Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31745 Publications
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
Biotechnologie.



Keywords: Si-basierte Lichtemission, Nanostrukturen
  • Lecture (others)
    VDI-Forum Nanoworld, Hannover Messe 2001, Hannover, 24. April 2001

Publ.-Id: 4836 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


Preface
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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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
considered.
  • Hyp. Int. 132 (2001) 75

Publ.-Id: 4753 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


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 - Permalink


Ion beam treatment of titanium surfaces for enhancing deposition of hydroxyapatite from solution
Maitz, M. F.; Pham, M. T.; Matz, W.; Reuther, H.; Steiner, G.; Richter, E.;
Surface coating with hydroxyapatite (HA) is a common way to improve the osseointegration of orthopaedic and dental titanium-based materials. The main problems with current techniques are changes in composition during heating and poor adhesion to the surface. An alternative method is deposition of HA onto an activated surface out of a solution.
The present work studies the surface treatment involving ion implantation of Na into Ti to induce a modification in chemistry and morphology, showing sodium titanate incorporated within the surface layer with concentration, depth distribution, and morphology depending on the parameters of the ion implantation. Such ion-implanted Ti surfaces actively induce heterogeneous precipitation of HA from a simulated body fluid containing physiological concentrations of calcium and phosphate ions. This is compared with the activation by NaOH etching. The growth of bone forming cells on the pure Na implanted surface is oriented without an increased bone formation. Cell growth on the NaOH etched surface is reduced. After deposition of HA on both surfaces cell the growth pattern was improved.

Keywords: hydroxyapatite, cell culture
  • Lecture (Conference)
    European Materials Research Society. 2001 Spring Meeting, 05.-08.06. 2001, Strasbourg, France
  • Biomol Engineer 19: 271-274 (2002)
  • Contribution to proceedings
    European Materials Research Society. 2001 Spring Meeting, 05.-08.06. 2001, Strasbourg, France

Publ.-Id: 4745 - Permalink


Deposition of Ti based coatings with different surface structure and chemistry for medical devices
Maitz, M. F.; Mukherjee, S.; Pham, M. T.; Richter, E.;
Titanium alloys with small amounts of Aluminium and Vanadium are by now the favourite base materials for orthopaedic implants for their good biocompatibility, but stainless steel is wider in use because of its lower material costs and easier handling. By Metal Plasma Immersion Ion Implantation and Deposition (MPIIID) coatings of Ti, TiN, TixAl1-x, and TixAl1-xN layers were deposited on mirror polished stainless steel with a different process parameters, i.e. the bias voltage was changed systematically.
Coatings produced with a bias voltage of -2000 V had a roughness up to 70 nm, whereas those with zero bias voltage were much smoother (6 nm). In coatings with higher voltage the ration Ti : Al shifted to Ti. Rat one marrow cells were seeded out on these surfaces in a serum free medium. After 5h cell spreading and organisation of the cytoskeleton was best on the smoother samples with best spreading on Ti and TixAl1-xN with 0 bias voltage. There was no significant necrosis as measured by lactate dehydrogenase release within 5 h, but up to 25% pyknotic and fragmented cell nuclei as signs of apoptosis. This behaviour was different for the different samples, but there was no correlation with the surface roughness or chemistry. The effect of the medium, direct induction of apoptosis by the coating or apoptotic cell death due to inhibited adhesion by roughness or surface chemistry will be discussed.
Keywords: Titanium nitride, Titanium aluminum nitride, biocompatibility
  • Poster
    EMRS Spring Meeting 18.-21.06.2002. Strasbourg, France http://www-emrs.c-strasbourg.fr/2002_Book_Abs/02_Prog_Rv2.pdf
  • Contribution to proceedings
    EMRS Spring Meeting 18.-21.06.2002. Strasbourg, France http://www-emrs.c-strasbourg.fr/2002_Book_Abs/02_Prog_Rv2.pdf

Publ.-Id: 4744 - Permalink


Synthesis of polyurethane coating with drug compounds on metal stents
in Russian
Romanova, V. A.; Begishev, V. P.; Guenzel, R.; Maitz, M.; Kondyurin, A. V.; Kondyurina, I. V.;
Russisches Abstrakt siehe Download
Keywords: Stents, polymer, drug release
  • Poster
    Conference "Oligomers 2002", Chernogolovka, Russia, 9.-14. September 2002

