Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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

32337 Publications
Optimization of a Cell Labeling Strategy for Magnetic Resonance Imaging
Wolf, G.; Strobel, K.; Gruener, S.; Koch, A.; Hietschold, V.; Abolmaali, N.;
With the currently available scanner technology and high field strengths, magnetic resonance imaging (MRI) allows a near cellular resolution and, thus, provides a non-invasive and repetitive means of tracking single cells or small groups of cells after their transplantation or injection in living organisms. Therefore, cells need to be labeled with a suitable MRI contrast agent (CA) in order to differntiate them from surrounding tissue in vivo. Using CA labeled tumor cells it would be possible to follow tumor progression over time with MRI after transplantation or injection.
  • Poster
    ISMRM 14. Scientific Meeting & Exhibition, 06.-12.05.2006, Seatle, USA
  • Contribution to proceedings
    ISMRM 14. Scientific Meeting, 06.-12.05.2006, Seatle, USA
    Proceedings of the International Society for Magnetic Resonance in Medicine 14, 1864

Publ.-Id: 8284 - Permalink


Two- and Threefold Intramolecular Bridging p-tert- Butylcalix[8]arene Triphosphates – Synthesis, Structure and Stereochemistry
Gloede, J.; Ozegowski, S.; Keitel, I.; Gruner, M.; Costisella, B.; Pritzkow, W.; Stephan, H.; Bartoschek, M.;
The phosphorylation of p-tert-butylcalix[8]arene (1) with phosphorus pentachloride and hydrolysis gives intramolecular bridging tert-butylcalix[8]arene triphosphates. The reactivity (esterification, dehydratisation, complexation), the structure (nmr and x-ray), and stereochemical behaviour of the phosphates will be discussed.
  • Zeitschrift für Anorganische und Allgemeine Chemie (2006)632, 123-132

Publ.-Id: 8283 - Permalink


Hunting Medium Modifications of the Chiral Condensate
Thomas, R.; Zschocke, S.; Hilger, T.; Kämpfer, B.;
With QCD sum rule evaluations, spectral changes of hadrons inside nuclear matter are considered, which shed light on QCD condensates and thus on the non-perturbative structure of the QCD ground state. For some light quark configurations, omega meson and nucleon, the relevance of four-quark condensates is compared; the D meson as a representative of heavy-light quark systems is also briefly discussed.
Keywords: QCD Sum Rules, Chiral Condensate
  • Contribution to proceedings
    44th International Winter Meeting on Nuclear Physics, 29.01.-05.02.2006, Bormio, Italy
  • Lecture (others)
    Int. Wintermeeting on Nuclear Physics, 20.01.-05.02.2006, Bormio, Italy

Publ.-Id: 8282 - Permalink


The growth and microstructure of magnetron sputtered Ti2AlN MAX phase thin films characterized by in-situ x-ray diffraction
Beckers, M.; Schell, N.; Martins, R. M. S.; Mücklich, A.; Möller, W.;
Kein Abstract vorhanden.
  • Lecture (Conference)
    14th International Summer School on Vacuum, Electron and Ion Technologies (VEIT), 12.-16.09.2005, Sunny Beach, Bulgaria

Publ.-Id: 8281 - Permalink


Amorphous-crystalline ripple formation in ion beam induced Si wafers
Grigorian, S.; Pietsch, U.; Grenzer, J.;
Kein Abstract vorhanden.
  • Lecture (Conference)
    348. Heraeus-Seminar "Ions at Surfaces: Patterns and Processes", 19.-23.06.2005, Bad Honnef, Germany

Publ.-Id: 8280 - Permalink


Modelling of differential pressure buildup during flow through beds of fibrous materials
Grahn, A.; Krepper, E.; Alt, S.; Kästner, W.;
The present paper reports on our efforts in modelling the pressure drop buildup across beds of fibrous materials at strainers. Special attention is drawn to the compressibility of the fibrous filter cake. The influence of penetration depth of sludge particles onto the overall pressure drop in conjunction with the thin-bed effect has been investigated. Numerical results are compared with pressure drop measurements.
Keywords: pressure drop, strainer blockage, fibrous filter cakes, compressible filter cakes

Publ.-Id: 8279 - Permalink


Formation of Au nanocrystals in TiO2, SrTiO3 and MgO by ion implantation
Fromknecht, R.; Linker, G.; Sun, K.; Zhu, S.; Wang, L. M.; van Veen, A.; van Huis, M. A.; Weimann, T.; Wang, J.; Niemeyer, J.; Eichhorn, F.; Wang, T.;
Kein Abstract vorhanden.
  • Lecture (Conference)
    10th Int. Symposium on Advanced Physical Fields (APF-10) "Nano-Fabrication and Nano-Characterization of Nanomaterials", 07.-10.03.2005, Tsukuba, Japan

Publ.-Id: 8278 - Permalink


Molecular structure and electronic properties of poly(3-hexylthiophene)
Zen, A.; Saphiannikova, M.; Neher, D.; Grenzer, J.; Pietsch, U.; Asawapirom, U.; Scherf, U.;
Kein Abstract vorhanden.
  • Lecture (Conference)
    DPG Frühjahrstagung, 04.-09.03.2005, Berlin, Germany

Publ.-Id: 8277 - Permalink


On the stability of boundary layer flows controlled by Lorentz forces
Albrecht, T.; Mutschke, G.; Grundmann, R.;
We investigate numerically the transition to turbulence in a flat-plate boundary layer controlled by electromagnetic forces. The fluid considered is incompressible, Newtonian and low conductive. Similar to boundary layer suction, when applying a steady, wall-parallel, and streamwise orientated Lorentz force as suggested by Gailitis and Lielausis [1] in the early 1960s, the Blasius velocity profile is transformed to an exponential one gaining a critical Reynolds number which is increased by two orders of magnitude.

Two and three dimensional direct numerical simulation (DNS) of both linear and nonlinear stages of the transition process were performed, as well as a linear stability analysis (LSA) of the intermediate velocity profiles. DNS and also LSA results confirm the expected increased stability of the controlled flow. Depending on Lorentz force strength transition to turbulence is delayed or even stopped by either damping primary instability, or, in the nonlinear case, by suppressing the emerge of Omega-vortices which usually preceeds the breakdown to turbulence. Surprisingly, both DNS and LSA results suggest interesting linear stability characteristics of the intermediate velocity profiles.

In DNS (Re based on inflow displacement thickness is 360), to initiate transition, small amplitude disturbances are introduced near the inflow boundary, forming Tollmien-Schlichting waves (TSW) which grow and decay in uncontrolled case corresponging to linear stability theory. When applying a Lorentz force, all investigated TSW are damped. The decay rate is maximum in a region near the onset of control and decreases as the velocity profile evolves towards the exponential shape. This observation could suggest that in the intermediate region there are profiles more stable than the exponential one, although we are aware that from these decay rates one cannot conclude directly the stability of a velocity profile, notably its critical Reynolds number. However, our assumption is confirmed by LSA results where critical Reynolds numbers of intermediate profiles are found to be larger than for the exponential profile.

References:

1. A. Gailitis, O. Lielausis , „On a possibility to reduce the hydrodynamic resistance of a plate in an electrolyte,“ Applied Magnetohydrodynamics, Reports of the Physics Institute Riga, v. 12, p. 143-146, 1961
Keywords: boundary layer, flow stability, flow control, magneto-hydrodynamics
  • Lecture (Conference)
    7th World Congress on Computational Mechanics, 16.-22.07.2006, Los Angeles, California, United States

Publ.-Id: 8276 - Permalink


Observation of the growth and microstructural development of MAX phase Ti2AlN thin films during magnetron sputtering using synchrotron radiation
Schell, N.; Beckers, M.; Martins, R. M. S.; Mücklich, A.; Möller, W.;
Kein Abstract vorhanden.
  • Lecture (Conference)
    AVS 52nd International Symposium & Exhibition, 30.10.-04.11.2005, Boston, USA

Publ.-Id: 8275 - Permalink


Electromagnetic control of separation at hydrofoils
Mutschke, G.; Weier, T.; Gerbeth, G.; Albrecht, T.; Grundmann, R.;
Lorentz forces originating from surface-mounted actuators of permanent magnets and electrodes in weakly conducting fluids like seawater can be used to control flow separation at hydrofoils [1].
As induction effects are typically weak, external currents have to be applied to achieve control. An alternating arrangement of electrodes and magnets is considered which creates a mainly streamwise Lorentz force that is exponentionally decaying in wall-normal direction. As spanwise influences are supposed to be small, the problem is treated as two-dimensional in the following.
We investigate control by steady forcing at the suction side and by oscillatory forcing near the leading edge of symmetric foils, mostly in the post-stall regime. Similarities to the onventional method of oscillatory blowing for separation control do exist [2].
The numerical results presented cover direct numerical simulations based on a highly accurate spectral element method in the laminar flow regime in order reveal basic control phenomena as well as simulations using turbulence modelling at higher Reynolds numbers which are closer to possible naval application.
Although strong-enough steady control is able to suppress separation completely, appropriate time-periodic control turns out to be more effective for finite lift-enhancement when comparing the energetical effort. Optimum control frequencies are found, typical flow structures are analyzed, and "lock-in" phenomena with the natural shedding process are discussed [3]. The scaling behaviour of the energetical effort is compared with recent experimental results [4].

References:

1. T.Weier, G.Gerbeth, G.Mutschke, O.Lielausis, G.Lammers, "Control of Flow Separation using electromagnetic Forces",
Flow, Turbulence and Combustion 71 (2003) 5-17.
2. D.Greenblatt, I.J.Wygnanski, "The control of flow separation by periodic excitation",
Prog. Aero. Sci. 36 (2000) 487-545.
3. G.Mutschke, G.Gerbeth, T.Albrecht, R.Grundmann, "Separation Control at Hydrofoils using Lorentz
Forces", European Journal of Mechanics/B - Fluids, 2006, in press.
4. T.Weier, G.Gerbeth, "Control of separated Flows by time-periodic Lorentz Forces",
European Journal of Mechanics/B - Fluids 23(2004) 835-849.
Keywords: flow control, magneto-hydrodynamics
  • Lecture (Conference)
    7th World Congress on Computational Mechanics., 16.-22.07.2006, Los Angeles, California, United States

Publ.-Id: 8274 - Permalink


Comparing the growth of magnetron sputter deposited Ti-Al-N and Ni-Ti thin layers by in-situ x-ray diffraction
Martins, R. M. S.; Beckers, M.; Mücklich, A.; Schell, N.; Silva, R. J. C.; Braz Fernandes, F. M.;
Kein Abstract vorhanden.
  • Lecture (Conference)
    EUROMAT 2005, 05.-08.09.2005, Prague, Czech Republic

Publ.-Id: 8273 - Permalink


Characterization of magnetron Sputtered Ni-Ti thin films by in-situ x-ray diffraction and complementary ex-situ techniques
Martins, R. M. S.; Beckers, M.; Mücklich, A.; Schell, N.; Silva, R. J. C.; Braz Fernandes, F. M.;
Kein Abstract vorhanden.
  • Lecture (Conference)
    EUROMAT 2005, 05.-08.09.2005, Prague, Czech Republic

Publ.-Id: 8272 - Permalink


In-situ observation of Ni-Ti thin film growth by synchrotron radiation scattering
Martins, R. M. S.; Braz Fernandes, F. M.; Silva, R. J. C.; Beckers, M.; Schell, N.;
Kein Abstract vorhanden.
  • Lecture (Conference)
    MATERIALS 2005 (III International Materials Symposium), 20.-23.03.2005, Aveiro, Portugal

Publ.-Id: 8271 - Permalink


Structural in-situ investigations of shape memory alloy (SMA) Ni-Ti thin films
Martins, R. M. S.; Schell, N.; Beckers, M.; Silva, R. J. C.; Braz Fernandes, F. M.;
Kein Abstract vorhanden.
  • Lecture (Conference)
    ESRF User's Meeting 2005, 08.-09.02.2005, Grenoble, France

Publ.-Id: 8270 - Permalink


Microstructure of expended austenite in ion-nitride AISI 316L single crystals
Reviere, J. P.; Templier, C.; Declermy, A.; Redjal, O.; Chumlyakov, Y.; Abrasonis, G.;
wird nachgereicht
Keywords: stainless steel, singel crystal, ion nitriding
  • Lecture (Conference)
    14th International Conference on Surface Modification of Materials by Ion Beams, 05.-09.09.2005, Kusadasi, Turkey

Publ.-Id: 8269 - Permalink


Analysing the growth of metal nanoparticles by in-situ ellipsometry
Oates, T. W. H.;
wird nachgereicht
Keywords: silver, nanoparticles, in-situ ellipsometry
  • Lecture (others)
    J.A. Woolham Spectroscopic Ellipsometry Application Seminar, 11.-12.10.2005, Darmstadt, Deutschland

