Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35175 Publications

Growth kinetic and properties of nitride layers produced by loe energy ion nitriding and plasma immersion ion implantation of Al and Al alloys

Richter, E.; Telbizova, T.; Möller, W.

no abstract delivered from author

  • Lecture (Conference)
    SMMIB, Marburg, 9.-14. September 2001

Publ.-Id: 4857

Ion beam synthesis of magnesium diboride

Richter, E.; Prokert, F.; Reuther, H.; Helm, M.

no abstract delivered from author

  • Lecture (Conference)
    SMMIB, Marburg, 9-14. September 2001

Publ.-Id: 4856

Modification of titanium surface by its alloying with silicon using intensive pulsed plasma beams

Richter, E.; Piekoszeski, J.; Wieser, E.; Prokert, F.; Stanislawski, J.; Walis, L.; Reuther, H.

Surface alloying of Ti with Si has been performed with the use of high intensity pulsed plasma beams. In this technique, short, intense (1 µs, 3-4 J/cm²) plasma pulses serve as a source of heat to melt the near surface layer (up to 2 µm) of the Ti substrate togehter with a Si film (30 and 70 µg/cm²) pre-deposited on it. In the molten state, lasting a couple of microseconds, rapid diffusion of Si into Ti occurs leading to formation of new phases during rapid solidification of the molten surface layer. In the present work, an attempt has been undertaken to improve the mechanical properties of titanium via precipitation of hard stable phases in the Ti-Si system, is formed by the transient heat treatment. During subsequent annealing for 1 h at 800°C a fraction (14-43%) of Ti5Si3 transforms into TiSi. The presence of silicide precipitates in the near surface region layer of titanium increases dramatically its wear resistance.

Keywords: Surface alloying; pulsed plasma beams; Ti substrate

  • Lecture (Conference)
    SMMIB, Marburg, 9.-14. September 2001
  • Surface and Coatings Technology 158-159 (2002) 324-327

Publ.-Id: 4855

AMS measurements of the 25Mg(p,gamma)26Al reaction at stellar energies

Arazi, A.; Bürger, W.; Faestermann, T.; Niello, J. F.; Knie, K.; Korschinek, G.; Richter, E.; Rugel, G.; Wallner, A.; Wallner, C.

no abstract delivered from author

  • Lecture (Conference)
    DPG-Tagung, Erlangen, 20. März 2001
  • Lecture (Conference)
    Astronomy with radioactivities III, Ringberg, 23.-26. Mai 2001
  • Lecture (Conference)
    International Conference on Applications of High Precision Atomic & Nuclear Methods, september 2-5, 2002, Neptun, Romania
  • Lecture (Conference)
    XXIV Brazilian Workshop on Nuclear Physics, august 31 - september 4, 2002, Dao Pablo, Brasil
  • Lecture (Conference)
    9th Accelerator Mass Spectrometry Conference, September 9-13, 2002, Nagoya, Japan

Publ.-Id: 4853

Elastic recoil detection analysis of ion-exchanged soda-lime glass substrates for a-Si:H devices

Pantchev, B.; Danesh, P.; Kreissig, U.; Schmidt, B.

Elastic recoil detection analysis has been used to study the interaction between the soda-lime glass substrates and the a-Si:H films. It has been established that H and Na ions penetrate from the near-surface region of the substrate into the deposited film. The results have shown that the influence of the substrate on the properties of a-Si:H can be strongly reduced by glass surface modification using the processes of ion exchange and ion extraction.

Keywords: elastic recoil detection analysis; soda-lime glass; ion exchange; hydrogenated amorphous silicon

  • Lecture (Conference)
    International Summer School VEIT 2001, Varna, Bulgaria, Sept. 17-21, 2001
  • Vacuum 69 (2003) 289

Publ.-Id: 4852

Application and Improvement of the spreading resistance method for p-type 6H-SiC

Gebel, T.; Panknin, D.; Riehn, R.; Parascandola, S.; Skorupa, W.

Since the end of the 1960's spreading resistance (SR) measurements have become a routinely used technique for determining charge carrier profiles in silicon. For wide band gap semiconductors however the application of this method is difficult because of the high barrier at the interface between probe tips and the semiconductor surface. In order to lower the barrier two different approaches can be taken. First, the material of the tips could be changed with respect to its work function. But there is a limited choice because of the required mechanical properties of the tips concerning high hardness and low brittleness. The other way is to lower the barrier by influencing the surface states of the semiconductor material. This is actually more promising.
A strong dependence of the SR values on the polishing material for beveling was reported in investigations for the wide band gap semiconductor GaAs [1]. For laser annealed 6H-SiC [2] and 3C-SiC [3] SR measurements have been reported, but very high measuring voltages (1 to 5 V) were used compared to the usual measurements on Si (10 mV). Ahmed et al. found an activation of more than 100% which points to problems in the interpretation of the measurement [2].

In this work the influence of mechanical processing, further annealing of the bevel and finally sputter cleaning on the SR measurements was investigated. The SiC - surface was beveled with a diamond emulsion on a rotating glass plate. Grain sizes of 1.0 µm and 0.1 µm were used. It was found that polishing with the smaller grain size leads to lower resistances. This is comparable to the results which are known for GaAs with Al2O3 emulsion from Ref. [1]. After beveling several of the samples were annealed under vacuum for 5 min at temperatures of 1300 to 1400°C. A modified thin layer (1 to 2 nm) at the surface was formed which resulted in a lowering of the barrier resistance. The measured resistance was lowered up to a factor of three but statistical variations increased.
In order to lower the barrier further, the influence of ion sputtering (Ar+, 2 keV) on the bevel before the measuring procedure was tested. The sputtering was carried out at a current density of 50 µAcm-2 for 300 s. During the process the temperature increased to 57 to 69°C. Subsequent SR measurements showed up to two orders of magnitude lower resistance. The shape of the depth profile remained the same and the statistical error of the SR dropped significantly. Samples with resistivities larger than 0.2 cm were not measurable after beveling but after subsequent sputtering. The resistivity range in which SR measurements can be carried out was extended to 3 cm. First investigations of SR depth profiles using this sputtering method show a very good reproducibility at remarkably small variations of the measured values.
The samples were implanted with Al+ at multiple energies of 450, 240, 115 and 50 keV to form a 500 nm thick homogeneously doped layer with plateau concentrations in the range of 5 1019 to 5 1021 cm-3. Various post annealing processes were carried out to cover a broad range of resistivities with the samples. Resistivities and mobilities were obtained from Hall measurements [4]. For SR profiling a SENTECH SR-210 device was used. The probe tips were made of sintered tungsten carbide with a tip diameter of 5 µm. The measuring voltage was kept constant at 10 mV allowing to measure resistance values up to 1 G . The highest spatial resolution of the apparatus was 5 nm and the probe tip load during the measurements 9 g.


[1] G. Queirolo, J. Electrochem. Soc., 125 (10), 1672 (1978).
[2] S. Ahmed, C.J. Barbero and T.W. Sigmon, Appl. Phys. Lett. 66 (6), 712 (1995).
[3] J. A. Edmond, S.P. Withrow, W. Wadlin, R.F. Davis, Mat. Res. Soc. Symp. Proc.,
Vol. 77, 193 (1987).
[4] D. Panknin , H. Wirth, M. Mücklich, W. Skorupa, Mat. Sci. Engin. B56 (1999), in print

Keywords: Spreading resistance

  • Lecture (Conference)
    ICSRCM Conference on SiC and related materials, Raleigh (NC) USA, 10.-15.10.1999
  • Mat. Sci. Forum 338-342 (2000) 741

Publ.-Id: 4851

Ion beam synthesized group IV nanoclusters in SiO2 layers: a promising approach for non-volatile memories and silicon-based light emitters

Gebel, T.; Rebohle, L.; Zhao, J.; von Borany, J.; Stegemann, K.-H.; Mrstik, B.; Skorupa, W.

Ion beam synthesis (IBS) as a powerful tool for the modification of ultrathin layers allows the formation of functional nanostructured layers for micro- and optoelectronics. Such modified SiO2 layers are promising candidates for future non-volatile memory devices. Furthermore SiO2 layers containing nanostructures produced by IBS using group IV elements show strong blue-violet photo- and electroluminescence (EL) which is of great interest for novel optoelectronic devices.
In this paper we will report on our recent progress in the microstructural and electrical investigation of Ge and Si rich silicon dioxide layers. The group IV elements were implanted into thermally grown SiO2 layers to atomic concentrations of 0.3 .. 6% followed by different annealing steps. The microstructural properties were investigated using TEM, RBS and EDX. Electrical measurements using IV, Photo - IV and CV methods were focused on the injection and conduction mechanism as well as charge storage properties. The determined position of the charge centroid correlates well with the microstructural results. It will also be shown by a method combining IV and CV measurements that not only electron injection from the substrate but also hole injection from the top electrode takes place. A direct comparison of these results to the EL properties provides new impact in the understanding of the EL excitation mechanism.

Keywords: nanocluster; memory; Si based light emitter

  • Lecture (Conference)
    MRS Spring Meeting, San Francisco (USA), 16.-20.04.2001

Publ.-Id: 4850

Silizium basierte Lichtemitter: Neue Möglichkeiten für Lab-on-Chip Systeme ?

Gebel, T.; Rebohle, L.; Howitz, S.; von Borany, J.; Skorupa, W.

In den hier beschriebenen Untersuchungen werden Nanostrukturen durch Ionenimplantation in thermisch auf einen Siliziumwafer (100, n-Typ) aufgewachsene SiO2 - Schichten erzeugt. Im Anschluß an die Ionenimplantation werden durch eine Temperung Strahlenschäden ausgeheilt und die Clusterbildung angeregt. Die so erhaltenen Nanocluster weisen Größen von 4 ... 6 nm auf. Als Frontkontakt der Lumineszenzstrukturen wird eine aufgesputterte transparente Indium-Zinnoxid (ITO) - Schicht lithographisch in kreisrunde Flächen von 0.2mm2 strukturiert. Der Rückseitenkontakt wird durch Al - Beschichtung der Wafersrückseite hergestellt.
Die Metall-Oxid-Halbleiter (MOS) - Anordnung mit clusterhaltigen Schichten wird durch eine zwischen der ITO - Deckelektrode und dem Si - Substrat angelegte Spannung zur Elektrolumineszenz (EL) angeregt. Die emittierte Lichtleistung hängt linear von der Anregungsleistung ab. Für Untersuchungen zur Photolumineszenz (PL) erfolgte die Anregung mit einer Xenon - Lampe bei einer Wellenlänge von 250 nm. Das Spektrum des emittierten Lichts liegt im blau/violetten Wellenlängenbereich und enthält zudem noch einen beträchtlichen UV - Lichtanteil. Die erzielten Leistungseffizienzen erreichen Werte bis zu 0.5%.
Ab Lichtleistungen von 10 nW, also bei ca. 5 µWcm-2 , ist das Licht mit bloßem Auge sichtbar. Maximale Lichtleistungen liegen derzeit bei einigen Hundert nW. Durch eine Verbesserung der Kantenpassivierung der Emitterstrukturen ist eine weitere Erhöhung der Betriebsleistung möglich.
Derzeit sind die für die Fluoreszenzanalyse verwendeten bioaktiven Substanzen nahezu alle auf die häufig verwendeten 633 nm - Laser optimiert. Es sind jedoch alternativ Farbstoffe, die blau/violett oder im UV angeregt werden können, verfügbar. Damit könnten derart integrierbare, in Siliziumtechnologie hergestellte Emitter - Strukturen in Lab-on-a-Chip Systemen Anwendung finden. Zudem wird eine ortsaufgelöste Anregung möglich, da die Lichtemitter mittels gängiger Photolithographie einfach strukturiert und dann durch entsprechende Chip - Ansteuerung gezielt geschaltet werden können. Eine kostengünstige Realisierung der Strukturen würde sogar die Verwendung als "Disposable" ermöglichen.

Im Vortrag werden die optischen und elektrischen Eigenschaften der Emitter vorgestellt. Ausgehend vom jetzigen Erkenntnisstand werden Anwendungen, wie z.B. ein integrierter Optokoppler, und Perspektiven siliziumbasierter Lichtemitter auf der Basis von Nanostrukturen aufgezeigt. Für zukünftige Applikationen sind dabei insbesondere Möglichkeiten der Einstellung der Wellenlänge durch geeignete Herstellungsvarianten interessant. Die internationalen Aktivitäten hinsichtlich der Realisierung von Si - basierten Lasern versprechen weitere interessante Aspekte für die Anwendung derartiger Strukturen.

Keywords: Biosensorik; nanocluster; Si based light emission

  • Poster
    2. Biosensor Symposium, Tübingen (Germany) 01.-03. April 2001

Publ.-Id: 4849

Emitterarray (violett/UV) für die Biotechnologie

Gebel, T.

Im Vortrag wird ein Überblick über mögliche Anwendungen Si-basierter Lichtemitter in der Biotechnologie vorgestellt. Dabei wird besonders auf die Anforderungen an den Emitter eingegangen.

Keywords: Si based light emission; fluorescence analysis; biotechnology

  • Lecture (others)
    Vortrag auf der Jahrestagung des Kompetenzzentrums Nanotechnologie "Ultradünne funktionale Schichten", Dresden, 29.11.2001

Publ.-Id: 4848

Si- and Ge nanoclusters in ion implanted SiO2: electrical properties and memory applications

Gebel, T.

The talk gives an overwiew about current results from IV and CV investigations of Ge and Si implanted oxide layers. The electric properties of the devices and the investigation of memory parameters will be discussed.

Keywords: non volatile memory; nanocluster

  • Lecture (others)
    Lecture at the Institute of Semiconductor Physics, Academy of Science, 16.11.2001, Kiev (Ukraine)

Publ.-Id: 4847

Subthreshold φ meson production in heavy-ion collisions

Zénétyi, M.; Barz, H. W.; Wolf, G.; Kämpfer, B.

Within a BUU type transport model we study φ meson production in subthreshold Ni+Ni and Ru+Ru reactions. For the first time we included in our model the elementary reaction channels φ+N, Δ → φ+N, π+N(1520)Δ+N and πρ → φ. In spite of a substantial increase of the φ multiplicities by these channels our results stay significantly below the preliminary experimental data.

