form the luminescing Si-ncs by the 20-ns pulses. This process occurs most likely via melting, favored by the release of the latent heat. Formation of the luminescing Si-ncs is feasible under the 20-ms and 1-s light pulses. In these cases the SiO2 layer has not been heated above the Si melting point. Comparison of the Si-ncs formation rate with their conjectural diffusion-limited growth suggests the existence of a transient non-diffusional mechanism at the beginning of the pulsed annealing.
-
Poster
16th International Conference on Ion Beam Modification of Materials, 31.08.-05.09.2008, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-12149
Light-emitting Si quantum dots formed by pulsed annealing
Kachurin, G. A.; Cherkova, S. G.; Yankov, R. A.; Marin, D. V.
Abstract
Pulsed anneals are of high practical importance as they enable one to perform heat treatment locally while affecting insignificantly the adjacent regions. This is particularly advantageous for the processing of low dimensional devices. The ongoing drive for smaller devices coupled with the discovery of strong luminescence from quantum-sized Si nanocrystals (Si-ncs) has spurred extensive research into the processes of their fabrication. Nowadays a decomposition of supersaturated solid solution of Si in SiO2 layers is mostly employed for this purpose. The fabrication of Si-ncs necessitates segregation of the Si atoms, availability of sinks to which these atoms may diffuse, availability of Si-phase nucleation centers, growth of the incipient clusters, and subsequent crystallization. Our work is an attempt to address the dependence of the light-emitting Si nanostructure formation on the length of the annealing light pulses. Implantation of Si ions in thin thermally grown SiO2 layers followed by intense light pulse annealing was used to form Si quantum dots. The ion doses provided the excess Si concentrations of about 10-15%. KrF excimer laser pulses, flash lamp annealing and rapid thermal annealing were used for the post-implantation heat treatments. The pulse durations were 20 ns, 20 ms and 1 s, respectively. Studies were carried out using photoluminescence excited at 20 °C by a N2 laser (λ = 337 nm). Due to the high temperatures resulting from intense light pulses, the different stages in the formation of light-emitting Si nanostructures may occur quite rapidly. Treatment for times as short as 20 ns is already sufficient for the segregation of the excess Si and the formation of low dimensional clusters that emit light in the visible range (400-600 nm). For 20 ns laser pulses of no formation of Si-ncs occurs, which is evidently associated with the insufficient growth time. However, if one creates in advance amorphous Si nanoprecipitates, it is possible to form Si-ncs by pulsed laser processing. The crystallization occurs most likely via melting rather than in a solid phase, favored by the release of latent heat and the reduction in temperature of melting of the low dimensional particles. Formation of the luminescing Si-ncs is feasible under the 20 ms and 1 s intense light pulses. In this case the temperatures never exceeded Si melting point. Comparison of the Si-ncs formation rate and the estimates of the expected diffusion-limited grain growth yields diffusivity of the excess Si in SiO2 that are several orders larger, than the values obtained in experiments using stationary annealing. Possible mechanism of Si-ncs formation is discussed.
-
Poster
Workshop on Recent Advances of Low Dimensional Structures and Devices (WRA-LDSD), 07.-09.04.2008, Nottingham, UK
Permalink: https://www.hzdr.de/publications/Publ-12148
Radiosynthesis and radiopharmacological evaluation of [N-methyl-11C]Org 34850 as a glucocorticoid receptor (GR)-binding radiotracer
Wüst, F.; Knieß, T.; Henry, B.; Peeters, B. W. M. M.; Wiegerinck, P. H. G.; Pietzsch, J.; Bergmann, R.
Abstract
The radiosynthesis of [N-methyl-11C]Org 34850 as a potential brain glucocorticoid receptor (GR)-binding radiotracer is described. The radiosynthesis was accomplished via N-methylation of the corresponding desmethyl precursor with [11C]methyl triflate in a remotely controlled synthesis module to give the desired compound in a radiochemical yield of 23+/-5% (decay-corrected, based upon [11C]CO2) at a specific activity of 47+/-12 GBq/mmol (n ¼ 15) at the end-of-synthesis (EOS). The radiochemical purity after semi-preparative HPLC purification exceeded 95%. The total synthesis time was 3540 min after end-of-bombardment (EOB).
The radiotracer is rapidly metabolized in rat plasma leading to the formation of two more hydrophilic metabolites as the major metabolites. Radiopharmacological evaluation involving biodistribution and small animal PET imaging in normal Wistar rats showed that the compound [N-methyl-11C]Org 34850 is not able to sufficiently penetrate the bloodbrain barrier. Therefore, compound [N-methyl-11C]Org 34850 seems not to be a suitable PET radiotracer for imaging rat brain GRs. However, involvement of Pgp or species differences requires further clarification to establish whether the radiotracer [N-methyl-11C]Org 34850 may still represent a suitable candidate for imaging GRs in humans.
Keywords: [N-methyl-11C]Org 34850; Glucocorticoid receptor; Positron emission tomography (PET)
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Applied Radiation and Isotopes 67(2009), 308-312
DOI: 10.1016/j.apradiso.2008.10.014
Cited 6 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12146
Messtechnik für Mehrphasenströmungen - Sensoren, Systeme und Anwendungen
Schleicher, E.; Da Silva, M. J.; Fischer, F.; Bieberle, A.; Bieberle, M.; Hampel, U.
Abstract
Die Untersuchung von Mehrphasenströmungen ist für viele Forschungs- und Industriebereiche von großer Bedeutung. Im Bereich der Verfahrenstechnik und Kernenergietechnik bestimmen beispielsweise das Verhalten und die Struktur von Gasblasen maßgeblich Effizienz und Sicherheit von Prozessen in Rohrsystemen, Behälter oder Reaktoren. Angesichts dieses breiten Anwendungsspektrums sind in der Vergangenheit verschiedene Messmethoden und Systeme entwickelt worden, um die Untersuchung von Mehrphasenströmungen zu ermöglichen, bestimmte Phänomene sichtbar zu machen und um numerische Strömungsmodelle s. g. CFD-Codes (computational fluid dynamics) zu validieren. Am Institut für Sicherheitsforschung des Forschungszentrums Dresden-Rossendorf wurden beispielsweise auf elektrischer Leifähigkeit sowie Kapazität basierende Systeme wie Nadelsonden und Gittersensoren entwickelt, die in Zweiphasenströmungen den Gasgehalt und die Phasenverteilung mit sehr hohen räumlichen und zeitlichen Auflösungen erfassen können. Darüber hinaus werden verstärkt auch nicht-invasive tomographische Verfahren wie die Gamma-CT und die ultraschnelle Röntgen-CT beforscht. Letztere ist in der Lage bis zu 7000 tomographische Schnittbilder pro Sekunde mit einer Ortsauflösung von bis zu 1 mm zu erzeugen.
Keywords: flow measurement; two-phase flow; Ultra fast X-ray CT; multi phase flow measurement; flow visualization; capacitance measurement; high resolution gamma ray tomography; void fraction determination; wire mesh sensor
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Invited lecture (Conferences)
Institutskolloquium, 25.11.2008, Dresden, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-12145
The Naimark dilated PT-symmetric brachistochrone
Günther, U.; Samsonov, B.
Abstract
The quantum mechanical brachistochrone system with PT-symmetric Hamiltonian is Naimark dilated and reinterpreted as subsystem of a Hermitian system in a higher-dimensional Hilbert space. This opens a way to a direct experimental implementation of the recently hypothesized PT-symmetric ultra-fast (wormhole-like) brachistochrone regime of [C. M. Bender et al, Phys. Rev. Lett. 98, 040403 (2007)] in an entangled two-spin system. The talk is mainly based on Phys. Rev. Lett. 101, 230404 (2008).
Keywords: quantum brachistochrone; quantum computing; PT quantum mechanics; strongly non-Hermitian regime; exceptional point; Anandan-Aharonov lower bound; ultra-fast evolution; POVM; Naimark dilation; Naimark extension; entangled state; two-qubit system; wormhole
-
Lecture (Conference)
QTRF5 - Quantum Theory: Reconsideration of Foundations, 5, 14.-19.06.2009, Vaxjo, Sweden
Permalink: https://www.hzdr.de/publications/Publ-12144
Photochemical reduction of UO22+ in the presence of alcohol studied by DFT calculations
Tsushima, S.
