Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

31745 Publications
Ion acoustic imaging of microstructures using a focused ion beam system
Akhmadaliev, C.; Bischoff, L.; Teichert, J.; Kazbekov, K.;
: 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 near 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, aluminum 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 - 1MHz. The obtained lateral resolution of the ion acoustic images at 80kHz was about 16 µm on silicon and about 7µm on glass and at 632 kHz it decreases to 7 µm and 3 µm respectively.
Keywords: ion acoustic effect, focused ion beams, buried structures, imaging
  • Lecture (Conference)
    3rd International Conference on Nuclear and Radiation Physics June 4 - 7, 2001, Almaty, Republic of Kazakstan

Publ.-Id: 4726 - Permalink

Quantum-Mechanical Approach to Planar Positron Channeling in a Longitudinal Hypersonic Field
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-channeled positron with energy
10 MeV£E£100 MeV
under the resonant influence of hypersound is calculated.
It is found that the longitudinal hypersound changes the spectral
distribution of the channeling radiation significantly.
With decreasing wavelength ls of the hypersound,
starting from ls=lE,
where lE is the characteristic
length related to one transverse oscillation of the channeled positron,
a new type of radiative transition occurs.
It is characterized by the stimulated enhancement of transverse
energy of the positron at channeling (inverse radiative transition).
When ls approaches lE/2 the inverse
transitions show a resonant behaviour.
  • Nucl. Instr. Meth. B 173 (2001) 132

Publ.-Id: 4725 - Permalink

Direct fabrication of Ordered Polymer nanocavity Arrays from Surface-Modified ion- nanostructured silicon Templates
Azzaroni, O.; Schilardi, P. L.; Gago, R.; Vázquez, L.; Salvarezza, R. C.;
Ion-beam nanopatterned silicon has been used as template for the direct molding of polymeric materials. The silicon surface was chemically modified by octadecyltrichlorosilane before molding in order to allows easy polymer release. This fabrication process allows us to produce a nanocavity polymer array from a nanodot structured silicon template with a lateral and vertical resolutions of 50 nm and 5 nm, respectively. Both, the use of the nanopatterned silicon template and tapping mode atomic force microscopy at low tip-sample interaction forces allow us to determine not only the lateral and vertical resolution of this new method but also the error involved in the transfer process, which results to be of 1nm. Thus. the new method fulfils the requirements of serial nanofabrication trends that requires sub-100 nm lateral resolution and sub-10nm vertical resolution involving only a few and very simple steps during the whole nanofabrication process. Besides, the method displays a proved high fidelity in the molding process showing its potential applications as a direct nanofabrication route for future information storage technologies.
  • Poster
    The IUVSTA Workshop #35 on “Pattern formation and atomic processes in epitaxial growth and ion erosion” June 9-13 2002, Trofaiach, Austria

Publ.-Id: 4724 - Permalink

X-ray absorption studies of the bonding structure of B-C-N compounds
Jiménez, I.; Gago, R.; Caretti, I.; Albella, J. M.;
Although cubic BCN compounds are desired for their attractive mechanical properties, the synthesis in thin film form of these compounds normally yields amorphous material containing different local structures like trigonal bonding (hexagonal structure), tegragonal bonding (cubic structure) and formation of B12 icosahedra. X-ray absorption (XANES) spectroscopy is a well suited technique to analyse the local structure of these amorphous coatings and discern between formation of single phase or multiple phase and ternary compounds or mixtures of binary grains. We have synthesized a variety of ternary BCN compounds by using Ion Beam Assisted Deposition (IBAD) techniques using B4C, B and C solid evaporation sources with concurrent ion bombardment from mixtures of N2, Ar and CH4 gases. In this way, hydrogenated and hydrogen-free BCN compounds with various compositions are obtained. The bonding structure of the different compounds is discussed in connection with the sample preparation method.
Keywords: Nitrides, BCN, XANES, bonding structure.
  • Poster
    13th European Conference on Diamond, Diamond-like Materials, Carbon Nanotubes, Nitrides and Silicon Carbide, 8-13 September 2002, Granada (Spain)

Publ.-Id: 4723 - Permalink

Evaluation of the Two-Photon Self-Energy Correction for Hydrogenlike Ions
Goidenko, I. A.; Labzowski, L. N.; Nefiodov, A. V.; Plunien, G.; Soff, G.; Zschocke, S.;
We report on the recent evaluation of the two-photon electron self energy to all orders in the
interaction with the Coulomb field of the nucleus. With the present results at hand the major theoretical
uncertainty is diminished, which provides predictions of the ground-state energy with a relative
accuracy of about 10(-6) for the hydrogenlike uranium and lead systems. This allows for
high-precision tests of quantum electrodynamics (QED) in strong fields that are expected to be
experimentally available in the near future.
  • Hyp. Int. 132 (2001) 397

Publ.-Id: 4722 - Permalink

Radiative Corrections in Highly Charged Ions and Tests of QED in Strong Electric and Magnetic Fields
Goidenko, I. A.; Labzowski, L. N.; Nefiodov, A. V.; Jentschura, U. D.; Plunien, G.; Zschocke, S.; Soff, G.;
To provide predictions of the Lamb shift of highly charged ions on the level of accuracy of about
10(-6) has been achieved after exact results for the contributions of all two-photon self-energy
diagrams have been performed. We report on the present status of our Lamb-shift calculations
including all QED-corrections of first- and second-order in the finestructure constant a and all
relevant nuclear effects. An excellent agreement between the most recent experimental data for Lamb
shift of the ls-ground state in hydrogenlike uranium can be stated. This can serve as a sensitive test
of QED in the strongest electric fields accessible in nature. In a second part of this article we report
about an all-order numerical evaluation of the one-photon selfenergy at low nuclear charge (Z =
1,...,5). A sensitive comparison of our numerical approach with analytical approach to the one-photon
selfenergy confirms the consistency of these two different approaches (numerical and analytic) to very
high precision.
  • Phys. Src. T 92 (2001) 426

Publ.-Id: 4721 - Permalink

Spectroscopy in the Z=49 108,110In isotopes: Lifetime measurements inshears bands
Chiara, C. J.; Fossan, D. B.; Janzen, V. P.; Koike, T.; Lafosse, D. R.; Lane, G. J.; Mullins, S. M.; Paul, E. S.; Radford, D. C.; Schnare, H.; Sears, J. M.; Smith, J. F.; Starosta, K.; Vaska, P.; Wadsworth, R.; Ward, D.; Frauendorf, S.;
Excited states have been populated in In-108 and In-110 in complementary
backed- and thin-target experiments, using the Stony Brook and the 8
pi Ge-detector arrays. The level schemes for both isotopes have been
extended and modified, including the first observation of DeltaI = 2
bands in In-110. Lifetimes of states in four DeltaI = 1 bands and one DeltaI = 2
band have been measured using the Doppler-shift attenuation method.
Experimental total angular momenta and reduced transition strengths for
the DeltaI = 1 bands have been compared with tilted axis cranking
predictions for shears bands with configurations involving one proton
g(9/2) hole and one or three valence quasineutrons from the h(11/2) and
g(7/2)/d(5/2) orbitals. The DeltaI = 2 bands have been compared with
principal axis cranking predictions for configurations with two g(9/2)
proton holes and a g(7/2) or d(5/2) proton and one- or three-quasineutron
configurations involving the h(11/2) and g(7/2)/d(5/2) orbitals. In
general, there is good overall agreement for both the angular momenta and reduced
transition strengths. The DeltaI = 1 and DeltaI = 2 bands have large
J((2))/B (E2) ratios as expected for the shears mechanism. The B (M1) strengths
deduced for the DeltaI = 1 bands show a decreasing trend as a function
of spin, which is also a feature of the shears mechanism. Configuration
assignments have been made for most observed bands based on comparisons
with theory and systematics of neighboring nuclei.
  • Phys. Rev. C 64 (2001) 054314

Publ.-Id: 4720 - Permalink

Emission of Unstable Clusters from Hot Yb Compound Nuclei
Charity, R. J.; Sobotka, L. G.; Cibor, J.; Hagel, K.; Murray, M.; Natowitz, J. B.; Wada, R.; El Masri, Y.; Fabris, D.; Nebbia, G.; Viesta, G.; Cinausero, M.; Fioretto, E.; Prete, G.; Wagner, A.; Xu, H.;
Neutrons and isotopically resolved light charged particles have been detected in coincidence with evaporation residues produced in the reaction E/A = 11 MeV 60Ni+100Mo. Multiplicities of evaporated particle-unstable clusters have been determined from correlations in the emission of these light particles. The decay of the short-lived 5He and 8Be (E* = 3.04 MeV) states was found to be affected by the Coulomb field of the compound nucleus in accordance with theoretical estimates. The contributions to the measured kinetic-energy distributions of stable fragments from the sequential decay of the unstable clusters was examined. Overall, the contributions from secondary fragments do not greatly influence the spectral shapes and specifically the location of the spectral peaks are not significantly shifted down in energy due to the presence of these secondary fragments. Therefore contrary to the suggestion of Charity et al.
[Phys. Rev. C 56, 873 (1997)], the lower peak energy of the experimental α-particle spectrum as compared to standard statistical-model calculations cannot be attributed to sequential α-particles from 5He and other clusters. Only for the extreme "subbarrier" regions of the α-particle, deuteron, 6,7Li, and 8Be spectra was the sequential contribution found to be dominant. Statistical-model calculations incorporating large initial deformations are shown to provide enhancements in the yield of low-energy fragments which are roughly appropriate for all the detected isotopes. This suggests that the origin of the sub-barrier enhancements may be a result of evaporation from highly deformed systems which are either produced dynamically during the fusion process or by thermal shape fluctuations.
  • Phys. Rev. C 63 (2001) 024611

Publ.-Id: 4719 - Permalink

Klonogenes Zellüberleben von Keratinozyten und Fibroblasten nach Bestrahlung mit weichen Röntgenstrahlen.
Brankovic, K.; Slonina, D.; Panteleeva, A.; Pawelke, J.; Dörr, W.;
Weiche Röntgenstrahlung wird in der diagnostischen Radiologie, aber auch in der Strahlentherapie angewandt. In der vorliegenden Untersuchung wurde die Wirkung weicher Röntgenstrahlen (25 kV) bzw. Referenzröntgenstrahlung (200 kV) für verschiedene Zelllinien (3T3/NIH Mausfibroblasten, V-79 Hamsterfibroblasten, primäre neonatale Haut-Keratinozyten des Menschen) verglichen. Zusammenfassend zeigen Fibroblasten ein vemindertes klonogenes Zellüberleben nach Bestrahlung mit weichen Röntgenstrahlen im Vergleich zu 200 kV Röntgenstrahlen. Dieser Unterschied geht einher mit einer Abnahme des alpha-Wertes und einer Zunahme von beta. Demgegenüber zeigen Keratinozyten keine deutliche Veränderung des
Zellüberlebens. Hier findet sich jedoch eine Zunahme von alpha.
  • Exp. Strahlenther. Klin. Strahlenbiol., Vol. 10 (2001) 71-75

Publ.-Id: 4718 - Permalink

Evidence for chiral symmetry in the mass A ~ 130 region
Beausang, C. W.; Hecht, A. A.; Zyromski, K. E.; Balabanski, D.; Barton, C. J.; Caprio, M. A.; Casten, R. F.; Cooper, J. R.; Hartley, D.; Krücken, R.; Novak, J. R.; Zamfir, N. V.; Zhang, J.; Dönau, F.;
Two new DI = 1 bands in the N = 75, doubly-odd nuclei 136Pm and 138Eu
are reported. These bands have been assigned the same
structure as the yrast band and show some of the features expected
from predicted chiral twin bands.
  • Nucl. Phys. A 682 (2001) 394