  • J. Phys. G 28 (2002) 2133

Publ.-Id: 4846

Evolution of microstructure of instrumental AISI M2 steel after plasma immersion nitrogen and carbon implantation

Uglov, V. V.; Fedotova, J. A.; Kuleshov, A. K.; Danilyuk, A. L.; Kvasov, N. T.; Günzel, R.; Reuther, H.; Richter, E.

Investigations of the elemental and phase composition, microstructure, microhardness and tribological properties of AISI M2 steel subjected to nitrogen and carbon plasma-immersion ion implantation (PIII) at different regimes arew presented

Keywords: Plasma immersion ion implantation; AISI M2 steel; Phase composition; Thermoelastic stress

  • Surface and Coatings Technology 136 (2001) 226-230

Publ.-Id: 4845

A combination of deltaE-E gas ionisation chamber and time-of-flight technique for heavy ion ERDA

Kreissig, U.; Grötzschel, R.; Liechtenstein, V. K.

A new TOF-energy telescope was installed at the ERDA beamline of the Rossendorf 5 MV tandem accelerator. The TOF-system consists of a small MCP-start-detector using a 45° tilted C-foil and a large mirror-type MCP-stop-detector with a flight path of about 100cm. In order to reduce the energy straggling of recoils in the start and stop detector diamond-like carbon (DLC) foils with thicknesses in the range of 0.5 up to 1.0 mg/cm2 are used. The energy detector is a large solid-angle DE-E gas ionisation chamber. This chamber is position sensitive in the scattering plane and enables kinematic correction. The total solid angle of this TOF- energy telescope amounts to about 3.2 msr and is mainly limited by the size of the stop-MCP. The most important features and advantages of this combination are as follows:

  • In contrast to conventional Si- energy detectors the ionisation chamber suffers no damage by heavy particles.
  • The ionisation chamber enables very easy a kinematic correction in the range of ±0.05° of the scattering angle.
  • There are different options to separate the detected particles according to their mass or to their atomic number and to use the energy information from the ionisation chamber or from the TOF.
Data for energy- and time- resolution and the resulting values for depth- and mass- resolution are given and the limiting parameters of the telescope are discussed. ERDA-spectra and resulting depth profiles obtained with 35 MeV Cl-ions at thin multilayer structures will be presented demonstrating the properties of this telescope.
  • Poster
    International Conference on Ion Beam Analysis, Cairns, Australia, 15-20 July 2001

Publ.-Id: 4844

Hydrogen depth resolution in multilayer metal structures, comparison of elastic recoil detection and resonant nuclear reaction method

Wielunski, L. S.; Grambole, D.; Kreissig, U.; Grötzschel, R.; Harding, G.; Szilagyi, E.

Four different metals: Al, Cu, Ag and An have been used to produce four special multilayer samples to study the depth resolution of hydrogen. The layer structure of each sample was analysed using 2 MeV He Rutherford backscattering spectrometry, 4.5 MeV He elastic recoil detection (ERD) and 30 MeV F6+ HIERD. Moreover the hydrogen distribution was analysed in all samples using H(N-15, alphagamma)C-12 nuclear reaction analysis (NRA) with resonance at 6.385 MeV. The results show that the best depth resolution and sensitivity for hydrogen detection are offered by resonance NRA. The He ERD shows good depth resolution only for the near surface hydrogen. In this technique the depth resolution is rapidly reduced with depth due to multiple scattering effects. The 30 MeV F6+ HIERD demonstrated similar hydrogen depth resolution to He ERD for low mass metals and HIERD resolution is substantially better for heavy metals and deep layers.

Keywords: Elastic recoil detection; Heavy ion elastic recoil detection; Hydrogen depth profiling; Ion multiple scattering; Nucler rection analysis

  • Nucler Instruments and Methods in Physics Research B #190 (2002)693-698
  • Poster
    International Conference on Ion Beam Analysis, Cairns, Australia, 15-20 July 2001

Publ.-Id: 4843

Renormalization of the Two-Photon Vacuum Polarization and the Self Energy Vacuum Polarization for a Tightly Bound Electron

Zschocke, S.; Plunien, G.; Soff, G.

The renormalization method of Bogoljubov-Parasiuk-Hepp-Zimmermann (BPHZ)
is used in order to derive the renormalized energy shift due to the
gauge invariant Källén-Sabry diagram of the two-photon vacuum
polarization (VPVP) as well as the self energy vacuum polarization
S(VP)E beyond the Uehling approximation.
It is outlined, that no outer renormalization is required for the
two-photon vacuum polarization and that only the inner renormalization
has to b e accomplished.
It is shown that the so-called nongauge invariant spurious term
is absent for a wide class of vacuum polarization (VP)
diagrams if one applies the widely used spherical expansion of bound
and free-electron propagator.
This simplifies significantly calculations in bound state quantum
As one result of our paper the use of the BPHZ-approach in bound
state QED is established.

  • Eur. Phys. J. D19 (2002) 147

Publ.-Id: 4842

PIII-nitriding of boron implanted stainless steel

Mändl, S.; Günzel, R.; Hammerl, C.; Richter, E.; Rauschenbach, B.; Möller, W.

In this report we present results of nitrogen PIII into 50 keV boron implanted austenitic stainless steel at 400°C and 40 kV. A surface layer of 90 nm consisting of expended austenite (lattice expansion 6.5%) and ferrite as well as containing 30 at% B was found. This layer was followed by another one containing expanded austenite with reduced expansion (lattice expansion 2.5%) before the base material was reached. Auger electron spectroscopy (AES) and X-ray diffraction (XRD) at variuos angels of incidence were used to obtain results. After annealing at 400°C for 5h further nitrogen diffusion, but no boron diffusion was observed.

Keywords: PIII; Stainless steel; Boron; Nitrogen

  • Surface and Coatings Technology 136 (2001) 176-180

Publ.-Id: 4841

Production of ω and φMesons in Near-Threshold πN Reactions: Baryon Resonances and the Okuba-Zweig-Iizuka Rule

Titov, I. A.; Kämpfer, B.; Reznik, B. L.

Results of a combined analysis are presented for the production of ω and φ mesons in π reactions in the near-threshold region using a conventional "nonstrange" dynamics based on processes that are allowed by the nonideal ω-φ mixing. We show that the interferences of the t channel (meson exchange) and s, u channels (nucleon and nucleon-resonances) differ significantly for the ω and φ production amplitudes. This leads to a decrease of the relative yields, in comparison with the expectations based on a one-component amplitude with standard ω-φ mixing.
We find a strong and nontrivial difference between observables in ω and φ production reactions caused by the different roles of the nucleon and nucleon-resonance amplitudes. A series of predictions for the experimental study of this effect is presented.

  • Phys. Rev. C 65 (2002) 065202

Publ.-Id: 4840

Integral Vessel Failure Experiment Analysis and Investigation of a Possible Vessel Support

Willschütz, H.-G.; Altstadt, E.

Integral scaled coupled melt pool convection and vessel creep failure experiments are being performed in the FOREVER program at the Royal Institute of Technology, Stockholm. These experiments are simulating the lower head of a pressurized reactor vessel under the thermal load of a melt pool with internal heat sources. Due to the multi axial creep deformation of the three-dimensional vessel with a highly non-uniform temperature field these experiments offer an excellent opportunity to validate numerical creep models. A Finite Element model is developed and using the Computational Fluid Dynamic module, the melt pool convection is simulated and the temperature field within the vessel wall is evaluated. The transient structural mechanical calculations are then performed applying a new creep modeling procedure. Additionally, the material damage is evaluated considering the creep deformation as well as the prompt plasticity.
Pre- and post-test calculations of at least 4 FOREVER experiments have been performed successfully. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios.
After analyzing the calculations, it seems to be advantageous to introduce a vessel support which can unburden the vessel from a part of the mechanical load and, therefore, avoid the vessel failure or at least prolong the time to failure. This can be a possible accident mitigation strategy. Additionally, it is possible to install an absolutely passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in the event of a core melt down. This idea has been patented.

Keywords: Severe Accident; Integral Vessel Failure Experiment; FEM Simulation; Vessel Support

  • Contribution to WWW
    Webseite der Arthur-und-Aenne-Feindt-Stiftung, Hamburg (

Publ.-Id: 4839

Blaue Lumineszenz aus Nanostrukturen

Gebel, T.

Ein großer Traum der Mikroelektronik ist die Realisierung von Lichtquellen in Silizium, da dieses Material die (billige) Grundlage der gängigen Mikroelektronik - Chips ist. Noch in den 80er Jahren erschien dies unmöglich, da Silizium als indirekter Halbleiter zur Lichtemission an sich ungeeignet ist. Teure und aufwendige andere Verfahren und Werkstoffe (z.B. Verbindungshalbleiter wie Gallium-Arsenid, Gallium-Nitrid, Silizium-Carbid usw.) werden derzeit für Leuchtdioden verwendet. Diese Technologien sind zwar weit entwickelt, vermögen aber eins nicht: die Integration einer solchen Lichtquelle in herkömmliche Chipstrukturen, also direkt auf einem Silizium - Chip in einem reinen Si- Herstellungsprozeß.
Seit Anfang der 90er Jahre kann mit dem Einzug der Nanotechnologien durch modifizierte Schichten und Strukturen im Nanometer - Bereich die bisherige Schranke des Siliziums überwunden werden: die in das Silizium oder in Siliziumdioxid eingebetteten Nanostrukturen können aufgrund ihrer speziellen Eigenschaften selbst zum Leuchten angeregt werden. Ein mögliches Verfahren zur Erzeugung derartiger Nanostrukturen ist die Ionenstrahlsynthese Durch die Verbindung von Ionenstrahl- und Temperverfahren können z.B. Nanocluster in SiO2 hergestellt werden. Derartige Schichten zeigen bei elektrischer Anregung eine blaue/violette Lumineszenz, die zudem auch noch einen beträchtlichen UV - Lichtanteil enthält. Der Beitrag gibt eine Übersicht über elektrische und optische Eigenschaften derart modifizierter Schichten und zeigt mögliche Anwendungen.

Keywords: Lumineszenz; Nanostrukturen

  • Lecture (Conference)
    2. Fachforum Nanotechnologie, OTTI-Technik Kolleg, Würzburg, 24. Oktober 2001
  • Contribution to external collection
    2. Fachforum Nanotechnologie, OTTI-Technik Kolleg, Würzburg, 24. Oktober 2001

Publ.-Id: 4838

Lichtemission aus Nanostrukturen: Neue Ansätze für integrierte optische Systeme in Siliziumtechnologie

Gebel, T.

Die Realisierung von Lichtquellen auf Silizium-Basis erschien noch in den 80er
Jahren unmöglich. Lichtemitter aus Verbindungshalbleitern hingegen sind
technologisch sehr weit entwickelt, vermögen aber eins nicht: die Integration in
herkömmliche Chipstrukturen, also direkt auf einem Silizium - Chip. Seit Anfang
der 90er Jahre kann mit dem Einzug der Nanotechnologien durch modifizierte
Schichten und Strukturen im Nanometer - Bereich diese bisherige Schranke des
Siliziums überwunden werden: Aufgrund ihrer speziellen Eigenschaften können in
einem reinen Si - Herstellungsprozeß erzeugte Nanostrukturen zum Leuchten
angeregt werden. Im Vortrag werden aktuelle Trends der siliziumbasierten
Lichtemission vorgestellt und Anwendungsfelder beschrieben, u. a. die mögliche
Verwendung integrierter optischer Strukturen in Lab-on-Chip Systemen für die

Keywords: Si-basierte Lichtemission; Nanostrukturen

  • Lecture (others)
    VDI-Forum Nanoworld, Hannover Messe 2001, Hannover, 24. April 2001

Publ.-Id: 4836

Neue Möglichkeiten für integrierte optische Systeme in Siliziumtechnologie durch Lichtemission aus Nanostrukturen

Gebel, T.

Der Vortrag gibt einen Überblick über aktuelle Entwicklungen im Bereich der Si-basierten Lichtemission. Insbesondere wird ein integrierter Optokoppler vorgestellt und es werden mögliche Anwendungsgebiete aufgezeigt.

Keywords: Nanostrukturen; Si-basierte Lichtemission

  • Lecture (others)
    Vortrag an der TU Chemnitz, 19. März 2001

Publ.-Id: 4835

Measurement of the 25Mg(p,gamma)26Al reaction at stellar energies

Arazi, A.; Faestermann, T.; Fernandez Niello, J.; Knie, K.; Korschinek, G.; Richter, E.; Rugel, G.; Wallner, C.

Stellar nuclear reactions, generally occurring at energies well below the Coulomb barrier, have extremely low cross sections posing a very difficult task for theri determination using the usual promt gammy-ray detection method. We describe here the application of the highly sensitive Accelerator Mass Spectrometry technique (AMS) as an alternative method for the determination of the resonance strenghts of the 25Ma(p,gamma) reaction, by off-line counting of the produced 26Al nuclei.

Keywords: Nuclear reactions; Mass spectroscopy

  • New Astronomy Reviews 46 (2002) 525-528

Publ.-Id: 4833

Monitoring-System mit adaptiven Wärmebilanzen für Batch-Reaktoren

Hessel, G.; Kryk, H.; Schmitt, W.; Seiler, T.; Hilpert, R.; Roth, M.; Deerberg, G.

