Abstract: Two CoSi2/Si1-xGex/Si(100) heterostructures, with different Ge content, made by molecular beam epitaxy are characterized by high resolution electron microscopy. In general, the interface between the CoSi2 thin film and the Si1-xGex layer is of a high structural quality and the strained Si1-xGex layer exhibits few defects. For both samples, different interface structures are present, although the dominant interfacial configuration is similar to the unreconstructed interface present at the CoSi2/Si(100) interface. Only occasionally (2x1) reconstructed interface regions are found which are just a few nanometers in length. Phenomena such as Ge segregation and the introduction of defects are also observed in the Si1-xGex layer. We attribute the minimal presence of the reconstructed interface to both the (2x8):Si1-xGex(100) surface reconstruction and the Ge segregation that takes place. (C) 1999 American Institute of Physics. [S0021-8979(99)02104-0].

Abstract: In situ irradiation experiments in a high resolution electron microscope JEOL-4000EX at room temperature resulted in discovery of the isolated and combined clustering of vacancies and self-interstitial atoms on {111}- and {113}-habit planes both leading to an extended defect formation in Si crystals. The type of the defect is strongly affected by the type of supersaturation of point defects depending on the crystal thickness during electron irradiation. Because of the existence of energy barriers against recombination of interstitials with the extended aggregates of vacancies, a large family of intermediate defect configurations (IDCs) is formed on {113}- and {111}-habit planes at a low temperature under interstitial supersaturation in addition to the well-known {133}-defects of interstitial type. The formation of metastable IDCs inside vacancy aggregates prevents a way of recombination of defects in extended shape.

Abstract: The potential of a prototype grazing-emission X-ray fluorescence spectrometer for reliable analysis of sample solutions, obtained by pressurized microwave oven digestion of Si-spiked organic and biological materials, was investigated as part of an inter-laboratory study. The fact that this grazing-emission technique is based on the total reflection phenomenon and wavelength-dispersive detection, gives it the benefit to determine light elements in a sensitive way. Results of the determination of silicon in pork liver, cellulose, urine, serum, spinach, beer, mineral water and horsetail (dry plant extract) samples are presented. Some of the results are compared with those obtained with other analytical techniques. The study proved that determination of silicon traces in biological matrices represents an extremely difficult task, however, measurements of silicon are achieved with acceptable precision. The most important problems still arise when sample pre-treatment is needed prior to analysis. (C) 1999 Elsevier Science B.V. All rights reserved.