Publ.-Id: 4717 - Permalink

Three-dimensional linear stability analysis of lid-driven MHD cavity flow
Shatrov, V.; Mutschke, G.; Gerbeth, G.;
We present numerical results of a linear 3-D stability analysis of a square lid-driven cavity flow under the influence of an external magnetic field which is directed parallel to the lid. For Reynolds numbers up to Re * 7800 the 2-D hydrodynamic flow is steady. The Lorentz force has a strong influence on the 2-D flow structure, thereby changing number, shape and strength of the eddies inside. The resulting 3-D stability behaviour is rather complex since it depends on the 2-D flow structure. Although increasing magnetic fields are able to damp 3-D instability, in a parameter region around Re = 3100, several branches of the neutral stability curve do exist. This leads to a non-monotonic behaviour of receptivity to 3-D disturbances as the strength of the magnetic field is increased.
  • Physics of Fluids (August 2003) Vol. 15, No. 8 , pp 2141-2151

Publ.-Id: 4716 - Permalink

Thin Films of Molecular Metals: TTF-TCNQ
Fraxedas, J.; Molas, S.; Figueras, A.; Jiménez, I.; Gago, R.; Auban-Senzier, P.; Goffman, M.;
We present recent results on the characterization of highly-ordered polycrystalline thin films of the charge transfer salt TTF-TCNQ (TTF = tetrathiafulvalene, TCNQ = tetracyanoquinodimethane) prepared by thermal sublimation in high vacuum under different conditions. The increase in orientation and microcrystal size as a function of substrate and annealing temperatures is addressed. A consequence of such an increase is the reduction of the conductivity activation energy, which eventually leads to the observation of the Peierls transition by resistivity measurements. X-ray Absorption Near Edge Spectroscopy (XANES) studies performed with synchrotron radiation reveal directly the influence of charge transfer on unoccupied states near the Fermi level.
Keywords: Molecular metals, molecular organic materials, thin films, TTF-TCNQ, Peierls transition, synchrotron radiation
  • Journal of Solid State Chemistry 168 (2002) 384-389

Publ.-Id: 4715 - Permalink

Investigation of Al-implanted 6H- and 4H-SiC layers after fast heating rate annealings
Ottaviani, L.; Lazar, M.; Locatelli, M. L.; Monteil, Y.; Heera, V.; Voelskow, M.; Skorupa, W.;
no abstract delivered from author
Keywords: SiC, Al Implantation, High Temperature Annealing
  • Appl. Surf. Sci. 184 (2001) 330-335

Publ.-Id: 4714 - Permalink

TEM Investigation of Si Implanted Natural Diamond
Pécz, B.; Barna, Á.; Heera, V.; Fontaine, F.; Skorupa, W.;
no abstract delivered from author
Keywords: Diamond, Electron Microscopy, Ion Implantation, Phase Formation
  • Lecture (Conference)
    ECSCRM 2002, Kloster Banz, Germany, September 2000; Mater.Sci.Forum Vols. 353-356 (2001) 199-202
  • Contribution to external collection
    ECSCRM 2002, Kloster Banz, Germany, September 2000; Mater.Sci.Forum Vols. 353-356 (2001) 199-202

Publ.-Id: 4713 - Permalink

Bloch oscillations and their coupling to optical phonons
Dekorsy, T.;
Bloch oscillations in semiconductor superlattices are an intriguing subject of electronic coherence in low dimensional semiconductor structures. The electronic coherence is destroyed by several scattering mechanisms, most important carrier-carrier scattering and carrier-phonon scattering. Especially in wide miniband superlattices with miniband widths larger than the LO phonon energy LO phonon emission is responsible for subpicosecond dephasing times. We investigate the dynamics of Bloch oscillations in GaAs/AlxGa1-xAs superlattices with large minibands tuned into resonance with LO phonons. The coherent excitation of coherent LO phonons via Bloch oscillations is observed at very low carrier densities. The peculiarities of the resonant excitation process are in agreement with theoretical considerations.
  • Invited lecture (Conferences)
    Second International Workshop on Quantum Nonplanar Nanostructures&Nanolectronics '02, Tsukuba, Japan, Sept. 9-11, 2002 (invited talk).

Publ.-Id: 4712 - Permalink

Investigation of Antimagnetic Rotation in 100Pd
Zhu, S.; Garg, U.; Afanasjev, A. V.; Frauendorf, S.; Kharraja, B.; Ghugre, S. S.; Chintalapudi, S. N.; Janssens, R. V. F.; Carpenter, M. P.; Kondev, F. G.; Lauritsen, T.;
High spin states have been studied in the nucleus 100Pd with the aim of investigating the novel phenomenon of "antimagnetic rotation." A cascade of four "rotational-band-like" transitions is proposed as corresponding to antimagnetic rotation, based on the observed spectroscopic properties and a comparison with calculations in the configuration-dependent cranked Nilsson-Strutinsky formalism.
  • Phys. Rev. C 64 (2001) 041302

Publ.-Id: 4711 - Permalink

Electroproduction of Kaons and Light Nuclei
Zeidman, B.; Abbott, D.; Ahmidouch, A.; Ambrozewicz, P.; Armstrong, C. S.; Arrington, J.; Asaturyan, R.; Assamagan, K.; Avery, S.; Bailey, K.; Baker, O. K.; Beedoe, S.; Bitao, H.; Breuer, H.; Brown, D. S.; Carlini, R.; Cha, J.; Chant, N.; Christy, E.; Cochran, A.; Cole, L.; Collins, G.; Cothran, C.; Crowder, J.; Cummings, W. J.; Danagoulian, S.; Dohrmann, F.; Duncan, F.; Dunne, J.; Dutta, D.; Eden, T.; Elaasar, M.; Ent, R.; Ewell, L.; Fenker, H.; Fortune, H. T.; Fujii, Y.; Gan, L.; Gao, H.; Garrow, K.; Geesaman, D.; Gueye, P.; Gustafsson, K.; Hafidi, K.; Hansen, J. O.; Hinton, W.; Jackson, H. E.; Juengst, H.; Keppel, C.; Klein, A.; Koltenuk, D.; Liang, Y.; Liu, J. H.; Lung, A.; Mack, D.; Madey, R.; Markowitz, P.; Martoff, C. J.; Meekins, D.; Mitchell, J.; Miyoshi, T.; Mkrtchyan, H.; Mohring, R.; Mtingwa, S. K.; Mueller, B.; O'Neill, T. G.; Niculescu, G.; Niculescu, I.; Potterveld, D.; Price, J. W.; Raue, B. A.; Reimer, P. E.; Reinhold, J.; Roche, J.; Roos, P.; Sarsour, M.; Sato, Y.; Savage, G.; Sawafta, R.; Schiffer, J. P.; Segel, R. E.; Semenov, A.; Stepanyan, S.; Tadevosian, V.; Tajima, S.; Tang, L.; Terburg, B.; Uzzle, A.; Wood, S.; Yamaguchi, H.; Yan (Jlab), C.; Yan (Kent), C.; Yuan, L.; Zeier, M.; Zihlmann, B.;
The A(e,e,K+YX reaction on H, D, 3He, and 4He was investigated in Hall C at CEBAF. Data were obtained for Q2≈0.35 and 0.5 GeV2 at 3.245 GeV. The missing mass spectra for both H and D are fitted with Monte-Carlo simulations incorporating peaks corresponding to Λ production on the proton and Σ production on both the proton and neutron. For D, the cross section ratio Σ0-≈2, and excess yield close to the thresholds for Λ and Σ production can be attributed to final-state interactions; models are compared to the data. The analysis of the data for the He targets is in a more preliminary state with broader quasi-free peaks resulting from the higher Fermi momenta. Evidence for bound Λ-hypernuclear states is seen and other structure may be present.
  • Nucl. Phys. A 691 (2001) 37

Publ.-Id: 4710 - Permalink

Characteristic Features of the Pseudogap and Superconducting States of YBa2Cu3O7 – x
Misochko, O. V.; Georgiev, N.; Dekorsy, T.; Helm, M.;
The relaxation dynamics of the lattice and low-energy quasiparticles in a YBa2Cu3O7 – x superconductor are studied by the light reflection technique with femtosecond temporal resolution in a wide temperature range. It is shown that, for T > Tc, there exist two temperature regions with qualitatively and quantitatively different excitation dynamics, and the transition between these regions is of a hysteretic nature. It is also found that the character of changes observed in the charge carrier relaxation dynamics in the superconducting state testifies to the presence of an anisotropic gap with nodes at the Fermi surface.
  • JETP Letters, Volume 75, Issue 12, pp. 642-645 (2002).

Publ.-Id: 4709 - Permalink

Coupled Bloch-phonon oscillations in biased InGaAs/InAlAs superlattices
Först, M.; Kurz, H.; Dekorsy, T.; Leavitt, R. P.;
The coupling of coherent Bloch oscillations to LO phonons is investigated in ternary
InGaAs/InAlAs superlattice. The coherent amplitudes of distinct superlattice phonon modes are selectively enhanced in resonance with the Bloch oscillations frequency.
  • Lecture (others)
    Quantum Electronics and Laser Sciences Conference (QELS) 2002, Long Beach, California, USA, May 19-24, 2002

Publ.-Id: 4708 - Permalink

Observation of a hysteretic pseudogap behavior via coherent phonons in high temperature superconductors
Dekorsy, T.; Georgiev, N.; Helm, M.; Misochko, O. V.;
We investigate ultrafast reflectivity changes of a near-optimally doped YBa2Cu3O7-x (123) superconductor. The amplitude of coherently excited phonons show strong changes as a function of temperature above the superconducting transition temperature. These changes give evidence for two crossover temperatures within the pseudogap regime. In addition, these crossover temperatures exhibit a clear hysteretic behavior as a function of temperature.
  • Lecture (Conference)
    13th Conference on Ultrafast Phenomena, Vancouver, Canada, May 12-17, 2002

Publ.-Id: 4707 - Permalink

IR spectroscopic possibilities with the Rossendorf free-electron laser
Dekorsy, T.;
The free-electron laser (FEL) facility at the Research Center Rossendorf will span the wavelength range from 5 µm to 150 µm. Driven by the superconducting linear accelerator ELBE (up to 40 MeV electron energies, bunch charge of 77 pC) the FEL will provide a continuous pulse train at 13 MHz with pulsewidths of 0.5 ps to 10 ps and pulse energies in the µJ range. These pulses will be used for time-resolved spectroscopy, nonlinear optics and optical near-field spectroscopy by three in-house groups working on semiconductors, bio-molecules and cells. We will describe the status of the FEL and of the experimental facilities. The combination of the FEL with high magnetic fields will represent unique experimental possibilities. These will be discussed with emphasis on semiconductor physics.
  • Lecture (others)
    1st Workshop on High Magnetic Fields, Dresden, June 20, 2002

Publ.-Id: 4706 - Permalink

Zeitaufgelöste Spektroskopie an Halbleiterheterostrukturen mit dem Freie-Elektronen Laser an ELBE
Dekorsy, T.;
Die Grundlagen der zeitaufgelösten Spektroskopie an Halbleitern und Halbleiterheterostrukturen mit dem Freie-Elektronen Laser an ELBE werden erläutert mit Schwerpunkt auf der Dynamik von Intersubbandübergängen. Neben Anrege-Abfrage Experimenten mit einer Wellenenlänge (degenerate pump-probe) liefern Mehrfarben-Experimente mit synchronisierten Femtosekunden Lasern zusätzliche wichtige Informationen über elektronische Nichtgleichgewichts-Verteilungsfunktionen. Desweiteren werden die Techniken des Vier-Wellen Mischens und des spektralen Lochbrennens diskutiert, die bei der Beantwortung von Fragen nach inhomogenen/homogenen Verbreiterungen von Übergängen wichtig sind.
  • Lecture (others)
    ELBE Palaver, FZR, Nov. 1, 2001

Publ.-Id: 4705 - Permalink

Von der Femtosekunden Spektroskopie zur -Technologie
Dekorsy, T.;
Die Entwicklung von Femtosekunden-Lasersystemen hat in den letzten Jahren einen rasanten Fortschritt gemacht. Vom Fernen Infrarot bis zur Röntgenstrahlung lassen sich auf einem optischen Tisch über nichtlineare optische Prozesse ultrakurze Pulse hoher Intensität erzeugen. Diese Laser erlauben die zeitliche Auflösung der wichtigsten Prozesse in Halbleitern, an Oberflächen, bei chemischen Reaktionen und in biologischen Systemen und sind damit zu einem wertvollen wissenschaftlichen Instrument geworden. Ihre Verknüpfung mit dem Freie-Elektronen Laser an ELBE ermöglicht weitere einzigartige spektroskopische Möglichkeiten.