Publ.-Id: 8268 - Permalink


Optical properties of silver nanoparticles on polymer films
Oates, T. W. H.; Mücklich, A.;
wid nachgereicht
Keywords: silver films, in situ ellipsometry
  • Lecture (Conference)
    2nd International Workshop on Polymer/Metal nanocomposites, 11.09.2005, Geesthacht, Deutschland

Publ.-Id: 8267 - Permalink


In-situ spectroscopic ellipsometry determination of morphological and electronic properties of plasma deposited untra-thin metal films
Oates, T. W. H.; Mücklich, A.; Ryves, L.; Bilek, M. M. M.; Mckenzie, D. R.; Mcculloch, D. G.; Burgmann, F. A.;
wird nachgereicht
Keywords: metal films, in-situ ellipsometry
  • Lecture (Conference)
    International Conference on Metallurgical Coatings and Thin Films, 04.-09.05.2005, San Diego, USA

Publ.-Id: 8266 - Permalink


Ultrathin metal film physical propertiesdetemined by in-situ spectroscopic ellipsometry
Oates, T. W. H.; Ryves, L.; Bilek, M. M. M.; Mücklich, A.; Mckenzie, D. R.;
wird nachgereicht
Keywords: metal film properties, in-situ ellipsometry
  • Lecture (Conference)
    Annual Meeting, 18.03.2005, Berlin, Deutschland

Publ.-Id: 8265 - Permalink


Aromatic clustering processes in C and CNx thin films during ion beam sputtering and ion beam deposition
Abrasonis, G.; Gago, R.; Czigany, Z.; Mücklich, A.; Jimenez, I.; Radnoczi, G.; Kolitsch, A.; Möller, W.;
wird nachgereicht
Keywords: CNx
  • Lecture (Conference)
    7th Biennal Workshop "Fullernes and Atomic Clusters", 27.06.-01.07.2005, St. Peterburg, Rußland

Publ.-Id: 8264 - Permalink


Deposition by ion beam sputtering of CNx thin films: the influence of the composition of the sputering ion beam and temperature
Abrasonis, G.; Gago, R.; Vinnichenko, M.; Kreissig, U.; Mücklich, A.; Kolitsch, A.; Möller, W.;
Abtrakt wird nachgereicht
Keywords: ion beam sputtering, CNx
  • Lecture (Conference)
    Workshop "Oberflächentechnologie mit Plasma- und IOnenstrahlprozessen", 16.-18.03.2005, Mühlleithen, Deutschland

Publ.-Id: 8263 - Permalink


Synthesis and in-situ ellipsometric monotoring of Ti/C nanostructured multilayers uisng a high-current, dial source pulsed cathodic arc
Ryves, L.; Bilek, M. M. M.; Oates, T. W. H.; Tarrant, R. N.; Mckenzie, D. R.; Burgmann, F. A.; Mcculloch, D. G.;
Multilayered materials have been shown to enhance mechanical properties compared to single-phase materials. In this paper, we describe the deposition of Ti/C multilayered systems using a novel high current pulsed cathodic arc system with dual cathodes. We have chosen this system because titanium forms a ductile crystalline layer (which can be hardened by alloying with carbon) and carbon forms an amorphous layer (which can be tailored from soft sp2 to hard sp3 material). The mechanical properties of both layers can thus be varied over a wide range. The multilayer deposition was monitored with in-situ spectroscopic ellipsometry to accurately determine the thickness and optical constants of the individual layers. Important information regarding film nucleation and growth in the interfacial regions is deduced from the ellipsomteric data. The film thicknesses determined from the ellipsometric analysis are compared with cross-sectional transmission electron microscopy (TEM) images.
Keywords: TiC, cathodic arc, in-situ ellipsometry
  • Thin Solid Films 482(2005), 133-137

Publ.-Id: 8262 - Permalink


Ion-implantation induced phase transformation in carbon and boron nitride thin films
Oates, T. W. H.; Ryves, L.; Burgmann, F. A.; Abendroth, B.; Bilke, M. M. M.; Mckenzie, D. R.; Mcculloch, D. G.;
The mechanism behind energetic ion impact induced stress reduction in highly stressed tetrahedral amorphous carbon and cubic boron nitride thin films is investigated by real time in situ spectroscopic ellipsometry and ex situ electron microscopy. Highly stressed carbon and boron nitride films were grown by filtered cathodic vacuum arc and RF magnetron sputtering, respectively. The films were then implanted by 5–10 keV argon ions and the film optical properties and thickness monitored in situ by spectroscopic ellipsometry. In both cases the films were observed to expand due to a reduction in the density of the ion-modified layer. Cross-sectional transmission electron microscopy and electron energy loss spectroscopy of the carbon films showed that this reduction in density is associated with a conversion of diamond-like bonding to graphite-like bonding. In situ stress measurements performed on the boron nitride films revealed a simultaneous reduction in stress with expansion of the material.
Keywords: phase transformation, CN, BN, iom implantation
  • Diamond and Related Materials 14(2005)8, 1395-1401

Publ.-Id: 8261 - Permalink


Accurate determination of optical and electronic properties ol ultra-thin silver films for biosensor applications
Oates, T. W. H.; Ryves, L.; Bilek, M. M. M.; Mckenzie, D. R.;
Ultra-thin metal films are widely utilised for surface-enhanced Raman scattering and surface adsorption spectroscopy. We present in situ spectroscopic ellipsometry investigations of the growth of ultra-thin silver films, from island growth through percolation and continuous film growth. Silver films are deposited using a pulsed filtered cathodic vacuum arc, which provides precise control and reproducibility of the film growth conditions. Plasmon polariton resonances are determined for the growing islands below the percolation threshold. As the surface coverage increases a second oscillator, attributed to bulk plasma resonances, is required to accurately model the ellipsometric data. Post-deposition optical and electronic changes are observed for island films and the origins of these changes are investigated using the ellipsometric data.
Keywords: biosensors, silver
  • Sensors and Actuators B 109(2005), 146-152

Publ.-Id: 8260 - Permalink


Cross linking polyurethane coatings on vascular stents for enhanced X-ray contrasts
Kondyurin, A.; Romanova, V.; Begishev, V.; Kondyurina, I.; Günzel, R.; Maitz, M. F.;
A coating of polyurethaneurea was made from a solution on the surface of metal stents. The influence of cleaning, etching, chemical and ion beam modification (plasma immersion ion implantation) of the metal surface on the adhesion strength of the polyurethaneurea was analysed. Polyurethaneurea films imbedded with tantalum particles as a radiopaque filler maintained their strength and elasticity and produced clear X-ray contrast images of vascular stents
Keywords: stenst, x-ray contrast, polyurethane
  • Journal of Bioactive and Compatible Polymers 20(2005), 77-93

Publ.-Id: 8259 - Permalink


Efficient oxidation protection of gamma-TiAl alloys by ion implantation of halogens
Yankov, R.; Richter, E.; Donchev, A.; Schütze, M.;
wird nachgereicht
Keywords: ion implantation, TiAl alloys, halogene, oxidation resistance
  • Lecture (Conference)
    International Conference on Novel Applications for Surface Modification, 18.-21.09.2005, Chester, United Kingdom

Publ.-Id: 8258 - Permalink


Phase formation, corrosion behaviour and mechanical properties of boron implanted near-alpha titanium alloy
Tsyganov, I.; Richter, E.;
wird nachgereicht
Keywords: titanium alloys, ion implantation, boron, phase formation
  • Poster
    14.th International Conference on Surface Modification of Materials by Ion Beams, 05.-09.09.2005, Kusadasi, Turkey

Publ.-Id: 8257 - Permalink


Ion-irradiation-induced chemical ordering of intermetallic alloys – Predictions based on atomistic simulations
Heinig, K.-H.; Röntzsch, L.; Bernas, H.;
The L10 transition temperatures for chemical ordering in FePd and FePt intermetallic alloys may be substantially reduced by ion irradiation [1]. Alignment of the strong magnetic axis normal to the surface layer was achieved. Recently, we showed via kinetic Monte Carlo simulations [2] that (i) ion-beam-induced reduction of the L10 transition temperature may be understood in terms of vacancy-assisted atomic ordering and that (ii) superstructure alignment results from a small initial directional short range order (DSRO).
In this contribution (i) we present systematic studies of the ion-irradiation-induced L10 ordering in thin layers, (ii) we predict the evolution of chemical ordering in layers with well-designed initial DSRO, (iii) we study in non-stoichiometric alloys (e.g. Fe1-xPdx) the competition of L10 ordering (FePd) with L12 ordering (Fe3Pd), (iv) we extend our atomistic simulations of ion-irradiation-induced ordering to more complex systems like Heusler alloys and (v) we evaluate the influence of interfaces in nanostructures on the ordering process.
[1] D. Ravelosona, C. Chappert, V. Mathet and H. Bernas, Appl. Phys. Lett. 76 (2000) 236.
[2] H. Bernas, J.-Ph. Attane, K.-H. Heinig, D. Halley, D. Ravelosona, A. Marty, P. Auric, C. Chappert, Y. Samson, Phys. Rev. Lett. 91 (2003) 77203.
Keywords: ion irradiation, chemical ordering, intermetallic alloys, kinetic Monte Carlo simulation
  • Lecture (Conference)
    14th International Conference on Ion Beam Modification of Materials (IBMM), 04.-10.09.2004, Monterey, USA

Publ.-Id: 8256 - Permalink


Multi-dot floating-gates in MOSFETS for nonvolatile memories – their ion beam synthesis and morphology
Müller, T.; Heinig, K.-H.; Bonafos, C.; Coffin, H.; Benassayag, G.; Schamm, S.; Zanchi, G.; Claverie, A.; Tencé, M.; Colliex, C.;
Scalability and performance of current flash memories can be improved substantially by novel devices based on Multi-Dot Floating Gate MOSFETs. The multi-dot layer in the very thin gate oxide can be fabricated CMOS-compatibly by ion beam synthesis (IBS). Here, we present both experimental and theoretical studies on IBS of multi-dot layers consisting of Si nanocrystals (NCs). The NCs are produced by ultra low energy Si+ ion implantation, which causes a high Si supersaturation in the shallow implantation region. During post-implantation annealing, this su-persaturation leads to phase separation of the excess Si from the SiO2. Till now, the study of this phase separation suffered from the weak z contrast between Si and SiO2 phases in Transmission Electron Microscopy (TEM). Here, this imaging problem is solved by Energy Filtered Scanning Transmission Electron Microscopy (EFSTEM). Additionally, kinetic lattice Monte Carlo simula-tions of Si phase separation have been performed and compared with EFSTEM images. It has been predicted theoretically that the morphology of the multi-dot Si floating gate changes with increasing ion fluence from isolated, spherical NCs to percolated spinodal Si pattern. These pattern agree remarkably with EFSTEM images. However, the predicted fluence for spinodal pattern is lower than the experimental one. Because oxidants of the ambient atmosphere penetrate into the as-implanted SiO2, a substantial fraction of the implanted Si is lost due to oxidation.
Keywords: ion beam synthesis, nonvolatile memories, process simulation
  • Lecture (Conference)
    DPG Conference, Regensburg, 08.-12.03.2004, Regensburg, Germany

Publ.-Id: 8255 - Permalink


Domain structure during magnetization reversal of PtMn/CoFe exchange bias micro-patterned lines
Liedke, M. O.; Potzger, K.; Bothmer, A.; Hillebrands, B.; Rickart, M.; Freitas, P. P.; Fassbender, J.ORC
The magnetic domain configuration and the magnetization reversal behavior of micropatterned exchange bias elements were investigated by means of magnetic force microscopy. In addition to the unidirectional anisotropy the shape anisotropy determines the overall magnetization reversal behavior. In order to modify the ratio between both anisotropy contributions the exchange bias field strength was reduced by means of 5 keV He+ ion irradiation. For the as-prepared samples a mono-domain magnetization state with the magnetization direction aligned along the exchange bias field direction was found regardless of the element shape. After irradiation the unidirectional anisotropy contribution is reduced and hence the previously homogeneous magnetization state brakes up into small domains with 360° domain walls in between. The appearance of these domain walls, which was mainly observed for the descending branch of the magnetization reversal, is found to depend strongly on the structure width and orientation.
Keywords: exchange bias, pattering, ion irradiation
  • Poster
    Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 27.-31.03.2006, Dresden, Deutschland
  • Journal of Applied Physics 100(2006)043918
    DOI: 10.1063/1.2335805

Publ.-Id: 8254 - Permalink


Computer experiments of nanoshaping
Heinig, K.-H.;
Abstract not available.
Keywords: heavy-ion irradiation, nanometal shaping, atomistic computer simulation
  • Invited lecture (Conferences)
    International Workshop on Ion Beam Shaping of Nanometals, 17.12.2004, Amsterdam, Netherlands