Zur Unterstützung des Bedienungspersonals bei der Prozessführung komplexer heterogener Hydrierprozesse in Batch-Reaktoren (Rührkesselreaktoren) wurde ein Online-Monitoring-System (MoSys) entwickelt. Die Industrieerprobung erfolgte im Rahmen eines entwickelten Batch-Informations-Management-Systems (BIMS), das in einem separaten Industrie-PC implementiert und über den Terminalbus in die vorhandene Automatisierungstechnik einer Mehrzweckanlage der Degussa AG eingebunden wurde. Neben den Online-Konzentrationsprofilen für das Edukt, das Endprodukt und ein summarisches Zwischenprodukt lieferte MoSys Informationen zur Umsatzgeschwindigkeit und zur verbleibenden Restdauer bis zum Ende der Hauptreaktion, ohne dass eine chemische Online-Prozessanalytik zwingend notwendig ist. Die Betriebserfahrungen von zwei Produktionskampagnen zeigten, dass das BIMS/MoSys stabil und zuverlässig arbeitete und die Konzentrationsprofile gut mit den erwarteten Konzentrationsverläufen übereinstimmten.
Ferner bietet BIMS/MoSys dem Prozessexperten die Möglichkeit, betrieblichen Nutzen zu ziehen, z. B. durch

  • Einsparung einer chemischen Online-Prozessanalytik,
  • Erweiterung und Archivierung des bestehenden Prozesswissens,
  • bessere Reproduzierbarkeit der Produktqualität bei komplexen Batch-Prozessen,
  • verbesserte Prozessführung durch die genauere Ermittlung anlagen- und prozessspezifischer Kenngrößen (H2-Verbrauch, Energieverbrauch, Produktausbeute, unerwünschte Zwischen- oder Nebenprodukte),
  • Fehler- und Ursachenanalyse anhand der archivierten Batches,
  • Rückverfolgbarkeit von Batches bei Problemen (z. B. Qualitätsbeanstandungen),
  • Aufbau eines automatisierten Batch-Reports.
Darüber hinaus können unerwünschte Betriebszustände mit erhöhter Zwischenproduktakkumulation und verringerter Raum-Zeit-Ausbeute frühzeitig erkannt und dadurch rechtzeitig Gegenmaßnahmen eingeleitet werden, um größere Verluste zu vermeiden. Das auf adaptiven Stoff- und Wärmebilanzen basierende Online-Monitoring-System ist bei allen ausreichend exothermen Semibatch-Prozessen einsetzbar, wenn geeignete Informationen in den Stoff- und Wärmebilanzen enthalten sind.
  • Chemie Ingenieur Technik 74, 12 (2002) S. 1692-1698

Publ.-Id: 4832

Charge-Exchange Reaction pD → n(pp) in the Bethe-Salpeter Approach

Semikh, S. S.; Dorkin, S. M.; Kaptari, L. P.; Kämpfer, B.

The deuteron charge - exchange reaction pD → n(pp) for the low values of momentum transfer and small excitation nergies of final pp - pair is considered in the framework of Bethe - Salpeter approach. The method of calculation of the observables is developed for the case, when the pp - pair is in 1S0 - state. The methodical numerical calculations of the differetial cross sections and tensor analysing powers are presented. The reaction under consideration is predicted to be a solid base for construction of the deuteron tensor polarimeter at high energies, and also to obtain some additional information about elementary nucleon - nucleon charge - exchange amplitude.

  • Phys.Atom.Nucl. 65 (2002) 442-455, Yad.Fiz. 65 (2002) 469-482

Publ.-Id: 4831

Ionenstrahlanalyse - ideal zur Charakterisierung historischer Gläser

Mäder, M.; Neelmeijer, C.

Die Glaskorrosion, hervorgerufen durch Umwelteinflüsse, ist eine ernstzunehmende Gefährdung vor allem für wertvolle historische Glasobjekte. Zur zerstörungsfreien Charakterisierung eines Glases werden drei ionenstrahlanalytische Techniken (PIXE, PIGE, RBS) in einer simultanen Messung mit dem externen, an Luft ausgeführten, Protonenstrahl kombiniert. Spezielle Auswerteprozeduren ermöglichen die Bestimmung der chemischen Zusammensetzung und die Beurteilung des Korrosionszustandes des Objektes. Neben Hinweisen auf die kunstgeschichtliche Einordnung können daraus vorsorgliche Empfehlungen für die Aufbewahrung besonders gefährdeter Gläser abgeleitet werden. Die Anwendung des Verfahrens wird an zahlreichen Glasobjekten aus dem Kunstgewerbemuseum Dresden und dem Kunstmuseum Düsseldorf demonstriert.

  • Lecture (Conference)
    DPG-Tagung, Regensburg, 11.-15. März 2002

Publ.-Id: 4829

Testing Mean-Field Models Near the N = Z Line: γ-ray Spectroscopy of the Tz=½ Nucleus 73Kr

Kelsall, N. S.; Fischer, S. M.; Balamuth, D. P.; Ball, G. C.; Carpenter, M. P.; Clark, R. M.; Durell, J.; Fallon, P.; Freeman, S. J.; Hausladen, P. A.; Janssens, R. V. F.; Jenkins, D. G.; Leddy, M. J.; Lister, C. J.; Macchiavelli, A. O.; Sarantites, D. G.; Schmidt, D. C.; Seweryniak, D.; Svensson, C. E.; Varley, B. J.; Vincent, S.; Wadsworth, R.; Wilson, A. N.; Afanasjev, A. V.; Frauendorf, S.; Ragnarsson, I.; Wyss, R.

Excited states in the N=Z + 1 nucleus 73Kr have been investigated using the 40Ca(36Ar,2pn) and 40Ca(40Ca,α2pn) reactions at 145 and 160 MeV, respectively. γ-rays were detected using the Gammasphere array and events were re corded in coincidence with charged-particle and neutron detectors.
The three previously observed bands were extended to high spin, and a new unfavored positive-parity band has been observed. The alignment characteristics and decay properties of the bands are all consistent with large-deformation prolate rotation, with no clear evidence for oblate bands or shape coexistence. This is quite different from neighboring 72,74Kr, indicating a strong shape-stabilizing role for the valence neutron. The experimental results are compared to extended total Routhian surface, cranked Nilsson Strutinsky, and cranked relativistic mean-field calculations. The results suggest that the paired calculations lack some important physics. Neutron-proton correlations may be the missing ingredient. There is also evidence for an unusual band crossing in the negative-parity bands, which may in dicate the presence of T = 0 pairing correlations. At high spin all the models can reproduce the experimental data.

  • Phys. Rev. C 65 (2002) 044331

Publ.-Id: 4828

Nachrechnung von mittelskaligen Experimenten zum Kriechbruchversagen von Druckbehältern

Altstadt, E.; Willschütz, H.-G.

For calculations of Lower Head Failure experiments like FOREVER (performed at the Royal Institute of Technology, Stockholm) it is necessary to model the melt pool convection and the temperature field within the vessel as well as creep and plasticity processes. Therefore a 2D Finite Element Model is developed based on the code ANSYS®. The CFD module is used to calculate the thermodynamics. The resulting temperature field of the vessel wall is applied to the mechanical model. To describe the visco-plastic deformation a numerical creep data base (CDB) is developed where the creep strain rate is evaluated in dependence on the current total strain, temperature and equivalent stress. In this way the use of a single creep law, which employs constants derived from the data for a limited stress and temperature range, is avoided. For an evaluation of the failure times a damage model according to an approach of Lemaitre is applied.
After post-test calculations for the FOREVER-C2 experiment, pre-test calculations for the forthcoming experiments are performed. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios. After analyzing the results of the calculations, it seems to be advantageous to provide a vessel support, which can unburden the vessel from a part of the mechanical load and, therefore, avoid the vessel failure or at least prolong the time to failure. This can be a possible accident mitigation strategy. Additionally, it may be advantageous to install a passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in the event of a core melt down.

  • Lecture (Conference)
    2. Workshop "Kompetenzverbund Kerntechnik" vom 18. - 19. 09. 2002 in Köln, Tagungsband, Vortrag Nr. 13
  • Contribution to proceedings
    2. Workshop "Kompetenzverbund Kerntechnik" vom 18. - 19. 09. 2002 in Köln, Tagungsband, Vortrag Nr. 13

Publ.-Id: 4827

Polarization Observables in the Reaction pn→dΦ

Kaptari, L. P.; Kämpfer, B.

The reaction pn→dΦ is studied within a covariant boson exchange model. The behavior of polarization observables being accessible in forthcoming experiments near threshold is predicted.

PACS. 13.75.-n Hadron-induced low- and intermediate-energy reactions and scattering (energy ≤ 10 GeV) - 14.20.-c Baryons (including antiparticles) - 21.45.+v Few-body systems
  • Eur. Phys. J. A 14 (2002) 211-217

Publ.-Id: 4826

Dileptons and Photons from Central Heavy-Ion Collisions at CERN-SPS

Kämpfer, B.; Gallmeister, K.; Pavlenko, O. P.; Gale, C.

A unique parameterization of secondary (thermal) dilepton and photon yields in heavy-ion experiments at CERN-SPS is proposed. Adding those thermal yields to background contributions the spectral shapes of the CERES/NA45, NA38, NA50, HELIOS/3 and WA98 data from experiments with lead and sulfur beams can be well described.

  • Nucl. Phys. A 698 (2002) 424

Publ.-Id: 4825

Bewertung der Neutronenversprödung russischer Druckbehälterstähle anhand der Ergebnisse der Bestrahlungsexperimente Rheinsberg

Böhmert, J.; Viehrig, H.-W.; Ulbricht, A.

Im WWER-Prototyp-Reaktor WWER-2 des KKW Rheinsberg ist ein umfangreiches Bestrahlungsprogramm zur Untersuchung der Anfälligkeit von WWER-Reaktordruckbehälterstählen und -schweißwerkstoffen gegen Neutronenversprödung durchgeführt worden. Bestrahlt wurden insgesamt 21 verschiedene Chargen derartiger Materialien. Vergleichend wurden auch ASTM-bezogene Druckbehälterstähle in das Programm einbezogen. Zur Charakterisierung der bestrahlungsbedingten Änderungen wurden Charpy-Kerbschlagbiegeversuche, Zugversuche, Härtemessungen, bruchmechanische Versuche und Neutronenkleinwinkelstreuexperimente herangezogen. In jedem Fall sind die für die Neutronenversprödung typischen Eigenschaftsänderungen, wie Erhöhung der Übergangstemperaturen, Absenkung der Kerbschlag-Hochlagenenergie und Härte- bzw. Festigkeitssteigerung, nachgewiesen worden. Der Effekt wächst mit der Neutronenfluenz, zeigt aber darüber hinaus beträchtliche stahlmarken- bzw. chargenabhängige Unterschiede. Ein wichtiger Einflussparameter ist der Gehalt an Kupfer und Phosphor, der aber allein die unterschiedliche Versprödungsempfindlichkeit nicht erklären kann.
Vergleicht man die Ergebnisse des Bestrahlungsprogrammes Rheinsberg mit der Vorhersage auf der Basis der im russischen Normenwerk verankerten Vorhersagegleichungen, so wird in etlichen Fällen auch für Werkstoffe, die innerhalb der WWER-Spezifikation liegen, das Verhallten nicht konservativ vorausgesagt. Damit werden Schwächen im System der russischen Vorhersageprozeduren aufgedeckt.

  • Lecture (Conference)
    2. Workshop "Kompetenzverbund Kerntechnik" vom 18. - 19. 09. 2002 in Köln, Tagungsband, Vortrag Nr. 17
  • Contribution to proceedings
    2. Workshop "Kompetenzverbund Kerntechnik" vom 18. - 19. 09. 2002 in Köln, Tagungsband, Vortrag Nr. 17

Publ.-Id: 4824

The colour of silver stained glass - analytical investigations carried out with XRF, SEM/EDX, TEM, and IBA

Jembrih-Simbürger, D.; Neelmeijer, C.; Schalm, O.; Fredrichx, P.; Schreiner, M.; de Vis, K.; Mäder, M.; Schryvers, D.; Caen, J.

Glass treated on its surface with silver compounds and an aluminosilicate, such as ochre or clay, at higher temperatures (between 550 and 650°C) accepts a wide variety of a yellow colour. It is the aim of this study to investigate the parameters of the manufacturing process affecting the final colour of silver stained glass and to correlate them with the final colour and colour intensity. Therefore, defined mixtures of ochre and a silver compound (AgCl, AgNO3, Ag2SO4, Ag3PO4, Ag2O) were prepared and applied on soda-lime glass. The firing process was modified within the range from 563 to 630°C and glass samples were analysed after treatment with energy dispersive X-ray fluorescence analysis (EDXRF), scanning electron microscopy (SEM/EDX), transmission electron microscopy (TEM), as well as ion beam analysis (IBA) with an external beam. Within the scope of IBA simultaneous measurements using particle-induced X-ray emission (PIXE), particle-induced gamma-ray emission (PIGE), and Rutherford backscattering spectrometry (RBS) were carried out in order to obtain the thickness of the Ag-rich surface layer and the depth distribution of Ag. By means of TEM the microstructure of the silver particles was visualised. XRF results show that the lowest amount of Ag could be detected on glass samples treated with silver stain mixtures containing AgCl and Ag2O. A low kiln temperature (e.g. 563°C) results in a higher silver concentration at the surface and lower penetration depths. Furthermore, the results obtained with SEM/EDX at cross-sections of the glass samples could be confirmed by PIXE, PIGE, RBS, and TEM.

  • Journal of Analytical Atomic Spectrometry 17(2002)4, 321-328
    DOI: 10.1039/b111024c

Publ.-Id: 4823

T=0 and T=1 States in the Odd-Odd N=Z Nucleus, 7035Br35

Jenkins, D. G.; Kelsall, N. S.; Lister, C. J.; Balamuth, D. P.; Carpenter, M. P.; Sienko, T. A.; Fischer, S. M.; Clark, R. M.; Fallon, P.; Görgen, A.; Macchiavelli, A. O.; Svensson, C. E.; Wadsworth, R.; Reviol, W.; Sarantites, D. G.; Ball, G. C.; Rikovska Stone, J.; Juillet, O.; van Isacker, P.; Afanasjev, A. V.; Frauendorf, S.

Excited states in 70Br were populated in the 40Ca(32S,pn) reaction at Ebeam = 80-100 MeV and the 40Ca(36Ar, αpn) reaction at Ebeam = 145 MeV. The resulting gamma decay was detected using the Gammasphere array triggered by a 30-element neutron detector. The cross-bombardment allowed the unambiguous assignment of levels to 70Br, comprising a total of 32 states built both on the Jπ=0+ ground state and a previously known Jπ=9+ isomer, which is located at an excitation energy of 2293 keV by the observation of linking transitions. The structures are discussed within the context of the two-quasiparticle plus rotor model, the IBM-4 model and the cranked Nilsson-Strutinsky formalism. The nonobservation of a doublet of J = 0, T = 1 and J = 1, T = 0 states at low excitation in 70Br is indicative that T = 0 proton-neutron pairing strength is weak in comparison to T = 1 pairing.