Ich werde einige Beispiele meiner Arbeiten auf dem Gebiet der Femtosekunden-Spektroskopie kohärenter Anregungen in Halbleitern geben, insbesondere zur Anregung kohärenter Wellenpakete und Gitterschwingungen in Halbleiter Quantenstrukturen. Desweiteren werde ich auf Beiträge zur technologischen Entwicklung des Feldes, wie die Realisierung des kompaktesten Femtosekunden Lasers auf Festkörperbasis, und deren Anwendungen eingehen.
  • Lecture (others)
    Kolloquium des FZR, May 31, 2001

Publ.-Id: 4704 - Permalink

Coherent phonons
Dekorsy, T.;
The excitation and detection of coherent phonon states in semiconductors
with femtosecond laser pulses reveals detailed insight into phonon dynamics on ultrashort time scales. I will review the generation mechanism responsible for
coherent phonon generation in different materials. I will present recent results on
the coupling of coherent electronic excitations to Bloch oscillations in superlattices
and the detection of phonon co-variances and their relation to squeezed phonon states.
  • Lecture (others)
    TU Wien, Austria, May 28, 2001

Publ.-Id: 4703 - Permalink

Coherent phonons and phonon co-variances
Dekorsy, T.;
The excitation and detection of coherent phonon states in semiconductors
with femtosecond laser pulses reveals detailed insight into phonon dynamics on ultrashort time scales. I will review the generation mechanism responsible for
coherent phonon generation in different materials. I will present recent results on
the coupling of coherent electronic excitations to Bloch oscillations in superlattices
and the detection of phonon co-variances and their relation to squeezed phonon states.
Keywords: excitation and detection of coherent phonon states in semiconductors coupling of coherent electronic excitations to Bloch oscillations in superlatices detection of phonon co-variances, squeezed phonon states
  • Lecture (others)
    FOM Institute AMOLF, Amsterdam, Netherlands, Jan. 29, 2001

Publ.-Id: 4702 - Permalink

Ultrafast Dynamics of excitons in crescent-shaped GaAs quantum wires
Komori, K.; Yasuhira, T.; Wang, X. L.; Ogura, M.; Först, M.; Dekorsy, T.; Kurz, H.;
Ultrafast exciton dynamics in crescent-shaped GaAs quantum-wires have
been investigated using pump-probe and Reflective-Electro-Optic-Sampling (REOS)
methods. The differential-reflectivity shows the exciton energy-shift and the subband-relaxation. Also ultrafast coherent dynamics are observed in the REOS measurement.
  • Poster
    Quantum Electronics and Laser Sciences Conference (QELS) 2001, Baltimore, MD, USA, May 6-11, 2001

Publ.-Id: 4701 - Permalink

Isoscalar-Isovector Interferences in pN®N e+ e- Reactions as a Probe of Baryon Resonance Dynamics
Titov, A. I.; Kämpfer, B.;
The isoscalar-isovector (r-w) interferences in the exclusive reactions
near the w threshold leads to a distinct difference of the dielectron invariant
mass distributions depending on beam energy.
The strength of this effect is determined by the coupling of resonances to the nucleon
vector-meson channels and other resonance properties. Therefore, a combined analysis of the
se reactions can be usedas a tool for determining the baryon resonance dynamics.
  • Eur. Phys. J. A 12 (2001) 217-229

Publ.-Id: 4700 - Permalink

Visualization of vacancy type defects in the RP/2 region of ion implanted and annealed silicon
Peeva, A.; Koegler, R.; Skorupa, W.;
Recently, a strong metal gettering in Si after ion implantation and annealing has been detected at depths between the surface and the projected ion range RP, indicating the presence of residual defects therein. The theoretical ballistic calculations ascribed the RP/2 effect to the excess vacancies resulting from the forward momentum transfer of the implanted ions into the silicon matrix. So far, the gettering centers for metals at RP/2 have been considered to be too small to be visible by Transmission Electron Microscopy (TEM). We show that the crucial point for visualization of the vacancy type defects at RP/2 by TEM is the specimen preparation technique. The very widely used conventional ion milling technique for TEM specimen preparation introduces damage on the surface of the XTEM specimen, which blurs the original defect structure at RP/2 and obscure it of being visualized. Only the TEM specimens prepared by cleaving reveals cavities at RP/2. Minimum damage production caused during the preparation of the TEM specimen using cleaving allows the imaging of the cavities at RP/2.
Keywords: Silicon, Gettering, Defects, Ion Implantation, Electron Microscopy
  • Nuclear Instruments and Methods in Physics Research B 206: 71-75 MAY 2003
  • Lecture (Conference)
    IBMM 2002 Conference, Kobe, Japan, 1-6 September 2002

Publ.-Id: 4699 - Permalink

Synthesis and Decay of Nanowires
Müller, T.;
no abstract delivered from author
  • Lecture (others)
    Ionenstrahltreffen, Uni Augsburg, Germany, October 1-2, 2001

Publ.-Id: 4697 - Permalink

Chiral Doublet Structures in Odd-Odd N=75 Isotones: Chiral Vibrations
Starosta, K.; Koike, T.; Chiara, C. J.; Fossan, D. B.; Lafosse, D. R.; Hecht, A. A.; Beausang, C. W.; Caprio, M. A.; Cooper, J. R.; Krücken, R.; Novak, J. R.; Zamfir, N. V.; Zyromski, K. E.; Hartley, D. J.; Balabanski, D. L.; Zhang, J.; Frauendorf, S.; Dimitrov, V. I.;
New sideband partners of the yrast bands built on the i
configuration were identified in 55Cs, 57La, and 61Pm
N = 75 isotones of 134Pr.
These bands form with 134Pr unique doublet-band systematics suggesting
a common basis. Aplanar solutions of 3D tilted axis cranking
calculations for triaxial shapes define left- and right-handed chiral
systems out of the three angular momenta provided by the valence
particles and the core rotation, which leads to spontaneous chiral symmetry
breaking and the doublet bands. Small energy differences between the
  • Phys. Rev. Lett. 86 (2001) 971

Publ.-Id: 4696 - Permalink

Nanocluster Formation by Low-Energy Ion Implantation - Basic Mechanisms
Müller, T.; Heinig, K.-H.;
no abstract delivered from author
  • Lecture (others)
    Projekttreffen, Uni Aarhus, Denmark, August 19-21, 2001

Publ.-Id: 4695 - Permalink

Template-Directed Ion Beam Synthesis of Ge Nanowires Using V-Grooves
Müller, T.; Heinig, K.-H.; Schmidt, B.;
Guided self-organization of Ge nanowires in templates has been studied experimentally and theoretically. V-grooves formed in (001)Si by anisotropic etching with 30% KOH at 80°C. About 200 nm were grown on the (001)Si wafer surface and on the (111)Si V-groove sidewalls by oxidation at 1000°C in dry O2. The resulting SiO2-V-grooves were used as templates for the Ge nanowire fabrication. Ge+ ions have been implanted into the SiO2 at 70 keV with a fluence of 1017 cm-2. The theoretically predicted enrichment of Ge in the V-groove bottom during homogeneous ion implantation has been proven by analytic TEM (EDX). Annealing of Ge+ implanted samples in N2 leads to phase separation of Ge from the SiO2 matrix. Cross sectional TEM studies have confirmed the self-organization of a Ge nanowire in the SiO2 at the V-groove bottom, whereas only a thin layer of isolated Ge nanoclusters has been found in the V-groove side-walls. The kinetics of the wire formation during annealing was studied 3D Kinetic Lattice Monte-Carlo simulations. The comparison to experimental results reveals self-organization phenomena during phase separation, caused by nucleation, Ostwald ripening and coalescence. Moreover, the simulations were used to study the stability of very thin Ge nanowires against thermal fluctuations.
  • Lecture (Conference)
    Annual Meeting of the German Physical Society, Hamburg, March 26-30, 2001

Publ.-Id: 4694 - Permalink

Resonant and non Resonant K--Production in pp Reactions at 2.85 GeV
Ritman, J.; Balestra, F.; Bedfer, Y.; Bertini, R.; Bland, L. C.; Brenschede, A.; Brochard, F.; Bussab, M. P.; Choi, S.; Debowski, M.; Dressler, R.; Dzemidzic, M.; Faivre, J.-C.; Falomkin, I. V.; Fava, L.; Ferrero, L.; Foryciarz, J.; Fröhlich, I.; Frolov, V.; Garfagnini, R.; Grasso, A.; Grosse, E.; 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.; Salabura, P.; Tchalyshev, V.; Tosello, F.; Vigdor, S. E.; Zosi, G.;
Inclusive and exclusive (i.e. via the f resonance) K- meson production
cross sections have been measured in proton-proton
reactions at Tbeam = 2.85 GeV. The inclusive K- cross section is
about a factor 20 lower than the K+ cross sections at the
same available energy above threshold.
The observed f/w cross section ratio is enhanced by about an order
of magnitude relative to naive predictions based upon the
Okubo-Zweig-Iizuka (OZI) rule.
Differential cross section results are presented which indicate significant contributions from higher partial
waves in the proton-proton entrance channel.
  • Nuclear Physics 69 (2001) 395

Publ.-Id: 4693 - Permalink

Coupled Bloch-phonon modes in superlattices
Ghosh, A. W.; Jönsson, L.; Wilkins, J. W.; Dekorsy, T.; Bartels, A.; Kurz, H.;
Experiments and microscopic theoretical analysis show that the coupling of Bloch
oscillations with coherent longitudinal optical phonons in a GaAs/AlGaAs
superlattice leads to resonant coherent phonon excitation but no gap in the Bloch-phonon spectrum.
  • Lecture (Conference)
    Quantum Electronics and Laser Sciences Conference (QELS) 2001, Baltimore, MD, USA, May 6-11, 2001