Publ.-Id: 8253 - Permalink


Atomistic simulations of nanofabrication with ion beams
Heinig, K.-H.; Müller, T.; Röntzsch, L.;
Kinetic Lattice Monte Carlo (KLMC) simulations can predict reaction pathways for the ion-beam-assisted fabrication of functional nanostructures. Three examples will be presented, which are based on different kinds of ion-solid-interaction: (i) High-dose ion implantation of species which are immiscible within the surface layer produces a far-from-equilibrium state. A post-implantation thermal treatment activates phase separation. According to predictive simulations the location and size of the nanoclusters can be controlled by boundary conditions (i.e. interfaces) and annealing parameters. (ii)Ion irradiation through an interface between immiscible phases leads to a thin interface film of an unstable alloy which is formed by collisional mixing. KLMC simulations of phase separation in this film predicts a self-organised/self-aligned nanocluster formation . (iii) Ion irradiation can produce chemical order in intermetallic alloys at low temperature. KLMC simulations show that chemical ordering requires mobile vacancies. Without irradiation the formation of vacancies requires high temperatures at which the ordered phase might be unstable. Thus, thermally activated ordering of some intermetallics like Heusler alloys is difficult, whereas ion irradiation orders them.
Process simulations of phase separation in Si implanted gate oxides and at ion irradiated Si/SiO2 interfaces have been performed in the framework of an European GROWTH, where a novel non-volatile memory transistor was developed. Irradiation-induced ordering studies are focussed on future magnetic recording materials (FePt) and materials for spintronics.
Keywords: nanostructures, ion beam processing, atomistic computer simulations
  • Invited lecture (Conferences)
    7th International Conference on Computer Simulation of Radiation Effects in Solids (COSIRES), 28.06.-02.07.2004, Helsinki, Finland

Publ.-Id: 8252 - Permalink


Manipulating magnetic nanostructures by ion irradiation: patterning and ordering
Bernas, H.; Chappert, C.; Devolder, T.; Ravelosona, D.; Ferre, J.; Jamet, J. P.; Chen, Y.; Samson, Y.; Marty, A.; Halley, D.; Attane, J.; Heinig, K.-H.; Strobel, M.; Kaitasov, O.; Gautrot, S.;
Abstract not available.
Keywords: Magnetic nanostructures, ion irradiation, atomistic computer simulation
  • Invited lecture (Conferences)
    IWINP Conference, 11.-13.03.2004, Shanghai, China

Publ.-Id: 8251 - Permalink


Self-organisation of nanostructures driven by ion irradiation
Möller, W.; Heinig, K.-H.; Müller, T.; Röntzsch, L.; Schmidt, B.;
For the generation of nanostructures for novel applications such as in electronics and optics, self-organisation under large-area processing appears to be the most promising way in terms of cost-efficiency. However, so far it has turned out to be extremely difficult to fulfil the requirements of macroscopic-range ordering, narrow particle size distribution, and, in the case of buried nanostructures, in-depth location control. The introduction of ion beams, which are widely established in industrial production, into this area is challenging but hampered by the statistical processes of ion slowing down and the physico-chemistry of precipitation and ripening during ion beam synthesis. These processes will, in general, result in disorded rather than ordered structures.
In the present paper it is demonstrated that, nevertheless, ion beam techniques may contribute to ordering. Different mechanism of ion-driven self-organisation are available for this purpose: (i) For ensembles of nanoclusters in a matrix material, ion-beam mixing may cause an inversion of the Ostwald ripening effect and thus drive the system towards a narrow particle size distribution. (ii) Processes of ion mixing, diffusion and precipitation at interfaces may result in a well-defined location of a nanocluster sheet close to the interface. (iii) Ordering of intermetallic nanostructures may be achieved at low temperature by ion-induced generation of mobile point defects.
For these phenomena, both theoretical predictions and experimental evidence will be presented. In addition, the results will be related to promising applications, such as for new non-volatile memories and novel media for magnetic recording.
Keywords: nanostructures, ion irradiation, inverse Ostwald ripening, theory
  • Invited lecture (Conferences)
    IWINP Conference, 11.-13.03.2004, Shanghai, China

Publ.-Id: 8250 - Permalink


Manipulation of 2D arrays of Si nanocrystals embedded in thin SiO2 layers by low energy ion implantation
Bonafos, C.; Carrada, M.; Cherkashin, N.; Coffin, H.; Chassaing, D.; Benassayag, G.; Claverie, A.; Müller, T.; Heinig, K.-H.; Perego, M.; Fanciulli, M.; Dimitrakis, P.; Normand, P.;
In silicon nanocrystal based metal–oxide–semiconductor memory structures, tuning of the electron tunneling distance between the Si substrate and Si nanocrystals located in the gate oxide is a crucial requirement for the pinpointing of optimal device architectures. In this work it is demonstrated that this tuning of the ‘‘injection distance’’ can be achieved by varying the Si1 ion energy or the oxide thickness during the fabrication of Si nanocrystals by ultralow-energy silicon implantation. Using an accurate cross-section transmission electron microscopy ~XTEM! method, it is demonstrated that two-dimensional arrays of Si nanocrystals cannot be positioned closer than 5 nm to the channel by increasing the implantation energy. It is shown that injection distances down to much smaller values ~2 nm! can be achieved only by decreasing the nominal thickness of the gate oxide. Depth profiles of excess silicon measured by time-of-flight secondary ion mass spectroscopy and Si nanocrystal locations determined by XTEM are compared with Monte-Carlo simulations of the implanted Si profiles taking into account dynamic target changes due to ion implantation, ion erosion, and ion beam mixing. This combination of experimental and theoretical studies gives a safe explanation regarding the unique technological route of obtaining Si nanocrystals at distances smaller than 5 nm from the channel: the formation of nanocrystals requires that the interface mixing due to collisional damage does not overlap with the range profile to the extent that there is no more a local maximum of Si excess buried in the SiO2 layer.
Keywords: Si nanocrystals, ion implantation, nonvolatile memories, process modelling
  • Journal of Applied Physics 95(2004)10, 5696-5702

Publ.-Id: 8249 - Permalink


Growth and Taming of Nanostructures with Ion Beams
Heinig, K.-H.;
Nanocluster ensembles and nanowires can be synthesised in surface layers of various substrates by high dose ion implantation. A detailed understanding of the complex processes like ion deposition and subsequent phase separation has been achieved by atomistic computer simulations. This understanding helps to tailor nanostructures for applications. Examples are the synthesis of very narrow Si nanocluster layers in SiO2 for nanodot memories and of ion-beam-shaped metallic nanorods for photonics. Recently it has been demonstrated that ion beams can be also used to change properties of nanostructures drastically. Thus, at elevated temperatures, irradiation of nanocluster ensembles results in a narrowing of the size distribution, which can be described as “inverse Ostwald ripening”. Irradiation of single-crystalline but chemically disordered nanostructures assists chemical ordering of alloys like FePt, which has a very high magnetic anisotropy and is, therefore, a favorite material for future magnetic recording.
Keywords: Nanostructures, ion beam synthesis, inverse Ostwald ripening, nanowires, atomistic computer simulation
  • Lecture (others)
    Seminar at the RWTH, 26.01.2006, Aachen, Germany

Publ.-Id: 8248 - Permalink


Ion Beam Synthesis and Processing of Nanostructures
Heinig, K.-H.;
An overview of our recent research on ion beam synthesis and processing of nanostructures will be presented. Predictions of atomistic simulations on reaction pathways of nanostructure formation and processing will be compared with experimental results. (i) delta-layers of nanoclusters were formed by ion beam mixing and phase separation at interfaces. In an industrial environment, these delta-layers have been proven to be good candidates as distributed charge storage centers in future FLASH memories. (ii) Nanowires formed by focussed ion implantation and other techniques can be processed into nanocluster chains and other functional structures for electronics and photonics. (iii) Metallic nanospheres can be shaped by swift heavy ions into rods and wires, which may have interesting applications in photonics.
Keywords: Ion beam synthesis, nanostructures, atomistic computer simulation
  • Lecture (others)
    Seminar an der Gesellschaft für Schwerionenforschung (GSI), 15.11.2005, Darmstadt, Germany

Publ.-Id: 8247 - Permalink


Ion beam shaping of nanometals
Vredenberg, A.; Polman, A.; Kooi, B. J.; Vandillen, T.; Heinig, K.-H.; Toulemonde, M.;
We present a novel type of ion-beam-induced deformation of metal nano-objects. Under heavy-ion irradiation Au nanospheres in a silica matrix first elongate, and at higher dodes combine into nanowires that continue to grow under the ion beam. Such anisotropically shaped metal nanoparticles may have great potential in a wide range of fields. For example, nanorods exhibit a split plasmon resonance, with one of the bands shifting as far as the infrared. Arrays of such nanoparticles have great potential as nanophotonic guides in the (infra)red, an important telecom wavelength regime, but outside the range of plasmon resonances of spherical particles. Our samples consist of Au spheres (15 nm) in a single plane 150 nm below the surface of the silica matrix. At low dose (2x10^14 cm^-2) the nanospheres elongate into nanorods, with their long axis oriented in the beam direction (also verified by changing the ion incidence angle). At high doses, nanowire form, still parallel with the ion path. This intriguing effect (the wires must have formed from many primary particles) will be discussed in detail, along with the elongation mechanism, based on kinetic Monte Carlo computer experiments. We also observe a clear threshold in the electronic energy loss. This threshold can be explained, assuming that the ion track have to be continuous for elongation to occur.
Keywords: ion irradiation, shaping of nanoparticles, atomistic computer simulation
  • Invited lecture (Conferences)
    Materials Research Society 2005 FALL Meeting, Symp. OO: Growth, Modification, and Analysis by Ion Beams at the Nanoscale, 28.11.-01.12.2005, Boston, USA

Publ.-Id: 8246 - Permalink


Halogen PIII for high-temperature oxidation protection of TiAl
Richter, E.; Yankov, R.; Möller, W.; Donchev, A.; Schütze, M.;
wird nachgereicht
Keywords: TiAl high temprature oxidation resistance, plasma immersion ion implantation, halogen
  • Poster
    8th International Workshop on Plasma-Based Ion implantation and Deposition, 20.-25.09.2005, Chengdu, China

Publ.-Id: 8245 - Permalink


Modelling of ion-driven nanostructures
Heinig, K.-H.;
Recently it has been demonstrated that ion irradiation of nanostructures, interfaces and ultrathin magnetic films can modify substantially the nanocluster size distribution [1], the spatial nanocluster alignment [2], the nanocluster shape [3] and the chemical order of metal alloys [4]. Furthermore, low-energy ion-erosion of semiconductor [5] and metal [6] surfaces can result in the formation and self-organization of nanostructures.
For all phenomena listed above (disregarding chemical ordering), ion-irradiation-activated interface/surface processes have been identified as the driving force. Thus, a fundamental understanding of the basic mechanisms of the interface/surface evolution under ion-irradiation might allow a controlled growth and a taming of properties of nanostructures.
This contribution will review theoretical studies and atomistic computer simulations which demonstrate that the above listed phenomena have the same origin: a competition of surface erosion or interface mixing on the one hand and diffusional processes on the other. The far-from-equilibrium processing of nanostructures can lead to exotic properties like “negative interface energy” and “inverse Ostwald ripening”.
[ 1] K.-H. Heinig, T. Müller, B.Schmidt, M. Strobel, W. Möller, Appl. Phys. A 77, 17–25 (2003).
[ 2] L. Röntzsch, K.-H. Heinig, and B. Schmidt, Mater. Sci. Semicond. Proc. 7, 357 (2004).
T. Müller, K.H. Heinig, and W. Möller, Appl. Phys. Lett. 81, 2373 (2002).
T. Müller, K.H. Heinig, W. Möller, C. Bonafos, H. Coffin, N. Cherkashin, G. Assayag,
S. Schamm, G. Zanchi, A. Claverie, M. Tencé, C. Colliex, Appl. Phys. Lett. 85, 2373 (2004).
[ 3] K.-H. Heinig, in Proc. Workshop „Ion Beam Shaping of Metal Nanoparticles“, ed. A. Polman, Amsterdam (Netherlands), Dec17 (2004).
[ 4] H. Bernas, J.-Ph. Attane, K.-H. Heinig, D. Halley, D. Ravelosona, A. Marty, P. Auric, C. Chappert, Y. Samson, Phys. Rev. Lett. 91, 077203 (2003).
[ 5] S. Facsko et al., Science 285, 1551 (1999).
[ 6] M. Strobel, K.H. Heinig, T. Michely, Surf. Sci. 486, 136 (2001).
T. Michely, M. Kalff, G. Comsa, M. Strobel, K.H. Heinig, Phys. Rev. Lett. 86, 2589 (2001).
Keywords: Nanostructures, ion irradiation, atomistic computer simulation
  • Invited lecture (Conferences)
    14th Int. summer school on Vacuum, Electron and Ion Technologies (VEIT2005), 12.-16.09.2005, Sunny Beach, Bulgarien