  • Phys. Rev. C 65 (2002) 064307

Publ.-Id: 4821

The effect of silicon ion implantation on the structure of tantalum-silicon contacts.

Peikert, M.; Bhandari, R.; Wieser, E.; Wenzel, C.; Mücklich, A.

The effect of ion beam mixing on the formation of tantalum-silicon contacts was studied. Silicon implantation into 50 nm Ta layers on n+-Si (100) was carried out at temperatures from 150 to 500°C and fluences between 1x1015 and 1x1017 Si/cm². To characterize the microstructural changes Auger electron spectroscopy (AES), X-ray diffraction and cross-sectional transmission electron microscopy (TEM) were used. The contact resistance was measured before and after implantation using the four-point Kelvin method. Implantation at low temperature (~150°C) leads to the formation of an amorphous Ta-Si interface-layer. The width of the mixed layer increases linearly with implanted dose and temperature. Substrate amorphisation up to a depth of about 200 nm results in an increase of the contact resistance. An improved contact resistance was achieved by implantation with 5x1016 Si/cm² at 400°C. TaSi2 formation at the interface was observed in this case.

Keywords: Tantalum; Silicon; Contact Resistance; Silicide Formation; Ion Implantation

  • Thin Solid Films 449(2004), 187-191

Publ.-Id: 4820

Non-destructive composition analysis of glass artefacts for precaution

Mäder, M.; Neelmeijer, C.; Schreiner, M.

Chemical composition analysis on historical objects of art and archaeology assists in clarifying their authenticity and provenience. In addition, special technologies of their manufacture can be elucidated. Knowledge on the chemical composition represents one of the fundamentals for conservation and preservation concepts for historic silicate materials. The ensemble of ion beam analytical techniques (IBA) using external beams is a tool if non-destructive investigation is required.
Glass corrosion caused by environmental attacks is a serious problem especially for valuable historic objects. This is because the glasses may lose their transparency and stability. Alterations proceeding on the glass surface include ion exchange processes where network modifiers such as potassium and calcium are replaced by hydrogen bearing species to form a hydrated silica-rich surface layer. In order to characterise the state of a glass object showing no visible effects of alteration or corrosion damage, three ion beam based techniques (PIXE, PIGE, RBS) are combined in simultaneous measurements at the Rossendorf external proton beam. Combining PIXE (Proton Induced X-ray Emission) and PIGE (Proton Induced Gamma-ray Emission) the yield of X- and g-radiation of the element Si is ideal to indicate thin leached layers. More extended regions can be characterised by external RBS (Rutherford Backscattering Spectrometry). For getting the composition of the glass bulk the PIXE spectra are treated using the GUPIX code taking into account the experimental findings about the surface corrosion state. The developed procedure allows evaluation of initial corrosion and the identification of glass materials which are sensitive to atmospheric corrosion processes. The analytical results may offer suggestions for storing sensitive glass objects under special atmospheric conditions.
The present contribution demonstrates the applicability and the advantages of IBA techniques by investigating three medieval glass beakers.

Keywords: IBA; PIXE; PIGE; glass corrosion; conservation

  • Lecture (Conference)
    1st International Conference Hyalos Vitrum Glass - History, Technology and Conservation of Glass and Vitreous Materials in the Hellenic World, April 1-4, 2001, Rhodes Greece
  • Contribution to proceedings
    1st International Conference Hyalos Vitrum Glass, 01.-04.04.2002, Rhodes, Greece
    Hyalos Vitrum Glass, Athen: Glasnet Publications, 960-86733-1-3, 249

Publ.-Id: 4819

Evidence for the Absence of Regularization Corrections to the Partial-Wave Renormalization Procedure in One-Loop Self-Energy Calculations in External Fields

Goidenko, I.; Plunien, G.; Zschocke, S.; Labzowsky, L.; Soff, G.

The equivalence of the covariant renormalization and the partial-wave
renormalization (PWR) approaches is proven explicitly for the
one-loop self-energy (SE) correction of a bound electron state in
the presence of external perturbation potentials.
No "spurious" correction terms to the noncovariant PWR scheme are
generated for Coulomb-type screening potentials and for external
magnetic fields.
It is shown that in numerical calculations of the SE with Coulombic
perturbation potential spurious terms result from an improper treatment
of the unphysical high-energy contribution.
A method for performing PWR utilizing the relativistic B-spline
approach for construction of the Dirac spectrum in external magnetic
fields is proposed.
This method is applied for calculating QED corrections to the
bound-electron g factor in H-like ions.
Within a level of accuracy of about 0.1 % no spurious
terms are generated in numerical calculations of the SE in magnetic fields

  • Phys. Rev. A 65 (2002) 042110

Publ.-Id: 4817

Dependence of Energy Loss of Hard Jets on the Initial Thermodynamic State of Deconfined Matter at RHIC

Gallmeister, K.; Kämpfer, B.; Pavlenko, O. P.

The dependence of the radiative energy loss of hard partons (E<10 GeV) on the initial thermodynamic parameters
is studied for deconfined matter to be expected at the Relativistic Heavy-Ion Collider (RHIC).
We demonstrate that the specific QCD radiation pattern with a nonlinear dependence of the energy
loss on the propagated distance leads to a strong increase of the energy loss with increasing initial
entropy of deconfined matter supposing its lifetime is less than the average time to pass through the medium.
This is in contrast to a parametrization with constant energy loss per unit length of propagation.
For a sufficiently high initial temperature a two-regime behavior of the energy loss as a function
of the initial parton momentum occurs. The angular structure of the energy loss of hard jets with
respect to the initial temperature is also discussed for RHIC conditions.

  • Phys. Rev. C 66 (2002) 014908

Publ.-Id: 4816

Centrality Dependence of Thermal Parameters in Heavy-Ion Collisions at Relativistic Energies

Cleymans, J.; Kämpfer, B.; Wheaton, S.

The centrality dependence of thermal parameters, characterizing the hadron multiplicities, is determined phenomenologically
for lead-on-lead collisions at CERN-SPS for a beam energy of 158 A GeV.
The strangeness equilibration factor shows a clear, approximately linear, increase with increasing centrality, while the freeze-out temperature and chemical potential remain constant.

  • Phys. Rev. C 65 (2002) 027901-1 bis 027901-4

Publ.-Id: 4815

SiC precipitates formed in Si by simultaneous dual beam implantation of C and Si ions

Kögler, R.; Eichhorn, F.; Mücklich, A.; Reuther, H.; Heera, V.; Skorupa, W.; Lindner, J.

Nanometer-sized SiC precipitates were synthesized at 450oC in Si by simultaneous dual beam implantation of C+ and Si+ ions and subsequent annealing. The results are compared with those of sequential dual beam implantation and of single beam implantation. Two types of SiC precipitates were found. Precipitates of type I with a diameter of d = 4 - 5nm consist of 3C-SiC epitaxially oriented with the Si matrix. They were formed already in the as-implanted state and do not grow further during subsequent annealing. The SiC precipitates of type II with d " 10nm are not oriented with the Si matrix and grow exclusively during the subsequent annealing. The high growth velocity, the misorientation in regard to the Si matrix and the lower concentration of type II precipitates can be explained by the assumption that these precipitates were formed in an amorphous substrate which modifies their interface energy.

Keywords: ion implantation; Si; SiC; material synthesis; nanocluster; precipitates

Publ.-Id: 4814

Evolution of ion implantation-caused vacancy-type defects in 6H-SiC probed by positron implantation spectroscopy

Brauer, G.; Anwand, W.; Skorupa, W.

no abstract delivered from author

Keywords: kein

  • Lecture (others)
    IIM Program Seminar, Marienthal Monastery, Germany, June 11-13, 2001

Publ.-Id: 4813

Evidence of vacancy-type defects at Rp/2 in ion-implanted Si after annealing

Kögler, R.

The contribution reviewed the state of the art regarding the so called Rp/2 gettering effect. It was shown that ion implantation induced excess vacancies and their agglomerates are the origin of metal gettering in the Rp/2 region of ion-implanted Si. Metal atoms are gettered at the inner wall of the cavities. The removal of the excess vacancies by defect engineering avoids metal gettering at Rp/2. Interstitial-type defects (small clusters of interstitials) are as well present in the Rp/2 region. However, their gettering capability for metal impurities is much smaller than that of the vacancy-type defects.

  • Lecture (Conference)
    Treffen des Arbeitskreises "Punktdefekte", Dresden, Feb. 12-13, 2001

Publ.-Id: 4812

Density gradient in SiO2 films on silicon as revealed by positron annihilation spectroscopy

Revesz, A. G.; Anwand, W.; Brauer, G.; Hughes, H. L.; Skorupa, W.

no abstract delivered from author

Keywords: kein

  • Lecture (Conference)
    32nd Semiconductor Interface Specialists Conference, Washington/DC, USA, Nov 29 - Dec 01, 2001

Publ.-Id: 4811

Density gradient in SiO2 films on silicon as revealed by positron annihilation spectroscopy

Revesz, A. G.; Anwand, W.; Brauer, G.; Hughes, H. L.; Skorupa, W.

no abstrct delivered from author

Keywords: kein

  • Lecture (Conference)
    9th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces (SLOPOS-9), Dresden, Germany, September 16-22, 2001

Publ.-Id: 4810

Positron characteristics of various SiO2 polymorphs

Kuriplach, J.; Anwand, W.; Brauer, G.; Skorupa, W.

no abstract delivered from author

Keywords: kein

  • Lecture (Conference)
    9th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces (SLOPOS-9), Dresden, Germany, September 16-22, 2001

Publ.-Id: 4809

The migration of defects and nitrogen atoms in nitrided surface layers of austenitic stainless steel followed by microscopic methods

Jiraskova, Y.; Brauer, G.; Schneeweiss, O.; Blawert, C.; Anwand, W.; Coleman, P. G.

no abstract delivered from author

Keywords: kein

  • Lecture (Conference)
    9th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces (SLOPOS-9), Dresden, Germany, September 16-22, 2001

Publ.-Id: 4808

Fluence dependence of damage production in Y-stabilized cubic zirconia by rare-gas ion irradiation

Fradin, J.; Grynszpan, R. I.; Thome, L.; Anwand, W.; Brauer, G.

no abstract delivered from author

Keywords: kein

  • Lecture (Conference)
    9th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces (SLOPOS-9), Dresden, Germany, September 16-22, 2001

Publ.-Id: 4807

Investigation of spatial distribution of defects in ultra-fine grained copper

Cizek, J.; Prochazka, I.; Melikhova, O.; Brauer, G.; Anwand, W.; Kuzel, R.; Cieslar, M.; Islamgaliev, R. K.

no abstract delivered from author

Keywords: kein

  • Lecture (Conference)
    9th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces (SLOPOS-9), Dresden, Germany, September 16-22, 2001

Publ.-Id: 4806

Depth-dependence recovery of helium-implanted 18 carats gold-silver alloy

Thome, T.; Fradin, J.; Grynszpan, R. I.; Anwand, W.; Brauer, G.

no abstract delivered from author

Keywords: kein

  • Contribution to external collection
    Materials Science Forum 363-365 (2001) 484

Publ.-Id: 4805

Positron implantation depth profiles in alpha-irradiated 18 carats gold

Thome, T.; Fradin, J.; Grynszpan, R. I.; Anwand, W.; Brauer, G.

Positron implantation profiles have been investigated over a range of about 1 m on a gold solid solution containing 40 at.% of Ag, after helium implantation at 300 keV. The S parameter lineshape of the annihilation radiation, sensitive to both the size and the concentration of vacancy type defects, was measured after isochronal annealing up to 930 K. Depending on the incident energy of the positron, i.e. the distance between its mean implantation depth and the helium concentration maximum, several recovery stages were unambiguously observed attributed, respectively, to free vacancy migration (I), helium stabilization of larger defects (II) and competitive processes of bubble nucleation (III) and breaking up (IV). These latter mechanisms lead to the observation of a lineshape maximum at T=0.5Tm (melting point), already observed for nickel.

Keywords: Positron; Annihilation; Gold; Silver; Helium; Implantation

  • Nuclear Instruments and Methods in Physics Research B 178 (2001) 342

Publ.-Id: 4804

Positron annihilation lifetime study of pur and doped LiF

Sendezera, E. J.; Davidson, A. T.; Anwand, W.; Brauer, G.; Nicht, E.-M.

no abstract delivered from author

Keywords: kein

  • Contribution to external collection
    Materials Science Forum 363-365 (2001) 386

Publ.-Id: 4803

Longtime aging behavioour of the alloy Al-2024 characterized by positron annihilation spectroscopy

Nicht, E.-M.; Brauer, G.; Tempus, G.

The reconstruction of the precipitation structure after solution treatment has been investigated by positron
annihilation spectroscopy. In this study the behaviour of samples taken from an aircraft "Airbus 300", being
in operation for 18 years, is compared to a reference material supplied by Alcoa. The results of position
annihilation spectroscopy show that there are no significant differences in both materials. This finding is in
agreement with the results obtained from other methods within the scope of the general research program
which points to a materials behaviour as predicted for a safe operation of this type of aircraft.

Keywords: kein

  • Acta Physica Polonica A 99 (2001) 441

Publ.-Id: 4802

Characterization of Sn films on silicon by slow positron implantation spectroscopy

Nancheva, N.; Docheva, P.; Anwand, W.; Brauer, G.

Sn films grown on silicon substrate by d.c. magnetron sputtering have been investigated by slow positron
implantation spectroscopy. As the substrate bias is one of the most important factors affecting the structure
of a sputtered film, films grown at various substrate bias (+80 V, 0 V, -80 V) are compared and their
properties are discussed.