Abstract
A well-known photochemical process of UVIO2
2+ reduction to UVO2
+ in the presence of alcohols was studied by density functional theory (DFT) calculations. It was found that the first process which takes place is a photoexcitation of the ground-state UO2
2+ to the triplet excited state (*UO2
2+) followed by a significant shortening of the *UO2
2+-to-alcohol Oax-H distance. A charge transfer from *UO2
2+ to alcohol and hydrogen abstraction takes place in the following step. Consequently, UVIO2
2+ gets reduced to UVO(OH)2+. The photochemical byproduct RC·HOH acts further as a reducing agent toward UO2
2+ to yield UO2
+ and RCHO (aldehyde). Only a combination of these two reactions can explain a high quantum yield of this reaction. In the absence of alcohol, the lowest-lying triplet state exhibits a different character, and photoreduction is unlikely to take place via the same mechanism. The present results agree well with recent experimental finding [J. Am. Chem. Soc. 2006, 128, 14024] and supports the idea that the Oax-H linkage between UO2
2+ and the solvent molecule is the key to the photochemical reduction process.
- Inorganic Chemistry 48(2009)11, 4856-4862
-
Lecture (Conference)
ROBL-Radiochemie Workshop, 18.12.2008, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-12143
Anisotropic scaling of ripple morphologies on high-fluence sputtered silicon
Keller, A.; Cuerno, R.; Facsko, S.; Möller, W.
Abstract
The evolution of Si(100) surfaces has been studied during oblique high-fluence ion sputtering by means of atomic force microscopy. The observed surface morphology is dominated by nanoscale ripples and kinetic roughening at small and large lateral scales, respectively. The large-scale morphology exhibits anisotropic scaling at high fluences with different roughness exponents an = 0.76 ± 0.04 and ap = 0.41 ± 0.04 in the directions normal and parallel to the incident ion beam, respectively. Comparison with the predictions of single field and two-field ("hydrodynamic") models of ion erosion suggests the relevance of nonlinearities that are not considered in the simpler anisotropic Kuramoto-Sivashinsky equation.
-
Physical Review B 79(2009)11, 115437
DOI: 10.1103/PhysRevB.79.115437
Cited 45 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12142
Sorption databases for increasing confidence in performance assessment
Richter, A.; Brendler, V.; Nebelung, C.; Payne, T.; Brasser, T.
Abstract
World-wide activities focus on the remediation of radioactively contaminated sites. One common aim is to deliver a more profound chemical base for risk assessment, namely all those physico-chemical phenomena governing the contamination plume development in time and space. Coupled transport codes able to tackle this challenge have to simplify the resulting very complex reaction pattern. To do so in an adequate way requires extending the knowledge about retardation and mobilisation phenomena and the underlying basic processes and interactions (e.g. physisorption, chemisorption, surface precipitation).
Interactions at the solid-liquid interface can be described by two complementary approaches, the empirical Kd concept and the mechanistic Surface Complexation Models (SCM).
Kds are used by most reactive transport and risk assessment codes due to the straightforward numerics involved. In addition, the Kd concept is often the only feasible option for complex solid phases. However, the Kd concept is a rather simplistic approach. Many very different basic physico-chemical phenomena are contained in just one conditional parameter. Therefore, extrapolating Kd values may yield very large uncertainties.
SCM allows for the partitioning of retardation into the most important underlying physico-chemical processes. Parameters are site-independent and applicable despite large variations in geochemical conditions. This presents a high potential to increase confidence in safety analysis and risk assessment studies (performance assessment). The mechanistic description of sorption processes with SCM allows a thermodynamically consistent calculation of the species distribution between liquid and solid phase combined with more reliable inter- and extrapolations. However, this requires that all mineral constituents of the solid phase are characterized. Another issue is the large number of required parameters combined with time-consuming iterations.
Addressing both approaches, we present two sorption databases, developed mainly by or under participation of the Forschungszentrum Dresden-Rossendorf (FZD). Both databases are implemented as relational databases, assist identification of critical data gaps and the evaluation of existing parameter sets, provide web based data search and analyses and permit the comparison of SCM predictions with Kd values.
RES³T (Rossendorf Expert System for Surface and Sorption Thermodynamics) is a digitized thermodynamic sorption database (see www.fzd.de/db/RES3T.login) and free of charge. It is mineral-specific and can therefore also be used for additive models of more complex solid phases.
ISDA (Integrated Sorption Database System) connects SCM with the Kd concept but focuses on conventional Kd. The integrated datasets are accessible through a unified user interface.
An application case, Kd values in Performance Assessment, is given.
Keywords: RES3T; ISDA; database; sorption; surface complexation; KD; prediction
-
Lecture (Conference)
ICEM'09 - 12th International Conference on Environmental Remediation and Radioactive Waste Management, 11.-15.10.2009, Liverpool, United Kingdom -
Contribution to proceedings
ICEM 2009, 11.-15.10.2009, Liverpool, United Kingdom
Proceedings of the 2009 12th International Conference on Environmental Remediation and Radioactive Waste Management, ICEM2009-16053
Permalink: https://www.hzdr.de/publications/Publ-12141
Sizing of safety valves using ANSYS CFX-Flo
Moncalvo, L.; Friedel, B.; Jörgensen, T.; Höhne, T.
Abstract
This work discusses the effect of the degree of fineness of the flow volume discretization and that of the turbulence model on the accuracy of reproduction of air mass flow rates in two safety valves using the CFD software ANSYS Flo. Calculations show that the degree of fineness of the discretization is the decisive factor
affecting the exactness of the calculations and that the best reproduction is achieved with grids where at least two cells are built on the smallest edge. The selection of the turbulence model has by far in comparison a lower impact; however, the best accuracy is obtained using the standard k-x model and the SST modification of Menter.
Keywords: CFD; Safety valves
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Chemical Engineering & Technology 32(2009)2, 1-6
DOI: 10.1002/ceat.200800530
Cited 24 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12140
Site-selective determination of coordination symmetries by anisotropic anomalous X-ray scattering
Zschornak, M.; Leisegang, T.; Stöcker, H.; Weißbach, T.; Gemming, S.; Meyer, D. C.
Abstract
Based on an experiment of Kirfel and Petcov on rutile (136) P42/mnm, which verified anisotropic anomalous scattering (AAS) by measuring Forbidden Reflection near Edge Diffraction (FRED), we aimed to extend the results with allowed reflections to extract more tensor symmetries of the Ti scattering factor tensor f ij by fitting the model of AAS to the experimental data. Results from DFT calculations will also be presented. Furthermore we intended to study possible restrictions for atomic site occupation of unknown structures in an identified space group due to these local symmetry relations exemplary for this model structure.
Experiments were carried out at DESY/HASYLAB BL C using a Si (111) double crystal monochromator tuned to an energy of 4985eV. An automated optimization and Y-scan routine for a sample setup with rotating degree of freedom assured AAS measurements at the reflection maxima. The rutile samples investigated were 10x10x1mm3 wafers in (001), (110) and (111) orientation and Y-scans were measured for the reflections 001, 220, 110 and 111.
Ti occupies Wyckoff site 2a, its tensor symmetry must follow the local symmetry m.mm leaving 3 complex elements f 11, f 12, f 33. Simulations showed dependencies: 001 to f 12, 220 to f 11- f 33, 110 to f 11- f 33, 111 to f 12. For the 001 reflection intensity real and imaginary part correlate, but the 111 intensity displays asymmetric influence so the ambiguity is separable.
The measured data show clear evidence of AAS and the 001 FRED and 111 intensities could be fitted:
f Ti d 12 = -5.44 * 0.5(8)
f Ti d 12 = 3.98 * 1.4(2)
Since f 13 and f 23 were refined to zero, the positioning of Ti in the unit cell would by inverse symmetry arguments only be consistent with respect to site symmetry on Wyckoff sites a, b, e, f, g (out of k ).
Keywords: Anisotropic Anomalous X-Ray Scattering; Resonant X-Ray Scattering; Forbidden Reflection near Edge Diffraction
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Poster
XXI Congress and General Assembly of the International Union of Crystallography, 23.-31.08.2008, Osaka, Japan
Permalink: https://www.hzdr.de/publications/Publ-12139
Anisotropic Anomalous Scattering in Rutile TiO2
Zschornak, M.; Leisegang, T.; Gutmann, E.; Stöcker, H.; Meyer, D. C.
Abstract
Based on an experiment of A. Kirfel and A. Petcov on rutile TiO2, space group (136) P42 mnm in 1989 [1], which verified the anisotropic anomalous scattering (AAS) in rutile through measuring Forbidden Reflection near Edge Diffraction (FRED) intensity at the 100 and 001 forbidden reflections just above the Ti-K absorption edge, we aimed to extend the results by measuring AAS not only for forbidden but also for allowed reflections, to find effects of anisotropy also in this case and to fit the model of anisotropic scattering [2] to the experimental data.
Experiments were carried out at DESY/HASYLAB beamline C1 (CEMO) using a (111) double crystal monochromator at the Ti resonance energy E = 4985 eV. An automated optimization and Y-scan routine called Peak-Optimized-Psi-Scan (POPS) which we programmed with LabView for a sample setup with rotating degree of freedom was tested for the first time for synchrotron conditions.