Publ.-Id: 8244 - Permalink


Improvement of the oxidation behaviour of TiAl-alloys by halogen treatment
Donchev, A.; Yankov, R.; Richter, E.; Schütze, M.;
wird nachgereicht
Keywords: halogen effect, TiAl, high temperature oxidation resistance
  • Poster
    European congress on advanced materials and processing EUROMAT´05, 05.-08.09.2005, Praha, Tchech Republic

Publ.-Id: 8243 - Permalink


Structural and optical properties of iron silicide formed by ion beam mixing
Ayache, R.; Boubelleou, A.; Eichhorn, F.; Richter, E.;
  • Poster
    E-MRS Fall Meeting, 11.09.2005, Warsawa, Poland

Publ.-Id: 8242 - Permalink


Fabrication of Si nanocrystals for nonvolatile memories using ion beams
Müller, T.; Heinig, K.-H.; Schmidt, B.; Röntzsch, L.; Stegemann, K.-H.;
Abstract is not available.
Keywords: ion implantation, nanocluster, atomistic computer simulations, nonvolatile memory
  • Invited lecture (Conferences)
    Intern. Workshop on Semiconductor Nanocrystals (SEMINANO), 10.-12.09.2005, Budapest, Hungary

Publ.-Id: 8241 - Permalink


Growth and taming of nanostructures with ion beams
Heinig, K.-H.; Müller, T.; Röntzsch, L.; Möller, W.;
Nanocluster ensembles and nanowires can be synthesised in surface layers of various substrates by high dose ion implantation. Atomistic computer simulation lead to a detailed understanding of ion deposition and subsequent precipitation [1]. Recently it has been demonstrated that ion beams can be also used to change properties of nanostructures drastically. Thus, at elevated temperatures, irradiation of nanocluster ensembles results in a narrowing of the size distribution, which can be described as “inverse Ostwald ripening” [2]. Irradiation of single-crystalline but chemically disordered nanostructures assists chemical ordering of alloys like FePt, which has a very high magnetic anisotropy in its well-ordered state and is, therefore, a favorite material for future magnetic recording [3]. And finally, metallic nano-spheres in SiO2 can be shaped into rods or even wires by high-energy ion irradiation [4].
This contribution will review theoretical studies and atomistic computer simulations on the phenomena listed above. It will be shown that all this phenomena have a common origin: the competition between ion beam induced disordering (interface mixing, defect generation, …) which drives the system far from equilibrium, and diffusion processes, which drives the system back towards the thermodynamic equilibrium.
[1] M. Strobel, K.-H. Heinig, W. Möller, Phys. Rev. B 64, 245422 (2001).
T. Müller, K.H. Heinig, and W. Möller, Appl. Phys. Lett. 81, 2373 (2002).
T. Müller, K.H. Heinig, W. Möller, C. Bonafos, H. Coffin, N. Cherkashin, G. Assayag,
S. Schamm, G. Zanchi, A. Claverie, M. Tencé, C. Colliex, Appl. Phys. Lett. 85, 2373 (2004).
[2] K.-H. Heinig, T. Müller, B.Schmidt, M. Strobel, W. Möller, Appl. Phys. A 77, 17–25 (2003).
[3] H. Bernas, J.-Ph. Attane, K.-H. Heinig, D. Halley, D. Ravelosona, A. Marty, P. Auric, C. Chappert, Y. Samson, Phys. Rev. Lett. 91, 077203 (2003).
[4] A. Vredenberg et al.; K.-H. Heinig, in Proc. Workshop „Ion Beam Shaping of Metal Nanoparticles“, ed. A. Polman, Amsterdam (Netherlands), Dec17 (2004).
Keywords: ion irradiation, nanostructures, atomistic computer simulation
  • Invited lecture (Conferences)
    International Symposium on Trends in Nanoscience: Structure and Functions, 08.-12.10.2005, Irsee, Germany

Publ.-Id: 8240 - Permalink


Ion-irradiation-induced chemical ordering of intermetallic alloys: predictions based on atomistic simulations
Heinig, K.-H.; Bernas, H.;
The L10 transition temperatures for chemical ordering in FePd and FePt intermetallic alloys may be substantially reduced by ion irradiation [1]. Alignment of the strong magnetic axis normal to the surface layer was achieved. Recently, we showed via kinetic Monte Carlo simulations [2] that (i) ion-beam-induced reduction of the L10 transition temperature may be understood in terms of vacancy-assisted atomic ordering and that (ii) superstructure alignment results from a small initial directional short range order (DSRO). In this contribution (i) we present systematic studies of the ion-irradiation-induced L10 ordering in thin layers, (ii) we predict the evolution of chemical ordering in layers with well-designed initial DSRO, (iii) we study in non-stoichiometric alloys (e.g. Fe1-xPdx) the competition of L10 ordering (FePd) with L12 ordering (Fe3Pd), and(iv) we evaluate the influence of interfaces in nanostructures on the ordering process.
[1] D. Ravelosona, C. Chappert, V. Mathet and H. Bernas, Appl. Phys. Lett. 76 (2000) 236.
[2] H. Bernas, J.-Ph. Attane, K.-H. Heinig, D. Halley, D. Ravelosona, A. Marty, P. Auric, C. Chappert, Y. Samson, Phys. Rev. Lett. 91 (2003) 77203
Keywords: atomistic computer simulation, intermetallic alloy, ion irradiation, chemical ordering
  • Lecture (Conference)
    DPG Conference, 04.-09.03.2005, Berlin, Germany

Publ.-Id: 8239 - Permalink


Mechanisms of ion beam shaping of metal nanoparticals
Heinig, K.-H.;
The functionality of nanoparticles can be extended further by shape anisotropy. Thus, for future hard disks, rod-like nanomagnets are more resistant against thermally activated spin flipping than spheres, and, for photonics, light is guided as surface plasmon-polariton along a chain of rods with less damping than along a chain of spheres.
Recently it has been shown [1] that Au nanospheres embedded in SiO2 can be shaped into rods (and even wires) by swift heavy ion irradiation. The underlying mechanisms are largely unknown. Van Dillen has proven [2] that the Trinkaus model [3], which describes successfully the ion beam shaping of dielectrics/semiconductors, can not be applied to ion beam shaping of metal nanoparticles.
Here, a consistent mechanism of ion beam shaping and nanowire ripening will be presented. Using the temperature-time profiles of ion tracks in SiO2 as delivered by Toulemonde [4], atomistic computer experiments performed with kinetic Monte-Carlo and Molecular Dynamics codes reproduce the experimental results [5]. Our comprehensive numerical studies facilitate a further optimisation of ion beam shaping.
[1] A. Vredenberg et al., Int. Conf. “Ion Beam Modification of Materials”, Monterey (USA), Sept. 5-10, 2004.
[2] T. van Dillen, Int. Workshop on “Ion Beam Shaping”, Amsterdam (Netherlands), Dec. 17, 2004.
[3] H. Trinkaus, J. Nucl. Mater. 223, 196 (1995).
[4] M. Toulemonde, Nucl. Instr. and Methods B66/67, 903 (2000), and private comm..
[5] K.-H. Heinig, Int. Workshop on “Ion Beam Shaping”, Amsterdam (Netherlands), Dec. 17, 2004.
Keywords: atomistic computer simulation, nanocluster, ion irradiation, shaping
  • Lecture (Conference)
    Materials Research Society 2005 FALL Meeting, Symp. OO: Growth, Modification, and Analysis by Ion Beams at the Nanoscale, 28.11.-01.12.2005, Boston, USA

Publ.-Id: 8238 - Permalink


Ion Beam Shaping of Nanometals
Vredenberg, A.; Polman, A.; Kooi, B. J.; Vandillen, T.; Heinig, K.-H.; Toulemonde, M.;
An abstract is not available.
Keywords: ion irradiation, nanocluster, shaping
  • Lecture (Conference)
    Sixth International Symposium Swift Heavy Ions in Matter, 28.-31.05.2005, Aschaffenburg, Germany

Publ.-Id: 8237 - Permalink


Manipulation of 2D Arrays of Si Nanocrystals by Ultra Low Energy Ion Beam Synthesis for non volatile memories applications
Bonafos, C.; Cherkashin, N.; Carrada, M.; Coffin, H.; Ben Assayag, G.; Schamm, S.; Dimitrakis, P.; Normand, P.; Perego, M.; Fanciulli, M.; Muller, T.; Heinig, K. H.; Argawal, A.; Claverie, A.;
In silicon nanocrystal (nc) based metal-oxide-semiconductor (MOS) memory structures a fine control of the Si nc location in the gate oxide is required for the pinpointing of optimal device architectures. In this work, we show how to manipulate and control the depth-position, size and surface density of two dimensional (2D) arrays of Si ncs embedded in thin (<10 nm) SiO2 layers, fabricated by ultra-low-energy (typically 1 keV) ion implantation and subsequent annealing. Particular emphasis is placed upon the influence of implantation and annealing conditions and oxide thickness on the nanocrystal characteristics (e.g. size, density) and the charge storage properties of associated MOS structures. Structural investigation is performed by using specific characterization methods including Fresnel imaging for the measurement of the injection distance between the substrate and the nc band, as well as spatially resolved Electron Energy Loss Spectroscopy using the spectrum-imaging mode of a Scanning Transmission Electron Microscope to evaluate the size distribution and density of the ncs.
Keywords: Nanocrystal ion-beam-synthesis memories
  • Materials Research Society Symposium Proceedings 830(2005), D5.2.1-D5.2.6

Publ.-Id: 8236 - Permalink


Hydrogen release and defect formation during heat treatments of SiNx:H/a-Si:H double passivation layer on c-Si substrate
Ulyashin, A. G.; Bentzen, A.; Diplas, S.; Suphellen, A.; Gunnaes, A. E.; Olsen, A.; Svensson, B. G.; Marstein, E. S.; Holt, A.; Grambole, D.; Sauar, E.;
The quality and temperature stability of surface passivation of silicon by a double layer consisting of a hydrogenated amorphous silicon thin film capped by a silicon nitride anti-reflection coating are studied. It is established that the passivation effect of the double layer can be significantly enhanced after short annealing for temperatures up to about 500 °C, whereas annealing at higher temperatures results in degradation of the passivation properties. It is found that the increased effective recombination lifetime after annealing at temperatures below 500 ºC results from hydrogen redistribution in the interface region. Furthermore, presence of interfacial structural defects formed due to hydrogen release at temperatures around 600 ºC, is believed to be the cause of the lifetime decrease after heat treatments at higher temperatures.
  • Poster
    2006 IEEE 4th World Conference on Photovoltaic Energy Conversion, 05.-12.05.2006, Hawaii, USA
  • Contribution to proceedings
    2006 IEEE 4th World Conference on Photovoltaic Energy Conversion, 05.-12.05.2006, Hawaii, USA
    IEEE Catalog Number 06CH37747C, 1-4244-0017-1, 1354-1357

Publ.-Id: 8234 - Permalink


Brillouin scattering and x-ray photoelectron studies of germanium nanoclusters synthesized in SiO2 by ion implantation
Zuk, J.; Krzyanowska, H.; Clouter, M. J.; Bromberek, M.; Bubert, H.; Rebohle, L.; Skorupa, W.;
Brillouin scattering and x-ray photoelectron spectroscopy (XPS) have been utilized to characterize Ge+-implanted thermal SiO2 layers on a Si substrate with subsequent annealing at 500 °C and 1100 °C. Sputtering depth profiling in conjunction with XPS studies have been applied to identify the chemical state of elemental Ge and GeO2 precipitations in the SiO2 matrices. The presence of a subsurface GeOx zone as predicted in kinetic 3-dimensional lattice simulations has been confirmed. It is concluded that the intermediate step of Ge oxide formation seems necessary for the creation of Ge nanoclusters. The Ge atomic concentrations obtained from XPS were used to compute the bulk and shear moduli, and consequently the surface acoustic wave (SAW) velocities, for the Ge/GeO2/SiO2 systems. These calculations confirm the character of SAW velocity softening as determined from the Brillouin scattering investigations.
  • Journal of Applied Physics 96(2004)9, 4952-4959

Publ.-Id: 8233 - Permalink


A new flash lamp apparatus for applications to millisecond heat treatments
Anwand, W.;
not available
  • Lecture (Conference)
    HeT-SiC-05, International topical workshop on heteroepitaxy of 3C-SiC on silicon and its application to sensor devices, 26.04.-01.05.2005, Krippen, Deutschland