Keywords: kein

  • Acta Physica Polonica A 99 (2001) 435

Publ.-Id: 4801

Lattice defects in industrial Al probed by positrons

Mohsen, M.; Ismail, H.; Ashry, A.; Brauer, G.; Mohamed, S.

no abstract delivered from author

Keywords: kein

  • Contribution to external collection
    Materials Science Forum 363-365 (2001) 216

Publ.-Id: 4800

Indentification of K+-Mesoms from Subthreshold pA Collisions with ANKE at COSY-Jülich

Büscher, M.; Junghans, H.; Koptev, V.; Nekipelov, M.; Sistemich, K.; Ströher, H.; Barsov, S.; Borchert, G.; Borgs, W.; Debowski, M.; Erven, W.; Esser, R.; Fedorets, P.; Gotta, D.; Hartmann, M.; Hejny, V.; Kacharava, A.; Koch, H. R.; Komarov, V.; Kulessa, P.; Kulikov, A.; Macharashvili, G.; Merzlyakov, S.; Mikirtychyants, S.; Müller, H.; Mussgiller, A.; Nellen, R.; Nioradze, M.; Ohm, H.; Petrus, A.; Rathmann, F.; Rudy, Z.; Schleichert, R.; Schneider, C.; Schult, O. W. B.; Stein, H. J.; Zychor, I.

The spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungszentrum Jülich in spring 1998.
An initial scientific goal is to study K+-production in pA collisions at subthreshold energies far below the free NN-threshold at Tp=1.58GeV. This requires the identification of K+-mesons in a background of pions and protons, about 106 times more intense.
In this paper the sophisticated detection system and the software procedures for kaon identification are described.
With the help of TOF, energy-loss and range measurements as well as the track information from wire chambers, it is possible to measure d2σ/dΩdp for deep subthreshold K+ production at beam energies down to Tp=1.0GeV.

  • Nucl. Instrum. Meth. A 481 (2002) 378-396

Publ.-Id: 4799

Development of Low-Mass Drift Chambers for the HADES Spectrometer

Bokemeyer, H.; Boyard, J. L.; Chepurnov, V.; Chernenko, S.; Daues, H.; Dohrmann, F.; Enghardt, W.; Fateev, O.; Garabatos, C.; Glonti, L.; Grosse, E.; Hehner, J.; Hennino, T.; Kempter, J.; Koenig, W.; Müntz, C.; Naumann, L.; Petrov, A.; Pouthas, J.; Rosier, P.; Smykov, L.; Stelzer, H.; Sobiella, M.; Stroth, J.; Wüstenfeld, J.; Zanevsky, Y.; Zumbruch, P.

The High Acceptance Di-Electron Spectrometer (HADES) is a detector arrangement combined with a superconducting toroid for lepton pair spectroscopy presently built up at GSI (Darmstadt). HADES is designed to cope with the high-multiplicity environment of heavy ion collisions at 1AGeV and intensities of up to 108 beam particles per second and central event rates of 105 s-1. The detector has a geometrical acceptance of almost 50% for e+e- pairs and a mass resolution of 0.8% for ρ and ω mesons. Four low-mass drift chamber systems, two before and two behind the magnet, serve for charged particle track reconstruction. Design aspects of the drift chambers and first results from beam tests are presented.

  • Nucl. Instr. Meth. A 477 (2002) 397-400

Publ.-Id: 4798

Laboratory-unit investigantions of palladium-treated titanium foil for dry scrubber application

Piekoszewski, J.; Chmielewski, A. G.; Licki, J.; Sartowska, B.; Werner, Z.; Barson, S. D.; Skeldon, P.; Thompson, G. E.; Richter, E.; Wieser, E.; Cerny, I.; Hnilica, F.; Fürbacher, I.

Titanium foil is employed for electron transparent windowsin the lectron beam dry scrubber process. The foil suffers corrsion, which limits the window life. Here, the examination of a palldium-coated window, prepared by ion beam assisted deposition and plasma source ion assisted deposition (PIIAD), after service in a pilot-scale plant is reported. Most significantly, the adhesion of the coating was reduced by the flue gas. Where the coating remained adherent, corrison was negligible. Elsewhere, general, intergranular and pitting corrosion occurred. A PSIAD coating provided the best performance.

Keywords: Electron beam treatment; Flue gases; Titanium; Palladium; Corrosion; Coatings

  • Radiation Physics and Chemistry 62 (2001) 253-260

Publ.-Id: 4797

An apparatus for sequential pulsed plasma beam treatment in combination with Arc PVD deposition

Stanislawski, J.; Piekoszewski, J.; Richter, E.; Werner, Z.

A hybrid type of apparatus is described which eneables one to form a thin multi-layer film on the surface of any kind of solid substrate. In one process, the surface is treated with a high intensity pulse plasma beam which introduces the chosen kind of atoms into the near-surface layer of the substrate. In the second process, following the first without breaking the vacuum, the coating is formed by arc PVD process. Two examples of coatings formed on metallic and ceramic substrates are presented.

Keywords: Arc PVD; interlayer; pilse plasma treatment

  • Nukleonika 47 (2002) 119-122

Publ.-Id: 4796

The Longitudinal Polarimeter at HERA

Beckmann, M.; Borissov, A.; Brauksiepe, S.; Burkart, F.; Fischer, H.; Franz, J.; Heinsius, F. H.; Königsmann, K.; Lorenzon, W.; Menden, F. M.; Most, A.; Rudnitsky, S.; Schill, C.; Seibert, J.; Simon, A.

The design, construction and operation of a Compton back-scattering laser
polarimeter at the HERA storage ring at DESY are described.
The device measures the longitudinal polarization of the electron
beam between the spin rotators at the HERMES
experiment with a fractional systematic uncertainty of 1.6 %. A measurement
of the beam polarization to an absolute statistical
precision of 0.01 requires typically one minute when the device is operated
in the multi-photon mode.
The polarimeter also measures the polarization of each individual
electron bunch to an absolute statistical precision of 0.06 in
approximately five minutes.
It was found that colliding and non-colliding bunches can
have substantially different polarizations.
This information is important to the collider
experiments H1 and ZEUS for their future longitudinally polarized
electron program because those experiments use the colliding
bunches only.

  • Nucl. Instr. Meth. A 479 (2002) 334

Publ.-Id: 4795

Integrated high voltage modulator for plasma immersion ion implantation with an RF plasma

Rogozin, A. I.; Astrelin, V. T.; Richter, E.; Möller, W.

The present investigation focuses on further development of the plasma based high voltage modulator for plasma immersion ion implantation (PIII) devices. The modulator produces high voltage pulses using grid controlled extraction of electrons from the plasma, which is used for the ion implantation. The operation features of the modulator in connection with an RF-plasma are described. The device is applied to implantations of stainless steel. The results indicate considerable hardness improvement, which confirm the practical use of the high voltage modulator.

Keywords: Plasma immersion ion implantation; High voltage modulation; RF-plasma

  • Plasma Sources Science and Technology 12 (2003) 495-499

Publ.-Id: 4794

A New Ti/H phase transformation in the H2+ implanted titanium alloy studied by XRD, NRA, ERDA and SEM

Wang, T.; Eichhorn, F.; Grambole, D.; Grötzschel, R.; Herrmann, F.; Kreissig, U.; Möller, W.

The titanium hydrogenation process in the H2+ implanted Ti225 titanium alloy has been studied in this work. The Ti/H phase transformation from hydrogen solid solution (hcp) to gamma phase titanium hydride (TiH(γ)) with a primitive tetragonal structure and then to a titanium-dihydride (TiH2(x)) with a body centred tetragonal (bct) structure has been characterized by X-ray diffraction, NRA and ERDA. This process is very different from the usual hydrogenation mechanism, in which the delta phase titanium-dihydride (TiH2(δ)) with a face centred cubic (fcc) structure is always involved. Both of the TiH(γ) and TiH2(x) are rare phase, which are formed under extreme conditions. The TiH(γ) was considered to be a metastable phase in low hydrogen concentrated titanium, and the TiH2(x) phase has not yet been notated. The characteristics of the TiH2(x) are unclear, but it is very stable at room temperature and exists as a mixture state with the titanium. A saturated fraction of the hydride to titanium phase has been obtained as about 15% (H/Ti~0.3) in a H2+ implanted sample.

Keywords: Titanium hydride; Hydrogen implantation; Phase transformation; X-ray diffraction; nuclear reaction analysis; elastic recoil detection analysis; scanning electron microscopy

  • Journal of Physics. Condensed Matter, 14(2002)1-10

Publ.-Id: 4792

GaN thin films on SiC substrates studied using variable energy positron annihilation spectroscopy

Hu, Y. F.; Shan, Y. Y.; Beling, C. D.; Fung, S.; Xie, M. H.; Cheung, S. H.; Tu, J.; Brauer, G.; Anwand, W.; Tong, D. S. Y.

no abstract delivered from author

Keywords: kein

  • Contribution to external collection
    Materials Science Forum 363-365 (2001) 478

Publ.-Id: 4791

Precursory stage of damage production in argon irradiated cubic zirconia

Fradin, J.; Thome, T.; Grynszpan, R. I.; Thome, L.; Anwand, W.; Brauer, G.

The damage accumulation in stabilized cubic ZrO2 single crystals irradiated with low-energy Ar ions was investigated,
combining Rutherford backscattering/channeling (RBS/C) and slow positron implantation (SPIS) spectroscopies. In the 3×1014¯1016 cm-2 range, the fluence dependence of the damage-induced dechanneling parameter (fD) exhibits three production stages (labeled 1, 2 and 3) already reported for ion-irradiated ceramics and attributed to the formation of small clusters and dislocation loops, either isolated or overlapping. Moreover, a precursory stage, never hitherto reported in RBS/C studies, is unveiled for fluences below 3×1014 cm-2. This "new" stage (labeled 0) is confirmed by SPIS and attributed to clustering of small vacancy-type defects. Although both techniques exhibit different specific sensitivities to defects, similarities in the fluence dependence allow to identify common limits to all observed damage production stages.

Keywords: Ion-irradiation; Zirconia; Radiation effects; RBS; Channeling; Positrons

  • Nuclear Instruments and Methods in Physics Research B 175-177 (2001) 516

Publ.-Id: 4789

Damage induced by argon ion implantation in cubic zirconia

Fradin, J.; Thome, T.; Grynszpan, R. I.; Thome, L.; Anwand, W.; Brauer, G.

no abstract delivered from author

Keywords: kein

  • Contribution to external collection
    Materials Science Forum 363-365 (2001) 514

Publ.-Id: 4788

Effects of neutron irradiation and thermal annealing on model alloys using positron annihilation techniques

Cumblidge, S. E.; Catchen, G. L.; Motta, A. T.; Brauer, G.; Böhmert, J.

no abstract delivered from author

Keywords: kein

  • Contribution to external collection
    ASTM STP 1405 (2001) p.247

Publ.-Id: 4787

Calculation of positron characteristics in silicon carbide

Barbiellini, B.; Kuriplach, J.; Anwand, W.; Brauer, G.

no abstract delivered from author

Keywords: kein

  • Contribution to proceedings
    Materials Research Society Symposium Proceedings Vol. 640 (2001) p. H5.25.1

Publ.-Id: 4786

Untersuchungen an SiO2 mittels Positronen-Annihilationsspektroskopie

Brauer, G.

no abstract delivered from author

Keywords: kein

  • Lecture (others)
    Geoforschungszentrum Potsdam, Potsdam, 13.08.2002

Publ.-Id: 4785

Positron annihilation spectroscopy studies of the SiO2/Si interface

Brauer, G.

no abstract delivered from author

Keywords: kein

  • Lecture (others)
    Department of Low-Temperature Physics, Charles University Prague, Prague, 28.05.2002

Publ.-Id: 4784

Use of slow positron implantation spectroscopy as a tool for investigation of hydrogen loaded Nb films

Cizek, J.; Kirchheim, R.; Pundt, A.; Brauer, G.; Anwand, W.

no abstract delivered from author

Keywords: kein

  • Lecture (Conference)
    9th TMR Workshop Switchable Metal-hydride Films, Mallorca, Spain, 16.-22.02.2002

Publ.-Id: 4783

The migration of defects and nitrogen atoms in nitrided surface layers of austenitic stainless steel followed by microscopic methods

Jiraskova, Y.; Brauer, G.; Schneeweiss, O.; Blawert, C.; Anwand, W.; Coleman, P. G.

The X6CrNiTi1810 austenitic stainless steel samples nitrided by plasma immersion ion implantation at 300 °C/3 h are studied by slow positron implantation and conversion electrons Mössbauer spectroscopies completed with X-ray diffraction (XRD) measurements. The surface layers consist of N-Fe expanded austenite and -Fe2N nitride. The changes in hyperfine parameters and relative representation of both phases during the interrupted long-time annealing at 150 °C are discussed from the point of view of nitrogen migration and changes in defect structure.

Keywords: Stainless steel surface; Nitriding; Defects; Phase composition; Slow positron implantation; Conversion electrons Mössbauer spectroscopy

  • Applied Surface Science 194 (2002) 145-149

Publ.-Id: 4782

Hydrogen redistribution in titanium due to bending stress studied by micro ERDA

Grambole, D.; Wang, T.; Herrmann, F.; Eichhorn, F.

The influence of bending stress on the hydrogen behaviour in titanium was investigated by elastic recoil detection analysis with a heavy ion microbeam (micro ERDA) and X-ray diffraction (XRD). The samples were made by hydrogen ion implantation into polished pure titanium sheets. Three-dimensional hydrogen distributions were obtained by scanning the microbeam over the sample using the depth information of ERDA. Inhomogeneous hydrogen distributions in the titanium were observed which vary with the depth. With mechanical bending of the samples the inhomogeneities increased in varied grade. The surface hydrogen loaded by surface polishing is stable, whereas the implanted hydrogen located inside of the sample is mobile under bending. These different hydrogen behaviours are relevant to the chemical states of hydrogen. Different titanium hydrides are formed by the different loading methods. An relatively unknown titanium dihydride phase (TiH2(x)) with a tetragonal texture was identified by XRD in the depth region of implanted hydrogen. It is less stable than the normal titanium-dihydride phase (TiH2(d)) observed in the surface region. The change of hydrogen distribution is related to the dehydrogenation of the TiH2(x) and TiH(g) under bending.