The rutile samples investigated were three 10 x 10 x 1 mm3 wafers synthesized by Crystec GmbH in (001), (110) and (111) orientation and Y-scans were measured for the reflections 001, 220, 110 and 111, respectively. Since the Ti in rutile occupies Wyckoff site 2a, its tensor symmetry must follow the local symmetry m.mm leaving 3 independent complex elements for the symmetric scattering tensor, f 11, f 12 and f 33. Calculations and simulations with the developed TensorScattering code (Fig. 1) showed following dependencies: 001 to f 12, 220 to f 11- f 33, 110 to f 11- f 33 and 111 to f 12. For the 001 reflection intensity the real and imaginary parts correlate, but the 111 intensity shows asymmetric influence so that the ambiguity should be separable.
The measured data show clear evidence of AAS and the 001 FRED and 111 reflection intensities could be fitted quite reasonably within the model. They were fitted simultaneously because both only depend on f 12, since the 111 is also forbidden within the Ti partial structure and the isotropic flat contribution is caused only by the oxygen partial structure. Within the fit the isotropic part of the 111 reflection intensity locks the constant and the asymmetry detangles f 12 and f 12. They were evaluated due to refinement as:
f 12 = f Ti(E=4985eV) * d 12 = -5.44 el * 0.58(2)
f 12 = f Ti(E=4985eV) * d 12 = 3.98 el * 1.42(0)
References
[1] A. Kirfel, A. Petcov, Anisotropy of anomalous dispersion. II. FRED (Forbidden Reflection near Edge Diffraction) in Rutile, TiO2, HASYLAB/DESY Jahresbericht (1989) 385-386.
[2] A. Kirfel, W. Morgenroth, Anisotropy of anomalous scattering in X-ray diffraction. III. `Forbidden' axial reflections in space groups up to orthorhombic symmetry, Acta Crystallogr. A 49 (1993) 35-45.
Keywords: Anisotropic Resonant X-Ray Scattering; Anisotropic Anomalous X-Ray Scattering; Forbidden Reflection near Edge Diffraction
-
Poster
16. Jahrestagung der Deutschen Gesellschaft für Kristallographie, 03.-06.03.2008, Erlangen, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-12138
Study of omega-meson production in pp collisions at ANKE
Barsov, S.; Buscher, M.; Hartmann, M.; Hejny, V.; Kacharava, A.; Keshelashvili, I.; Khoukaz, A.; Koptev, V.; Kulessa, P.; Kulikov, A.; Lehmann, I.; Leontyev, V.; Macharashvili, G.; Maeda, Y.; Mersmann, T.; Merzliakov, S.; Mikirtytchyants, S.; Mussgiller, A.; Oellers, D.; Ohm, H.; Rathmann, F.; Schleichert, R.; Seyfarth, H.; Stroher, H.; Trusov, S.; Valdau, Y.; Wustner, P.; Yaschenko, S.; Wilkin, C.
Abstract
The production of omega-mesons in the pp --> pp omega reaction has been investigated with the COSY-ANKE spectrometer for excess energies of 60 and 92 MeV by detecting the two final protons and reconstructing their missing mass. The large physical background was subtracted using an event-by-event transformation of the proton momenta between the two energies. Differential distributions and total cross-sections were obtained after careful studies of possible systematic uncertainties in the overall ANKE acceptance. The results are compared with the predictions of theoretical models. Combined with data on the phi-meson, a more refined estimate is made of the Okubo-Zweig-Iizuka rule violation in the phi/omega production ratio.
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European Physical Journal A 31(2007), 95
DOI: 10.1140/epja/i2006-10161-2
ISSN: 1434-6001
Cited 22 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12137
Prediabetic and diabetic in vivo modification of circulating low density lipoprotein attenuates its stimulatory effect on adrenal mineralocorticoid secretion
Kopprasch, S.; Pietzsch, J.; Ansurudeen, I.; Graessler, J.; Krug, A. W.; Erhart-Bornstein, M.; Bornstein, S. R.
Abstract
Modification of low-density lipoprotein (LDL) and abnormal aldosterone and cortisol metabolism have been implicated in the pathogenesis of type 2 diabetes (DM2) and diabetic vascular disease. Since LDL serves as a major cholesterol source for adrenal steroidogenesis, we investigated whether LDL modification in prediabetic and diabetic subjects influences adrenocortical aldosterone and cortisol release. LDL was isolated from 30 subjects with normal glucose tolerance (NGT-LDL), 30 subjects with impaired glucose tolerance (IGT-LDL), and 26 patients with DM2 (DM2-LDL). Oxidation and glycoxidation characteristics of LDL apolipoprotein B100 of each individual was assessed by gas chromatography-mass spectrometry analysis. Human adrenocortical cells (NCI-H295R) were incubated for 24 h with 100 microg/ml LDL and after removal of supernatants stimulated for a further 24 h with angiotensin II (AngII). In supernatants, aldosterone and cortisol secretion was measured. IGT-LDL and DM2-LDL were substantially more modified than NGT-LDL. Each of the five measured oxidation/glycoxidation markers was significantly positively associated with glycemic control, measured as HbA(1c). LDL from all subjects stimulated both the basal and AngII-induced aldosterone and cortisol release from adrenocortical cells. However, hormone secretion was significantly inversely related to the degree of LDL oxidation/glycoxidation. We conclude that LDL modifications in IGT and DM2 subjects may have significant clinical benefits by counteracting prediabetic and diabetic overactivity of the renin-angiotensin-aldosterone system and enhanced cortisol generation.
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Journal of Endocrinology 200(2009), 45-52
DOI: 10.1677/JOE-08-0293
Cited 11 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12136
Resonant two-photon transitions, quadratic detection, and photocurrent autocorrelation using multiple quantum wells
Schneider, H.; Liu, H. C.; Winnerl, S.; Drachenko, O.; Helm, M.; Walther, M.; Faist, J.
Abstract
We report on two-photon detection based on quantum well intersubband nonlinear absorption. Three equidistant subbands, two of which are bound in the quantum well, and the third one in the continuum, result in a resonantly enhanced optical nonlinearity, which is by six orders of magnitude stronger than in usual semiconductors [1]. This device is very promising for quadratic autocorrelation measurements of pulsed mid-infrared sources, including modelocked quantum cascade lasers, radiation obtained by nonlinear optical frequency conversion, and free-electron lasers (FEL). Using these detectors as a quadratic autocorrelator for mid-infrared pulses, temporal resolution is only limited by the sub-ps intrinsic time constants of the intersubband transitions, namely the intersubband relaxation time and the phase relaxation time. We have investigated the performance of devices operating at various wavelengths from the mid-infrared to the Terahertz regimes using ps optical pulses from the FEL at the Forschungszentrum Dresden Rossendorf. In particular, device operation at shorter wavelengths around 5.5 µm is still possible at room temperature, which is crucial for applications in practical systems.
[1] H. Schneider, T. Maier, H. C. Liu, M. Walther, and P. Koidl, Optics Lett. 30, 287 (2005).
Keywords: intersubband transition; two-photon absorption; quantum well infrared photodetector; autocorrelation; free-electron laser
-
Invited lecture (Conferences)
SPIE Photonics West, 24.-29.01.2009, San Jose, CA, USA
Permalink: https://www.hzdr.de/publications/Publ-12135
Two-photon photocurrent spectroscopy of quantum well intersubband relaxation and dephasing
Schneider, H.; Liu, H. C.; Maier, T.; Walther, M.
Abstract
We have studied electron intersubband relaxation and dephasing in n-type InGaAs/AlGaAs quantum wells by femtosecond two-photon photocurrent spectroscopy using mid-infrared pulses of 165 fs duration. The approach enables us to determine systematically the dependence of these time constants on structural parameters, including carrier density and modulation/well doping, and to discriminate between different scattering processes [1]. By varying the excitation energy, we also tuned the two-photon transition from resonant, yielding optimum resonant enhancement with a real intermediate state, to nearly-resonant, with a virtual but resonantly enhanced intermediate state [2]. For autocorrelation purposes, the latter configuration improves time resolution whilst partially retaining a resonant enhancement of the two-photon transition strength.
[1] H. Schneider, T. Maier, M. Walther, H. C. Liu, Appl. Phys. Lett. 91, 191116 (2007).
[2] H. Schneider, T. Maier, H. C. Liu, M. Walther, Opt. Express 16, 1523 (2008).
Keywords: intersubband transition; two-photon absorption; quantum well infrared photodetector; phase relaxation; autocorrelation
-
Invited lecture (Conferences)
SPIE Photonics West, 24.-29.01.2009, San Jose, CA, USA
Permalink: https://www.hzdr.de/publications/Publ-12134
Quadratic detection with two-photon quantum well infrared photodetectors
Schneider, H.; Liu, H. C.; Winnerl, S.; Drachenko, O.; Helm, M.; Walther, M.; Faist, J.