Publ.-Id: 8232 - Permalink


Positron annihilation investigation in ion-implanted Yttria-stabilized zirconia
Grynszpan, R. I.; Brauer, G.; Anwand, W.;
Implantation with a variety of sub-MeV ions (He, Ar, Xe, O, and I) were performed on cubic single crystals of yttria-stabilized zirconia in order to assess the capability of such material to withstand high fluences as a confinement matrix for nuclear waste. In this work, we confronted the results of both Doppler Broadening using slow positron implantation spectroscopy (DB-SPIS) and the Rutherford Backscattering/Channeling spectroscopy (RBS-C) which are sensitive to lattice defects almost opposite in nature. In spite of their difference in defect specific sensitivity, and except for a precursory damage production stage almost exclusively exhibited by SPIS for very low doses (< 0.1 dpa), either techniques show a similar fluence dependence, which exhibits 3 stages starting respectively around 0.1, 2 and 3 dpa, regardless of the damaging ion. However, owing to the stage I plateau displayed in the variation of the DB-SPIS lineshape parameter, we were able to estimate an ion-mass dependence of the critical size of open-volume defects reached before the production of new predominant defects.
  • Invited lecture (Conferences)
    MRS Fall Meeting 2005, 28.11.-02.12.2005, Boston/MA, USA
  • Contribution to proceedings
    MRS Fall Meeting 2005, 28.11.-02.12.2005, Boston/MA, USA
    Growth, Modification and Analysis by Ion Beams at the Nanoscale 2006, 908E

Publ.-Id: 8231 - Permalink


P-type doping of zinc oxide obtained by arsenic ion implantation
Braunstein, G.; Muraviev, A.; Saxena, H.; Dhere, N.; Richter, V.; Kalish, R.; Benndorf, G.; Wenckstern, V. H.; Lorenz, M.; Brauer, G.;
not available
  • Lecture (Conference)
    Materials Research Society (MRS), 2005 Fall Meeting, 28.11.-02.12.2005, Boston/MA, USA

Publ.-Id: 8230 - Permalink


The (upcoming) digital real-time positron lifetime measurement of EPOS
Krille, A.; Krause-Rehberg, R.; Becvar, F.; Brauer, G.;
not available
  • Lecture (Conference)
    Scientific Workshop “The application of high intensity positron beam techniques and digital lifetime positron spectroscopy in materials science”, 17.11.2005, Bergen, Netherlands

Publ.-Id: 8229 - Permalink


The intense positron source EPOS at Research Center Rossendorf
Krause-Rehberg, R.; Brauer, G.; Sachert, S.; Krille, A.; Bondarenko, V.;
not available
  • Lecture (Conference)
    Scientific Workshop “The application of high intensity positron beam techniques and digital lifetime positron spectroscopy in materials science”, 17.-18.11.2005, Bergen, Netherlands

Publ.-Id: 8228 - Permalink


Slow positron implantation spectroscopy - a tool to characterize vacancy-type damage
Anwand, W.; Brauer, G.;
not available
  • Lecture (Conference)
    First Humboldt-institute-partnership workshop an der Universität Göttingen (Institut für Materialphysik), 24.-26.10.2005, Göttingen, Deutschland

Publ.-Id: 8227 - Permalink


Indications for a low quartz structure at the SiO2/Si interface revealed by positron annihilation spectroscopies
Brauer, G.;
not available
  • Lecture (Conference)
    First Humboldt-institute-partnership workshop an der Universität Göttingen (Institut für Materialphysik), 24.-26.10.2005, Göttingen, Deutschland

Publ.-Id: 8226 - Permalink


Die intensive Positronenquelle EPOS an der Strahlungsquelle ELBE im FZ Rossendorf
Krause-Rehberg, R.; Brauer, G.;
nicht vorhanden
  • Lecture (Conference)
    Arbeitstreffen „Komitee für Forschung mit Sonden und Ionen (KFSI)“, 06.-07.10.2005, Neubiberg, Deutschland

Publ.-Id: 8225 - Permalink


Optimization of In-Beam Positron Emission Tomography for Monitoring Heavy Ion Tumor Therapy
Crespo, P.;
In-beam positron emission tomography (in-beam PET) is currently the only method for an in-situ monitoring of highly tumor-conformed charged hadron therapy. In such therapy, the clinical effect of deviations from treatment planning is highly minimized by implementing safety margins around the tumor and selecting proper beam portals. Nevertheless, in-beam PET is able to detect eventual, undesirable range deviations and anatomical modifications during fractionated irradiation, to verify the accuracy of the beam portal delivered and to provide the radiotherapist with an estimation of the difference in dosage if the treatment delivered differs from the planned one. In a first study within this work, a set of simulation and fully-3D reconstruction routines shows that minimizing the opening angle of a cylindrical camera is determinant for an optimum quality of the in-beam PET images. The study yields two favorite detector geometries: a closed ring or a dual-head tomograph with narrow gaps. The implementation of either detector geometry onto an isocentric, ion beam delivery (gantry) is feasible by mounting the PET scanner at the beam nozzle. The implementation of an in-beam PET scanner with the mentioned detector geometries at therapeutic sites with a fixed, horizontal beam line is also feasible. Nevertheless, knowing that previous in-beam PET research in Berkeley was abandoned due to detector activation (Bismuth Germanate, BGO), arising most probably from passive beam shaping contaminations, the proposed detector configurations had to be tested in-beam. For that, BGO was substituted with a state-of-the-art scintillator (lutetium oxyorthosilicate, LSO) and two position sensitive detectors were built. Each detector contains 32 pixels, consisting of LSO finger-like crystals coupled to avalanche photodiode arrays (APDA). In order to readout the two detectors operated in coincidence, either in standalone mode or at the GSI medical beam line, a multi-channel, zero-suppressing free, list mode data acquisition system was built.The APDA were chosen for scintillation detection instead of photomultiplier tubes (PMT) due to their higher compactness and magnetic field resistance. A magnetic field resistant detector is necessary if the in-beam PET scanner is operated close to the last beam bending magnet, due to its fringe magnetic field. This is the case at the isocentric, ion beam delivery planned for the dedicated, heavy ion hospital facility under construction in Heidelberg, Germany. In-beam imaging with the LSO/APDA detectors positioned at small target angles, both upbeam and downbeam from the target, was successful. This proves that the detectors provide a solution for the proposed next-generation, improved in-beam PET scanners. Further confirming this result are germanium-detector-based, spectroscopic gamma-ray measurements: no scintillator activation is observed in patient irradiation conditions. Although a closed ring or a dual-head tomograph with narrow gaps is expected to provide improved in-beam PET images, low count rates in in-beam PET represent a second problem to image quality. More importantly, new accelerator developments will further enhance this problem to the point of making impossible in-beam PET data taking if the present acquisition system is used. For these reasons, two random-suppression methods allowing to collect in-beam PET events even during particle extraction were tested. Image counts raised almost twofold. This proves that the methods and associated data acquisition technique provide a solution for next-generation, in-beam positron emission tomographs installed at synchrotron or cyclotron radiotherapy facilities.
Keywords: PET, radiation therapy, radiotherapy, ion therapy, LSO, APD
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-444 2006
  • Lecture (others)
    Zentrum für Innovationskompetenz Oncoray, 12.12.2005, Dresden, Deutschland

Downloads:

Publ.-Id: 8224 - Permalink


Acceptor formation by ion implantation of nitrogen into ZnO
Braunstein, G.; Hamad, O.; Benndorf, G.; Wenckstern, V. H.; Lorenz, M.; Brauer, G.;
not available
  • Lecture (Conference)
    12th International Workshop on Oxide Electronics (WOE-12),, 02.-05.10.2005, Cape Cod/MA, USA

Publ.-Id: 8223 - Permalink


Positron depth profiling in ion-implanted zirconia stabilized with trivalent cations
Grynszpan, R. I.; Saude, S.; Mazerolles, L.; Anwand, W.; Brauer, G.;
Slow positron implantation spectroscopy has been performed on a series of (ZrO2)(1-x)(M2O3), solid solutions, either stabilized in the cubic phase (with M:Y, Dy or Er and x = 0.095, 0.16 or 0.16, respectively) or in the tetragonal metastable phase (M:Y and x = 0.03). Stabilization induces native oxygen-vacancy complexes, which lead to saturation trapping of positrons in the cubic crystals, regardless of the cation type. The positron diffusion length in the tetragonal phase (L+ approximate to 60 nm, vs. approximate to 2.5 nm in the cubic phase) suggests that Y atoms segregate around antiphase boundaries formed in the lattice. Implantations of helium and oxygen ions induce new defects, more trapping effective than the native defects. However, their production rate and temperature stability seem primarily dependent on the crystal structure, hence on the concentration of trivalent cations, irrespective of their chemical nature.
  • Lecture (Conference)
    8th International Workshop on Positron and Positronium Chemistry (PPC-8), 04.-09.09.2005, Coimbra, Portugal
  • Radiation Physics and Chemistry 76(2007)2, 333-336

Publ.-Id: 8222 - Permalink


Positron annihilation at SiO2/Si interface
Kuriplach, J.; Melikhova, O.; Anwand, W.; Brauer, G.;
not available
  • Lecture (Conference)
    8th International Workshop on Positron and Positronium Chemistry (PPC-8), 04.-09.09.2005, Coimbra, Portugal

Publ.-Id: 8221 - Permalink


Basic positron properties of oxides: a computational study
Kuriplach, J.; Melikhova, O.; Brauer, G.;
In this contribution we concentrate on two selected oxides, MgO and BeO, and examine theoretically their basic positron characteristics. In particular, we calculate the bulk positron lifetime and affinity and determine the positron distribution in defect free systems. Both self-consistent and non-self-consistent computational methods are used in calculations. Obtained characteristics are then discussed in terms of the structure and bonding properties of oxides and are compared to experimental data available. The issue of electron-positron correlations in insulating materials is also mentioned.
  • Lecture (Conference)
    8th International Workshop on Positron and Positronium Chemistry (PPC-8), 04.-09.09.2005, Coimbra, Portugal
  • Radiation Physics and Chemistry 76(2007)2, 101-105

Publ.-Id: 8220 - Permalink


Characterization of various crystalline structures at the SiO2/Si interface by positrons
Brauer, G.; Kuriplach, J.; Anwand, W.; Becvar, F.; Skorupa, W.;
The nature of the interface of the Si (001) surface with grown, native oxide is examined by a slow-positron beam equipped with coincidence Doppler broadening (DB). Measurements are combined with theoretical calculations of high-momentum DB profiles of Si, divacancy in Si, Brazilian quartz and the interface itself. From this comparison, the conclusion is drawn that an ordered structure exists at the interface. This structure resembles low quartz or a SiO2 structure with a lower density than low quartz.
  • Lecture (Conference)
    8th International Workshop on Positron and Positronium Chemistry (PPC-8), 04.-09.09.2005, Coimbra, Portugal
  • Radiation Physics and Chemistry 76(2007)2, 195-199

Publ.-Id: 8219 - Permalink


Structure and ferromagnetism of Mn+ ion implanted ZnO thin films on sapphire
Brauer, G.; Anwand, W.; Skorupa, W.; Schmidt, H.; Diaconu, M.; Lorenz, M.; Grundmann, M.;
Slow Positron Implantation Spectroscopy (SPIS), based on the generation, implantation and subsequent annihilation of mono-energetic positrons in a sample, has been used to study depth dependent vacancy-type damage in three ZnO films grown by pulsed laser deposition on c-plane sapphire. Doping was achieved by implantation of 250 keV Mn+ ions at 300 ◦C with three different fluences—1016, 3 × 1016, and 6 × 1016 cm−2, and subsequent thermal annealing in air. Evolution of the open volume damage, its depth distribution, and the magnetic behavior was investigated by
SPIS and Magnetic Force Microscopy. No indication of magnetic domain formation was found in any of the three films after implantation and the first annealing at 500 ◦C, whereas after the second annealing at 750 ◦C the two samples having the higher fluence showed stripe-like magnetic domains.
  • Lecture (Conference)
    European Materials Research Society Spring Meeting, 31.05.-03.06.2005, Strasbourg, France
  • Superlattices and Microstructures 39(2006), 41-49