Keywords: Microprobe; Elastic recoil detection analysis; Hydrogen diffusion; Titanium; Titanium hydride; Mechanical bending

  • Poster
    8th International Conference on Nuclear Microprobe Technology and Applications (ICNMTA2002), Takasaki, Japan, September 8-13, 2002
  • Nuclear Instruments and Methods in Physics Research B 210 (2003) 526 - 530

Publ.-Id: 4781

Investigation of spatial distribution of defects in ultra-fine grained copper

Cizek, J.; Prochazka, I.; Melikhova, O.; Brauer, G.; Anwand, W.; Kuzel, R.; Cieslar, M.; Islamgaliev, R. K.

Ultra-fine grained copper prepared by high pressure torsion has been studied by means of slow positron implantation
spectroscopy with Doppler broadening measurement. In addition, conventional positron lifetime and Doppler broadening spectroscopy have been utilised. Defects present in the specimens were identified, their spatial distribution and depth profile have been determined. The results are discussed in correlation with those obtained by XRD and TEM.

Keywords: Ultra-fine grained metal; Positron annihilation; Dislocation; Microvoid

  • Applied Surface Science 194 (2002) 140-144

Publ.-Id: 4780

Density gradient in SiO2 films on silicon as revealed by positron annihilation spectroscopy

Revesz, A. G.; Anwand, W.; Brauer, G.; Hughes, H. L.; Skorupa, W.

Positron annihilation spectroscopy of thermally grown and deposited SiO2 films on silicon shows in a non-destructive manner that these films have a gradient in their density. The gradient is most pronounced for the oxide grown in dry oxygen. Oxidation in water-containing ambient results in an oxide with reduced gradient, similarly to the gradient in the deposited oxide. These observations are in accordance with earlier optical and other studies using stepwise etching or a set of samples of varying thickness. The effective oxygen charge, which is very likely one of the reasons for the difference in the W parameters of silica glass and quartz crystal, could be even higher at some localized configurations in the SiO2 films resulting in increased positron trapping.

Keywords: Positron annihilation; Si/SiO2 structures

  • Applied Surface Science 194 (2002) 101-105

Publ.-Id: 4779

Positron characteristics of various SiO2 polymorphs

Kuriplach, J.; Anwand, W.; Brauer, G.; Skorupa, W.

Theoretical calculations of positron lifetimes, affinities and core electron contributions to Doppler broadening spectra are carried out for several phases (polymorphs) of SiO2. An interesting feature of SiO2 is that not all polymorphs have the same coordination of Si and O atoms, which also affects positron properties. The calculated quantities are compared with available experimental data and discussed with reference to SiO2/Si interfaces.

Keywords: Silica polymorphs; Positron lifetime; Positron affinity; Momentum distribution; SiO2/Si interface

  • Applied Surface Science 194 (2002) 84-88

Publ.-Id: 4778


Brauer, G.; Anwand, W.

The Ninth International Workshop on Slow Positron Beam Techniques for Solids and Surfaces, SLOPOS-9, was held at Dresden, Germany, from 16 to 22 September 2001. This series is devoted to provide an informal platform of presentation and discussion of latest results in this quickly advancing field, covering such scientific topics as positron beam development and design, including intense beams and microscopes, developments in experimental and analytical techniques, positroni-defect interactions and defect structure, defect profiling in bulk and layered structures, positron implantation and thermalisation, positronic and other surface processes, surface modification and coatings, and positron atomic physics.

At the moment of printing the Program/Abstract (31 August), 92 persons from 20 countries all over the world had registered for participation. The program represented a careful balance of invited (12), oral (50), and poster (28) presentations, mixed with cultural events (welcome reception, visit to the superconducting accelerator ELBE (under construction at Rossendorf), excursion, and banquet). The awful terrorist attacks in the US on 11 September had a minor but noticeable impact on our conference. Several American colleagues had to cancel their participation for subjective or objective reasons, or could finally participate only in part due to unavailability of airline capacity in time. Four participants from other countries had to cancel their participation at the last minute for other reasons.

Finally, 86 persons from 18 countries participated in the workshop, and the program still consisted of 11 invited, 43 oral, and 28 poster contributions. The program was organised into 14 oral sessions, 2 poster sessions, and 2 round-table discussions. The last dealt with special aspects of positron sources, including intense ones, and the question of where to meet in 2004 for SLOPOS-10. The competition was decided in an open and direct vote in favour of Doha, Qatar. The participants of the
workshop expressed their feelings of great sadness and sympathy for those directly and indirectly involved in the terrorist attacks in the US in a book of condolence during the workshop. In our opinion, the decision to meet next time in Doha, Qatar underlines the internationality of science which may not be influenced by terrorist activities. The closing remarks given on behalf of all colleagues by Philip Sterne from Lawrence Livermore National Laboratory, USA confirmed that this workshop was an outstanding success both from the scientific program and from its infrastructure and stimulating atmosphere, including all the cultural events.

In total, 59 papers have been accepted for publication after extensive reviewing. For their cooperative and very conscientious work we are grateful to the referees. We would like to thank the editors of Applied Surface Science for giving continuity to the publication series of SLOPOS proceedings.

The location of the workshop in the new part of Germany, in Dresden, allowed us to keep the average costs per participant to an acceptable level. In addition, due to generous sponsorship from our local ministry it was possible to arrange the participation of 10 colleagues from eastern Europe. However, we would like to express our thanks to all the sponsors, and especially all un-named people at the venue, Forschungszentrum Rossendorf, and the locations of our cultural events who have been very involved in contributing to the overall success of the workshop.

  • Applied Surface Science 194 (2002) 1

Publ.-Id: 4777

Proceedings of the Ninth International Workshop on Slow Positron Beam Techniques for Solids and Surfaces

Brauer, G.; Anwand, W.; (Editors)

no abstract delivered from author

Keywords: kein

  • Book (Authorship)
    Applied Surface Science 194 (2002)

Publ.-Id: 4776

Experimental determination of positron-related surface characteristics of 6H-SiC

Nangia, A.; Kim, J. H.; Weiss, A. H.; Brauer, G.

The positron work function of 6H-SiC was determined to be –2.1±0.1 eV from an analysis of the energy spectrum of
positrons reemitted from the surface. The positron reemission yield, highest in the sample inserted into vacuum after
atmospheric exposure and cleaning with ethanol, was significantly reduced after sputtering with 3 keV, 125 µA min Ne+ ions.
The yield was not recovered even after annealing at 900 °C, presumably due to the stability of sputter induced defects.
Sputtering at lower energies caused a smaller decrease in the reemission yield that was largely recovered after annealing at 850 °C. Analysis using electron induced Auger electron spectroscopy and positron-annihilation-induced Auger electron spectroscopy indicated that the surface was Si enriched after sputtering and C enriched after subsequent annealing. Values of positron diffusion length and mobility in the unsputtered material were extracted from the dependence of the reemission yield on the beam energy. The application of SiC as a field-assisted positron moderator is discussed.

Keywords: kein

  • Journal of Applied Physics 91 (2002) 2818-2826

Publ.-Id: 4775

Comparative study of defects in LiF implanted with 100 keV Al+, Mg+ and Ar+ by slow positron annihilation spectroscopy

Sendezera, E. J.; Davidson, A. T.; Kozakiewicz, A. G.; Anwand, W.; Brauer, G.; Nicht, E.-M.

no abstract delivered from author

Keywords: kein

  • Radiation effects and defects in solids 155 (2001) 139-144

Publ.-Id: 4774

Characterisation of defects in LiF implanted with Ar+ using variable energy positron beam

Sendezera, E. J.; Davidson, A. T.; Jili, P. T.; Chithambo, M. L.; Anwand, W.; Brauer, G.; Nicht, E.-M.

Slow positron implantation spectroscopy has been used to determine the surface and near surface defect profile in LiF after implantation with 100 keV argon ions for a range of fluences from 1013 to 1016 cm-2. The measured S-parameter is used to characterise the radiation damage as a function of depth. The spatial extent of the defect distributions was estimated by employing the computer program VEPFIT. Maximum lattice damage is shown to occur at incident positron energy of 4.0 keV for low doses and 5.0 keV for the high dose. This energy corresponds to a sample depth of about 200 nm. The positron annihilation spectroscopy results are correlated with optical absorption measurements on the crystals.

Keywords: Positron beam; Radiation damage; LiF:Ar+

  • Nuclear Instruments and Methods in Physics Research B 192 (2002) 202-205

Publ.-Id: 4773

Al+ implantation into epitaxial 6H-SiC: evolution of vacancy-type damage influenced by the substrate temperature

Anwand, W.; Brauer, G.; Skorupa, W.

Slow Positron Implantation Spectroscopy (SPIS) is a nondestructive method whereby positrons of a predetermined energy are implanted into a solid. In a certain depth region they annihilate with electrons. The motion of the positron-electron pair prior to the annihilation causes a Doppler broadening of the photopeak. The Doppler broadening of the annihilation line, characterized by two lineshape parameters, is measured in dependence on the incident positron energy and thereby on the depth where the annihilation took place.
SPIS is well known for its sensitivity to vacancy-type defects in solids. For this reason, this method has been applied to investigate the damage created by implantation of Al+ ions into epitaxial 6H-SiC. Al+ was implanted at an energy of 200 keV and a fluence of 1x1015 cm-2. In order to minimize the implantation-induced damage the substrate temperature was varied from room temperature up to 800 oC in steps of 200 degrees. Depth dependent defect profiles were calculated from the measured lineshape parameters versus the incident positron energy using the software package VEPFIT [1]. These depth profiles show significantly deeper reaching defects as calculated by TRIM [2]: whereas TRIM calculations result in a maximum depth of vacancies of about 300 nm, the positron measurements show that multiple vacancy clusters can be found up to a depth of more than 1µm below the surface. In addition to the extraction of the depth distribution of the damage it was possible to estimate the size of the vacancy agglomerates from the positron data in dependence on the substrate temperature and the depth position. The size of the damage and its depth distribution will be compared for different substrate temperatures during implantation and it will be shown that the damage minimum is obtained at a substrate temperature of 190 oC.

[1] A. van Veen, H. Schut, J. de Vries, R. A. Hakvoort, and M. R. Ijpma, in Positron beams for solids and surfaces, edited by P. J. Schultz, G. R. Massoumi, J. P. Simpson (American Institute of Physics, New York, 1990), p. 171
[2] The Stopping and Range of Ions in Solids, eds. J. F. Ziegler, J. P. Biersack, and U. Littmark (Pergamon Press, NewYork, 1999)

Keywords: ion implantation; 6H-SiC; positron annihilation

  • Poster
    European Conference on Silicon Carbide and Related Materials, Linköping, Sweden, September, 1-6, 2002

Publ.-Id: 4772

Plasma Analysis of a DC Sputtering Discharge in an N2/Ar atmosphere for the Deposition of Fullerene like Carbon Nitride

Neidhardt, J.; Hultman, L.; Fritsche, B.; Gago, R.; Möller, W.

Fullerene like carbon nitride (CNx) is a nanostructured material consisting of bent and intersecting graphitic layers. It combines the unique properties of being hard and elastic at the same time, which results in a fracture though and compliant material. Homogeneous well-structured fullerene like CNx thin films are commonly grown by DC reactive magnetron sputtering of graphite in an N2/Ar mixture. The nitrogen content in the films is fairly constant, limited due to the formation of volatile CN species at the substrate surface. Even though the composition is similar the structure and properties of these films can be varied over a very wide range in a comparatively narrow process window. This suggests that beside C and N ions and atoms other species like CN clusters might play an important role during growth. Here direct effects as growth templates or nucleation sites should be considered.

Plasma analysis was carried out during this study in order to investigate the presence, number, and energy of clusters consisting of C and N and their possible effects upon the growing film. A number of techniques, such as spatially resolved wire and ion probe measurements and energy selective mass spectrometry were used to characterize the composition and energetic conditions of a N2/Ar DC sputtering plasma in front of a single graphite target, depending on discharge current, total pressure and gas composition.

  • Lecture (Conference)
    International Conference on Metallurgical Coatings and Thin Films - ICMCTF 2002, 22-26 April 2002, San Diego (USA)

Publ.-Id: 4771

Anwendung des Master-Curve-Konzeptes bei dynamischer Belastung

Viehrig, H.-W.; Böhmert, J.; Dzugan, J.; Gokhman, A.