Abstract
Two-photon quantum well infrared photodetectors (QWIPs) are based on three equidistant subbands, two of which are bound in the quantum well, and the third one in the continuum. This configuration leads to a resonantly enhanced optical nonlinearity, which is by six orders of magnitude stronger than in bulk semiconductors [1]. This device is useful for quadratic autocorrelation measurements of pulsed mid-infrared sources, including modelocked quantum cascade lasers, radiation obtained by nonlinear optical frequency conversion, and free-electron lasers (FEL). In quadratic autocorrelation experiments, temporal resolution of two-photon QWIPs is only limited by the sub-ps intrinsic time constants of the intersubband transitions, namely the intersubband relaxation time and the phase relaxation time.
We will report on autocorrelation measurements at various wavelengths from the mid-infrared to the Terahertz regimes using ps optical pulses from the FEL at the Forschungszentrum Dresden Rossendorf. In particular, quadratic detection at wavelengths around 5.5 µm is still possible at room temperature [2], which is crucial for applications in practical systems. Two-photon detection beyond the Reststrahlen band will also be addressed.
[1] H. Schneider, T. Maier, H. C. Liu, M. Walther, and P. Koidl, Optics Lett. 30, 287 (2005).
[2] H. Schneider, H. C. Liu, S. Winnerl, O. Drachenko, M. Helm, J. Faist, App. Phys. Lett. 93, 101114 (2008).
Keywords: intersubband transition; two-photon absorption; quantum well infrared photodetector; autocorrelation
Involved research facilities
- F-ELBE
-
Lecture (Conference)
Quantum Structure Infrared Photodetector (QSIP) 2009 International Conference, 18.-23.01.2009, Yosemite, USA -
Infrared Physics and Technology 52(2009), 419
DOI: 10.1016/j.infrared.2009.05.036
Cited 8 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12133
A field-focusing imaging sensor for fast visualization of multiphase flows
Da Silva, M. J.; Hampel, U.
Abstract
A novel imaging sensor based on multichannel capacitance measurement is introduced in this article. The field-focusing sensor uses a multitude of strip electrodes located at two opposing and parallel walls of a vessel, whereby the opposing electrodes run perpendicular to each other. By the use of a special multiplexed excitation-sensing scheme a focusing of the electrical field to well-defined regions within the sensor is achieved which allows the sensor to individually interrogate each one of those regions and thus to two-dimensionally map the flow constituents contained by the sensor. Associated electronics can generate up to 625 frames per second. The sensor can be considered as a high-speed capacitance camera for a channel flow. Electrical field simulations with finite element method confirm the focusing effect explored by the sensor. The imaging capability is shown by the visualization of a stratified air-water mixture. Furthermore, the sensor was used to monitor the transient behaviour of the mixing of two substances with different densities.
Keywords: electrical capacitance; sensor; flow visualization; multiphase flow; electrical field simulation; finite element method
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Measurement Science and Technology 20(2009)10, 104009
DOI: 10.1088/0957-0233/20/10/104009
Cited 22 times in Scopus
Downloads
Permalink: https://www.hzdr.de/publications/Publ-12132
Photosensitive defects in silica layers implanted with germanium ions
Zatsepin, A. F.; Fitting, H.-J.; Kortov, V. S.; Pustovarov, V. A.; Schmidt, B.; Buntov, E. A.
Abstract
Ge-implanted silica layers have been investigated by high-power pulsed synchrotron-photoluminescence (PL), photoluminescence excitation spectroscopy (PLE), and optically stimulated electron emission (OSEE) with respect to association of excitation and absorption bands to respective emission bands and lifetimes of excited defect states. In this way singletsinglet (4.35 eV) and tripletsinglet (3.18 eV) radiative transitions from excited states of oxygen-deficient centers (ODC) in Ge-doped silica glass are characterized by their absorption and emission bands as well as their lifetimes. The main channel for non-radiative relaxation of photoexcitation is electron emission by the OSEE effect. The OSEE shows non-radiative transitions of surface E's and bulk E'-centers found with concentrations of (2.73.4)x1012 cm-2 and (24)x1016 cm-3, respectively.
Keywords: Synchrotron radiation; Radiation effects; Defects; Optical properties; Absorption Luminescence; Optical spectroscopy; Photoinduced effects; Time resolved measurements; Oxide glasses; Silica; Structure defects; Short-range order
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Journal of Non-Crystalline Solids 355(2009), 61-67
DOI: 10.1016/j.jnoncrysol.2008.08.025
Cited 16 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12131
QCD equation of state: Physical quark masses and asymptotic temperatures
Bluhm, M.; Kämpfer, B.; Schulze, R.; Seipt, D.
Abstract
Within a phenomenological quasiparticle model, the quark mass and temperature dependence of the QCD equation of state is discussed and compared with lattice QCD results. Different approximations for the quasiparticle dispersion relations are employed, scaling properties of the equation of state with quark mass and deconfinement temperature are investigated and a continuation to asymptotically large temperatures is presented.
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Contribution to proceedings
International School of Nuclear Physics - 30th Course: Heavy-Ion Collisions from the Coulomb Barrier to the Quark-Gluon Plasma, 16.-24.09.2008, Erice, Sicilia, Italia
QCD equation of state: Physical quark masses and asymptotic temperatures -
Progress in Particle and Nuclear Physics 62(2009), 512-517
DOI: 10.1016/j.ppnp.2008.12.041
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12130
Sintes prekursora alumooxidnoj keramiki, uprotschnennoj dioxidom zirkonija, is neorganitscheskich sojedinenii v prisutstvii motschevini
Scharnylskaja, A. L.; Wolchin, W. W.; Schtscherban, M. G.; Reuther, H.
Abstract
Sintes prekursora alumooxidnoj keramiki, uprotschnennoj dioxidom zirkonija, is neorganitscheskich sojedinenii v prisutstvii motschevini
- Zurnal prikladnoj chimii 81(2008), 1069-1074
Permalink: https://www.hzdr.de/publications/Publ-12129
Surface nanostructuring of TiO2 thin films by ion beam irradiation
Romero-Gomez, P.; Palmero, A.; Yubero, F.; Vinnichenko, M.; Kolitsch, A.; Gonzalez-Elipe, A. R.
Abstract
This work reports a procedure to modify the surface nanostructure of TiO2 anatase thin films through ion beam irradiation with energies in the keV range. Irradiation with N+ ions leads to the formation of a layer with voids at a depth similar to the ion-projected range. By setting the ion-projected range a few tens of nanometers below the surface of the film, well-ordered nanorods appear aligned with the angle of incidence of the ion beam. Slightly different results were obtained by using heavier (S+) and lighter (B+) ions under similar conditions.
Keywords: ion beam irradiation; titanium dioxide; anatase
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Scripta Materialia 60(2009), 574-577
DOI: 10.1016/j.scriptamat.2008.12.014
Cited 23 times in Scopus
Downloads
Permalink: https://www.hzdr.de/publications/Publ-12128
Surface Doping of VT6 Alloy with Zirconium by Pulsed Electron-Beam Mixing of Predeposited Multilayer Zr/Ti Film
Rotshtein, V. P.; Markov, A. B.; Shevchenko, N.; Reuther, H.; Oskomov, K. V.; Shulov, V. A.
Abstract
We have studied characteristics of the surface doping of VT6 alloy (Ti-6Al-4V) with zirconium, which was effected in order to reduce the concentrations of Al and V at the surface. The doping was performed by liquid-phase mixing of a Zr(20 nm)/Ti(20 nm). It is established that the pulsed beam-induced melting leads to the homogeneous mixing of all Ti/Zr nanolayers and the diffusion of Zr into substrate to a depth of similar to 0.5 µm. As a result, the surface layer with a thickness of similar to 0.5 µm is free of Al and V atoms and has a single-phase submicrocrystalline structure of alpha-Ti70Zr30 solid solution. Subsequent vacuum annealing leads to a decrease in the average grain size in the nearsurface layer to 90 nm and to an increase in the nanohardness of the doped layer.
Keywords: Ti alloy; multilayer; electron beam; surface treatment; nanohardness
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Technical Physics Letters 34(2008)10, 891-894
ISSN: 1063-7850
Permalink: https://www.hzdr.de/publications/Publ-12127
In situ study of the effect of Sn doping on the electrical properties of indium oxide
Rogozin, A.; Vinnichenko, M.; Shevchenko, N.; Kreissig, U.; Kolitsch, A.; Möller, W.