Publ.-Id: 4743 - Permalink


Ionenbehandlung von Gefäßstents erhöhen Blutkompatibilität und Röntgenkontrast
Maitz, M.; Pham, M. T.;
Gefäßstents werden nach der Aufweitung eines arteriosklerotisch verengten Herzkranzgefäßes eingebracht und sollen den erneuten Verschluss des Gefäßes verhindern. Sie stellen einen der wesentlichen Fortschritte in der Kardiologie des letzten Jahrzehnts dar. Durch sie konnte die Zahl der teuren und belastenden Bypass-Operation wesentlich gesenkt und die Aufenthaltsdauer der Patienten im Krankenhaus verkürzt werden.

Trotz des heute millionenfachen Einsatzes dieser filigranen Metallgeflechte, werden von den anwendenden Ärzten noch eine Reihe von Verbesserungen gewünscht, die eine genaue Kenntnis der Körperreaktionen und eine Materialbehandlung mit modernen Methoden erfordern.

Die Gefäßstents werden unter Röntgenkontrolle eingesetzt und auch radiologisch beurteilt. Die dünnen Stahl- oder Nickel-Titan-Drähte, aus denen der Stent besteht, bieten nur einen unbefriedigenden Röntgenkontrast. Durch die Aufbringung einer einige Mikrometer (µm) dicken Schicht eines Metalls hoher Ordnungszahl kann der Röntgenkontrast der Drähte erhöht werden. Dabei bieten sich Metalle wie Tantal an, die ähnlich wie das aus der Orthopädie bekannte Titan eine sehr stabile Oxidschicht ausbilden und dadurch auch gut biokompatibel sind.

Eine gute Haftung der Schicht auf dem Untergrund ist hier besonders wichtig, weil abgelöste Anteile der Schicht sonst mit dem arteriellen Blutstrom in das feinere Gefäßnetz der Herzmuskulatur transportiert werden und dort einen Verschluss herbeiführen würden. Die aufgebrachte Schicht darf keine inneren Spannungen aufweisen, die bei den erforderlichen Schichtdicken ansonsten zu Lamellierung sowie beim Aufweiten des Stents zur Rissbildung führen würden. Die Aufbringung dieser Schicht wird am Forschungszentrum Rossendorf durch Metallplasma Ionenimplantation und -abscheidung erreicht, wobei die Haftfestigkeit durch eine Zwischenschicht vermittelt ist.

Ein weiteres noch nicht befriedigend gelöstes Problem bei Gefäßstents ist die Aktivierung der Blutgerinnung und ein Wachstumsreiz auf die innerste Gefäßschicht. Diese beiden Reaktionen können zum Verschluss des Stents führen und sind eine der Ursachen, warum im Vergleich zur Bypass-Operation noch häufig eine Nachbehandlung nötig ist. Auch hier ist Tantal ein gutes Metall für die Beschichtung, weil es mit der Oxidschicht eine sehr gute Blutverträglichkeit aufweist, die wie bei Titan durch die Implantation weiterer Ionen wie Phosphor, Stickstoff, Kalzium noch verbessert werden kann.
  • Dresdner Transferbrief 9(4/2001): 12 (2001)

Publ.-Id: 4742 - Permalink


Principles of biomaterials testing
Maitz, M.;
no abstract delivered from author
Keywords: Biomaterials, testing
  • Lecture (others)
    Southwest Jiaotong University, Institute of Biomaterials & Surface Engineering, Chengdu, December 14, 2001

Publ.-Id: 4741 - Permalink


The MatMed Database
Maitz, M. F.;
no abstract delivered from author
Keywords: database, materials in medicine, MatMed, EC Project
  • Lecture (others)
    MatMed EU Project meeting, Rhodos May 09-11, 2001

Publ.-Id: 4740 - Permalink


Principles of Biological Testing of Implant Materials
Maitz, M. F.;
no abstract delivered from author
  • Lecture (others)
    Kyiv Taras Shevchenko University, Faculty of Physics, May 03, 2001

