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The magnetization reversal of the magnetically soft permalloy (Fe20Ni80) layer in a spin-valve-like FeNi/Cu/Co trilayer was studied using photoelectron emission microscopy combined with X-ray magnetic circular dichroism, which allows to image the magnetic domain structure in an element-selective way. Nanosecond-short magnetic field pulses with amplitudes between 3.3 and 16.3 mT were applied one by one to reverse the magnetization of the FeNi layer. Images of the magnetic domain structure were taken after application of each pulse, and the mobility of magnetic domain wall motion in the FeNi layer was deduced. The reversal mechanism of the FeNi layer was found to depend on the applied pulse length, amplitude, and on the energy and direction of the coupling between the two ferromagnetic layers.

We report results of photoluminescence (PL) and Light Beam Induced Current (LBIC) analysis of extended defects in 6H-SiC. The spectroscopical results have been correlated with optical and Atomic Force Microscopy (AFM) analysis of samples before and after selective etching. The PL spectra performed by optical excitation above the band gap in the 10-300 K range show, in particular, an intense emission at 1.8 eV, which could be related to a deep level. PL measurements with optical excitation below the gap have confirmed the presence of another mid gap level. Spatially resolved analysis carried out by LBIC on defective zones suggests that this last mid gap level could be associated to the extended defects.

26th European Photovoltaic Solar Energy Conference and Exhibition; 1981-1985, The forthcoming diamond wire wafering technology is stirring up increasing interest in the PV community and, in turn, the chance to recycle the silicon kerf is gaining momentum. Garbo is working to develop a recycling process for the silicon kerf out of the machining on PV silicon ingots and bricks. One of the main challenges for the reutilization of the recycled silicon kerf in directional solidification processes derives from the large surface area to volume ratio of the powders leading to substantial surface oxidation and to SiO-induced carbon contamination of the melt resulting in SiC precipitation. The goal of this paper is to bring some insight on how different oxygen levels in recycled silicon kerf affect the quality of ingots and cells. The main conclusion is that an oxygen content of 0,03-0,045% in reclaimed compacted powders - the lowest tested value – yields comparable solar cells performances of reference production with virgin feedstock although generates supersaturated carbon concentration in solid silicon and larger SiC inclusion formation.

X-ray spectroscopy measurements have been performed on a series of Pt/Co/AlOx trilayers to investigate the role of Co oxidation in the perpendicular magnetic anisotropy of the Co/AlOx interface. It is observed that high temperature annealing modifies the magnetic properties of the Co layer, inducing an enhancement of the perpendicular magnetic anisotropy. The microscopic structural properties are analyzed via X-ray Absorption Spectroscopy, X-ray Magnetic Circular Dichroism and X-ray Photoelectron Spectroscopy measurements. It is shown that annealing enhances the amount of interfacial oxide, which may be at the origin of a strong perpendicular magnetic anisotropy. (C) 2008 Elsevier B. V. All rights reserved.

23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain; 2388-2392, Low-energy plasma-enhanced chemical vapour deposition (LEPECVD) is a new technique for growth of hydrogenated microcrystalline silicon (μc-Si:H) at high growth rate. For all existing growing techniques, a silane dilution threshold exists below which the material’s electronic and optical properties are crystalline-like and above which they are amorphous-like. As known in literature, optimized μc-Si:H materials for photovoltaics are always grown around this threshold. Our previous studies have demonstrated that up to 10% silane dilution (d = [SiH4] / ([SiH4] + [H2])), the grown material showed a rather crystalline behaviour. Therefore our present study focuses on higher dilution samples (30 and 50%) characterized electrically (dark and illuminated conductivity) and structurally (confocal Raman spectroscopy) in order to identify this dilution threshold for LEPECVD. The conductivity measured in a solar cell configuration allowed us to draw only a semi-quantitative picture. This was, however, sufficient to reveal that reducing the silane flow (from 20 to 12 sccm) leads to an increase of the structural homogeneity in the growth direction, of the surface crystallinity, and of the conductivity (dark and illuminated) while varying the silane dilution induces nearly no change of these properties. Then, from a conductivity criterion, the most suitable material seems to be obtained at a flow of 16 sccm of silane and a dilution d of 30%. However, this material shows an inhomogeneity of the microstructure in the growth direction which could be detrimental to the performance of the solar cell.

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. Soft x-ray resonant magnetic scattering has been used to investigate the element-selective microscopic magnetization reversal behavior of room temperature perpendicular exchange coupled ferromagnetic∕antiferromagnetic (F∕AF) systems and to study the role of the interfacial coupling strength on it. Different nucleation processes and domain size distributions along the decreasing and increasing branches of the reversal have been found. The size of the magnetic domains during reversal depends on both the F anisotropy and F∕AF coupling strength, decreasing when one of them increases. Evidence of the exchange bias(coercivity enhancement) being induced by pinned (unpinned) uncompensated AF interfacial spins is also shown.

Physical Review Letters