Abstract
Indium oxide (In2O3) and ITO (In2O3 :Sn) amorphous films grown by pulsed reactive magnetron sputtering have been annealed in vacuum. The film structure and properties have been studied during annealing using in-situ diagnostics. The evolution of the film structure has been continuously monitored by synchrotron X-ray diffraction at the European Synchrotron Radiation Facility in Grenoble, France. Four point probe measurements, spectroscopic ellipsometry, and elastic recoil detection analysis have been undertaken to determine and correlate with the structure in real time the evolution of the film resistivity (ρ), the free electron density (Ne), and the film stoichiometry. At the start of annealing both the In2O3 and the ITO films show a fast decrease in ρ and an increase in Ne, which is explained by the formation of oxygen vacancies and reordering of the amorphous phase. Subsequent film crystallization does not influence the In2O3 film electrical properties, but causes a further decrease in ITO resistivity due to the Sn donor activation. The estimated efficiency of the Sn donor activation is 40%. All the films show during annealing a resistivity decrease which is caused not only by an increase in the free carrier density, but also by a rise in the electron mobility.
Keywords: Indium oxide; ITO; annealing; in-situ; electrical properties; Sn donor
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Lecture (Conference)
14th International Conference on Thin Films & Reactive Sputter Deposition 2008, 17.-20.11.2008, Ghent, Belgium
Permalink: https://www.hzdr.de/publications/Publ-12126
Equation of state for strongly interacting matter within a HTL quasiparticle model
Schulze, R.
Abstract
Equation of state for strongly interacting matter within a HTL quasiparticle model
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Lecture (Conference)
International School of Nuclear Physics, 22.09.2008, Erice, Italy
Permalink: https://www.hzdr.de/publications/Publ-12125
Estrogen detection in drinking water by Silicon based light emitters
Cherkouk, C.; Rebohle, L.; Skorupa, W.; Helm, M.
Abstract
The immediate and accurate monitoring of chemical and biological substances is essential in environmental analysis for minimizing the health risk for citizens and their exposure to pollutants. Recently, considerable attention has been focused on endocrine-disrupting compounds EDCs, such as estrogens, which constitute a wide group of environmental pollutants, especially in drinking water.
A new concept for measuring the concentration of such organic compounds by using Si-based integrated light sources for fluorescence analysis is presented. In that concept the analyte, estrogen in this example, is labelled with a Fluorescence marker and is immobilized at the passivated surface of the light emitter by receptor molecules. This kind of labelling opens a way to extremely small device dimensions and is of great interest for point-of-care measurements.
The current system has been characterized by FTIR, Raman and electroluminescence measurements.
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Lecture (Conference)
E-MRS 2008 Spring Meeting, 26.-30.05.2008, Straßburg, France
Permalink: https://www.hzdr.de/publications/Publ-12124
The effect of ITO film thickness on the microstructure evolution and crystallization kinetics during annealing
Shevchenko, N.; Rogozin, A.; Vinnichenko, M.; Kolitsch, A.; Moeller, W.
Abstract
Amorphous indium tin oxide (ITO) films have been grown by reactive pulsed medium-frequency dual magnetron sputtering on Si substrates covered with SiO2. The real-time evolution of the ITO film structure during annealing has been investigated by synchrotron X-ray diffraction at ROssendorf Beam Line (ROBL) located at the European Synchrotron Radiation Facility in Grenoble, France. The annealing experiments have been carried out in a UHV annealing chamber equipped with a beryllium dome at a constant temperature of 310 C. The XRD experiment has been performed in BraggBrentano geometry over a range of scattering angles of 27° to 37°. The incident X-ray beam has been monochromatized to 8.048 keV (λ=0.154 nm). An in situ four-point probe technique has been used to characterize the film resistivity. The microstructure of the annealed films has been examined by transmission electron microscopy (TEM).
This work is focused on the effect of ITO film thickness on the crystallization kinetics during annealing. Three series of samples with thicknesses of ~50, 170 180, and 310-320 nm have been investigated. The evolution of the (222) and (400) peaks of the In2O3 phase has been monitored. The time dependence of the integral intensity of these peaks exhibits an s-like shape, which is typical of a crystallization process. The XRD data have been analyzed in the frame of the Kolmogorov Johnson Mehl Avrami (KJMA) model. The activation energy and the kinetic parameters of the crystallization process have been determined. The value of the KJMA exponent of about 2 obtained for all ITO films points toward two-dimensional grain growth in the site saturated mode. However, detailed TEM studies of partly crystallized ITO samples display two-dimensional grain growth only during the crystallization of the 50 nm ITO films. In contrast, the thicker films show two stages of crystallization. During the first stage, the single grains grow from the film surface to the interface, after which lateral growth of the grain has been observed to occur. The KJMA model is unable to predict the difference in the crystallization kinetics for films of different thicknesses. The specific film anisotropy and the limited thickness are discussed as the main reasons for the change in the crystallization kinetics. The film resistivity decrease correlating with the film crystallization depends non-linearly on the degree of crystallization.
Keywords: ITO; in-situ; synchrotron X-ray diffraction; microstructure; annealing; crystallization kinetics
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Poster
14th International Conference on Thin Films & Reactive Sputter Deposition 2008, 17.-20.11.2008, Ghent, Belgium
Permalink: https://www.hzdr.de/publications/Publ-12122
Porous metal surfaces produced by ion implantation
Shevchenko, N.; Kolitsch, A.
Abstract
Development of novel materials and structures for drug delivery systems is currently a very active field of research. Plasma immersion ion implantation (PIII) using helium or argon plasmas has been employed for porous layers creation on metal surfaces. These void structures may show unique characteristics which offer potential for medical applications such as metal-based drug-eluting stents. The paper addresses the influence of implantation parameters on surface morphology, cavity characteristics and mechanical properties of stainless steel stents. Argon and/or helium PIII processing of stainless steel samples has been performed at ion energies ranging from 5 to 35 keV, ion fluence of more than 1e17 cm-2, and substrate temperature in the range 50 400 C. Scanning electron microscopy, grazing incidence X-ray diffraction analysis, X-ray photoelectron spectroscopy, and elastic recoil detection analysis have been employed for sample characterization. Argon PIII treatment at elevated temperatures of 200 350 C leads to spongy structure formation of a size of 1-2 micron. Helium implantation results in a surface roughening and creation of voids in high concentration with size in the range 300 500 nm as well as nano-scale cavities (5-50 nm). So, varying the ion species (helium or argon), ion energy and fluence, and substrate temperature has been found to produce either void or sponge like structures at the nano- (~10 nm) to micro-scale (~1 micron). The best mechanical properties have been obtained in the stainless steel samples implanted at elevated temperature (higher than 250 C). Surface flaking and cracks formation have been greatly reduced by subsequent post-implantation annealing at temperatures of 600 800 C.
Keywords: Plasma immersion ion implantation; surface morphology; porous; stainless steel; stent; annealing
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Lecture (Conference)
9th International Conference on Modification of Materials with Particle Beams and Plasma Flows, 21.-26.09.2008, Tomsk, Russia
Permalink: https://www.hzdr.de/publications/Publ-12121
Real-time monitoring of ITO film structure during annealing: effect of film thickness
Shevchenko, N.; Rogozin, A.; Vinnichenko, M.; Kolitsch, A.; Moeller, W.
Abstract
The amorphous indium tin oxide (ITO) films were grown by reactive pulsed middle frequency dual magnetron sputtering on the Si substrates covered with SiO2. The real-time evolution of the ITO film structure during annealing was continuously investigated by synchrotron X-ray diffraction at ROssendorf Beam Line (ROBL), which is located at the European Synchrotron Radiation Facility in Grenoble, France. The annealing experiments were carried out in UHV annealing chamber equipped with beryllium dome at constant temperature of 310 C. In situ four-point probe technique was applied to characterize film resistivity. Three series of samples with thicknesses of ~50, 170 180, and 310-320 nm have been investigated.
The time dependence of the integral intensity exhibits an s-like shape, which is typical of the crystallization process. The XRD data were analyzed in a frame of the Kolmogorov Johnson Mehl Avrami (KJMA) model. The kinetic parameters of crystallization process were determined. The range of KJMA exponent of approximately 2 obtained for all ITO films points to two-dimensional grain growth in the site saturated mode. However, detailed TEM studies of partly crystallized ITO samples display two-dimensional grain growth only during crystallization of 50 nm ITO films. In contrast, the thicker films show two stages of crystallization process. During the first stage, the single grains grew from a film surface to interface, after that, lateral growth of the grain was observed. The KJMA model can not predict the difference in the crystallization kinetics for the films with diverse thicknesses. The essential anisotropy and limited thickness of the films are discussed as the main reasons for the change of the crystallization kinetics.
Keywords: ITO; annealing; structure; grain growth; synchrotron X-ray diffraction; crystallization
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Poster
9th International Conference on Modification of Materials with Particle Beams and Plasma Flows, 21.-26.09.2008, Tomsk, Russia
Permalink: https://www.hzdr.de/publications/Publ-12120
Surface Alloying of Ti6Al4V with Zirconium by Pulsed Electron-beam Melting of Zr/Ti Multilayers
Rotshtein, V. P.; Markov, A. B.; Shevchenko, N.; Reuther, H.; Oskomov, K. V.; Shulov, V. A.