Publ.-Id: 8218 - Permalink


Defects in nanocrystalline Nb films: effect of sputtering temperature
Cizek, J.; Melikhova, O.; Prochazka, I.; Brauer, G.; Anwand, W.; Mücklich, A.; Kirchheim, R.; Pundt, A.;
Thin niobium (Nb) films (thickness 350–400 nm) were prepared on (1 0 0)Si substrate in a UHV chamber using the cathode beam sputtering. The sputtering temperature Ts was varied from 40 up to 500 8C and the influence of the sputtering temperature on the microstructure of thin Nb films was investigated. Defect studies of the thin Nb films sputtered at various temperatures were performed by slow positron implantation spectroscopy (SPIS) with measurement of the Doppler broadening of the annihilation line. SPIS was combined with transmission electron microscopy (TEM) and X-ray diffraction (XRD). We have found that the films sputtered at Ts = 40 8C exhibit elongated, column-like nanocrystalline grains. No significant increase of grain size with Ts (up to 500 8C) was observed by TEM. The thin Nb films sputtered at Ts = 40 8C contain a high density of defects. It is demonstrated by shortened positron diffusion length and a high value of the S parameter for Nb layer compared to the well-annealed (defect-free) bulk Nb reference sample. A drastic decrease of defect density was found in the films sputtered at Ts ≥ 300 8C. It is reflected by a significant increase of the positron diffusion length and a decrease of the S parameter for the Nb layer. The defect density in the Nb layer is, however, still substantially higher than in the well-annealed reference bulk Nb sample. Moreover, there is a layer at the interface between the Nb film and the substrate with very high density of defects comparable to that in the films sputtered at Ts < 300 8C. All the Nb films studied exhibit a strong (1 1 0) texture. The films sputtered at Ts < 300 8C are characterized by a compressive macroscopic in-plane stress due to lattice mismatch between the film and the substrate. Relaxation of the in-plane stress was observed in the films sputtered at Ts ≥ 300 °C. The width of the XRD profiles of the films sputtered at Ts ≥ 300 °C is significantly smaller compared to the films sputtered at lower temperatures. This is most probably due to a lower defect density which results in reduced microstrains in the films sputtered at higher temperatures.
  • Lecture (Conference)
    10th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces (SLOPOS-10), 19.-25.03.2005, Doha, Qatar
  • Applied Surface Science 252(2006), 3245-3251

Publ.-Id: 8217 - Permalink


Defect studies of hydrogen-loaded thin Nb films
Cizek, J.; Prochazka, I.; Brauer, G.; Anwand, W.; Mücklich, A.; Kirchheim, R.; Pundt, A.; Bähtz, C.; Knapp, M.;
Hydrogen interaction with defects in thin niobium (Nb) films was investigated using slow positron implantation spectroscopy (SPIS) combined with X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thin Nb films on Si substrates were prepared using cathode beam sputtering at room temperature. Initially, the microstructure of the virgin (hydrogen-free) films was characterized. Subsequently, the films were step-by-step electrochemically charged with hydrogen and the evolution of the microstructure with increasing hydrogen concentration was monitored. Hydrogen loading leads to a significant lattice expansion which was measured by XRD. Contrary to free-standing bulk metals, thin films are highly anisotropic. The in-plane expansion is prevented because the films are clamped on the elastically hard substrate. On the other hand, the out-of-plane
expansion is substantially higher than in the bulk samples. Moreover, an enhanced hydrogen solubility in the a-phase was found in nanocrystalline Nb films. It was found that most of positrons in the films are trapped at open-volume defects at grain boundaries (GBs). These defects represent trapping sites also for hydrogen atoms. Hydrogen trapping at vacancy-like defects like GBs leads to a local increase of the electron density and is reflected by a pronounced decrease of the S parameter in the hydrogen-loaded samples. In addition, it was found that new defects are introduced at higher concentrations of hydrogen due to the formation of NbH (b-phase) particles.
  • Lecture (Conference)
    10th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces (SLOPOS-10), 19.-25.03.2005, Doha, Qatar
  • Applied Surface Science 252(2006), 3237-3244

Publ.-Id: 8216 - Permalink


EPOS – an intense positron beam project at the Research Center Rossendorf
Krause-Rehberg, R.; Sachert, S.; Brauer, G.; Rogov, A.; Noack, K.;
EPOS, the acronym of ELBE Positron Source, describes a running project to build an intense pulsed beam of mono-energetic positrons (0.2-40 keV) for materials research. Positrons will be created via pair production at a tungsten target using the pulsed 40 MeV electron beam of the superconducting electron linac with high brilliance and low emittance (ELBE) at Forschungszentrum Rossendorf (near Dresden, Germany). The chosen design of the system under construction is described and results of calculations simulating the interaction of the electron beam with the target are presented, and positron beam formations and transportation are also discussed.
  • Lecture (Conference)
    Invited talk, 10th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces (SLOPOS-10), 19.-25.03.2005, Doha, Qatar
  • Applied Surface Science 252(2006), 3106-3110

Publ.-Id: 8215 - Permalink


Surface studies of SiC
Brauer, G.; Anwand, W.; Eichhorn, F.; Skorupa, W.; Hofer, C.; Brandstetter, S.; Teichert, C.; Kuriplach, J.; Cizek, J.; Prochazka, I.; Coleman, P. G.; Nozawa, T.; Kohyama, A.;
not available
  • Lecture (Conference)
    10th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces (SLOPOS-10), 19.-25.03.2005, Doha, Qatar

Publ.-Id: 8214 - Permalink


Positron and deuteron depth profiling in He-implanted electrum-like alloy
Grynszpan, R. I.; Saude, S.; Thome, T.; Baclet, N.; Darque, A.; Jolly, L.; Flament, J. L.; Zielinski, F.; Anwand, W.; Brauer, G.;
In spite of previous extensive studies, the helium behavior in metals still remains an issue in microelectronics as well as in nuclear technology. A gold–silver solid solution (Au60Ag40: synthetic gold-rich electrum) was chosen as a relevant model to study helium irradiation of heavy metals. After helium-3 ion implantation at an energy ranging from 4.2 to 5.6 MeV, nuclear reaction analysis (NRA) based on the 3He(d,p)4He reaction, was performed in order to study the thermal diffusion of helium atoms. At room temperature, NRA data reveal that a single Gaussian can fit the He-distribution, which remains unchanged after annealing at temperatures below 0.45 of the melting point. Slow positron implantation spectroscopy, used to monitor the fluence dependence of induced defects unveils a positron saturation trapping, which occurs for He contents of the order of 50–100 appm, whereas concentrations larger than 500 appm seem to favor an increase in the S-parameter of Doppler broadening. Moreover, at high temperature, NRA results clearly show that helium long range diffusion occurs, though, without following a simple Fick law.
  • Lecture (Conference)
    10th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces (SLOPOS-10), 19.-25.03.2005, Doha, Qatar

Publ.-Id: 8213 - Permalink


Praseodymium compound formation in silicon by ion beam synthesis
Kögler, R.; Mücklich, A.; Eichhorn, F.; Schell, N.; Skorupa, W.; Christensen, J. S.;
The compound formation in the ternary system Pr-Si-O initiated by ion beam synthesis inside bulk-Si material was studied by transmission electron microscopy and x-ray diffraction. The oxygen content was varied by additional O ion implantation and by oxidation or implantation into SiO2. For annealing temperatures of 1100°C Pr silicate grains were observed consisting of Pr9.33Si6O26 or Pr2Si2O7. Pr silicide was found in minor fraction also in samples with enhanced oxygen content and for lower annealing temperatures such as 900°C. Pr oxide, the promising high-k material, was not definitely verified. The obtained results can be explained by the simple consideration that the energy should be minimized related with reordering inside the Si material during compound formation.
Keywords: Ion implantation, ion beam synthesis, Pr, Pr compounds, Si, high-k dielectrics
  • Vacuum 81(2007)10, 1318-1322
  • Invited lecture (Conferences)
    VI-th International Conference on Ion Implantation and other Applications of Ions and Electrons (ION2006), 26.-29.06.2006, Kazimierz Dolny, Poland

Publ.-Id: 8212 - Permalink


Real time observation of silver nanoparticle growth in ultrathin polymer films
Oates, T. W. H.;
Silver nanoparticles are formed in a polystyrene film by temperature induced dissociation of an organometallic precursor dispersed in the polymer. Further heating of the sample above the polymer boiling point allows control over the fill content of the silver particles. The process is recorded in real time by spectroscopic ellipsometry. The ellipsometric data is modeled using the Maxwell-Garnett effective medium approximation. Modeling the silver component using a Drude term with a modified electronic relaxation frequency allows the particle size to be inferred by scaling the relaxation frequency with microstructural observations of the particle dimensions. The particle size can subsequently be determined during the growth process from the final radius of 7.4 nm back to 2.3 nm, at which point quantum size effects limit the effectiveness of the model.
Keywords: Nanoparticles; surface plasmon polaritons; spectroscopic ellipsometry; polymer nanocomposites
  • Applied Physics Letters 88(2006), 213115

Publ.-Id: 8211 - Permalink


High temperature investigations of Si/SiGe based cascade structures using x-ray scattering methods
Meduňa, M.; Novák, J.; Falub, C. V.; Bauer, G.; Tsujino, S.; Grützmacher, D.; Müller, E.; Campidelli, Y.; Kermarrec, O.; Bensahel, D.; Schell, N.;
We have investigated strain compensated Si/Si0.2Ge0.8 multilayers, which were grown pseudomorphically on relaxed Si0.5Ge0.5 pseudosubstrates by molecular beam epitaxy. The stability of these highly strained Si/SiGe structures upon in situ annealing has been measured by means of x-ray reflectivity (XRR) up to 830°C. The temporal evolution of XRR reciprocal space maps was recorded, and a gradual disappearance of the multilayer structure was detected after annealing for 7 h at a temperature of 790°C. From the temporal evolution of the optical constants of the layers, deduced from the simulations and fits of the specular reflectivity, we obtained an interdiffusion coefficient D = (1.01 ± 0.03) × 10-21 m2 s-1 at 790°C.
  • Journal of Physics D: Applied Physics 38(2005), A121-A125

Publ.-Id: 8210 - Permalink


New developments in fast needle probe sensors for multiphase flow measurements
Schleicher, E.; Da Silva, M. J.; Hampel, U.;
Measurement with local needle probes is a well-established method for the investigation of multiphase flows. Different measuring techniques have been employed for the needle probes in the past. The most known techniques are based on: conductivity, capacitance, optical and/or temperature measurements [1-3]. Based on the detection of single phases, these probes can provide information about void fraction, bubble size, frequency, and velocity, among others. The existing needle probe systems have limitations regarding the range of substances they are able to measure, the environmental conditions they can be applied to as well as their time resolution. In this paper we describe two new developed needle probe sensors, which will enhance their application field. On one hand we present the further development of ultra-fast thermo needle probes for the phase-resolved temperature measurement aiming the investigation of interfacial areas in the multiphase flow. On the other hand we introduce a new complex admittance needle probe, which is able to measure either conducting or non-conducting fluids, thus enabling the investigation of multiphase flow problems (e.g. three-phase flow of oil, water and gas in the oil extraction).
Keywords: needle probe, temperature measurement, micro-thermocouple, admittance, complex permittivity, multiphase flows
  • Contribution to HZDR-Annual report
    Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-457 November 2006, 45-52

Publ.-Id: 8209 - Permalink


Enhanced local void and temperature measurements for high-transient two-phase flows
Schleicher, E.; Da Silva, M. J.; Hampel, U.;
Local void fractions measurements in two-phase flow phenomena are commonly carried out by the use of needle probes. The measuring principle of these probes is based on conductivity or optical measurements. In the past advanced needle probes with integrated micro-thermocouples have been introduced by Prasser et al., making possible to measure local temperatures at the same position where the void fractions are determined because the sheath of the micro-thermocouple serves as the measuring electrode for the conductivity measurement. Thereby - in principle - the temperatures of the two different phases (e. g. steam and water) can be distinguished. The big disadvantage of this technique is the relative long time constant (~20 ms) of mineral-insulated sheathed thermocouples. The usage of this type of thermocouples was necessary because the electronic was not able to separate the two signals (temperature and conductivity) from each other. Measuring of high-transient two phase flows were impossible due to the slow time response. Additionally the two signals had to be sampled sequentially because of influence of the rectangular excitation signal into the small temperature voltage. Investigations of temperature changing in the interfacial area between gas and liquid were therefore very difficult. To solve this problem we have developed a new combined temperature and conductivity needle probe measuring system, which is able to handle grounded or direct sheathed thermocouples (where the thermocouple wires are electrically-joined to the protective sheath) as well as open thermocouples (exposed junction).
Keywords: needle probe, temperature measurement, two-phase flows, micro-thermocouple
  • Contribution to proceedings
    23rd IEEE Instrumentation and Measurement Technology Conference, 24.-27.04.2006, Sorrento, Italy
    Proceedings, Piscataway, NJ 08855-1331 USA: IEEE, 0-7803-9360-0, 596-599
  • Poster
    IEEE Instrumentation and Measurement Technology Conference, 24.-27.04.2006, Sorrento, Italy

Publ.-Id: 8208 - Permalink


Evolution of plasmon resonances during plasma deposition of silver nanoparticles
Oates, T. W. H.; Mücklich, A.;
In situ real-time spectroscopic ellipsometry is used to monitor the growth of magnetron sputtered silver nanoparticles on SiO2 substrates, through the percolation threshold and into the bulk film regime. The plasmon polariton resonances in the nanoparticulate regime are effectively modelled by a Lorentz oscillator. The resonance energy of the oscillator is observed to reduce to zero shortly after the percolation threshold, whereby the oscillation is described by Drude free electron theory. From the Drude theory, the electronic mean free path is observed to increase dramatically at the percolation threshold, to a value of 16 nm in the bulk regime, in good agreement with x-ray diffraction and transmission electron microscope measurements of the crystallite size in the films. Shortly before the percolation threshold the data is better modelled by two Lorentz oscillators, attributed to coupling between the plasmon polaritons. The onset of the coupling is determined to occur at a surface area coverage of 52%.
  • Nanotechnology 16(2005), 2606