In dieser Arbeit wurde das Master-Curve (MC)-Konzept zur Charakterisierung der Zähig-keitseigenschaften über die Wanddicke eines Blockes aus Reaktordruckbehälterstahl ASTM A533B Cl. 1 angewendet. Es handelt sich dabei um das IAEA-Referenzmaterial JRQ. Die Prüfung von SENB-Proben mit Charpy-Geometrie erfolgte bei quasi-statischer und dynami-scher Belastung. Dynamisch wurden die Proben mit einem instrumentierten Pendelschlag-werk bei einer Schlaggeschwindigkeit von 2,8 m/s und quasi-statisch mit einem servohydrau-lischen Prüfsystem bei 0,2 mm/min geprüft. Im unterem Bereich des Duktil-Spröd-Übergangs (DBT) sind beim Versagen der Proben durch Spaltbruch Bruchzähigkeitswerte KJc nach ASTM E1921 ermittelt und ausgewertet worden. Die Berechnung der Referenztemperaturen T0 erfolgte nach der Multi-Temperatur (MT)-Methode des Master-Curve-Konzeptes. Zum Vergleich zu diesen bruchmechanischen Referenztemperaturen sind zusätzlich konventionelle Charpy-V-Übergangstemperaturen ermittelt worden.
Der Temperaturbereich für die Ermittlung gültiger KJcd-Werte mit dem instrumentierten Kerbschlagbiegeversuch wird bei kleinen Werten durch die Messung der wahren Schlagkraft (3J-Kriterium) bestimmt und zu höheren Werten durch das Gültigkeitskriterium nach ASTM E1921 begrenzt. Bei den realisierten Schlaggeschwindigkeiten von 2,8 m/s reicht der Gültig-keitsbereich für die KJcd-Werte von ca. 80 MPam1/2 bis 160 MPam1/2.
Der Verlauf der bei quasi-statischer und dynamischer Belastung ermittelten und nach dem Master-Curve-Konzept auf eine Probengröße von 25,4 mm (1T) umgerechneten KJc-1T-Werte folgt der Master-Curve. Eine direkte Anwendung der Master-Curve auf modifizierte Charpy-Test-Bedingungen ist nach den Ergebnissen dieser Arbeit möglich. Die Belastungsgeschwin-digkeit beeinflusst deutlich die Referenztemperatur T0. Die mit einer Belastungsgeschwindig-keit von 2,8 m/s ermittelten dynamische Referenztemperaturen T0dy liegen ca. 74 K höher als das quasi-statisch ermittelte Äquivalent T0st. Sie liegen auch höher als die Charpy-V-Übergangstemperaturen. Das Ergebnis ordnet sich in die in der Literatur für unterschiedliche Belastungsgeschwindigkeiten angegebenen Spanne der Erhöhung von T0 von 30 bis 120 K ein.
Die Ergebnisse zeigen, dass mit den dynamischen Referenztemperaturen wie auch mit den quasi-statischen Referenztemperaturen unterschiedliche Materialzustände charakterisiert wer-den können. Master-Curve-Referenztemperaturen und Charpy-V-Übergangstemperaturen zeigen den gleichen Verlauf über die Wanddicke des untersuchten RDB-Stahlblockes mit starken Unterschieden im Gefüge an den Randlagen und in der Blockmitte. In der Blockmitte ist das Gefüge des untersuchten RDB-Stahls sehr inhomogen und die in der ASTM E1921-97 genannte Mindestprobenzahl von 6 reichte zur Ermittlung von T0 nicht aus. Bei der Anwen-dung der MT-Methode waren mindestens 8 Proben notwendig, um eine gültige T0 zu erhalten. Die Anwendung der MT-Methode ist der Eintemperaturmethode vorzuziehen. Sowohl bei quasi-statischer Belastung als auch bei dynamischer Belastung wurde ein geringer Einfluss der Prüftemperatur auf die T0 ermittelt.

Keywords: reactor pressure vessel steel; instrumented impact test; fracture toughness; Master Curve

  • Lecture (Conference)
    2. Workshop “Kompetenzverbund Kerntechnik”, am 18. und 19. September 2002 in Köln, Tagungsband, Vortrag Nr. 11
  • Contribution to proceedings
    2. Workshop “Kompetenzverbund Kerntechnik”, am 18. und 19. September 2002 in Köln, Tagungsband, Vortrag Nr. 11

Publ.-Id: 4770

Solution deposition of hydroxyapatite on titanium pretreated with a sodium ion implantation

Pham, M. T.; Matz, W.; Grambole, D.; Hermann, F.; Reuther, H.; Richter, E.; Steiner, G.

Titanium surfaces were treated by exposing them to a beam of sodium ions. Sodium titanate was shown to be incorporated within the oxidic titanium surface. The ion- implanted surfaces were examined for their reactivity by immersion in a simulated body fluid, which showed the formation of surface-bound hydroxyapatite. The surface was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and optical and electron microscopy. The surface hydroxyl concentration was determined using the nuclear reaction 1H(15N,alpha, gamma)12C. Surface-related parameters that may affect hydroxyapatite nucleation are discussed in term of the electrical double layer.

Keywords: titanium; hydroxyapatite; ion implantation; nucleation

  • J. Biomed. Mater. Res. 59(2002)716-724

Publ.-Id: 4769

Associated Strangeness Production at Threshold with the TOF Experiment at COSY

Marcello, S.; Abd El-Samad, S.; Bilger, R.; Brinkmann, K.-T.; Clement, H.; Dshemuchadse, S.; Dutz, H.; Eyrich, W.; Erhardt, A.; Fanara, C.; Filges, D.; Filippi, A.; Freiesleben, H.; Fritsch, M.; Geyer, R.; Hassan, A.; Hauffe, J.; Hesselbarth, D.; Jakob, B.; Karsch, L.; Kilian, K.; Koch, H.; Kress, J.; Kuhlmann, E.; Marwinski, S.; Mauro, S.; Meyer, W.; Möller, K.; Morsch, H. P.; Naumann, L.; Nünighoff, K.; Paul, N.; Plettner, C.; Richter, M.; Roderburg, E.; Rogge, M.; Schamlott, A.; Schmitz, M.; Schönmeier, P.; Schulte-Wissermann, M.; Schroeder, W.; Sefzick, T.; Stinzing, F.; Sun, G. Y.; Wagner, G. J.; Wagner, M.; Wilms, A.; Wirth, S.; Zupranski, P.

Measurements of exclusive pp ® NKY reactions with beam momenta in
the range 2.5÷3.2 GeV/c are underway at COSY using the Time-of-Flight spectrometer TOF.
The high granularity of the detector, which covers almost the full phase space, allows to measure
differential distributions and total cross sections as well.
Moreover the hyperon polarization can be studied either with polarized beam
or target. Some preliminary results at different energies are given.

  • Nucl. Phys. A 691 (2001) 344

Publ.-Id: 4768

Dependence of electrical conductance of a-Si:H films on Na concentration in glass substrate

Pantchev, B.; Danesh, P.; Kreissig, U.; Schmidt, B.

The electrical conductance of a-Si:H is studied in films deposited on ion-exchanged optical waveguides in glass substrates. The effect of chemical composition of the near-surface region of the waveguide is considered from the viewpoint of the electrical instability of a-Si:H related with the penetration of Na ions from the substrate into the film. The optical waveguides have been prepared by Ag+-Na+ or K+-Na+ thermal or field-assisted ion exchange in soda-lime glass (SLG). The Na concentration in the near-surface region of the glass substrate has been established by means of elastic recoil detection analysis (ERDA). The obtained results demonstrate the possibility of reduction of electrical instability of a-Si:H films deposited on optical waveguides in glass. It is shown that in some cases an additional Na depletion of the near-surface region is necessary to avoid Na contamination of the a-Si:H films.

Keywords: hydrogenated amorphous silicon; electrical instability; optical waveguides; ion-exchange in glass

  • Opto-Electronics Review 9(4)(2001)431-434

Publ.-Id: 4766

Mobility and Retention of Implanted Hydrogen in Ti225 Titanium Alloy

Wang, T.; Grambole, D.; Grötzschel, R.; Herrmann, F.; Kreissig, U.; Eichhorn, F.; Brauer, G.; Möller, W.

The behaviours of implanted hydrogen in Ti225 alloy is investigated in this work. Hydrogen ion beam implantation was used to load hydrogen into the sample. Resonant Nuclear Reaction Analysis (NRA) and Elastic Recoil Detection Analysis (ERDA) were applied to obtain the depth profiles of hydrogen versus implantation dose. Two kinds of hydrogen have been found in the samples, one is as quasi-mobile and another is chemically bonded hydrogen. Three hydrogen precipitation stages, which relate to the different chemical states of hydrogen, are determined. Using X-Ray Diffraction (XRD), the hydride phase transformation from solid solution in titanium to titanium hydride (TiH1) and then titanium dehydrate (TiH2) tetragonal structure has been observed. The change is dose dependent in the implantation dose range between 2x1016 and 6x1017 H/cm2. The phase transformation from TiH1 to TiH2 occurs at an implantation dose greater than 1x1017 H/cm2 but finishes at a dose of 6x1017H/cm2 with the saturation of hydrogen concentration at about 23 at. %. The inhomogeneous planar distribution of the hydrogen was also observed using both scanning micro-probe ERDA and Scanning Electron Microscopy (SEM).

Keywords: Hydrogen; Titanium; Diffusion; Concentration

  • Surface & Coating Technoloy, vol 158-159(2002)138-144

Publ.-Id: 4765

Spin Transfer in Exclusive L Production from pp Collisions at 3.67 GeV/c

Balestra, F.; Bedfer, Y.; Bertini, R.; Bland, L. C.; Brenschede, A.; Brochard, F.; Bussa, M. P.; Chalyshev, V.; Seonho, C.; Debowski, M.; Dzemidzic, M.; Faivre, J.-C.; Falomkin, I. V.; Fava, L.; Ferrero, L.; Foryciarz, J.; Frolov, V.; Garfagnini, R.; Gill, D.; Grasso, A.; Heinz, S.; Ivanov, V. V.; Jacobs, W. W.; Kühn, W.; Maggiora, A.; Maggiora, M.; Manara, A.; Panzieri, D.; Pfaff, H.-W.; Piragino, G.; Pontecorvo, G. B.; Popov, A.; Ritman, J.; Salabura, P.; Tosello, F.; Vigdor, S. E.; Zosi, G.

We report the first polarization transfer measurements for exclusive hyperon production reactions.
The normal spin transfer coefficient DNN for
pp®pK+K- L is large and negative for
forward L production at a beam momentum of 3.67GeV/c, a result
qualitatively consistent with expectations for a mechanism dominated by kaon-exchange and rescattering.
The sign of DNN is opposite to that observed in the fragmentation regime for
inclusive L production at much higher energies.

  • Physical Review Letters 38 (1999) 1534

Publ.-Id: 4764

Hydrogen corrosion and mobility in T225 titanium alloy by ion beam and material analysis methods

Wang, T.; Grambole, D.; Grötzschel, R.; Herrman, F.; Kreissig, U.; Eichhorn, F.; Brauer, G.; Möller, W.

The behaviour of hydrogen implanted into Ti225 alloy is studied in this work. The hydrogen depth profiles vs. different implantation doses and ion energies were measured with resonant Nuclear Reaction Analysis (NRA) and Elastic Recoil Detection Analysis (ERDA). The hydrogen diffusion to the surface at room temperature is found from the depth profiles which differ from their theoretical simulation due to a more complex diffusion and hydrogenation than described at present by theory. A rapid formation of titanium hydrides, i.e. TiH1 and TiH2 , is found in the implantation dose range between 6x1016 and 2x1017 H1/cm2 by X-ray diffraction. The phase transformation from TiH1 to TiH2 crystal structure starts after implantation of 1x1017 H1/cm2, and is finished at a dose of 6x1017H1/cm2 at which a saturation of the hydrogen concentration of about 23 at.% is found from the depth profiles. The titanium hydrides are inhomogeneously distributed in the sample. The hydrogen contour maps measured by the scan of micro-beam ERDA show dose-dependent inhomogeneities due to the hydride formation process. The radiation damage affects also the hydrogen concentration and out-diffusion. A defect-related trapping of hydrogen is observed by slow positron implantation spectroscopy (SPIS). The surface hydride layer on titanium acts as a highly effective barrier to oxygen. It is found that the oxidation ratio is strongly reduced already by implantation of only 2x1016 H1/cm2.

Keywords: Titanium; Hydrogen implantation; Titanium hydrogenation; Ion beam analysis; X-ray diffraction

  • Lecture (Conference)
    International conference on Surface Modification of Materials by Ion Beam, (SMMIB 2001), Marburg, Germany, Sept. 7-13, 2001

Publ.-Id: 4763

Hydrogen isotope depth profiling in carbon samples from the erosion dominated inner vessel walls of JET

Stan-Sion, C.; Behrisch, R.; Coad, J. P.; Kreissig, U.; Kubo, F.; Lazarev, V.; Lindig, S.; Mayer, M.; Nolte, E.; Peacock, A.; Rohrer, L.; Roth, J.

In order to investigate the hydrogen isotope accumulation at the erosion dominated inner walls of fusion experiments, several small carbon samples have been mounted in the inner wall tiles of the torus of the JET Joint Undertaking. After about 2.5 years of JET operation, including the extended D/T phase and the D/D cleaning phase, the samples have been removed and analysed by RBS, ERDA and AMS. In the near surface region only small T concentrations are measured. A much larger T concentration is found at depths between about 1 and 2 m. This may originate from energetic (~1 MeV) T which is produced during the D/D discharges and implanted to large depth. The lower energy (keV) T which is implanted during the D/T discharges became effectively removed from the inner wall, by isotope exchange with implanted D or H and/or by erosion of the wall. The total amount of T within a depth of about 2 m was found to be about 1-3×1013 T/cm2, while in a surface layer of about 0.5 m about 1-3×1012 T/cm2, about 2-4×1016 D/cm2 and about 4-9×1016 H/cm2 were measured.

Keywords: Hydrogen retention; Deuterium retention; Tritium retention; JET; Erosion

  • Journal of Nuclear Materials 290-293 (2001) 491-495

Publ.-Id: 4762

High resolution IBA analysis of spin dependent tunnel junctions

Barradas, N. P.; Da Silva, M. F.; Soares, J. C.; Kreissig, U.; Arnoldbik, W. M.; Cardoso, S.; Freitas, P. P.

Spin dependent tunnel junctions are of technological interest for applications in magnetic non-volatile random access memories due to their large tunneling magnetoresistance effect and low junction resistance-area product. Typical structures are Si/Al2O3 600Å/Ta 70Å/NiFe 70Å/CoFe 30Å/AlxNyOz t/CoFe 40Å/MnIr 200Å/Ta 30Å, with t=6-30 Å, annealed to temperatures up to 400ºC. The properties of these junctions are strongly influenced by the layer thicknesses and composition, and change on annealing. Standard technology for integrated circuits requires annealing at 400-450ºC, and an understanding of the changing magnetic properties of the tunnel junction requires detailed knowledge of the behavior of the different interfaces. We performed Rutherford backscattering (RBS) experiments at a grazing angle of incidence to achieve high depth resolution for the transition metals signal. The composition of the AlxNyOz layers was determined with Heavy Ion Elastic Recoil Detection Analysis. We also performed heavy ion RBS experiments for improved mass resolution. The thickness and composition of the individual layers is determined, and a high sensitivity to diffusion and layer intermixing is achieved.

  • Modern Physics Letters B, Vol. 15, 28/29 (2001) 1288-1296

Publ.-Id: 4759

Elementanalytik dünner Schichten mit MeV-Ionenstrahlen

Grötzschel, R.