Publ.-Id: 4692 - Permalink

Ordered quantum dot arrays via sputtering
Facsko, S.; Bobek, T.; Kurz, H.; Dekorsy, T.;
The erosion of III -V compound semiconductors by low-energy Ar ions
under normal incidence leads to the formation of regular nanoscale
quantum dot arrays. We present the dependence of the formation
on ion energy for GaSb and compare them to simulations based on
a continuum equation.
  • Lecture (Conference)
    Gordon Conference "Material processes far from equilibrium", Meriden, NH, USA, July 1-6, 2001

Publ.-Id: 4691 - Permalink

Wavelength tunable femtosecoond Ti:sapphire ring laser with up to 1.5 GHz repetition rate
Bartels, A.; Dekorsy, T.; Kurz, H.;
We demonstrate a wavelength-tunable Ti:sapphire femtosecond laser with a repetition
rate between 500 MHz and 1.5 GHz. A “half-Brewster-prism” is introduced into
the cavity to achieve tuning from 733 nm to 840 nm by tilting a cavity mirror.
  • Lecture (Conference)
    Conference on Lasers and Electro-Optics (CLEO) 2001, Baltimore, MD, USA, May 6-10, 2001

Publ.-Id: 4690 - Permalink

Ion-induced Formation of Quantum Dots
Kurz, H.; Facsko, S.; Bobek, T.; Dekorsy, T.;
We review the mechanism of the ion-induced formation of nanoscale quantum dots on III-V semiconductor surfaces and their potential applications.
  • Lecture (Conference)
    APS March Meeting, Seattle, USA, March 12-16, 2001

Publ.-Id: 4689 - Permalink

Electroproduction of Kaons and Light Hypernuclei
Reinhold, J.; Abbott, D.; Ahmidouch, A.; Ambrozewicz, P.; Armstrong, C. S.; Arrington, J.; Asaturyan, R.; Assamagan, K.; Avery, S.; Bailey, K.; Baker, O. K.; Beedoe, S.; Bitao, H.; Boeglin, W.; Breuer, H.; Brown, D. S.; Carlini, R.; Cha, J.; Chant, N.; Christy, E.; Cochran, A.; Cole, L.; Collins, G.; Cochran, C.; Crowder, J.; Cummings, W. J.; Danagoulian, S.; Dohrmann, F.; Duncan, F.; Dunne, J.; Dutta, D.; Eden, T.; Elaasar, M.; Ent, R.; Ewell, L.; Fenker, H.; Fortune, H. T.; Fujii, Y.; Gan, L.; Gao, H.; Garrow, K.; Geesaman, D. F.; Gueye, P.; Gustafsson, K.; Hafidi, K.; Hansen, J. O.; Hinton, W.; Jackson, H. E.; Juengst, H.; Keppel, C.; Klein, A.; Koltenuk, D.; Liang, Y.; Liu, J. H.; Lung, A.; Mack, D.; Madey, R.; Markovitz, P.; Martoff, C. J.; Meekins, D.; Mitchell, J.; Miyoshi, T.; Mkrtchyan, H.; Mohring, R.; Mtingwa, S. K.; Mueller, B.; O'Neill, T. G.; Niculescu, G.; Niculescu, I.; Potterveld, D.; Price, J. W.; Raue, B. A.; Reimer, P. E.; Roche, J.; Roos, P.; Sarsour, M.; Sato, Y.; Savage, G.; Sawafta, R.; Schiffer, J. P.; Segel, R. E.; Semenov, A.; Stepanyan, S.; Tadevosian, V.; Tajima, S.; Tang, L.; Terburg, B.; Uzzle, A.; Wood, S.; Yamaguchi, H.; Yan, C.; Yan, C.; Yuan, L.; Zeidman, B.; Zeier, M.; Zihlmann, B.;
Kaon electroproduction on hydrogen, deuterium and helium targets has been
measured at a beam energy of 3.245 GeV and four-momentum transfer, Q2, ranging
from 0.34 to 0.5 GeV. Associated hyperon production off a nucleon in the
deuteron exhibits a quasifree production mechanism.
Excess yield close to the respective thresholds for L and S
production is observed. This can be accounted for be final-state interaction
between the electroproduced hyperon and the spectator nucleon. The effects
predicted from three different hyperon-nucleon potentials are compared to
the data. The measurements on the helium targets is the first ever performed.
Very preliminary results are presented.
  • Nucl. Phys. A 684 (2001) 470

Publ.-Id: 4688 - Permalink

Deposition of thick cubic boron nitride thin films by dual ion beam deposition
Gago, R.; Kolitsch, A.; Möller, W.;
In this work we report on the production of cubic boron nitride (c-BN) thin films by Dual Ion Beam Deposition (DIBD). The interest of this work is to search for an ion-beam-assisted deposition (IBAD) method able to produce thick (> 1 um) low-stress c-BN thin films and, hence, with potential industrial application. This is not applicable in the case of IBAD using electron beam evaporation, since the material contained in the liner limits the maximum process time and, in addition, the fact that boron sublimes, makes difficult a fine control over the evaporation rate. Our DIBD system is equipped with two commercial Kauffman-type ion guns. Boron atoms were sputtered by direct Ar+ bombardment of a 3” boron target. The ions impinge under an angle of 45° and are produced with a 3 cm beam-diameter ion gun. The growth process was assisted by concurrent bombardment from a mixture of argon and nitrogen ions extracted from a 5 cm beam-diameter ion gun. For the cubic phase growth, the substrate temperature and ion assisting parameters were chosen in order to reach the required momentum transfer per incoming atom [1]. The stress release was achieved by additional ion bombardment with medium-energy N2+ ions (35 keV) during the growth process [2].

[1] D.J. Kester, R. Messier, J. Appl. Phys. 72 (1992) 504.
[2] C. Fitz, A. Kolitsch, W. Möller, Appl. Phy. Lett. 80 (2001) 55.
  • Poster
    13th European Conference on Diamond, Diamond-like Materials, Carbon Nanotubes, Nitrides and Silicon Carbide, 8-13 September 2002, Granada (Spain)

Publ.-Id: 4686 - Permalink

Hydrogen incorporation on CNx films deposited by ECR Chemical Vapor Deposition
Camero, M.; Gago, R.; Gómez-Aleixandre, C.; Albella, J. M.;
Amorphous CNxHy films have been deposited by ECR-CVD from argon, nitrogen and methane gas mixtures. The composition and bonding environment of the films, consisting in one-dimensional polymeric chains with amine groups, have been studied by ERDA and IRS. By proper selection of the gas mixture composition, hydrogen incorporation in the films can be controlled. For low methane concentrations (CH4/(N2+CH4)<0.5) hydrogen atoms are predominantly joined as NHx radicals whereas for higher methane concentrations the CHx percentage in the films strongly increases. Furthermore, as the methane concentration increases, the substitution of NHx by larger size CHx radicals accounts for the decrease in the H content of the films, as detected by ERDA (Elastic Recoil Detection Analysis). The influence on the hydrogen incorporation of the argon content in the gas mixture has also been evaluated.
  • Diamond and Related Materials 12 (2003) 632-635
  • Poster
    13th European Conference on Diamond, Diamond-like Materials, Carbon Nanotubes, Nitrides and Silicon Carbide, 8-13 September 2002, Granada (Spain)

Publ.-Id: 4685 - Permalink

Fine structure at the x-ray absorption pi* and sigma* bands of amorphous carbon: distorted trigonal and tetragonal bonding?
Jiménez, I.; Gago, R.; Albella, J. M.;
X-ray absorption near edge spectroscopy (XANES) of amorphous carbon films shows a fine structure at the pi* and sigma* bands that is not present in the reference crystalline graphite and diamond materials. Thermal treatments of the amorphous carbon films in a vacuum induce clear changes in the fine structure, hence indicating that it is due to the presence of multiple bonding states. The intensity and energy position of the multiple pi* and sigma* states is directly correlated, confirming its origin as different bonding states of sp2 hybridized carbon atoms. The presence of the fine structure in amorphous carbon is interpreted as due to the presence of distorted trigonal and tetragonal bonding structures, in addition to the ideal hexagonal and cubic structures.
  • Diamond and Related Materials 12 (2003) 110-115
  • Lecture (Conference)
    4th SPECIALIST MEETING ON AMORPHOUS CARBON (SMAC 2002), 5-6 September 2002, Barcelona (Spain)

Publ.-Id: 4684 - Permalink

Direct molding of nanopatterned polymeric films: Resolution and errors
Azzarozi, O.; Schilardi, P. L.; Salvarezza, R. C.; Gago, R.; Vázquez, L.;
The capability of the direct polymer molding method to transfer ordered nanopatterns from a surface-modified silicon template to polymeric materials, such as polystyrene (PS) and high-impact polystyrene (HIPS) is investigated by tapping mode atomic force microscopy (AFM). The lateral resolution of the method for both materials is 54 ± 1 nm while the vertical resolution is 56 ± 1 nm and 3 ± 1 nm, for PS and HIPS, respectively. This difference is explained by considering the different nanomechanical properties of the polymers. In contrast, HIPS surfaces are more resistant to the wear induced by the repetitive ‘‘reading’’ of the surface structure with the AFM tip.
  • Applied Physics Letters 82 (2003) 457-459
  • Virtual Journal of Nanoscale Science & Technology 7/4 (Compilation of links to selected articles covering a focused area of frontier research published by the American Institute of Physics and the American Physical Society)

Publ.-Id: 4683 - Permalink

Production of a+0-Mesons in the Production of a+0-Mesons in the Reaction pp ® da+0
Müller, H.;
We investigate the reaction pp ® da0+ at COSY and SIS energies
together with accompanying background reactions and inclusive particle yields.
The a0+ is considered as a usual quark model state with two decay channels
a0+® K+[`(K0)] and a0+®p+ h.
Cross sections for a0+ production as well as for the corresponding nonresonant channels
pp ® dK+[` (K0)] and pp ®dp+hare compared.
Especially in case of the final channel dp +h
high statistics measurements are necessary to extract the a0+ signal from the nonresonant background.
  • Eur. Phys. J. A 11 (2001) 113

Publ.-Id: 4682 - Permalink

Deposition of TiN/AlN bilayers on a rotating substrate by reactive sputtering
Auger, M. A.; Gago, R.; Fernández, M.; Sánchez, O.; Albella, J. M.;
A balanced dual-cathode reactive magnetron sputtering system has been developed, which allows the growth of TiN/AlN bilayers from pure titanium and aluminium targets in a mixture of argon and nitrogen gases. One important property of the TiN/AlN coatings is that they combine two important requirements for protective coatings: good adhesion properties of the TiN films and the chemical stability of the AlN films. The chemical composition of the grown layers has been studied by Auger electron spectroscopy (AES), elastic recoil detection analysis (ERDA) and Rutherford backscattering spectroscopy (RBS) techniques, and nitrogen incorporation in the nitrides has been correlated to the argonynitrogen ratio in the sputtering gas. Structural properties have been studied by X-ray diffraction (XRD), and the results showed the presence of cubic TiN and hexagonal AlN phases in the grown bilayer. Mechanical properties have been extracted from nano-indentation measurements, giving hardness values for TiN/AlN bilayer in the range of the reported values for TiN coatings.
Keywords: Reactive sputtering; Titanium nitride; Aluminium nitride
  • Surface and Coatings Technology 157 (2002) 26-33