Publ.-Id: 4739 - Permalink


Grundlagen der Gerinnungsaktivierung an Fremdmaterialien
Maitz, M. F.;
Die Blutgerinnung ist ein komplex regulierter Vorgang. Es gibt eine Reihe von Faktoren, die die Gerinnung initiieren können. Beteiligt sind die Proteasen der Gerinnungskaskade, Blutplättchen, die Endothelzellen der Gefäßwand und verschiedene Proteine, die an Oberflächen adsorbiert sind. Die Ursachen der Blutgerinnung liegen allgemein an geänderten Strömungsverhältnissen, erhöhter Gerinnungsfähigkeit des Blutes und an den Oberflächen.
Die Aktivierung der Blutgerinnung ist meist bei Implantaten im Blutstrom nicht gewünscht. Der Schwerpunkt dieser Übersicht liegt darauf, wie durch veränderte Oberflächeneigenschaften die direkte Aktivierung der plasmatischen Blutgerinnung, Aktivierung von Blutplättchen und der Endothelzellen unterdrückt werden können. Dabei werden physikalische Eigenschaften wie die Oberflächenrauhigkeit und Oberflächenenergie optimiert, biochemisch funktionelle Gruppen auf der Oberfläche aufgebracht, als lokale Pharmaka werden Heparin und Hirudin als gerinnungshemmende Substanzen angewandt, Thrombozyten-Rezeptorblocker und antiproliferative Medikamente sind in vorklinischen oder klinischen Studien. Weiter wird darauf gesetzt, eine intakte Endothelschicht zu erreichen, indem das Endothelwachstum auf der Oberfläche gefördert wird oder Endothelzellen auf den Implantatoberflächen in vitro im Sinn von Tissue Engineering zu züchten.
Keywords: Hemocompatibility, clotting cascade
  • Lecture (Conference)
    3. Thüringer Biomaterial-Kolloquium, Jena, November 09, 2001
  • Contribution to external collection
    3. Thüringer Biomaterial-Kolloquium, Jena, November 09, 2001

Publ.-Id: 4738 - Permalink


Ta implantation and deposition for increased X-Ray visibility and hemocompatibility of vascular stents
Maitz, M. F.; Günzel, R.; Pham, M. T.; Langping, W.; Chu, P.; Richter, E.;
Objectives: Coronary stents are seen as the most important step in cardiology of the decade, as they reduce the risk of restenosis after angioplasty and the risk of a second invasive procedure. But still problems concerning occlusion by restenosis or thrombosis have to be overcome, and x-ray contrast of the thin wires has to be improved. The suggested way is coating of the stents with tantalum which is known for its good biocompatibility and hemocompatibility, and its high x-ray absorption.
Deposition of tantalum on stainless steel, the basis of the stent material, is not trivial with common techniques, because of poor adhesion of tantalum. Plasma immersion ion implantation and plasma ion deposition of tantalum are promising ways to create an adherent tantalum layer.
Methods: Tantalum was deposited on flat samples of stainless steel in an argon plasma, 1A Magnetron currency, WHF = 1000 W and 5µs pulse time. Various voltages, bias voltages, pulse counts and temperatures were used.
The adhesion of the tantalum layer was measured in a scratch test. Potentiodynamic corrosion measurement was performed with 0.05M H2SO4 as an electrolyte.
For blood compatibility the activation of freshly prepared blood platelets on the surface was investigated and the clotting time with standard plasma was measured.
Results: For thin coatings (< 1µm) the result of the scratch test was 250mN as a promising result. The coating showed very high corrosion resistance with a corrosion potential between 225 mV and 355 mV and corrosion current densities between 20 nA and 40 nA cm-2.
Results of thrombocyte adhesion, thrombocyte activation and blood clotting time will be presented.
Production of thicker coatings caused problems because of internal stress in the coating.
Conclusion: Coating of stainless steel with tantalum by plasma ion deposition is a good means to increase corrosion resistance and blood compatibility. The production of a thick layer with increased X-ray contrast needs further work.