Abstract
Surface alloying of Ti6Al4V with Zr aiming at depletion of Al and V was realized by liquid-phase intermixing of multi-layer film [Zr(20 nm)/Ti(20 nm)]12 of total thickness of 480 nm with substrate (Ti6Al4V) using a low energy (~20 keV), high-current electron beam (2.5 μs, 3.5 J/cm2). Scanning electron microscopy and energy dispersive X-ray spectroscopy, Auger electron spectroscopy, X-ray diffraction, and atomic force microscopy were used to study the surface morphology, microstructure, elemental and phase compositions of the alloyed layer. It was found that a homogeneous intermixing of all Zr/Ti nanolayers and diffusion of Zr into the substrate up to a depth of ≈1 μm take place after a singleshot pulsed melting. The surface layer of depth ≈ 0.5 μm is free of Al and V and contain ≈ 30 at % Zr. The near-surface layer, due to quenching from the melt, has a sub-microcrystalline grain structure with an average grain size of 112 nm. The post-irradiation vacuum annealing (500 °С, 2 h) leads to enrichment of alloyed layer with O and С impurities, and decrease of grain size up to 90 nm. As a result, the nanohardness of the alloyed layer was increased in comparison with the substrate.
Keywords: Ti alloy; Zr/Ti multilayers; electron beam; nanohardness; microstructure
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Poster
9th International Conference on Modification of Materials with Particle Beams and Plasma Flows, 21.-26.09.2008, Tomsk, Russia -
Contribution to proceedings
9th International Conference on Modification of Materials with Particle Beams and Plasma Flows, 21.-26.09.2008, Tomsk, Russia, 327-330
Permalink: https://www.hzdr.de/publications/Publ-12119
Nanoporous stainless steel surfaces produced by plasma immersion ion implantation
Shevchenko, N.; Kolitsch, A.
Abstract
Plasma immersion ion implantation (PIII) using helium or argon plasmas has been employed for porous layers creation on metal surfaces. These void structures may show unique characteristics which offer potential for medical applications such as metal-based drug-eluting stents. The paper addresses the influence of implantation parameters on surface morphology, cavity characteristics and mechanical properties of stainless steel stents. Argon and/or helium PIII processing of stainless steel samples has been performed at ion energies ranging from 5 to 35 keV, ion fluence of more than 1e17 cm-2, and substrate temperature in the range 50 400 ° C. Scanning electron microscopy, grazing incidence X-ray diffraction analysis, X-ray photoelectron spectroscopy, and elastic recoil detection analysis have been employed for sample characterization. Argon PIII treatment at elevated temperatures of 200 350 °C leads to spongy structure formation of a size of 1-2 µm. Helium implantation results in a surface roughening and creation of voids in high concentration with size in the range 300 500 nm as well as nano-scale cavities (5-50 nm). So, varying the ion species (helium or argon), ion energy and fluence, and substrate temperature has been found to produce either void or sponge like structures at the nano- (~10 nm) to micro-scale (~1 µm). The best mechanical properties have been obtained in the stainless steel samples implanted at elevated temperature (higher than 250 °C). Surface flaking and cracks formation have been greatly reduced by subsequent post-implantation annealing at temperatures of 600 800 °C.
Keywords: ion implantation; PIII; nanoporous; surface morphology; stainless steel stents
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Poster
16th International Conference on Ion Beam Modification of Materials, 31.08.-05.09.2008, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-12118
Bacterial biomineralization: New insights from Myxococcus induced mineral precipitation
González-Muñoz, M. T.; Rodriguez-Navarro, C.; Martínez-Ruiz, F.; Maria Arias, J.; Merroun, M.; Rodriguez-Gallego, M.
Abstract
There is growing evidence showing that bacteria have contributed to the formation of minerals since the advent of life on Earth. Bacterial biomineralization thus appears to be crucial for the complex interactions of biological, chemical, and physical processes which drive modern and ancient biogeochemical cycles. On the other hand, the technological and environmental applications of bacterial mineralization are now being demonstrated to be far reaching. Despite the numerous efforts to better understand how bacteria induce/mediate or control mineralization, our current knowledge is far from complete. Considering that the number of recent publications on bacterial biomineralization has been overwhelming, here we attempt to show the importance of bacteria-mineral interactions by focusing in a single bacterial genus, Myxococcus, which displays an unusual capacity of producing mineral precipitates of varying compositions and morphologies. The first part of this review presents an overview of the recent history of bacterial mineralization, and briefly describes the most common bacteriogenic minerals as well as current models on bacterial biomineralization. The second part presents a description of myxobacteria. Myxococcus induced precipitation of a number of phosphates, carbonates, sulphates, chlorides, oxalates, and silicates is described and discussed in lieu of the information presented in the first part. Finally, implications of bacterial mineralization and perspectives for future research are outlined. This review strives to show that the mechanisms which control bacterial biomineralization are not mineral- or bacterial-specific. On the contrary, they appear to be universal and depend on the environment in which bacteria dwell.
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Contribution to external collection
in: Tufas and Speleothems: Unravelling the Microbial and Physical Controls 336, London: Geological Society of London, 2009, 31-50
Permalink: https://www.hzdr.de/publications/Publ-12117
Surface structure of Sn-doped In2O3 (111) thin films by STM
Morales, E. H.; He, Y.; Vinnichenko, M.; Delley, B.; Diebold, U.
Abstract
High-quality Sn-doped In2O3 (ITO) films were grown epitaxially on yttria stabilized zirconia (111) with oxygen-plasma assisted molecular beam epitaxy (MBE). The 12 nm thick films, containing 26% Sn, are fully oxidized. Angle-resolved x-ray photoelectron spectroscopy (ARXPS) confirms that the Sn dopant substitutes In atoms in the bixbyite lattice. From XPS peak shape analysis and spectroscopic ellipsometry measurements it is estimated that, in a film with 6 at.% Sn, ~1/3 of the Sn atoms are electrically active. Reflection high energy electron diffraction (RHEED) shows a flat surface morphology and scanning tunneling microscopy (STM) shows terraces several hundred nanometers in width. The terraces consist of 10 nm wide orientational domains, which are attributed to the initial nucleation of the film. Low energy electron diffraction (LEED) and STM results show a bulk-terminated (1×1) surface, which is supported by first-principles density functional theory (DFT) calculations. Atomically resolved STM images are consistent with TersoffHamann calculations that show that surface In atoms are imaged bright or dark, depending on the configuration of their O neighbors. The coordination of surface atoms on the In2O3(111)1×1 surface is analyzed in terms of their possible role in surface chemical reactions.
Keywords: transparent conductive oxides; tin-doped indium oxide; molecular beam epitaxy; scanning tunneling microscopy; spectroscopic ellipsometry; free electron density
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New Journal of Physics 10(2008), 125030
DOI: 10.1088/1367-2630/10/12/125030
Cited 64 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12116
Die Mobilisierung von Actiniden durch mikrobiell produzierte Liganden unter Berücksichtigung der Endlagerung von radioaktivem Abfall
Moll, H.; Bernhard, G.
Abstract
- wird nachgereicht
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Lecture (others)
8. Projektstatusgespräch zur Forschungsförderung zur Entsorgung gefährlicher Abfälle in tiefen geologischen Formationen, 06.-07.05.2008, Karlsruhe, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-12115
Controlled Assembly and Nanoscale Doping of Epitaxial Si(Ge) Quantum Dot Nanostructures
Graham, J. F.; Kell, C. D.; Gray, J. L.; Wolf, S. A.; Floro, J. A.; Bischoff, L.; Hull, R.
Abstract
Self-assembled Si(Ge) quantum dots (QDs) may prove useful in future nanoelectronic device architectures. For this, they must be spatially arranged in specific patterns and possess the electronic or magnetic properties required for device operation. Previous work demonstrated Ga+ focused ion beam (FIB) templating of Si surfaces prior to epitaxial growth for fabricating patterned QDs with any desired complexity.1, 2
Our current research employs a mass-selecting FIB to template QD structures and to individually dope them. Ion species can be selected according to isotope mass and charge state using a Wien filter. Working with suitable liquid metal alloy ion sources (LMISs) provides the means to template with electrically non-invasive ions (e.g. Si+ from AuSi), then implant dopant ions for electronic or magnetic activation (e.g. with B+ from AsPdB or Mn+ from GeMn), with resolution of tens of nm and doses down to a few ions per dot.