Publ.-Id: 4681 - Permalink

X-Ray absorption study of the bonding structure of BCN compounds enriched in carbon by CH4 ion assistance
Gago, R.; Jimenez, I.; Kreissig, U.; Albella, J. M.;
Ternary BCN compounds can be grown by B4C evaporation and concurrent N2/Ar ion assistance in both hexagonal and cubic structures, depending on the deposition parameters. However, the films are always carbon poor, with a maximum carbon content of approximately 10 at.% in hexagonal BCN, and 5 at.% of C in cubic BCN. In order to increase the carbon content in the films, we have added CH4 to the bombarding gas mixture. In the case of hexagonal structures, the additional carbon atoms are efficiently incorporated to the h-BCN without finding a solubility limit. For the cubic structures, the carbon enrichment induces a disruption of the structure and segregation into h-BCN and BxC domains.
Keywords: Nitrides; Carbides; Ternary BCN; X-Ray absorption near edge spectroscopy
  • Diamond and Related Materials 11 (2002) 1295-1299

Publ.-Id: 4680 - Permalink

On the bonding structure of hydrogenated carbon nitrides grown by electron cyclotron resonance chemical vapour deposition: towards the synthesis of non-graphitic carbon nitrides
Alonso, F.; Gago, R.; Jiménez, I.; Gómez-Aleixandre, C.; Kreissig, U.; Albella, J. M.;
This work compares the composition and bonding structure of hydrogenated carbon nitride films (CNx:H) obtained by electron cyclotron resonance chemical vapour deposition (ECR-CVD) with those of hydrogen-free carbon nitrides (CNx) obtained by nitrogen ion beam assisted deposition (IBAD) of graphite.The composition and structure of the films was analysed by ion scattering techniques well suited to the detection of hydrogen, in addition to the more conventional infrared spectroscopy.The bonding structure was examined by X-ray absorption spectroscopy (XANES).The typical IBAD CNx films are graphitic with a N/C content below 0.3. However, the ECR-CVD films show a less graphitic bonding structure. The ECR-CVD films were synthesised in a conventional microwave ECR reactor (2.25 GHz, 875 Gauss, 250 W) using as precursor gases N2 and Ar in the reactor chamber, and CH4 directly in the deposition chamber.
Keywords: Electron cyclotron resonance chemical vapour deposition ; hydrogenated carbon nitride, Bonding structure, X-Ray absorption spectroscopy
  • Diamond and Related Materials 11 (2002) 1161-1165

Publ.-Id: 4678 - Permalink

Binding and extraction of oxyanions by dendrimers and cryptands
Gloe, K.; Grotjahn, M.; Rambusch, T.; Wichmann, K.; Johannsen, B.; Spies, H.; Stephan, H.; Bharadwaj, P. K.; Chand, D. K.; Gorka, M.; Müller, W. M.; Vögtle, F.;
  • Poster
    26 International Symposium on Macrocyclic Chemistry, Fukuoka/Japan, 15.-20.07.2001

Publ.-Id: 4677 - Permalink

Abtrennung von Uran aus wässriger Lösung durch Calixarene
Schmeide, K.;
Abtrennung von Uranylionen aus Sicker- und Grundwässern mit uranophilen Calixarenen-Integrierter Umweltschutz in der Textilindustrie
  • Lecture (others)
    FWR - 21.8.2001

Publ.-Id: 4676 - Permalink

Structural Studies of Actinide Complexation with Humic Substances
Reich, T.; Sachs, S.; Schmeide, K.; Bubner, M.; Brendler, V.; Funke, H.; Geipel, G.; Hennig, C.; Roßberg, A.; Heise, K. H.; Bernhard, G.;
kein Abstract
  • Lecture (Conference)
    Intern. Konferenz Actinides 2001, Hayama, Japan 4.-9-11-2001

Publ.-Id: 4675 - Permalink

Ions for materials research: surface modification and analysis at Rossendorf
Möller, W.;
  • Lecture (others)
    Institute of Applied Physics, University of West Bohemia, Pilsen, CZ, 20.12.2001

Publ.-Id: 4674 - Permalink

Grundlagen der Ionen-Festkörper-Wechselwirkung
Möller, W.;
  • Lecture (others)
    Sommerschule "Nukleare Sonden und Ionenstrahlen", Bad Blankenburg, 24.09.2001

Publ.-Id: 4672 - Permalink

Ionenstrahlen in der Materialforschung
Möller, W.;
  • Lecture (others)
    FhI für Keramische Technologien und Sinterwerkstoffe, Dresden, 18.6.2001

Publ.-Id: 4671 - Permalink

Interaction of Actinides with the Predominant Indigenous in Äspö Aquifer
Moll, H.;
kein Abstract
  • Lecture (others)
    Workshop University of Gotheburg, 16.-18.10.2001

Publ.-Id: 4669 - Permalink

Solvent Effects on Uranium(VI) Fluoride and Hydroxide Complexes Studied by EXAFS and Quantum Chemistry
Vallet, V.; Wahlgren, U.; Schimmelpfennig, B.; Moll, H.; Szabó, H.; Grenthe, I.;
  • Inorg. Chemie 40, 3516-3525 (2001)

Publ.-Id: 4666 - Permalink

Seminar-Vortrag am Institut für Tieftemperaturphysik der TU Dresden (23.05.2002): Gateoxides with embedded Si-nanoclusters for memory applications - preparation by magnetron sputtering, electrical and optical characterization
Schmidt, J. U.;
In silicon-nanocluster (Si-NC) memories, Si-NC embedded in the gate oxide of a MOSFET are used to store and release electrons thereby modifying the threshold of a transistor. This article describes the formation of its core functional structure, the Si-NC MOS memory capacitor, by annealing a SiO2/SiOX (x < 2) stack, deposited onto a thin direct tunneling oxide on silicon by a sputtering method. To achieve a high density of isolated Si-NC, both, the initial silicon excess in the SiOX layer and the thermal annealing treatment must be optimized. Optimum conditions are expected just at the end of the nucleation stage of the NC ensemble. Therefore the effect of various rapid thermal anneals (RTA) on SiOX/Si structures with different silicon excess x was investigated focusing on two optical methods: infrared absorption and photoluminescence (PL). The rate of nucleation and phase separation was found to depend strongly on both, silicon excess and annealing temperature. The characteristic size dependence of Si-NC PL was used to differentiate annealing regimes yielding NC ensembles being 'frozen' in the process of nucleation or in their growth/ripening phase respectively. Additionally, Si-NC MOS memory capacitors were prepared and characterized using both, optical and electrical tests. The devices prepared under optimized conditions yield a high flat-band shift and good charge retention characteristics.
Keywords: Silicon rich oxide, Silicon Nanocclusters, Photoluminescence
  • Lecture (others)
    Seminar-Vortrag am Institut für Tieftemperaturphysik der TU Dresden (23.05.2002)

Publ.-Id: 4665 - Permalink

Consequences of Neutron-Proton Pairing Correlations for the Rational Motion of the N=Z Nucleus 72Kr
Kelsall, N. S.; Wadsworth, R.; Wilson, A. N.; Fallon, P.; Macchiavelli, A. O.; Clark, R. M.; Sarantites, D. G.; Seweryniak, D.; Svensson, C. E.; Vincent, S. M.; Frauendorf, S.; Sheikh, J. A.; Ball, G. C.;
High-spin states in the N = Z nucleus 72Kr were populated using
the 40Ca(36Ar,2p2n) reaction at a beam energy of 145 MeV.
The yrast band has been observed up to a tentative spin of 20 h.
Nonyrast rotational structures have also been observed for the first time.
The alignment of g9/2 protons and neutrons in the yrast band is observed to
be significantly delayed relative to the heavier even-even Kr isotopes.
Exact deformed cranked shell model calculations suggest that this could be due to the combined effect
of isovector (T = 1) and isoscalar (T = 0) neutron-proton pairing correlations.
  • Phys. Rev. C 64 (2001) 024309

Publ.-Id: 4657 - Permalink

Tritium depth profiling by AMS
Pilz, W.; Friedrich, M.; Bekris, N.; Glugla, M.; Kiisk, M.; Liechtenstein, V.; (Editors)
Tritium depth profiles in carbon have been determined at the Rossendorf AMS facilities during the past seven years. The samples have been cut from tiles of the inner walls of the fusion reactors ASDEX-upgrade Garching, JET Culham and TFTR Princeton. The high tritium content required a dedicated AMS facility to prevent any contamination of the versatile 3 MV Tandetron. It is based on an SF6-insulated 100 kV tandem accelerator equipped with a DLC stripper foil of about 1µg/cm². Depth profiles of deuterium and other light elements can also be measured in SIMS mode or AMS mode depending on concentrations.
Keywords: Mass spectrometry; Tritium; Fusion; Electrostatic accelerators.
  • Contribution to proceedings
    proceedings of conference HIPAN02,Neptun,Romania,September 2-6,2002

Publ.-Id: 4656 - Permalink

Comparison of the scintillation properties of LSO:Ce manufactured by different laboratories and of LGSO:Ce.
Kapusta, M.; Moszynski, M.; Balcerzyk, M.; Braziewicz, J.; Wolski, D.; Pawelke, J.; Klamra, W.;
We measured photoelectron yield, light output, decay times of the light pulses, cerium concentration, energy resolution and time resolution of LSO:Ce manufactured by different laboratories and LGSO:Ce. The LSO samples show excellent scintillation properties: high light output, close to 30,000 ph/MeV and good energy resolution of 7.3% FWHM for 137Cs gamma-source full energy peak. Time resolution measured in geometry fulfilling the PET scanners requirements is equal to 450 ps.
We also present results from the measurements with LGSO:Ce by Hitachi Chemical Co., which is of similar chemical composition to LSO. LGSO, at present stage of development, shows about 20% lower light output than LSO and energy resolution of 12.4% FWHM for 662 keV gamma-rays.
LSO crystals used in our studies posses similar in scintillation properties, although we suppose that the details of the productions method are different due to the differences in Ce concentration. LGSO is a new and very promising scintillator due to lower background radiation in comparison to LSO, but it features worse energy resolution and smaller number of photoelectrons.
  • IEEE Trans. Nucl. Sci. 47 (2000) 1341-1345

Publ.-Id: 4655 - Permalink

Probing Meson Spectral Functions with Double Differential Dilepton Spectra in Heavy-Ion Collisions
Kämpfer, B.; Pavlenko, O. P.;
The double differential dilepton spectrum dN/ (dM2 dM^2)
at fixed transverse mass M^ allows a direct access to the vector meson spectral
functions. Within a fireball model the sensitivity of dN/ (dM2dM^2) against variations of both the in-medium properties of mesons and the dynamics of the fireball is investigated. In contrast to the integrated invariant-mass spectrum dN/dM2, in the spectrum dN/dM2dM^2 with fixed M^ the ω signal is clearly seen as bump riding on the ρ background even in case of strong in-medium modifications.
  • Eur. Phys. J. A 10 (2001) 101-107

Publ.-Id: 4653 - Permalink

Evidence for Chiral Symmetry in 136Pm and 138Eu
Hecht, A. A.; Beausang, C. W.; Zyromski, K. E.; Balabanski, D. L.; Barton, C. J.; Caprio, M. A.; Casten, R. F.; Cooper, J. R.; Hartley, D. J.; Krücken, R.; Meyer, D.; Newman, H.; Novak, J. R.; Paul, E. S.; Pietralla, N.; Wolf, A.; Zamfir, N. V.; Jing-Ye, Z.; Dönau, F.;
High-spin states in the doubly odd N=75 nuclei Pm-136 and Eu-138 were populated following the Sn-116(Mg-24,p3n) and Cd-106(Cl-35,2pn) reactions, respectively. A new ΔI = 1 band is reported in Eu-138 and new data are presented for the recently reported band in Pm-136. Polarization and angular correlation measurements have been performed to establish the relative spin and parity assignments for these bands. Both bands have been assigned the same πh11/2νh11/2 structure as the yrast band and are suggested as candidates for chiral twin bands.