Keywords: vascular stent, tantalum, coating, radiopacity, x-ray contrast, hemocompatibility
  • Lecture (Conference)
    5th Asian Symposium on Biomedical Materials, Hongkong, December 9-12, 2001
  • Contribution to proceedings
    5th Asian Symposium on Biomedical Materials, Hongkong, December 9-12, 2001

Publ.-Id: 4737 - Permalink


Hydroxyapatite precipitation on Na implanted titanium
Maitz, M. F.; Pham, M. T.; Matz, W.; Reuther, H.; Steiner, G.; Richter, E.;
Objectives: Titanium is known for its good biocompatibility as an implant material. But a structural integration of a foreign material into the body is known only for hydroxyapatite because of its osteoconductive properties. Surface coating of titanium with hydroxyapatite by means of plasma spraying is the current technique to improve the osteointegration of implants. Problems with this method are the high thickness and limited adhesion of the apatite coating on titanium. Further there are changes in crystallinity of the apatite due to the heating process. A surface preparation that spontaneously induces hydroxyapatite nucleation on its surface is desired.
Methods: By ion beam implantation of Na (3 x 1017 ions cm-1, 50 keV) in titanium a sodium titanate surface was created. Hydrolysis of this layer in deionidised water resulted in formation of TiOH. By incubation in simulated body fluid a hydroxyapatite layer was precipitated on the surface. The human osteosarcoma cell line was seeded out on samples after hydrolysis and after hydroxyapatite precipitation. Reference samples were untreated or activated by soaking in hot NaOH. After 3, 14, and 28 days samples ware investigated for cell growth, alkaline phosphatase activity and calcification.
Results: Cell growth on Na implanted hydrolysed samples was decreased compared with pure titanium at any time. After hydroxyapatite precipitation cell growth after two weeks and four weeks was significantly higher on Na implanted samples than on untreated or NaOH treated samples. Without previous hydroxyapatite deposition only on NaOH treated samples a production of hydroxyapatite could be detected, after hydroxyapatite precipitation there was also better calcification by the cells. Alkaline phosphatase did not differ significantly in the cells on the different substrates.
Conclusion: Na ion implantation in titanium can activate the surface for hydroxyapatite nucleation out of aqueous solutions. The surface without further treatment is too reactive for direct cell contact. After a calciumphosphate deposition on the surface the growth of bone forming cells is enhanced.

Keywords: Apatit, Simulated Body Fluid
  • Lecture (Conference)
    5th Asian Symposium on Biomedical Materials, Hongkong, December 9-12, 2001
  • Contribution to proceedings
    5th Asian Symposium on Biomedical Materials, Hongkong, December 9-12, 2001

Publ.-Id: 4736 - Permalink


Surface stimuli to precipitating hydroxyapatite on titanium
Pham, M. T.; Maitz, M. F.; Grambole, D.; Herrmann, F.; Reuther, H.; Richter, E.;
no abstract delivered from author
Keywords: hydroxyapatite, titanium, simulated body fluid
  • Journal of Materials Science Letters 20 (2001) 295-296

Publ.-Id: 4735 - Permalink


Principles of Biological Testing of Implant Materials
Maitz, M.; Günzel, R.;
no abstract delivered from author
Keywords: Biomaterials, biocompatibility testing
  • Lecture (others)
    City University of Hong Kong, 9.-14. November 2000

Publ.-Id: 4734 - Permalink


The MatMed database
Maitz, M.;
no abstract delivered from author
Keywords: MatMed, EU-Projekt, Materials in Medicine
  • Lecture (others)
    MatMed Workshop, Brehna bei Leipzig, Deutschland, 08.05.2002

Publ.-Id: 4733 - Permalink


Aspekte der Implantatmaterial-Organismus-Wechselwirkung
Maitz, M.;
Seminarvortrag ohne Abstract
Keywords: Biomaterial
  • Lecture (others)
    Physik, Univ Regensburg, 08.12.2000 http://www.physik.uni-regensburg.de/forschung/gk_nichtlin/vortraege.html

