281 research outputs found
Lutz Ilisch, Michael Matzke, Werner Seibt, Die mittelalterlichen Fundmünzen, Siegel u. Gewichte von Santueri, Mallorca
No full textMorrisson C. Lutz Ilisch, Michael Matzke, Werner Seibt, Die mittelalterlichen Fundmünzen, Siegel u. Gewichte von Santueri, Mallorca. In: Revue numismatique, 6e série - Tome 162, année 2006 pp. 469-471
Recombination and Charge Collection at Nickel Silicide Precipitates in Silicon Studied by Electron Beam‐Induced Current
No full textRecombination and Charge Collection at Nickel Silicide Precipitates in Silicon Studied by Electron Beam‐Induced Current
No full textLong-range order on the atomic scale induced at CoFeB/MgO interfaces
No full textEilers G, Ulrichs H, Muenzenberg M, Thomas A, Thiel K, Seibt M. Long-range order on the atomic scale induced at CoFeB/MgO interfaces. JOURNAL OF APPLIED PHYSICS. 2009;105(7):073701.The amorphous (a-) CoFeB/crystalline (c-) MgO based tunneling system interface has been studied by means of quantitative high resolution transmission electron microscopy from atomic to micrometer length scales with increasing annealing temperatures. On the micron scale an irregular nucleation is found. On the atomic scale a long-range order is induced by the MgO interface, explaining the high tunnel magnetoresistance values > 100% even for not fully crystallized CoFeB/MgO/CoFeB tunnel junctions. (C) 2009 American Institute of Physics. [DOI:10.1063/1.3100044
Nucleation of Nickel Disilicide Precipitates in Float‐Zone Silicon: The Role of Vacancies
No full text
Nucleation of Nickel Disilicide Precipitates in Float‐Zone Silicon: The Role of Vacancies
No full textNickel is one of the fast diffusion transition metal impurities in silicon that tends to form precipitates during cooling from processing temperature. The typically observed NiSi2 plate-shaped precipitates are well-understood from structural and electrical perspectives with the exception of the initial stages of particle nucleation. Herein, the fact that excess vacancies bound into nitrogen-vacancy complexes react with interstitial nickel to form substitutional nickel atoms, Nis is exploited. Furthermore, excess vacancies can be removed by thermal annealing thus providing a scheme, where nickel precipitation can be studied with and without the presence of Nis. It is shown by deep-level transient spectrocopy (DLTS) that Nis considerably enhances nickel precipitate nucleation by reducing the nucleation barrier by about 1.7 eV and that Nis is consumed by precipitate formation. Simple energy considerations and an atomistic model of particle nucleation will be discussed
Pattern recognition in high-resolution electron microscopy of complex materials
No full textStructural features like defects or heterointerfaces in crystals or amorphous phases give rise to different local patterns in high-resolution electron micrographs or object wave functions. Pattern recognition techniques can be used to identify these typical patterns that constitute the image itself, as was already demonstrated for compositional changes in isostructural heterostructures, where the patterns within unit cells of the lattice were analyzed. To extend such analyses to more complex materials, we examined patterns in small circular areas centered on intensity maxima of the image. Nonsupervised clustering, namely, Ward's clustering method, was applied to these patterns. In two examples, a highly defective ZnMnTe layer on GaAs and a tunnel magneto resistance device, we demonstrate how typical patterns are identified by this method and how these results can be used for a further investigation of the microstructural properties of the sample
Deposition and properties of high-carbon iron films
No full textThin high-carbon iron films were deposited by pulsed laser deposition onto grids for transmission electron microscopy using pre-combined carbon/iron targets with equal area ratio. The deposited films of about 20 nm in thickness were directly characterized by transmission electron microscopy. The films showed a variety of phases, surprisingly also including the NaCl-type FeC phase, which was theoretically predicted in the literature. For comparison, thin high-carbon stainless-steel films were deposited onto oxidized Si wafers with different carbon ratios in the targets (10, 20,40 and 50 at.%). These films were characterized by means of Mossbauer Spectroscopy, the magneto-optical Kerr-effect, grazing incidence X-ray diffraction and Rutherford backscattering spectrometry. With these methods clearly defined multilayer-structures were observed which could lead to interesting magneto-resistance phenomena if the thickness of the multilayers can be controlled by the processing parameters. (C) 2007 Published by Elsevier B.V
Electronic states at dislocations and metal silicide precipitates in crystalline silicon and their role in solar cell materials
No full textPredominant dislocation types in solar silicon are dissociated into 30A degrees- and 90A degrees-partials with reconstructed cores. Besides shallow 1D-band localized in their strain field and a quasi-2D band at the stacking fault connecting the two partials, the existence of several intrinsic core defects with deep lying levels has been demonstrated by electron spin resonance. The majority of core defects occur in nonequilibrium situations and, with the exception of a small EPR-signal assigned to a reconstruction defect, vanish after careful annealing above 800A degrees C. There is good evidence now that part of deep levels observed in dislocated silicon is associated with impurities, especially with transition metal impurities. Electron-hole-pair recombination at a dislocation mainly runs via its shallow bands and is strongly increased by impurities bound to its core or in the strain field. The concentration of these impurities can be reduced by gettering processes to such a low level that radiative recombination at dislocations yields a luminescence efficiency of 0.1% at room temperature. A quite coherent picture has emerged for metal impurity precipitation in silicon. Early stages of precipitation in defect-free silicon are characterised by kinetically selected metastable defects forming as a result of large chemical driving forces for precipitation. Such defects are associated with deep level spectra which show the properties of extended multielectron defects. The evolution of the system to energetically more favourable configurations proceeds via ordinary particle coarsening but also via internal ripening, a process reminiscent of the above-mentioned metastable defects. Electronically, the defects evolve into metal-like inclusions which in general seem to act as strong recombination centers for minority carriers. In the presence of dislocations metastable defects quickly transform into equilibrium structures in the course of precipitation or do not form at all. In the presence of several metal impurities silicide precipitates which can be described as solid solutions of the respective metal atoms are observed, which is at least qualitatively in accord with ternary phase diagrams. Like single-metal silicide precipitates, strong minority carrier recombination is also typical for those multi-metal silicide particles
- …