Publ.-Id: 4652 - Permalink

Detailed Spectroscopy of the Chiral-Twin Candidate Bands in 136Pm
Hartley, D. J.; Riedinger, L. L.; Riley, M. A.; Balabanski, D. L.; Kondev, F. G.; Laird, R. W.; Pfohl, J.; Archer, D. E.; Brown, T. B.; Clark, R. M.; Devlin, M.; Fallon, P.; Hibbert, I. M.; Joss, D. T.; Lafosse, D. R.; Nolan, P. J.; O'Brien, N. J.; Paul, E. S.; Sarantites, D. G.; Sheline, R. K.; Shepherd, S. L.; Simpson, J.; Wadsworth, R.; Jing-Ye, Z.; Semmes, P. B.; Dönau, F.;
The chiral-twin candidate bands recently observed in 136Pm have been extended to high spins [I = (21)] using the Gammasphere γ-ray spectrometer and the Microball charged-particle detector array.
A more-detailed spectroscopy of the bands was possible, where the rotational alignments and B(M1)/B(E2) ratios confirm that both sequences have the πh11/2νh11/2 configuration. Particle-rotor calculations of intraband and interband transition
strength ratios of the chiral-twin bands are compared with experimental values for the first time. Good agreement was found between the predicted transition strength ratios and the experimental values, thus supporting the possible chiral nature of the configuration in πh11/2νh11/2

Publ.-Id: 4651 - Permalink

Symmetries of the Rotating Mean Field
Frauendorf, S.;
The discrete symmetries of the rotating mean field lead to a variety of rotation
al bands with different sequences of spin and parity. We focus on the
breaking of chiral symmetry in rotating triaxial nuclei.
  • Acta Phys. Polonica B 32 (2001) 2661

Publ.-Id: 4650 - Permalink

Atomic Clusters as a Branch of Nuclear Physics
Frauendorf, S.; Guet, C.;
The conduction electrons in clusters of simple metal atoms are approximatively i
ndependent and free. Nucleons in nuclei also behave as delocalized
and independent fermions. This generic behavior generates analogies between
metal clusters and nuclei, such as the shell structure, the shapes,
and the dipole vibration mode. However, there are also major differences
that arise from the presence of ions in metal clusters. Fission of nuclei and
clusters, and particle emission from them, reveal these differences.
  • Ann. Rev. of Nucl. and Part. Scien. 51 (2001) 219

Publ.-Id: 4649 - Permalink

Spontaneous Symmetry Breaking in Rotating Nuclei
Frauendorf, S.;
The concept of spontaneous symmetry breaking is applied to the rotating mean field of nuclei. The description is based on the tilted-axis cranking model, which takes into account that the rotational axis can take any orientation with respect to the deformed density distribution. The appearance of rotational bands in nuclei is analyzed, focusing on weakly deformed nuclei at high angular moment um. The quantization of the angular momentum of the valence nucleons leads to new phenomena. Magnetic rotation represents the quantized rotation of the anisotropic current distribution in a near pherical nucleus. The restricted amount of angular momentum of the valence particles causes band termination. The discrete symmetries of the mean-field Hamiltonian provide a classification scheme of rotational bands. New symmetries result from the combination of the spatial symmetries of the density distribution with the vector of the angular momentum. The author discusses in detail which symmetries appear for a reflection-symmetric density distribution and how they show up in the properties of the rotational bands. In particular, the consequences of rotation about a nonprincipal axis and of breaking the chiral symmetry are analyzed. Also discussed are which symmetries and band structures appear for non-reflection-symmetric mean fields. The consequences of breaking the symmetry with respect to gauge and isospin rotations are sketched. Some analogies outside nuclear physics are mentioned. The application of symmetry-restoring methods to states with large angular momentum is reviewed.
  • Rev. Mod. Phys. 73 (2001) 463

Publ.-Id: 4648 - Permalink

Results from FOPI on Strangeness in Nuclear Matter at SIS Energies
Crochet, P.; Alard, J. P.; Andronic, A.; Averbeck, R.; Barret, V.; Basrak, Z.; Bastid, N.; Belyaev, I.; Bendarag, A.; Berek, G.; Caplar, R.; Cindro, N.; Devismes, A.; Dupieux, P.; Dzelalija, M.; Eskef, M.; Finck, C.; Fodor, Z.; Gobbi, A.; Grishkin, Y. L.; Hartmann, O.; Herrmann, N.; Hildenbrand, K. D.; Hong, B.; Kecskemeti, J.; Kim, Y. J.; Kirejczyk, M.; Koczon, P.; Korolija, M.; Kotte, R.; Kowalczyk, M.; Kress, T.; Kutsche, R.; Lebedev, A.; Lee, K. S.; Leifels, Y.; Manko, V.; Merlitz, H.; Mohren, S.; Moisa, D.; Neubert, W.; Nianine, A.; Pelte, D.; Petrovici, M.; Plettner, C.; Rami, F.; Reisdorf, W.; de Schauenburg, B.; Schüll, D.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczynka, K.; Smolyankin, V.; Somov, A.; Stockmeier, M. R.; Stoicea, G.; Vasilev, M.; Wagner, P.; Wisniewski, K.; Wohlfarth, D.; Yang, J. T.; Yushmanov, I.; Zhilin, A.;
Experimental data on charged kaon phase space distributions and strangeness sidewards
flow measured with the FOPI detector at SIS/GSI are presented.
Comparisons are made with the predictions of transport models investigating the in-medium
kaon-nucleon potential.
  • J. Phys. G: Nucl. Part. Phys. 27 (2001) 267

Publ.-Id: 4647 - Permalink

The halogen effect in the oxidation of intermetallic titanium aluminides
Schütze, M.; Schumacher, G.; Dettenwanger, F.; Hornauer, U.; Richter, E.; Wieser, E.; Möller, W.;
Stoichiometric TiAl and two quasi-technical TiAl alloys were investigated in the temperature range of 800¯1000°C with regard to the halogen microalloying effect on oxidation resistance. The halogens Br, Cl, F and I were introduced into the material surface by ion implantation with different doses and energies before the thermogravimetric oxidation experiments were started. The results show that a very low "homeopathic" amount of these halogens at the oxide scale/metal interface activates a mechanism of selective Al-oxidation which changes oxidation behavior
from fast mixed titania/alumina kinetics to slow pure alumina kinetics. A model is described which explains this change in kinetics supported by quantitative data from thermodynamic calculations. The halogen microalloying effect offers a high potential for the improvement of oxidation resistance of TiAl alloys for technical applications.

Keywords: Intermetallics; Ion implantation; Chlorination; Interfaces; Selective oxidation
  • Corrosion Science 44 Issue 2 (2002) 303-318

Publ.-Id: 4646 - Permalink

On the Way to a Superconducting RF-Gun: First Measurements with the Gun Cavity
Barthels, E.; Büttig, H.; Gabriel, F.; Grosse, E.; Janssen, D.; Bushuev, A.; Karliner, M.; Konstantinov, S.; Kruchkov, S.; Myshkin, O.; Petrov, V.; Sedlyarov I, I.; Tribendis, A.; Volkov, V.; Sandner, W.; Will, I.; von Stein, P.; Vogel, H.; Matheisen, A.; Pekeler, M.; Thiel, C.;
The parameters of a superconducting RF gun cavity have been measured in a test cryostat of DESY. A field strength of 31.8 MV/m at the cathode has been obtained.
  • Nucl. Instr. Meth. A 445 (2000) 408

Publ.-Id: 4645 - Permalink

Synthesis of epitaxial diamond grains in cubic SiC by high temperature carbon implantation
Pécz, B.; Tóth, L.; Heera, V.; Skorupa, W.;
3C-SiC have been implanted with carbon ions at 60 keV to a dose of 3x10^17 and 1x10^18 cm^-2. All of the implantation experiments were carried out at elevated temperature in the range of 900°C-1200°C to study the phases, which are formed, when excess carbon is introduced into the SiC lattice. At 1100^C and at 1200°C small diamond grains are formed; these are embedded in the SiC and form perfectly oriented crystallites of a few nm size. Diamond is formed in SiC at 900°C as well, however, at high dose rate the impinging carbon ions can destroy the nucleated diamond grains.
Keywords: Ion beam synthesis, diamond, SiC
  • Contribution to external collection
    Inst. Phys. Conf. Ser. No 169 (2001) 367-370

Publ.-Id: 4644 - Permalink

Entwicklung eines Justierdetektors für Elektronenstrahlanlagen
von Borany, J.; Beyer, V.;
no abstract delivered from author
Keywords: Justierdetektor, MeV-Ionenimplantation, Elektronenstrahl-Lithografie, Si-Technologie
  • Other report
    Abschlußbericht zum BMBF/Leica Projekt "JD-50", Oktober 2001

Publ.-Id: 4643 - Permalink

Physikalische und technologische Grundlagen zum Engineering von Nanoclustern für nichtflüchtige Speicherzellen
von Borany, J.; Gebel, T.; Grötzschel, R.; Heinig, K.-H.; Klimenkov, M.; Schmidt, B.;
no abstract delivered from author
Keywords: Nanocluster, Ionenstrahlsynthese, Nichtflüchtige Speicher, Si-Technologie
  • Other report
    Abschlußbericht zum SMWK-Projekt 4-7531.50-03-844-98/4, Juni 2001

Publ.-Id: 4642 - Permalink

Implantationsdotierung von Diamantschichten für Mikrosystem-Anwendungen
von Borany, J.; Fontaine, F.; Heera, V.;
no abstract delivered from author
Keywords: Diamant, Dotierung, Ionenimplantation
  • Other report
    Abschlußbericht zum BMBF-Projekt 16SV 548/2, Juni 2001

Publ.-Id: 4641 - Permalink

Ionenstrahlmodifizierung und Synthese von Halbleiter-Nanoclustern in dünnen Gate-Dielektrika für Flash- und EEPROM-Anwendungen
von Borany, J.; Keywords: Nanocluster, Ionenstrahlsynthese, Gateoxide, Nichtflüchtige Speicher, Si-Technologie
  • Lecture (others)
    Kickoff-Meeting zum Projekt "KONSUL", Infineon Dresden, 23. August 2001

Publ.-Id: 4640 - Permalink

Emitter doping of silicon solar cells by phosphorous plasma-immersion ion implantation
von Borany, J.; Keywords: Solar cells, Doping, Si-technology, Plasma ion implantation
  • Lecture (others)
    Universität Konstanz, Jan. 11, 2001

Publ.-Id: 4639 - Permalink

In-situ study of the phase transformation and the correlated mechanical properties of nitrogen implanted Ti-6Al-4V alloys
Berberich, F.; Keywords: Light metals, Hardness, Ion implantation, X-ray diffraction
  • Lecture (others)
    ESRF PhD Seminar, Grenoble, France, Feb. 22, 2001
  • Lecture (others)
    ESRF Seminar, Grenoble, France, Oct. 23, 2001