Übersicht über Methoden der Materialanalytik an Beschleunigern

Keywords: IBA

  • Lecture (others)
    Institutsseminar IFW Dresden

Publ.-Id: 4758

Ion beam analysis of thin films with heavy MeV ions

Grötzschel, R.; Klein, C.; Kreissig, U.; Mäder, M.

Among the wide choice of physical analysis methods to characterise thin and ultra thin films both Rutherford backscattering spectrometry (RBS) and the elastic recoil atom spectrometry (ERDA) have a unique feature. The binary elastic scattering at the Coulomb potential of the involved nuclei can be described analytically by the Ruther-ford cross section formula. This allows an easy and accurate determination of quan-tities like area densities of elements or composition of thin films.
For the detection of all light elements ERDA with heavy incidence ions of energies
> 1 MeV/u is the method of choice. As recoil atom spectrometers heavy ion detec-tors are used which provide not only the energy signal but also particle identification and position information for kinematical corrections, which is particularly necessary at large acceptance angles. We use at the Rossendorf 5 MV tandem Bragg peak ioni-sation chambers, dE-E-ionisation chamber telescopes, time-of-flight (TOF) spectrome-ters or combinations of those. The specific merits and drawbacks of these detectors are discussed. A common feature is the moderate energy resolution dE/E of roughly 0.01. This is the limiting parameter for the obtainable depth resolution. To overcome this limit magnetic spectrometers have to be used which enable depth resolutions in the order of monolayers. We have installed at the tandem a QQDS spectrometer for ERDA with variable dispersion, which is shortly described.
An analogue situation we have in the case of RBS. Despite of many physical advanta-ges of heavy incidence ions [1] mostly He ions are used due to the fact that the energy resolution of solid state detectors decreases with increasing Z of the detected particles. When using magnetic spectrometers for RBS it is possible to profit fully from the high stopping powers of heavy ions. Thus depth resolutions of one monolayer can be achieved. We have installed a magnetic spectrometer of the simple Browne-Buechner type at the 3 MV Tandetron for RBS. The first results with this instrument are discussed.

[1] D.J.O´Connor, T.Chunyu, Nucl. Instr. And Meth. B 36 (1989) 178

Keywords: Ion Beam Analysis; Heavy Ions

  • Lecture (Conference)
    Conf. ION 2002, Kazimirz Dolny, Poland, June 10 - 13, 2002

Publ.-Id: 4756

Interplay of Equilibrium and Nonequilibrium Phenomena in the Nuclear Liquid-Gas Phase Transition

Zwieglinski, B.; Odeh, T.; Gross, C.; Schwarz, C.; Bassini, R.; Begemann-Blaich, M.; Fritz, S.; Gaff-Ejakov, S. J.; Gourio, D.; Imme, G.; Iori, I.; Kleinevoss, U.; Kunde, G. J.; Kunze, W. D.; Lynen, U.; Maddalena, V.; Mahi, M.; Moroni, A.; Möhlenkamp, T.; Müller, W. F. J.; Nociforo, C.; Ocker, B.; Petruzzelli, F.; Pochodzalla, J.; Raciti, G.; Riccobene, G.; Romano, F. P.; Saija, A.; Sann, H.; Schnittker, M.; Schüttauf, A.; Seidel, W.; Serfling, V.; Sfienti, C.; Trautmann, W.; Trzcinski, A.; Verde, G.; Wörner, A.; Xi, H. F.

Energy spectra of protons emitted by the target residue in Au+Au collisions at 1 GeV/u reveal two
components with different slopes attributed to preequilibrium and equilibrium emission. The relative
contribution of the latter decreases rapidly with excitation energy, so that its presence becomes not
apparent for the highest energy bins. It is argued therefore, that equilibrium may not be reached on
the gas branch of the caloric curve. The nuclear liquid-gas phase transition thus belongs to the
category of nonequilibrium phase transitions for which the concepts developed in synergetics, such as
self-organized criticality, provide the proper framework.

  • Nucl. Phys. A 681 (2001) 275

Publ.-Id: 4755

Fragment Isotope Distributions and the Isospin Dependent Equation of State

Tan, W. P.; Li, B.-A.; Donangelo, R.; Gelbke, C. K.; van Goetherm, M.-J.; Liu, X. D.; Lynch, W. G.; Souza, S.; Tsang, M. B.; Verde, G.; Wagner, A.; Xu, N. S.

Calculations predict a connection between the isotopic composition of particles emitted during an energetic nucleus-nucleus collision and the density dependence of the asymmetry term of the nuclear equation of state (EOS). This connection is investigated for central 112Sn+112Sn and 124Sn+124Sn collisions at E/A=50 MeV in the limit of an equilibrated freezeout condition. Comparisons between measured isotopic yields ratios and theoretical predictions in the equilibrium limit are used to assess the sensitivity to the density dependence of the asymmetry term of the EOS. This analysis suggests that such comparisons may provide an opportunity to constrain the asymmetry term of the EOS.

  • Phys. Rev. C 64 (2001) 051901

Publ.-Id: 4754

Effects of QED and Beyond from the Atomic Binding Energy

Soff, G.; Bedniakov, I.; Beier, T.; Erler, F.; Goidenko, I. A.; Jentschura, U. D.; Labzowski, L. N.; Nefiodov, A. V.; Plunien, G.; Schützhold, R.; Zschocke, S.

Atomic binding energies are calculated at utmost precision. A report on the current status of
Lamb-shift predictions for hydrogenlike ions, including all quantum electrodynamical corrections to first
and second order in the fine structure constant alpha is presented. All relevant nuclear effects are
taken into account. High-precision calculations for the Lamb shift in hydrogen are presented. The
hyperfine structure splitting and the g factor of a bound electron in the strong electromagnetic field of a
heavy nucleus is considered. Special emphasis is also put on parity violation effects in atomic systems.
For all systems possible investigations beyond precision tests of quantum electrodynamics are

  • Hyp. Int. 132 (2001) 75

Publ.-Id: 4753

Time Scales in Spectator Fragmentation

Schwarz, C.; Fritz, S.; Bassini, R.; Begemann-Blaich, M.; Gaff-Ejakov, S. J.; Gourio, D.; Gross, C.; Imme, G.; Iori, I.; Kleinevoss, U.; Kunde, G. J.; Kunze, W. D.; Lynen, U.; Maddalena, V.; Mahi, M.; Möhlenkamp, T.; Moroni, A.; Nociforo, W. F. J. M. C.; Ocker, B.; Odeh, T.; Petruzzelli, F.; Pochodzalla, J.; Raciti, G.; Riccobene, G.; Romano, F. P.; Saija, A.; Schnittker, M.; Schüttauf, A.; Seidel, W.; Serfling, V.; Sfienti, C.; Trautmann, W.; Trzcinski, A.; Verde, G.; Wörner, A.; Hongfei, X.; Zwieglinski, B.

Proton-proton correlations and correlations of
p-a, d-a, and t-a
from spectator decays following 197$Au + 197Au
collisions at 1000 AMeV have been measured with an highly efficient detector hodoscope.
The constructed correlation functions indicate a moderate expansion and low breakup densities similar to
assumptions made in statistical multifragmentation models. In agreement with a volume breakup
rather short time scales were deduced employing directional cuts in proton-proton correlations.

  • Nucl. Phys. A 681 (2001) 279

Publ.-Id: 4752

Ion acoustic microscopy for imaging of buried structures based on a focused ion beam system

Akhmadaliev, C.; Bischoff, L.; Teichert, J.; Kazbekov, K.; Köhler, B.

An intensity modulated focused ion beam (FIB) which is hitting the surface of a solid, leads to a small temperature variation in the near subsurface region which is sufficient for thermal elastic wave generation. The measurement of these waves can be used for analysis and imaging of surface as well as subsurface structures in the material. The modified FIB equipment IMSA-100 working with 35 keV Ga+ and Au+ ions and a current of about 3 nA was employed to obtain acoustic images from structures on silicon and glass targets. The acoustic signals were detected using a PZT transducer delivering an output voltage of 50 - 100 nV. The modulation frequency was varied in the range of 60kHz - 170kHz. The obtained lateral resolution of the ion acoustic images at these frequencies was about 15 µm on silicon and about 7µm on glass. We are going to increase the modulation frequency up to MHz range in order to reach sub-micron resolution.

Keywords: intensity modulated focused ion beam; thermal elastic wave generation

  • Lecture (Conference)
    DPG Tagungen 2001, Hamburg March 26 - 30

Publ.-Id: 4751

Temperature Dependence of the Electronics Characterization and mass spectra of Liquid Metal Alloy Ion Sources

Ganetsos, T.; Mair, G. L. R.; Bischoff, L.

This is a comprehensive study of the characteristics of an AuGeSi and CoNd Liquid Metal Alloy Ion Source (LMAISs) [1]. Such characteristics include current-voltage curves and ion beam mass-spectra. A careful investigation has been undertaken where the temperature is one of the main variable experiment parameters [2]. Theoretical models support the experimental results.
[1] P.D. Prewett and GLR. Mair, "Focused Ion Beams from Liquid Metal Ion Sources", Research Studies Press, Taunton, Somerset, UK, 1991
[2] L. Bischoff, J. Teichert, Th. Ganetsos and GLR. Mair
J. Phys. D: Appl. Phys. 33 (2000) 692.

Keywords: Liquid Metal Alloy Ion Source (LMAISs); mass-spectra; I-V curves; temperature

  • Lecture (Conference)
    IFES 2001, 47th International Field Emission Symposium. July 29 - Aug. 3, 2001, Berlin, Germany

Publ.-Id: 4750

Investigation of elastic waves generation in a solid target by a pulsed ion beam

Akhmadaliev, C.; Bischoff, L.

The generation of elastic waves in solids during irradiation with pulsed ion beams is investigated. There are two main mechanisms of the elastic wave emission. First is a simple momentum transfer from the beam particles to the target atoms. Also the heating of the material yields an acoustic wave due to a local thermal expansion. Other effects, like a change of the density, local amorphization, charging up of the target near the surface etc. can also generate elastic waves.
The measurements are carried out using a IMSA-100 focused ion beam (FIB) system and a 3 MV-TANDETRON accelerator. The energy of the FIB is 30-35 keV at a current of 1-3nA and a spot size of about 1mm. On the accelerator a current of some mA and energies up to some MeV with Au+, Ge2+, Si2+, Si3+and Si4+ ions and beam pulse duration of some microseconds were used. The elastic waves is registered by a piezoelectric sensor on the back surface of the sample. Then the signal is amplified and digitized on a PC. The dependence of the amplitude of the acoustic signal in silicon, titanium, brass and aluminum are measured for different beams. The change of the charge state of the ions up to 6 shows no significant influence. The amplitude depends on the power of the beam linearly at low current densities. These elastic waves can be used for acoustic imaging of surface and buried structures in a scanning ion acoustic microscope.

Keywords: elastic waves; pulsed ion beams; scanning ion acoustic microscope

  • Lecture (Conference)
    DPG Tagungen 2002, Regensburg March, 11 - 15, 2002, O 30.8

Publ.-Id: 4749

Solidified liquid metal ion sources - formation of a nanoemitter for electron field emission

Knapp, W.; Bischoff, L.; Teichert, J.

Solidified liquid metal ion sources (LMISs) operating with Au alloy wetted hair-pin emitters can be used as high-intensity electron point sources with nanometer dimension for electron field emission application. A nanoemitter tip on a solidified LMIS emitter can be formed by quenching during ion emission mode. I-V characteristics and the performance of the electron emitting LMIS are presented.

Keywords: Solidified liquid metal ion sources; electron emitting; nanoemitter tip

  • Lecture (Conference)
    12th International Summer School on Vacuum, Electron and Ion Technologies VEIT2001, September 17 - 21, 2001, Varna, Bulgaria Vacuum

Publ.-Id: 4748

Optical Pattern Formation in a-SiC:H Films by Ga+ Ion Implantation

Bischoff, L.; Teichert, J.; Kitova, S.; Tsvetkova, T.

The optical modification effect of Ga+ ion implantation in a-SiC:H films has been studied. As a result of the implantation a well expressed "darkening" effect (i.e. absorption edge shift to the longer-wavelength/lower-photon-energy region) has been registered. It is accompanied by a remarkable increase of the absorption coefficient up to 2 orders of magnitude in the measured photon energy range (1.5-3.1 eV). The optical contrast thus obtained (between implanted and unimplanted regions of the film material) has been made use of in the form of optical pattern formation by computer operated Ga+ focused ion beam. Possible applications of this effect in the area of sub-micron lithography and high-density optical data storage have been suggested with regard to the most widely spread focused micro-beam systems based on Ga+ liquid metal ion sources. The physical basis for the advantages in cases of applications in adverse environments have also been discussed.

Keywords: a-SiC:H films; optical modification; Ga+ ion implantation; focused micro-beam

  • Lecture (Conference)
    12th International Summer School on Vacuum, Electron and Ion Technologies VEIT2001, September 17 - 21, 2001, Varna, Bulgaria
  • Vacuum 69 (2003) 73-77

Publ.-Id: 4747

Promoted hydroxyapatite nucleation on titanium ion implanted with sodium

Pham, M. T.; Maitz, M. F.; Matz, W.; Reuther, H.; Richter, E.; Steiner, G.

Precipitation of hydroxyapatite on titanium from aqueous solution offers the possibility of creating biologically active coatings for bone fixated implants by mimicking the physiological properties of the bone. While solution-related factors have been well established, the research into surface-related stimuli for promoting hydroxyapatite nucleation is still underway. In the present work titanium surfaces were pretreated by implantation of sodium ions yielding sodium titanate incorporated within the surface layer with concentration, depth distribution, and morphology depending on the parameters of the ion implantation and the subsequent thermal treatment. Such ion-implanted surfaces were observed to promote hydroxyapatite nucleation and growth from simulated body fluid. Surface properties were studied using spectroscopic and microscopic methods. The mechanisms of heterogeneous nucleation of hydroxyapatite were discussed in terms of the electrical double layer.

Keywords: Apatit; Titanium; sodium; simulated body fluid

  • Thin Solid Films 379 (2000) 50-56

Publ.-Id: 4746

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