Publ.-Id: 8207 - Permalink


Chitosan-encapsulated Keggin anion [Ti2W10PO40]7-: Synthesis, characterization and cellular uptake studies
Meißner, T.; Bergmann, R.; Oswald, J.; Rode, K.; Richter, W.; Zänker, H.; Kraus, W.; Emmerling, F.; Reck, G.; Stephan, H.;
The Keggin type polyoxotungstate [Ti2W10PO40]7- forms stable associates with the biopolymer chitosan in the nanometer size range. The cluster compound crystallizes from aqueous solution as K4H3[Ti2W10PO40]×15H2O having a tetragonal structure. Both, the cluster compound and the chitosan/[Ti2W10PO40] associates show a high hydrolytic stability at pH 7.4. The associates formed of the cluster anion [Ti2W10PO40]7- with the polyaminosaccharide chitosan have been characterised by photon correlation spectroscopy, scanning electron microscopy, filtration, centrifugation and zeta potential measurements. The size of the associates formed is in the range of about 5 ∙ 10E+1 to 5 ∙ 10E+2 nm. These particles have a defined stoichiometry with 5-6 cluster anions bound per molecule chitosan. The isoelectric point determined by zeta potential measurements was found at a cluster anion to chitosan molar ratio of 5.5 indicating the charge neutralization between protonated chitosan and [Ti2W10PO40]7- anions. Cellular uptake studies with [Ti2W10PO40]7- using tumor cell lines FaDu (human squamous carcinoma) and HT-29 (human adenocarcinoma) showed that the tungsten amount inside the cells is remarkably enhanced in the presence of chitosan.
Keywords: Cellular uptake, Crystal Structure, Chitosan, Nanoparticles, Polyoxometalates.

Publ.-Id: 8206 - Permalink


In-situ high temperature texture characterization in NiTi shape memory alloy using synchrotron radiation
Paula, A. S.; Mahesh, K. K.; Braz Fernandes, F. M.; Martins, R. M. S.; Cardoso, A. M. A.; Schell, N.;
The aim of the present experiment was to analyse the structural evolution during annealing of Nickel-Titanium (Ni-Ti) SMA subjected to different thermomechanical treatments. As structural evolutions are accompanied by the changes in preferential orientations, pole figures were employed to study the in-situ conditions.
  • Materials Science Forum 495-497(2005), 125-130

Publ.-Id: 8205 - Permalink


Optimised two layer overgrowth of a lateral strain-modulated nanostructure
Zeimer, U.; Pietsch, U.; Grenzer, J.; Fricke, J.; Knauer, A.; Weyers, M.;
Recently it has been shown that lateral carrier confinement in an InGaAs quantum well (QW) embedded in GaAs can be achieved by using a laterally patterned InGaP stressor layer on top of the heterostructure. To exploit this effect in a device the structure has to be planarized by a second epitaxial step. It has been shown that the lateral strain modulation almost vanishes after overgrowth with GaAs, whereas overgrowth with a single ternary layer of opposite strain compared to the stressor layer suffers from strain induced decomposition. Here we show that the lateral carrier confinement of the initially free standing nanostructure can almost be maintained using a two step process for overgrowth, where a strained thin ternary layer is grown first followed by GaAs up to complete planarization of the patterned structure. Thickness and composition of the ternary layer are adjusted on the basis of finite element calculations of the strain distribution (FEM). The strain field achieved after overgrowth is probed by X-ray grazing-incidence diffraction (GID).
Keywords: Keywords: Nanostructures; Strain engineering; Finite-element method; X-ray grazing-incidence diffraction
  • Journal of Alloys and Compounds 401(2005), 226-230

Publ.-Id: 8204 - Permalink


Spectroscopic ellipsometry of tin-doped indium oxide at elevated temperatures: properties evolution during film growth and annealing
Vinnichenko, M.; Rogozin, A.; Shevchenko, N.; Kolitsch, A.; Möller, W.;
Thin films of indium tin oxide (ITO) are widely used in optoelectronic devices due to the materials transparency in the visible range of the spectrum and its low electrical resistivity. The ITO film formation and evolution at elevated temperatures is not properly addressed because the phase diagram of this material is not known. The amorphous-to-crystalline transition is often assumed as the reason for decrease of ITO resistivity at enhanced temperatures due to a Sn donor activation, but the physical mechanisms behind the experimental observations are not clear.
This study is focused on in situ spectroscopic ellipsometry (SE) monitoring of the film properties during growth at elevated temperatures (Ts=RT-500 °C) as well as during postdeposition annealing (Ta=200-300 °C). In addition, during annealing, the SE results are contrasted with data of in situ four point probe resistivity measurement technique, the in situ X-ray diffraction (XRD) and elastic recoil detection analysis (ERDA). The atomic force microscopy and cross-sectional transmission electron microscopy were used to study the film morphology ex situ.
The free electron parameters were determined from parameterization of the film optical constants in Drude-Lorentz approach. The applicability of spectroscopic ellipsometry as a non-contact and in situ tool for monitoring of the film resistivity is shown. However, quantitative characterization of the resistivity by SE requires further improvement of the optical model for the growing film. The existence of the resistivity grading through the film thickness was indicated by this method for the growth without heating. ITO film resistivity rapidly deteriorates at thickness below 40 nm if the substrate temperature is less or equal 270 °C due to decrease of the free electron density and mobility. It can be explained by formation of an amorphous layer or layer with chaotically oriented crystallites on initial stages of the film growth, depending on the film temperature. There is no such layer observed at deposition temperatures higher than 400°C that denotes change in the film growth mode.
Spectroscopic ellipsometry provides valuable information both on the properties and the morphology modification during isothermal annealing of ITO films. Isothermal heating modifies the film properties in two stages which are attributed to: (i) relaxation of In-O bonds in the amorphous phase, (ii) Sn-donor activation by removal of interstitial oxygen. Different crystallization modes at 210 and 240 °C are suggested both by the real-time roughness behavior from SE and in situ XRD analysis.
Keywords: tin doped indium oxide, in situ spectroscopic ellipsometry, isothermal annealing, crystallization, optical properties
  • Lecture (Conference)
    Woollam Applications Seminar, 11.-12.10.2005, Darmstadt, Germany

Publ.-Id: 8203 - Permalink


Krein space related perturbation theory for MHD α²-dynamos and resonant unfolding of diabolical points
Günther, U.; Kirillov, O.;
The spectrum of the spherically symmetric α²-dynamo is studied in the case of idealized boundary conditions. Starting from the exact analytical solutions of models with constant α-profiles a perturbation theory and a Galerkin technique are developed in a Krein-space approach. With the help of these tools a very pronounced α-resonance pattern is found in the deformations of the spectral mesh as well as in the unfolding of the diabolical points located at the nodes of this mesh. Non-oscillatory as well as oscillatory dynamo regimes are obtained. Finally, Fréchet derivative (gradient) based methods are developed, suitable for further numerical investigations of Krein-space related setups like MHD α²-dynamos or models of PT-symmetric quantum mechanics.
Keywords: Krein space, MHD dynamo, diabolical point, exceptional point, spectral deformation, perturbation theory, resonance, Galerkin method

Publ.-Id: 8201 - Permalink


USJ-Related and Non-Related Applications of Flash Lamp Annealing
Skorupa, W.;
No abstract available!
  • Invited lecture (Conferences)
    Deutsches Nutzertreffen Kurzzeit-Temperung, Reutte, Austria, Nov. 10, 2005, 10.11.2005, Reutte, Austria

Publ.-Id: 8200 - Permalink


Thermobehandlung von Halbleitermaterialien im msec-Bereich
Skorupa, W.; Anwand, W.;
Halbleitermaterialien, insbesondere Silizium, erfordern nach bestimmten Prozessschritten wie der strahlenschädigenden Ionenimplantations-Dotierung eine Temperbehandlung, deren Zeitdauer im Verlauf der letzten Jahre im Extremfall nur noch ca. 1 sec betrug. Solche kurzen Temperzeiten erfordern Anlagen, bei denen die Oberflächen durch Lichteinstrahlung bewirkt werden kann, um schnelle Zykluszeiten und eine geringe Aufheizung der Probenumgebung zu gewährleisten. Kürzlich wurden diese Anforderungen noch verschärft, indem die Forderung nach Temperzeiten im msec-Bereich erhoben wurde. Während Temperzeiten bis hinab zu einer Sekunde noch mit relativ langsam reagierenden Halogenlampen gewährleistet werden können, sind kürzere Temperzeiten nur noch mit schnell schaltbaren Xenon-Blitzlampen oder gerasterten Laserstrahlen realisierbar. Der Vorteil solch einer extrem kurzen Oberflächen-Wärmebehandlung liegt vor allem darin, dass das Volumen der Probe nicht mehr unbedingt durchgeheizt wird, andererseits aber auch ein gezieltes Anschmelzen von Oberflächen möglich wird. Ebenso sind mit solchen Techniken extrem kurze Zykluszeiten in Produktionsabläufen realisierbar. Im Vortrag werden Fragen der Anlagentechnik sowie Anwendungsbeispiele aus der fortgeschrittenen Halbleitertechnologie behandelt: a) Unterdrückung der beschleunigten Diffusion von Bor-Implantaten, sowie b) Unterstützung der Heteroepitaxie von Siliziumkarbid auf Silizium durch nanoskalige Phasenverflüssigung an der Grenzfläche. Es wird ein kurzer Ausblick zu Anwendungen ausserhalb der Welt der Halbleiter gegeben.
  • Invited lecture (Conferences)
    Summerschool S2B Nanotronics 2005, Science to Business Center Nanotronics, 29.-30.08.2005, Marl, Deutschland

Publ.-Id: 8199 - Permalink


Basics and Advances of Ion Beam Synthesis
Skorupa, W.;
No abstract available!
  • Invited lecture (Conferences)
    Nordic Summer School on Defects and Diffusion in Semiconductors and Heterostructures, 18.-21.08.2005, Sundvolden, Norway

Publ.-Id: 8198 - Permalink


Seltenerden-Implantation für die Si-basierte Lichtemission
Skorupa, W.;
No abstract available!
  • Invited lecture (Conferences)
    Workshop "Ionenstrahlphysik und -technologie", Leipzig, April 11-12, 2005, 11.-12.04.2005, Leipzig, Deutschland
  • Invited lecture (Conferences)
    Deutsches Nutzertreffen Ionenimplantation, 13.05.2005, Erlangen, Deutschland

Publ.-Id: 8197 - Permalink


Advanced Thermal Processing of Silicon in the msec-Range using Flash Lamps
Skorupa, W.; Panknin, D.; Anwand, W.; Voelskow, M.; European, F. C.; Yankov, R. A.; Gebel, T.; Paul, S.; Lerch, W.; Downey, D. E.; Arevalo, E.; Mannino, G.;
NO abstract available!
  • Invited lecture (Conferences)
    EU-Workshop on “Non-conventional thermal processes for advanced CMOS”, 21.01.2005, Rom, Italy

Publ.-Id: 8196 - Permalink


Erratum: “Brillouin scattering and x-ray photoelectron studies of germanium nanoclusters synthesized in SiO2 by ion implantation” ( J. Appl. Phys. 96 (2004) 4952)
Zuk, J.; Krzyzanowska, H.; Clouter, M. J.; Bromberek, M.; Bubert, H.; Rebohle, L.; Skorupa, W.;
Some of the references were numbered incorrectly. The correct reference list is as follows...