Publ.-Id: 4638 - Permalink

In-situ Untersuchungen der Phsentransformation und der mechnaischen Eigenschaften stickstoffimplantierter Ti-6Al-4V Legierungen
Berbereich, F.; Keywords: Leichtmetalle, Härtung, Ionenimplantation, X-ray Diffraktion
  • Lecture (others)
    Seminarvortrag, TU Chemitz, 18.Mai 2001
  • Lecture (others)
    Seminarvortrag, HMI Berlin, 31. Oktober 2001

Publ.-Id: 4637 - Permalink

Si-based light emission from Ge-implanted SiO2 layers: Electric and optoelectronic properties
Rebohle, L.; Gebel, T.; von Borany, J.; Skorupa, W.; Helm, M.; Keywords: Light emission, Si-technology, Ion implantation
  • Poster
    10th Intern. Conference on Modulated Semiconductor Structures, Linz, July 23-27, 2001

Publ.-Id: 4636 - Permalink

Strong visible electroluminescence from Ge- and Sn-nanocluster rich silicon dioxide layers
Rebohle, L.; Gebel, T.; von Borany, J.; Fröb, H.; Borchert, D.; Skorupa, W.;
no abstract delivered from author
Keywords: Ion beam synthesis, Nanoclusters, Luminescence, Light emitters, Si-technology
  • Lecture (Conference)
    E-MRS Spring Meeting, Strabourg, France, June 5-8, 2001
  • Contribution to proceedings
    E-MRS Spring Meeting, Strabourg, France, June 5-8, 2001

Publ.-Id: 4635 - Permalink

Strong blue photo- and electroluminescence from tin implanted silicon dioxide
Rebohle, L.; Gebel, T.; von Borany, J.; Fröb, H.; Klimenkov, M.; Skorupa, W.;
no abstract delivered from author
Keywords: Ion beam synthesis, Luminescence, Light emitter, Si-technology
  • Poster
    MRS Spring meeting, San Francisco, USA, April 16-20, 2001
  • Contribution to proceedings
    MRS Spring meeting, San Francisco, USA, April 16-20, 2001

Publ.-Id: 4634 - Permalink

ANKE, a New Facility for Medium Energy Hadron Physics at COSY-Jülich
Barsov, S.; Bechstedt, U.; Bothe, W.; Bongers, N.; Borchert, G.; Borgs, W.; Bräutigam, W.; Büscher, M.; Cassing, W.; Chernyshev, V.; Chiladze, B.; Dietrich, J.; Drochner, M.; Dymov, S.; Erven, W.; Esser, R.; Franzen, A.; Golubeva, E. S.; Gotta, D.; Grande, T.; Grzonka, D.; Hardt, A.; Hartmann, M.; Hejny, V.; von Horn, L.; Jarczyk, L.; Junghans, H.; Kacharava, A.; Kamys, B.; Khoukaz, A.; Kirchner, T.; Klehr, F.; Klein, W.; Koch, H. R.; Komarov, V. I.; Kondratyuk, L.; Koptev, V.; Kopyto, S.; Krause, R.; Kravtsov, P.; Kruglov, V.; Kulessa, P.; Kulikov, A.; Lang, N.; Langenhagen, H.; Lepges, A.; Ley, J.; Maier, R.; Martin, S.; Macharashvili, G.; Merzlyakov, S.; Meyer, K.; Mikirtychyants, S.; Müller, H.; Munhofen, P.; Mussgiller, A.; Nekipelov, M.; Nelyubin, V.; Nioradze, M.; Ohm, H.; Petrus, A.; Prasuhn, D.; Prietzschk, B.; Probst, H. J.; Pysz, K.; Rathmann, F.; Rimarzig, B.; Rudy, Z.; Santo, R.; Schieck, H. P. G.; Schleichert, R.; Schneider, A.; Schneider, C.; Schneider, H.; Schwarz, U.; Seyfarth, H.; Sibirtsev, A.; Sieling, U.; Sistemich, K.; Selikov, A.; Stechemesser, H.; Stein, H. J.; Strzalkowski, A.; Watzlawik, K. H.; Wüstner, P.; Yashchenko, S.; Zalikhanov, B.; Zhuravlev, N.; Zwoll, K.; Zychor, I.; Schult, O. W. B.; Ströher, H.;
ANKE is a new experimental facility for the spectroscopy of products from proton
-induced reactions on internal targets. It has recently been implemented in the accelerator ring of the cooler synchrotron COSY of the Forschungszentrum Jülich (FZ-Jülich), Germany. The device consists of three dipole magnets, various target installatio ns and dedicated detection systems. It will enable a variety of hadron-physics experiments like meson production in elementary proton-nucleon processes and studies of medium modifications in proton-nucleus interactions.
  • Nucl. Instr. Meth. A 462 (2001) 364

Publ.-Id: 4632 - Permalink

Luminescence properties of ion-beam synthesized "point defects" in silicon dioxide
Rebohle, L.; von Borany, J.; Fröb, H.; Klimenkov, M.; Skorupa, W.;
no abstract delivered from author
Keywords: Ion beam synthesis, Luminescence, Si-technology, SiO2
  • Lecture (others)
    39.Arbeitskreis Punktdefekte, Dresden, 12.-13. Februar 2001

Publ.-Id: 4631 - Permalink

Calculation of the unstressed lattice spacing of Al-doped c-BN thin films using data from synchrotron radiation diffraction experiments
Linss, V.; Pfeifer, T.; Halm, T.; Hoyer, W.; Richter, F.; Schell, N.; Keywords: Hard coatings, c-BN, Stress, Synchrotron radiation, X-ray diffraction
  • Poster
    12th Intern. School on Vacuum, Electron and Ion Technologies (VEIT 2001), Varna, Bulgaria, Sept. 17-21, 2001

Publ.-Id: 4630 - Permalink

Formation of metastable structures in metalls and alloys
Wieser, E.; Noetzel, J.; Peikert, M.; Reuther, H.; Wenzel, C.; Tselev, A. A.;
Formation and transformation of metastable alloys by ion irradiation are discussed on example of the systems Al-Fe, Ta(N), Ta(O), Fe-Cr. By ion beam mixing of Al-Fe multilayers with an overall composition of 60 to 85 at.% Al using 150 keV Fe ions metastable structures were formed. For 80 to 85 at% Al amorphous alloys have been observed. The formation amorphous interface regions cross-beam pulsed laser deposition (CBPLD) is demonstrated. Amorphus thin diffusion barriers of Ta were formed by ion implantation of nitrogen and oxygen. Fe-Cr thin layers with Cr concentration from 27 to 62 at.% Cr prepared by CBPLD show different metastable structures depending on the Cr content. These layers are paramagnetic at rom temperature. By ion irradiation it is possible to transform these alloys into a bcc structure with a ferromagnetion iron rich component.
Keywords: Metastable alloys, Ion irradiation
  • Lecture (Conference)
    Fourth International Ural Seminar "Radiation Damage Physics of Metalls and Alloys", Snezhinsk, Russia, February 25 to March 03, 2001

Publ.-Id: 4629 - Permalink

Strukturelle Charakterisierung der Härtung von Ti-Al-V Legierungen nach Plasma-Immersions-Ionen-Implantation mit Stickstoff
Berberich, F.; Matz, W.; Kreißig, U.; Schell, N.; Richter, E.; Möller, W.;
no abstract delivered from author
Keywords: Ti-Al Legierung, Härtung, Ionenimplantation, Röntgen-Diffraktometrie, Ionenstrahlanalytik
  • Lecture (Conference)
    65. Physikertagung, Hamburg, 26.-30.03.2001

Publ.-Id: 4625 - Permalink

Ion beam synthesized nanoclusters for silicon-based light emission
Rebohle, L.; von Borany, J.; Fröb, H.; Gebel, T.; Helm, M.; Skorupa, W.;
no abstract delivered from author
Keywords: Ion beam synthesis, Nanoclusters, Light emission, Optoelectronics
  • Invited lecture (Conferences)
    7th European Conference on Accelerators in Applied Research and Technology, University of Surrey, Guildford, UK, August 21-24, 2001 (Invited Talk)

Publ.-Id: 4624 - Permalink

Formation and decomposition of laser-deposited metastable Fe-Cr phases
Gorbunov, A.; Levin, A. A.; Wieser, E.; Bischoff, L.; Eckert, D.; Mensch, A.; Mertig, M.; Meyer, D. C.; Reuther, H.; Paufler, P.; Pompe, W.;
Contrary to expectations to obtain a continuous series of supersaturated b.c.c. Fe-Cr solid solutions by co-deposition of both metals in cross-beam PLD, there form unusual for this materials system metastable intermetallic phases. The structure of alloys develops from a tetragonally distorted bcc at low Cr-content through a face centered orthorhombic to a partly ordered promitive orthorhombic crystal structure of the A15- like type at nearly equiatomiccomposition. It seems to be the first observation of an ordering of restrictedly soluble components under the bombardment of hyperthermal species in PLD. Intriguing fact is that these metastable phases are initially paramagnetic (PM) at room temperature but become ferromagnetic (FM)after annealing in a temperature range 400-500 C ore under ion bombardment. The induced PM-FM transformation in the alloys is demonstrated to be useful for formation of stable lateral magnetic microstructures.
  • Lecture (Conference)
    IQEC/LAT 2002, International Quantum Electronics Conference 2002, Conference on Lasers, Applications and Technologies, Moscow, Russia, June 22-28, 2002
  • Proc. SPIE 5121 (2003) 306

Publ.-Id: 4622 - Permalink

Laboratory -unit investigations 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.;
Titanium foil is employed for electron transparent windows in the electron beam dry scrubber process. The foil suffers corrosion, which limits the window life. Here, the examination of palladium-coated window, prepared by ion beam assisted deposition and plasma source ion assisted deposition (PSIAD), 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, corrosion was negligible. Elswhere, generalmintergranular and pitting corrosin occured. A PSIAD coating provided the best performance.
Keywords: Electron beam treatment, Flue gases, Ttanium, Palladiumn, Corrosion, Coatings
  • Radiation Physics and Chemistry 62 (2001) 253-260

Publ.-Id: 4621 - Permalink

Reflektivitätsuntersuchungen mittels Synchrotronstrahlung an durch MBE erzeugten Fe/Cr-Multischichten
Prokert, F.; Kravtsov, E.; Milayev, M.; Romashev, L.; Ustinov, V.; Schell, N.;
Fe/Cr-Multischichten zeigen GMR (giant magnetoresistance) Effekte, die in der Anwendungstechnik (Magnetoelektrik, Sensorik, Speichertechnologie) von besonderer Bedeutung sind. Magnetische Multischichten werden deshalb gegenwärtig vielerorts untersucht. In diesem Zusammenhang werden die Einflüsse der unterschiedlichen Verfahren der Schichtabscheidung studiert.
Durch die Reflektivitätsuntersuchungen mittels Synchrotronstrahlung können die durch MBE abgeschiedenen Einzelschichten auch im Fe/Cr-Multischichtsystem hinsichtlich Schichtdicke, Dichte, Rauhigkeit und Interface-Morphologie recht genau charakterisiert werden.
Keywords: Fe/Cr- Multischichten; SR-Reflektometrie; Anomale Streuung
  • Poster
    Zeitschrift für Kristallographie, Supplement Issue No. 19, S. 58 Referate, 10. Jahrestagung der Deutschen Gesellschaft für Kristallographie (DGK) vom 4. bis 7. März 2002 in Kiel
  • Contribution to proceedings
    Zeitschrift für Kristallographie, Supplement Issue No. 19, S. 58 Referate, 10. Jahrestagung der Deutschen Gesellschaft für Kristallographie (DGK) vom 4. bis 7. März 2002 in Kiel