Publ.-Id: 4732 - Permalink


Quantum Mechanical Approach to Planar Electron Channeling in a Hypersonic Field (II) - Resonant Influence on the Radiation
Grigoryan, L. S.; Mkrtchyan, A. R.; Mkrtchyan, A. H.; Khachatryan, H. F.; Wagner, W.; Piestrup, M. A.;
The spectral intensity of the radiation emitted by a planar channeled
electron in a single crystal excited by a longitudinal hypersonic
wave propagating along the channeling direction has been calculated
for the energy range 10 MeV£E£100 MeV.
It has bben found that the hypersound can excite inverse transitions
through which the transversal energy of the channeled electron is increased.
These transitions have a resonant nature and can lead to a considerable
intensification of the electron channeling radiation.
  • Radiation Effects & Defects in Solids 153 (2001) 307

Publ.-Id: 4731 - Permalink


Quantum Mechanical Approach to Planar Electron Channeling in a Hypersonic Field (I)
Grigoryan, L. S.; Mkrtchyan, A. R.; Mkrtchyan, A. H.; Khachatryan, H. F.; Wagner, W.; Piestrup, M. A.;
The wave function of an electron 10 MeV £E£100 MeV
planar channeled in a longitudinal hypersonic superlatice has been found.
Conditions for the resonant influence of the acoustic waves on the quantum states of the electron were deduced.
The expression obtained for the wave finction is applicable at resonance.
  • Radiation Effects & Defects in Solids 153 (2001) 289

Publ.-Id: 4730 - Permalink


Resonant Influence of Hypersound on the Radiation of an Axially Channeled Electron
Grigoryan, L. S.; Mkrtchyan, A. R.; Mkrtchyan, A. H.; Khachatryan, H. F.; Wagner, W.; Piestrup, M. A.;
The spectral intensity of the radiation emitted by an axially channeled
electron in a single crystal excited by a longitudinal hypersonic wave
propagating along the channeling direction has been calculated for the
energy range 10 MeV £E£100 MeV.
It has been shown that under the influence of acoustic vibrations excited
in the single crystal a resonant intensification of the electron
channeling radiation, a variation of its spectral distribution as well as inverse
radiative transitions are possible.
  • Radiation Effects & Defects in Solids 153 (2001) 221

Publ.-Id: 4729 - Permalink


Der Fokussierte Ionenstrahl in der Nanotechnologie
Bischoff, L.;
Die Arbeit mit dem Fokussierten Ionenstrahl (focused ion beam = FIB) wird vorgestellt und erläutert. Beginnend mit den Ionenquellen (Flüssigmetall, - Flüssiglegierungs- Ionenquellen) über die Ionenoptik bis hin zu anlagenspezifischen Teilen werden Funktionsweise und Parameter dargestellt. Verschiedene Beispiele der Anwendung dieser hochauflösenden Strukturierungstechnik, speziell in der Nanotechnologie, werden aufgezeigt und insbesondere die Flexibilität und Vielseitigkeit dieser modernen Ionenstrahltechnik demonstriert.
Keywords: Focused Ion Beam, Liquid Metal Ion Source, Ion Optics, Nanotechnology
  • Lecture (others)
    DFG-Graduierten-Kolleg "Sensorik" (GK 51) Technische Universität Dresden, Dec. 5, 2001

Publ.-Id: 4728 - Permalink


Resonant Influence of a Longitudinal Hypersonic Field on the Radiation from Channeled Electrons
Grigoryan, L. S.; Mkrtchyan, A. R.; Mkrtchyan, A. H.; Khachatryan, H. F.; Prade, H.; Wagner, W.; Piestrup, M. A.;
The wave function of a planar/axially channeled electron with energy 10 MeV≤E≤1 GeV under the influence of a longitudinal hypersonic wave excited in a single crystal is calculated. Conditions for the resonant influence of the hypersonic wave on the quantum state of the channeled electron are deduced. Expressions for the wave function that are applicable in the case of resonance are obtained.
Angular and spectral distributions of the radiation intensity from the planar/axially channeled electron are also calculated. The possibility of significant amplification of channeling radiation by a hypersonic wave is substantiated. It is found that the hypersound can excite inverse radiative transitions through which the transversal energy of the channeled electron is increased. These transitions have a resonant nature and can lead to a considerable intensification of the electron channeling radiation. In the case of axial channeling, the resonance radiation is sustained also by direct radiative transitions of the electron.
  • Nucl. Instr. Meth. B 173 (2001) 184

Publ.-Id: 4727 - Permalink


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