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Publ.-Id: 8195 - Permalink


Epitaxial SiC formation at the SiO2/Si interface by C+ implantation into SiO2 and subsequent annealing
Voelskow, M.; Panknin, D.; Polychroniadis, E. K.; Ferro, G.; Godignon, P.; Mestres, N.; Skorupa, W.; Monteil, Y.; Stoemenos, J.;
An approach for the defect density reduction in 3C-SiC epitaxially grown on Si is to improve the quality of the carbonized layer during the early stage of growth. For this reason the conventional carbonization process was replaced by a slower and nearer equilibrium carbonization method. Carbon is introduced by implantation into oxide of an ocidized Si substrate, near the SiO2/Si interface, and then it is transferred to the Si surface by annealing. Good quality 3C-SiC grains are formed embedded into the Si substrate, which are absolutely flat at the SiO2/Si interface. Another advantage of the new carbonization process is the elimination of the cavities due to the suppression of Si out-diffusion.
  • Materials Science Forum 483-487(2005), 233

Publ.-Id: 8194 - Permalink


Influence of electric field on the photoluminescence of silicon nanocrystals
Vandyshev, E. N.; Zhuravlev, K. S.; Gilinsky, A. M.; Lisitsyn, V. M.; Skorupa, W.;
We studied the effect of electric field generated on photoluminescence (PL) of silicon nanocrystals embedded in SiO2 films. We show that the application of electric field generated by means of surface acoustic waves (SAW) results in an increase of the PL intensity of nanocrystal photoluminescence by as much as 10% at a field amplitude of 12 kV/cm at temperatures below 15 K. At temperatures above 20 K the PL intensity decreases as the electric field is applied. The results are discussed within the frame of the self-trapped exciton model.
Keywords: Silicon nanocrystals; Photoluminescence; Self-trapped exciton
  • Thin Solid Films 493(2005), 297

Publ.-Id: 8193 - Permalink


A thermal model for flash lamp annealing of 3C-SiC/Si multi-layer systems (i-FLASiC)
Smith, M.; Mcmahon, R. A.; Skorupa, W.; Voelskow, M.; Stoemenos, J.;
This paper gives an insight into the thermal modeling of the i-FLASiC process, which is the flash lamp annealing of a 3C-SiC and silicon multilayer system. The model uses a standard heat flow model combined with an advanced multilayer optical model. Results from the model are consistent with experimentally observed phenomenon and have been used to explain diffusion mechanisms for the LPE of SiC.
  • Materials Science Forum 483-487(2005), 217

Publ.-Id: 8192 - Permalink


Modelling of flash-lamp-induced crystallization of amorphous silicon thin films on glass
Smith, M.; Mcmahon, R.; Voelskow, M.; Panknin, D.; Skorupa, W.;
Thin poly-crystalline silicon films are attractive for the fabrication of active matrix liquid crystal displays. We propose the use of flash lamp annealing to recrystallize amorphous silicon layers on glass substrates as a low cost manufacturing route. In this process amorphous silicon can be crystallized both by solid phase crystallization (SPC) and in the super lateral growth (SLG) regime. We present a thermal model which incorporates the phase transitions during annealing and we have shown that predictions from the model are in good agreement with experimental observations. In addition, the model is a valuable aid to optimizing the process conditions.
  • Journal of Crystal Growth 285(2005), 249

Publ.-Id: 8191 - Permalink


Rare earth ion implantation for silicon based light emission
Skorupa, W.; Sun, J. M.; Prucnal, S.; Rebohle, L.; Gebel, T.; Nazarov, A. N.; Osiyuk, I. N.; Helm, M.;
Using ion implantation different rare earth luminescent centers (Gd3+, Tb3+, Eu3+, Ce3+, Tm3+, Er3+) were formed in the silicon dioxide layer of a purpose-designed Metal Oxide Silicon (MOS) capacitor with advanced electrical performance, further called a MOS-light emitting device (MOSLED). Efficient electroluminescence was obtained for the wavelength range from UV to infrared with a transparent top electrode made of indium-tin oxide. Top values of the efficiency of 0.3 % corresponding to external quantum efficiencies distinctly above the percent range were reached. The electrical properties of these devices such as current-voltage and charge trapping characteristics, were also evaluated. Finally, application aspects to the field of biosensing will be shown.
Keywords: Eletroluminescence, Silicon-based light emission, Rare earth ion implantation, Biosensing
  • Solid State Phenomena 108-109(2005), 755
  • Lecture (Conference)
    11th Conf. on Gettering and Defect Engineering in Semiconductor Technology (GADEST 2005), 25.-30.09.2005, Giens, France

Publ.-Id: 8190 - Permalink


Advanced thermal processing of materials in the msec range (invited)
Skorupa, W.; Panknin, D.; Voelskow, M.; Anwand, W.; Gebel, T.; Yankov, R. A.;
The paper gives an overview of our recent work in the field of thermal processing of advanced semiconductor structures by millisecond flash lamp annealing (FLA). Topics covered include ultra-shallow junction (USJ) formation and heteroepitaxial growth of improved quality thin films of cubic silicon carbide (3C-SiC). The latter is a new development, which opens up promising 3C-SiC growth possibilities and may lead to wider application of FLA. The so-called FLASiC process (Flash LAmp Supported Deposition of SiC) is based on a new type of nanoscale liquid-phase epitaxy at the SiC/Si interface resulting in the formation of a thin, low defect density seed layer of SiC onto which thicker epitaxial SiC layers can be grown.
  • Vacuum 78(2005), 673
  • Invited lecture (Conferences)
    V -th International Conference on Ion Implantation and Other Applications of Ions and Electrons (ION 2004), 14.-17.06.2004, Kazimierz Dolny, Poland

Publ.-Id: 8189 - Permalink


Advanced thermal processing of semiconductor materials in the msec range (invited)
Skorupa, W.; Yankov, R. A.; Voelskow, M.; Anwand, W.; Panknin, D.; Mcmahon, R. A.; Smith, M.; Gebel, T.; Rebohle, L.; Fendler, R.; Hentsch, W.;
Recently a new interest evolved in short time annealing far below 1 sec, i.e. the lower limit of Rapid Thermal Processing (RTP). This was driven by the need of suppressing the so-called Transient Enhanced Diffusion in advanced boron-implanted shallow pn-junctions. After a short common overview about the new opportunities in materials processing, in this talk two examples will serve for the demonstration of the new interest in flash lamp annealing (time duration < 20 msec) within the framework of semiconductor materials processing: (i) For ultra-shallow junction formation in silicon Flash Lamp Processing (FLP) has become one of the challenging methods to meet the requirements for the next technology nodes defined by the ITRS roadmap. Low energy boron implants have been heat-treated in this way using peak temperatures in the range of 1100o to 1300oC and effective anneal times of 20 msec and 3 msec. Optimum processing conditions using a pulse time of 3 msec have been identified, under which one can obtain combinations of junction depth and sheet resistance values that meet even the 45 nm technology node requirements (ITRS 2001). (ii) The production of cubic SiC (3C-SiC) layers in device quality through the epitaxial growth on (100) Si wafers has remained a challenging task yet to overcome for selected applications the need in high cost bulk SiC wafers. It will be demonstrated that the use of Flash Lamp Processing (FLP) shows a new and promising way to the production of high quality 3C-layers. The FLASiC process bases on a new type of nanoscale liquid epitaxy at the interface SiC/Silicon leading to the formation of SiC seed layers with low defect density on which thicker SiC layers were epigrown.
  • Contribution to proceedings
    XIII. International Conference Advanced Thermal Processing of Semiconductors (RTP 2005) Oct. 4-7, 2005, Santa Barbara, USA, 04.10.2005, Santa Barbara, USA
    IEEE Cat.No.05EX1090, 53-71, 0-7803-9223-X,
  • Invited lecture (Conferences)
    XIII. Int. Conf. Advanced Thermal Processing of Semiconductors (RTP 2005), 04.-07.10.2005, Santa Barbara, USA

Publ.-Id: 8188 - Permalink


Rare earth ion implantation for silicon based light emission: From infrared to ultraviolet (invited)
Skorupa, W.; Sun, J. M.; Prucnal, S.; Rebohle, L.; Gebel, T.; Nazarov, A. N.; Osiyuk, I. N.; Dekorsy, T.; Helm, M.;
Using ion implantation different rare earth luminescent centers (Gd3+, Tb3+, Eu3+, Ce3+, Tm3+, Er3+) were incorporated into the silicon dioxide layer of a purpose-designed Metal Oxide Silicon (MOS) capacitor with advanced electrical performance, further called a MOS-light emitting device (MOSLED). The silicon dioxide layer did not contain silicon nanoclusters. Efficient electroluminescence was obtained from UV to infrared with a transparent top electrode made of indium-tin oxide. The electroluminescence properties were studied with respect to the luminescence spectra, decay time, impact excitation, cross relaxation (Tb3+), and power efficiency. Top values of the efficiency of 0.3 % corresponding to external quantum efficiencies well above the percent range were reached. The electrical properties of these devices such as current-voltage and charge trapping characteristics, were also evaluated. Moreover, we demonstrate photo- and electroluminescence in correlation to charge trapping characteristics for Er-rich MOSLEDs with a varying silicon cluster content. Finally, application aspects to the field of biosensing will be discussed.
Keywords: Silicon-based light emission, Ion implantation, Rare earth atoms.
  • Contribution to proceedings
    MRS Spring Meeting, 29.03.2005, San Francisco, USA
    Materials Research Society Symposium Proceedings 866(2005) V4.1.1/FF4.1.1, V4.1.1/FF4
  • Invited lecture (Conferences)
    Materials Research Society Spring Meeting, 29.03.-01.04.2005, San Francisco, USA

Publ.-Id: 8187 - Permalink


Microarrays of silicon-based light emitters for novel biosensor and lab-on-a-chip applications
Rebohle, L.; Gebel, T.; Yankov, R.; Trautmann, T.; Skorupa, W.; Sun, J. M.; Gauglitz, G.; Frank, R.;
We have demonstrated intense violet electroluminescence (EL) from thermally-grown SiO2 films containing Ge nanocrystals produced by ion beam synthesis. An outline is given of the electrical and optical characteristics of ITO/SiO2/Al light-emitting devices incorporating Ge nanocluster-rich oxide films. Optimization schemes based on the use of local oxidation of Si (LOCOS) have been developed and tested successfully. Arrays of 4 × 6 light-emitting devices with a diameter of 300 μm and spacing of 500 μm between the adjacent devices have been formed using standard lithography patterning. Bioanalyses have been carried out following fluorescent-based detection procedures. As distinct from the standard case of diagnostics in which the light source is typically a laser and the necessary spatial resolution is provided by a CCD camera, our light sources are small enough to immediately ensure high resolution while permitting their light emission to be detected by single inexpensive Si diodes. The relevance of the all-Si light sources to microarray, miniaturized sensor and lab-on-a-chip systems for point-of-care diagnostics is discussed. Finally, first EL spectra of Si-based light sources containing Tb are shown.
  • Optical Materials 27(2005), 1055

Publ.-Id: 8186 - Permalink


Nucleation control in FLASIC assisted short time liquid phase epitaxy by melt modification
Pezoldt, J.; Polychroniadis, E.; Stauden, T.; Ecke, G.; Chassagne, T.; Vennegues, P.; Leycuras, A.; Panknin, D.; Stoemenos, J.; Skorupa, W.;
The influence of the different additions to the melt on the nucleation behavior during short time flash lamp processing was investigated. It was observed that germanium and carbon additions to the silicone melt led to an increase of the mass transport to the growing surface and to an increase of the nuclei size. In the case of germanium additions to the silicon melt an incorporation of germanium in the silicon substrate was observed.
  • Materials Science Forum 483-487(2005), 213-216

Publ.-Id: 8185 - Permalink


The effect of radio-frequency plasma treatment on the electroluminescent properties of violet light-emitting germanium implanted metal-oxide-semiconductor structures
Nazarov, A. N.; Vovk, J. N.; Osiyuk, I. N.; Tkachenko, A. S.; Tyagulskii, I. P.; Lysenko, V. S.; Gebel, T.; Rebohle, L.; Skorupa, W.; Yankov, R. A.;
We have studied the effect of plasma treatment on both the electroluminescent (EL) properties of Ge-implanted light-emitting metal-oxide–silicon (MOS) devices and the charge trapping processes occurring therein. Under optimum conditions of plasma treatment, an appreciable increase in the device lifetime has been observed while maintaining unchanged the intensity of the light emission in the violet portion of the spectrum. These phenomena are believed to be associated with recovery of the oxide network resulting from a relief of internal mechanical stresses, and bond rearrangement that leads to a decrease in generation efficiency of electron traps, which are responsible for the device degradation.
  • Materials Science and Engineering B 124(2005), 458

Publ.-Id: 8184 - Permalink


Charge trapping in SiO2 layers implanted with rare earths and Ge ions
Prucnal, S.; Sun, J. M.; Cheng, X.; Skorupa, W.;
Metal-oxide-silicon (MOS) structures containing different rare earth and germanium ions exhibit strong luminescence from 300 to 1540 nm.
It is very interesting from the viewpoint of the formation of silicon-based light-emitting devices. The different behaviour of charge trapping in Ge, Tb, Gd and Eu enriched SiO2 layer was studied under constant current regime. High-frequency (100 kHz) capacitors-voltage (C-V) characteristics exhibit a strong dependence of the charge trapping on the type of elements implanted into the SiO2 layer. The increase of the Eu concentration up to 3 percent leads to a shift of the C-V characteristics towards negative voltage in comparison with fresh samples, which reveals positive charge trapping. The capture cross section and the concentration of the different type of charge traps can also be strongly influenced by changing the annealing temperature and annealing time.
Keywords: charge trapping, Ge, rare earth
  • Lecture (Conference)
    Berlin 2005, "Physik seit Einstein", 04.03.-09.03.2005 Hinweise für Tagungsteilnehmer und Tagesübersicht, 04.-09.03.2005, Berlin, Germany

Publ.-Id: 8183 - Permalink


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