Publ.-Id: 4620 - Permalink

Use of anomalous scattering for synchrotron X-ray reflectivity studies of Fe-Cr and Co-Cu double layers
Prokert, F.; Schell, N.; Gorbunov, A.;
Double layers of Fe-Cr and Co-Cu, respectively, were prepared on oxidized Si substrates by pulsed laser deposition (PLD). The interfacial roughness structure was studied by synchrotron X-ray reflectivity measurements at the absorption K-edges using the contrast enhancement due to resonant scattering. The results are determined from simulations of the measured specular and diffuse scans. Whereas in Fe-Cr double layers the rms-interface width for Fe deposition on Cr (sigma_Cr = 0.70 ± 0.1 nm) is not very different from that of Cr deposition on Fe (sigma_Fe = 0.85 ± 0.1 nm), in Co-Cu double layers, in contrast, for Cu deposition on Co, the width (sigma_Co = 0.65 ± 0.1 nm) is much smaller than for Co deposition on Cu (sigma_Cu = 1.5 ± 0.15 nm). On the basis of the fractal model to describe the interface roughness morphology, from the off-specular scans the lateral roughness correlation length, xi, and the roughness exponent, h, were determined. For both types of double layers extremely high xi-values (larger than 2 µm) were found. However, the flatness is accompanied by a high short-scale roughness (jaggedness), expressed by a small h-parameter (h = 0.25 ± 0.05). Both facts were found to be characteristic for the 'as-deposited' state of such metal/metal layers prepared by PLD.
Keywords: X-ray reflectometry; interfaces; anomalous scattering
  • Nuclear Instruments and Methods in Physics Research B 199 (2003) 123-127

Publ.-Id: 4619 - Permalink

Φ and ω Meson Production in pp Reactions at plab=3.67 GeV/c
Balestra, F.; Bedfer, Y.; Bertini, R.; Bland, L. C.; Brenschede, A.; Brochard, F.; Bussa, M. P.; Choi, S.; Debowski, M.; Dressler, R.; Dzemidzic, M.; Faivre, J.-C.; Falomkin, I. V.; Fava, L.; Ferrero, L.; Foryciarz, J.; Fröhlich, I.; Frolov, V.; Garfagnini, R.; Grasso, A.; Grosse, E.; 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.; Tchalyshev, V.; Tosello, F.; Vigdor, S. E.; Zosi, G.;
The exclusive production cross sections for ω and Φ mesons have been measured in proton-proton reactions at plab=3.67 GeV/c.
The observed Φ/ω cross section ratio is (3.8±0.2+1.2-0.9)×10-3.
After phase space corrections, this ratio is enhanced by about an order of magnitude relative to naive predictions based upon the Okubo-Zweig-Iizuka (OZI) rule, in comparison to an enhancement by a factor ~ 3 previously observed at higher beam momenta. The modest increase of this enhancement near the production threshold is compared to the much larger increase of the Φ/ω ratio observed in specific channels of pp annihilation experiments.
Furthermore, differential cross section results are also presented which indicate that although the Φ meson is predominantly produced from a 3P1 proton-proton entrance channel, other partial waves contribute significantly to the production mechanism at this beam momentum.

Publ.-Id: 4618 - Permalink

YSO, LSO, GSO and LGSO. A study of energy resolution and nonproportionality.
Balcerzyk, M.; Moszynski, M.; Kapusta, M.; Wolski, D.; Pawelke, J.; Melcher, M.;
We have studied the nonproportionality and intrinsic energy resolution of cerium doped YSO, GSO, LSO and LGSO crystals. While LSO and YSO have similar light output, GSO and LGSO have ca. 70% and 20% lower light output than LSO, respectively. YSO, a compound containing fairly light elements, was expected to have proportional light output vs. energy, like YAP:Ce. Surprisingly it has almost the same nonproportional as LSO and GSO. The nonproportionality of YSO is followed by large values of intrinsic energy resolution. The comparison of the nonproportionality of YSO-LSO and YAP-LuAP pairs indicates that high proportionality is connected with the structure of the crystal and not with the presence of light elements. To our knowledge, this is the first study of nonproportionality and intrinsic resolution for LGSO.
  • IEEE Transactions on Nuclear Science, Vol. 47, No. 4 (2000) 1319-1323

Publ.-Id: 4617 - Permalink

Synthese und Verwendung uranophiler Calicarene
Keil, D.; Schmeide, K.;
kein Abstract
  • Lecture (others)
    Mikrosymposium FCS im Technologie- und Gründerzentrum Bitterfeld-Wolfen 27.11.2001

Publ.-Id: 4616 - Permalink

Double injection of charge carriers in chemical vapor deposited diamond-based diodes
Weima, J. A.; von Borany, J.; Messinger, K.; Horstmann, J.; Fahrner, W. R.;
Boron ion implantation of thermochemically polished chemical vapor deposited diamond films with multienergies ranging between 24 and 150 keV and a total dose of about 2E16 cm-2 is used to get p-type conductivity. n-type conductivity is achieved by lithium ion implantation of the diamond films with a single energy of 50 keV and a dose of 2E16 cm-2. The intrinsic areas separating the p- and n-doped regions form the active areas of the diodes into which charge carriers are simultaneously injected upon bias. Onset voltages of < 10 V are due to the low concentration (~1E14 cm-3) of nitrogen related centers in the diamond films. The current–voltage (I–V) characteristics of the p-i-n diodes manifest trap filling, Frenkel–Poole emission, thermionic emission, and space charge limited current regimes. At 300°C, currents as high as 12 mA are measured at a forward bias of 100 V. Rectification ratios of up to about four orders of magnitude are achieved. They increase with increasing width of the i-region within the measured i-region of 3–10 µm, as a result of the considerable decrease of the reverse bias current relative to the forward bias current.
Keywords: diamond, pin-diodes, conduction mechanism
  • Journal of Applied Physics 92(7)(2002) 4047-4052

Publ.-Id: 4615 - Permalink

Static Quadrupole Moment of the Five-Quasiparticle K=35/2 Isomer in 179W Studied with the Level-Mixing Spectroscopy Method
Balabanski, D. L.; Vyvey, K.; Neyens, G.; Coulier, N.; Coussement, R.; Georgiev, G.; Lépine-Szily, A.; Ternier, S.; Teughels, S.; Mineva, M.; Walker, P. M.; Blaha, P.; Almehed, D.; Frauendorf, S.;
The spectroscopic quadrupole moment of the high-spin, high-K five-quasiparticle isomer (Kπ=[(35-)/2], T1/2=750(80) ns, Ei = 3349 keV) in 179W has been determined using the level mixing spectroscopy method.
A value Qs = 4.00([(+0.83) || (-1.06)])e b was derived, which corresponds to an intrinsic quadrupole moment Q0 = 4.73([(+0.98) || (-1.25)])e b and to a quadrupole deformation β2 = 0.185([(+0.038) || (-0.049)]).
These values differ significantly from the deduced ground-state quadrupole moments and are in disagreement with the current theoretical predictions in this mass region.

Publ.-Id: 4614 - Permalink

Development of a Tritium AMS Detection Method for Biomedical Applications
Kiisk, M.; Friedrich, M.; Hellborg, R.; Mattson, S.; Pilz, W.; Vesanen, R.;
There are numerous applications for tritium (3H) as a tracer isotope in biomedicine commonly combined with the liquid scintillation counting method. The use of accelerator mass spectrometry (AMS), a rather new detection method, would enlarge and open new possibilities for tritium applications in biomedicine, especially when sample volumes are small. The tritium in the samples has to be transformed to solid form yielding high output of negative hydrogen current. The sample preparation for tritiated water is done in two steps: firstly extracting water from the biological sample and secondly, extracting hydrogen/tritium from the water and forming a chemically suitable compound for the AMS system.
In this paper a chemical procedure for the sample preparation is described. The results of the first measurements of tritiated water with known activity using AMS detection technique will also be presented.

Keywords: AMS, tritium AMS, Biomedical applications
  • Contribution to external collection
    HIPAN-02, Neptun, Romania, September 2-6, 2002

Publ.-Id: 4613 - Permalink

Untersuchungen über die Komplexierung und die Migration von Actiniden und nichtradioaktiven Stoffen mit Huminsäuren unter geogenen Bedingungen
Bernhard, G.; Pompe, S.; Schmeide, K.; Heise, K. H.; Brendler, V.; Trautmann, N.; Kuczewski, B.; Seibert, A.; Kratz, J. V.; Beck, H. P.;
kein Abstract
  • Lecture (others)
    5. Projektstatusgespräch zu F+E-Vorhaben auf dem Gebiet der Entsorgung gefährlicher Abfälle in tiefen geologischen Formationen, Leipzig 15.-16.5.2001

Publ.-Id: 4611 - Permalink

Magnetic Dipole Rotational Bands in Odd-A Rb Isotopes
Amita, A.; Jain, K.; Dimitrov, V. I.; Frauendorf, S.;
The hybrid version of tilted axis cranking has been used to study the existence of magnetic rotation in the ΔI = 1 bands of odd-A 79,81,83,85Rb isotopes.
The bands are found to be built on prolate three quasiparticle π(g9/2) Ä n[g9/2(fp)1] configuration.
The results exhibit a rapid onset and decline of magnetic rotation as we go from N = 42 to 48.
The 83Rb appears to be a better case of magnetic rotation among these four Rb isotopes.

Publ.-Id: 4610 - Permalink

Contribution of the FZR to the HUPA Project
Schmeide, K.; Sachs, S.;
Humic Substances in Performance Assessment of Nuclear Waste Disposal: Actinide and Iodine Migration in the Far-Field
  • Lecture (others)
    Workshop zum Forschungsvorhaben FZK 3.-4.12.2001

Publ.-Id: 4609 - Permalink

EXAFS-Untersuchungen an Pu(III)-Humaten sowie erste Ergebnisse zur Np(V)-Sorption an Granit in Ab- und Anwesenheit von Huminsäure.
Schmeide, K.;
Untersuchungen über die Komplexierung und die Migration von Actiniden und nichtradioaktiven Stoffen mit Huminsäuren unter geogenen Bedingungen - Komplexierung von Huminsäuren mit Actiniden in der Oxidationsstufe IV Th, U, Np
  • Lecture (others)
    Workshop zum Forschungsvorhaben FZK 15.-16.11.2001

Publ.-Id: 4607 - Permalink

Huminsäureforschung im FZR/IfR - Synthetische Huminsäuren
Schmeide, K.; Pompe, S.;
kein Abstract
  • Lecture (others)
    Vortrag anläßlich des Besuchs von Vertretern der HS Zittau-Görlitz im FZR, 30.4.2001

Publ.-Id: 4605 - Permalink

Quantum Correlations in Rotating Nuclei
Almehed, D.; Dönau, F.; Nazmitdinov, R. G.;
Using the Hamiltonian that consists of the separable quadrupole + pairing forces and the cranking term, we analyze the correlations associated with shape, orientation, and particle-number fluctuations in rotating nuclei. Quantum fluctuations around mean field solutions are treated in the random phase approximation (RPA), with special emphasis on the restoration of
rotational symmetry and particle number conservation. The mean field calculations have been made within the self-consistent cranking model. The effect of the RPA correlation energy for the moment of inertia is studied with the integral representation method proposed.
  • Physics of Atomic Nuclei 64 (2001) 1076

Publ.-Id: 4604 - Permalink

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