Keywords: quantum dots; focused ion beam; liquid metal alloy ion sources
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Poster
2008 MRS Fall Meating, 01.-05.12.2008, Boston, USA
Permalink: https://www.hzdr.de/publications/Publ-12114
In-situ grazing incidence scattering investigations during magnetron sputtering deposition of FePt/Ag thin films
Cantelli, V.; von Borany, J.; Jeutter, N.; Grenzer, J.
Abstract
Using synchrotron in-situ X-ray diffraction and grazing incidence small angle scattering, we studied the growth of FePt islands incorporated into a Ag matrix. The deposition, by dual DC magnetron sputtering on amorphous Si/SiO2 substrate, was carried out at 400°C to support the formation of the hard ferromagnetic L10-FePt phase during growth. Thin Ag interspacing layers provide a granular FePt film but, by depositing 6 nm Ag layer directly on the SiO2 substrate, we obtained well defined FePt clusters. FePt nanoislands have been achieved without degradation of the magnetic properties. We obtained a magnetic asymmetry with magnetic moments preferentially oriented parallel to the layer surface.
Keywords: FePt; nanoclusters; GISAXS
- Advanced Engineering Materials 11(2009)6, 478-482
Permalink: https://www.hzdr.de/publications/Publ-12113
Direct spectroscopic characterization of aqueous actinyl(VI) species: A Comparative Study of Np and U
Müller, K.; Foerstendorf, H.; Tsushima, S.; Brendler, V.; Bernhard, G.
Abstract
For the first time the hydrolysis reactions of submillimoar aqueous Np(VI) and U(VI) solutions was investigated comparatively, applying Attenuated Total Reflection Fourier-transform Infrared (ATR FT-IR) and NIR absorption spectroscopy. Actinyl(VI) concentration was set to 500 µM in a pH range from 2 to 5.3 under ambient conditions. Both spectroscopic methods give evidence that three different Np(VI) species contribute to the speciation. Using the structural information obtained from the FT-IR spectra these species are the fully hydrated NpO2
2+ ion at pH ≤ 3, a monomeric complex probably formed by hydrolysis reactions at pH 3 − 5 and a carbonate containing complex at pH ≥ 5. A comparison of the obtained results to the updated NEA thermodynamic data confirms the presence of the free neptunyl(VI) ion and neptunyl(VI) carbonate complexation within the investigated pH range. The monomeric hydrolysis complex is not predicted to be relevant by the current thermodynamic data. In comparison to U(VI) forms structural similar species at pH ≤ 4, namely the fully hydrated AnO2
2+ and monomeric hydroxo species. In contrast to Np(VI), the infrared spectroscopic data of U(VI) does not evidence carbonate complexation at higher pH.
Keywords: neptunyl(VI); uranyl(VI); ATR FT-IR spectroscopy; NIR spectroscopy; hydrolysis
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Journal of Physical Chemistry A 113(2009)24, 6626-6632
DOI: 10.1021/jp9008948
Cited 36 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12112
Residence time measurements in pilot-scale electrolytic cells Application of laser induced fluorescence
Schubert, M.; Kryk, H.; Hessel, G.; Friedrich, H.-J.
Abstract
The flow distribution in the rectangular channel of a pilot-scale electrolytic cell was observed using an imperfect tracer-pulse injection technique in order to study residence time distribution (RTD), back-mixing effects and velocity profiles of the electrolyte liquids within the cathode compartment. The electrolytic cell was operated under cold flow and at process conditions. While residence time studies performed in a vast number of applications are mainly based on classical conductometric measurements, alternative measurement methods have to be applied in electrochemical systems. Hence, the paper deals with the investigation of the residence time distribution (RTD) using laser induced fluorescence (LIF) visualization. Back-mixing effects of the electrolyte are quantified using the axial dispersion flow model. RTD studies for the overall cell as well as velocity profile analysis for selected individual regions are conducted. Additionally, the effects of the non-stabilized membrane and of the membrane stabilizing spacer grid are investigated.
Keywords: electrolytic cell; laser induced fluorescence; axial dispersion; imperfect pulse; hydrodynamics method
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Chemical Engineering Communications 197(2010), 1172-1186
DOI: 10.1080/00986440903574800
Cited 4 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12111
Ultra-sensitive in-beam gamma-ray spectroscopy for nuclear astrophysics at LUNA
Caciolli, A.; Agostino, L.; Bemmerer, D.; Bonetti, R.; Broggini, C.; Confortola, F.; Corvisiero, P.; Costantini, H.; Elekes, Z.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyurky, G.; Imbriani, G.; Junker, M.; Laubenstein, M.; Lemut, A.; Limata, B.; Marta, M.; Mazzocchi, C.; Menegazzo, R.; Prati, P.; Roca, V.; Rolfs, C.; Rossi Alvarez, C.; Somorjai, E.; Straniero, O.; Strieder, F.; Terrasi, F.; Trautvetter, H. P.
Abstract
Ultra-sensitive in-beam gamma-ray spectroscopy studies for nuclear astrophysics are performed at the LUNA (Laboratory for Underground Nuclear Astrophysics) 400 kV accelerator, deep underground in Italy's Gran Sasso laboratory. By virtue of a specially constructed passive shield, the laboratory gamma-ray background for E_\gamma < 3 MeV at LUNA has been reduced to levels comparable to those experienced in dedicated offline underground gamma-counting setups. The gamma-ray background induced by an incident alpha-beam has been studied. The data are used to evaluate the feasibility of sensitive in-beam experiments at LUNA and, by extension, at similar proposed facilities.
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Contribution to WWW
http://arxiv.org/abs/0812.3223v1 -
European Physical Journal A 39(2009), 179-186
DOI: 10.1140/epja/i2008-10706-3
Cited 81 times in Scopus -
Poster
Nuclear Physics in Astrophysics IV, 08.-12.06.2009, Frascati, Italien
Permalink: https://www.hzdr.de/publications/Publ-12110
Uporaba metode datiranja povrsinske izpostavljenosti na primeru podora Veliki vrh
Mrak, I.; Merchel, S.; Benedetti, L.; Braucher, R.; Bourlès, D. L.; Finkel, R. C.; Reitner, J. M.
Abstract
O podoru v Velikem vrhu (Kouta, Karavanke) ni zanesljivih zgodovinskih zapisov, vendar pa le ti obstajajo o podoru na Dobraču (25.1.1348), ki je od Velikega vrha oddaljen 46 km. Podor je povzročil potres in naa hipoteza je bila, da je tudi podor v Velikem vrhu posledica istega dogodka. Tako smo s pomočjo metode datiranja povrinske izpostavljenosti analizirali vzorce matične kamnine v steni Velikega vrha ter vzorce s povrine podornih blokov. Ugotavljali smo vsebnost 36Cl, ki se je začel tvoriti po podoru. Na podlagi poznavanja tevila atomov 36Cl na gram Ca na leto izpostavljenosti, čas dogodka (podor) izračunamo iz koncentracij 36Cl izmerjenih s pomočjo pospeevalnika (AMS). Prvi rezultati kaejo, da sta se podora na Dobraču in Velikem vrhu posledica potresa v Furlaniji Julijski krajini. Starost podora v Velikem vrhu je (740 +- 71) a. Za bolj zanesljive rezultate bo potrebno izboljati sam model in upotevati več dejavnikov - predvsem nadmorsko viino in klimatske razmere.
There are no reliable historical data about the Veliki vrh rockfall (Kouta, Karavanke Mountains) but the records exist about the Dobrach rockfall (25th of January 1348) 46 km to the West of Veliki vrh. The rockfall was triggered by the earthquake and our hypothesis was that Veliki vrh rockfall was induced by the same event. Therefore we used the surface exposure dating method to analyze the bedrock samples in the Veliki vrh rock face as well as the samples of the boulder surface. The content of 36Cl, that started to produce after the earthquake, was measured. On the basis of the known number of 36Cl per gram Ca per year of exposure, the time of the rockfall can be calculated from the concentration of 36Cl measured by accelerator mass spectrometry (AMS). Preliminary results show the correlation of the two rockfalls (Dobrach and Veliki vrh) as the consequence of the earthquake in Friuli Venezia Julia. The age of Veliki vrh rockfall is (740 +- 71) a. For more reliable results further research should be conducted using also the data on altitude and climate.
Keywords: historic rockfall; cosmogenic nuclide exposure dating; Karavanke Mountains; Veliki vrh; terrestrial cosmogenic nuclides (TCN); accelerator mass spectrometry
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Contribution to proceedings
1. Trienalni Posvet, Naravne Nesrece v Sloveniji (NNS '08 - 1st seminar on natural hazards in Slovenia), 11.12.2008, Ljubljana, Slovenia
NARAVNE NESREČE 1 OD RAZUMEVANJA DO UPRAVLJANJA, 978-961-254-185-9, 105-111
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Permalink: https://www.hzdr.de/publications/Publ-12109
The chemical potential for the inhomogeneous electron liquid in terms of its kinetic and potential parts with special consideration of the surface potential step and BCS-BEC crossover
Morawetz, K.; March, N. H.; Squire, R. H.
Abstract
The chemical potential μ of a many-body system is valuable since it carries fingerprints of phase changes. Here, we summarize results for μ
for a three-dimensional electron liquid in terms of average kinetic and potential energies per particle. The difference between μ and the energy
per particle is found to be exactly the electrostatic potential step at the surface. We also present calculations for an integrable one-dimensional
many-body system with delta function interactions, exhibiting a BCSBEC crossover. It is shown that in the BCS regime the chemical potential
can be expressed solely in terms of the ground-state energy per particle. A brief discussion is also included of the strong coupling BEC limit.
- Physics Letters A 372(2008), 1707-1711
Permalink: https://www.hzdr.de/publications/Publ-12108
Transport in OFETs by surface Green functions
Morawetz, K.
Abstract
Theorieseminar TU Chemnitz
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Lecture (others)
Theorieseminar Professur Theorie ungeordneter Systeme, 17.12.2008, Chemnitz, Germany
Permalink: https://www.hzdr.de/publications/Publ-12106
Bose condensation for attractive interaction?
Maennel, M.; Lipavský, P.; Morawetz, K.; Schreiber, M.
Abstract
We investigate an interacting Bose gas using a scheme to eliminate successive collisions. For attractive interaction we find a two-particle bound state. When the binding energy of this bound state becomes twice the chemical potential there is a second order phase transition and a gap appears in the dispersion relation. The gap decreases with increasing density. At the critical point the gap vanishes, the dispersion becomes linear for small momenta and a Bose condensate appears. We interpret the appearance of the gap as a sign of structure formation.
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Poster
International Workshop on Nonequilibrium Nanostructures, 01.-06.12.2008, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-12105
Phase diagram for interacting Bose systems
Maennel, M.; Morawetz, K.; Schreiber, M.
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Poster
72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.03.2008, Berlin, Germany
Permalink: https://www.hzdr.de/publications/Publ-12104
Enhancement of Tc due to charge transfer
Morawetz, K.
Abstract
International Workshop on Physics and Chemistry of FeAs-based Superconductors,
Dresden: Enhancement of Tc due to charge transfer
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Poster
International Workshop on Physics and Chemistry of FeAs-based Superconductors, Dresden, 27.-29.10.2008, Dresden, Germany
Permalink: https://www.hzdr.de/publications/Publ-12103
Quantum Kinetic Theory beyond Quasiparticle Picture - Bernoulli Potential in Superconductors
Morawetz, K.
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Lecture (others)
Interviewtalk for Professorship, 16.11.2008, Loughborogh, Great Britain
Permalink: https://www.hzdr.de/publications/Publ-12102
Quantum Kinetic Theory beyond Quasiparticle Picture - Bernoulli potential in Superconductors
Morawetz, K.
Abstract
International Center for Condensed Matter Physics, Bras´ılia:
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Lecture (others)
International Center for Condensed Matter Physics, 29.09.2008, Brasilia, Brazil
Permalink: https://www.hzdr.de/publications/Publ-12101
Nonlocal kinetic theory
Morawetz, K.
Abstract
Talk for Professorship at University College Dublin
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Lecture (others)
Colloquium talk, 14.08.2008, UCD, Ireland
Permalink: https://www.hzdr.de/publications/Publ-12100
Counter-current flow limitation experiments in a model of the hot leg of a pressurised water reactor - comparison between high pressure steam/water experiments and low pressure air/water experiments
Vallee, C.; Seidel, T.; Lucas, D.; Beyer, M.; Prasser, H.-M.; Pietruske, H.; Schütz, P.; Carl, H.
Abstract
In order to investigate the two-phase flow behaviour in a complex reactor-typical geometry and to supply suitable data for CFD code validation, a model of the hot leg of a pressurised water reactor was built at Forschungszentrum Dresden-Rossendorf (FZD). The hot leg model is devoted to optical measurement techniques, therefore, a flat test section design was chosen and equipped with large windows. In order to enable the operation at high pressures, the test section is installed in the pressure chamber of the TOPFLOW test facility of FZD, which is used to perform the experiments under pressure equilibrium with the inside atmosphere. Counter-current flow limitation (CCFL) experiments were performed, simulating the refluxcondenser cooling mode appearing in small break LOCA scenarios. The fluids used were air and water at room temperature and pressures of up to 3.0 bar, as well as steam and water at pressures of up to 50 bar and the corresponding saturation temperature of 264°C. One selected 50 bar experiment is presented in detail: the observed behaviour is analysed and illustrated by typical high-speed camera images of the flow.
Furthermore, the flooding characteristic obtained from the different experimental runs are presented in terms of the Wallis parameter and Kutateladze number, which are commonly used in the literature. However, both parameters fail to properly correlate the data: a discrepancy is observed between the air/water and steam/water series. Therefore, a modified Wallis parameter is proposed, which takes into account the effect of the fluid viscosities on the CCFL. The new parameter is validated against comparable data found in the literature, even though no data was found with such a large range of viscosities. This analysis points out that the effect of the dynamic viscosity on flooding has already been observed, but not identified. Furthermore, it is shown that the proposed modification of the Wallis parameter allows a significant improvement for experimental series with variation of the viscosities.
Keywords: two-phase flow; flooding; counter-current flow limitation; hot leg; pressurised water reactor; Wallis parameter; viscosity
Involved research facilities
- TOPFLOW Facility
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Contribution to proceedings
13th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-13), 27.09.-02.10.2009, Kanazawa, Japan, N13P1107 -
Lecture (Conference)
13th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-13), 27.09.-02.10.2009, Kanazawa, Japan
Permalink: https://www.hzdr.de/publications/Publ-12099
Borverdünnungsanalysen beim Start der ersten HKP - Ergänzende Nachweise
Kliem, S.
Abstract
In diesem Bericht werden die offenen Punkte OP1 bis OP3 aus der TÜV-Stellungnahme A-Nr.: 5576 vom 24.09.2008 durch ergänzende Nachweise zur von uns vorgelegten Borverdünnungsanalyse abgearbeitet.
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Article, self-published (no contribution to HZDR-Annual report)
Forschungszentrum Rossendorf 2008
FZD\FWS\2008\12
12 Seiten
ISSN: 1437-322X
Permalink: https://www.hzdr.de/publications/Publ-12098
Evaluation Scheme for a Positron Emission Tomography System Used in Monitoring of Radiation Therapy
Shakirin, G.; Fiedler, F.; Enghardt, W.
Abstract
Positron emission tomography (PET) is used for independent monitoring of dose delivery in ion therapy. An in-beam PET scanner registers the annihilation γ-rays following the decay of β+-radioactive nuclei produced via nuclear reactions between the ions of the therapeutic beam and the irradiated tissue. From a comparison of the reconstructed activity distributions with those predicted from the treatment plan, deviations between the prescribed and the applied dose can be detected. In-beam PET, therefore, allows to verify the physical beam model of the treatment planning, to detect patient dislocations and density changes in the irradiated tissue. Issues related to the image quality and evaluation of a whole PET imaging system are discussed in this paper.
Keywords: in-beam PET; radiation therapy; image quality
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Contribution to proceedings
Workshop Bildverarbeitung für die Medizin - Algorithmen, Systeme, Anwendungen (BVM), 22.-25.03.2009, Heidelberg, Germany
Evaluation Scheme for a Positron Emission Tomography System Used in Monitoring of Radiation Therapy: Springer-Verlag -
Lecture (Conference)
Workshop Bildverarbeitung für die Medizin, 22.-25.03.2009, Heidelberg, Germany
Permalink: https://www.hzdr.de/publications/Publ-12097
Study of the ELBE RF-couplers with a new 1.3 GHz RF- coupler test bench driven by a resonant ring
Büttig, H.; Arnold, A.; Büchner, A.; Freitag, M.; Krätzig, M.; Lehnert, U.; Michel, P.; Schurig, R.; Staats, G.; Teichert, J.; Voigtländer, J.; Winter, A.
Abstract
To study the performance of the ELBE RF-couplers until their limits a 1.3 GHz resonant ring driven by a 10 kW CW klystron (VKL7811St, CPI) has been built to operate a RF-coupler and RF-window test bench. The ring allows tests with RF power up to 100 kW in continuous wave (CW) mode and 200 kW in pulsed mode.
Details of the resonant ring, the test bench design and results of the ELBE RF-coupler tests will be presented.
Keywords: RF power couplers; Superconducting CW RF; Resonant Ring; Travelling wave resonator; Waveguide window; RF test bench; Linac RF-system
Involved research facilities
- SRF Gun
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Nuclear Instruments and Methods in Physics Research A A 612(2010), 427-437
DOI: 10.1016/j.nima.2009.10.148
Cited 10 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-12096
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