The effect of hydrogen passivation on the photoluminescence of Si-rich superlattices is investigated. The as-grown samples show many defect-related luminescence signals and several additional luminescence peaks believed to originate from the superlattice. The background luminescence along with the dislocation and defect lines are found to be passivated by the hydrogen atoms. The intensity of the superlattice peak increases after passivation and its phonon replica, initially submerged in the background and defect luminescence signals, is highlighted. After a subsequent temperature annealing in N2, the background luminescence is increased as hydrogen outdiffuses but the superlattice main peak decreases, perhaps due to the change of the carrier lifetime.

Evidence of native gallium antisite defects in semiinsulating liquidencapsulated Czochralskigrown GaAsThe shallow defect evolution in Si-implanted and -annealed liquid-encapsulated Czochralskigrown GaAs is investigated by photoluminescence experiments. Three major emission lines are found. The first emission line located at 1.492 eV corresponds to the Si Ga -CAS radiative recombination. The remaining two lines located at 1.44 and 1.40 eV are shown to correspond to Gal-Si.",s and VAs-Si As radiative recombinations, respectively. The effects of these three shallow centers on the silicon activation efficiency are discussed with respect to different annealing and implantation conditions. 1246

Statement of the problemThe ease and extensive use of digital imaging systems raise serious questions about integrity and authenticity of digital images particularly in medical applications. A medical image requires great integrity of content since any change in the image might affect the diagnosis even if it is ofsmall amount. Fragile watermark could be the best technique to provide efficient image authentication tool for medical images, in this paper we present different methods developed in image watermarking used in order to verify integrity and authenticity of images We will present after that our proposed method and validated the embedding and extracting procedures

The visual interpretation of gestures provides the most natural and intuitive interaction. However its implementation remains very difficult. Consequently gesture recognition research tries to developing systems that are able to analyze, recognize and interpret the gestures captured by a camera. In this article we give an overview of a current research. Firstly by defining a specific number of terms then by presenting the current methods and examples of applications in gesture recognition.

Ultrathin Ge/Si strained-layer superlattices (SLS’s) with periodicities of a few monolayers have been successfully grown and characterized by Raman scattering spectroscopy. Structures with alternating Ge and Si layers were grown on Si substrates of different orientations. A thick 200 nm Ge0.4Si0.6 buffer layer was grown prior to the growth of the superlattice to make the strain distribution of the superlattice symmetrical and thus to maintain the pseudomorphic growth of the superlattices. Folded acoustic phonon peaks observed from these Ge/Si SLS samples can be used to determine the superlattice periodicity. The observed optical phonon frequencies were found to depend strongly on superlattice periodicity. A quantitative interpretation of this phenomenon was presented. Subsequent annealing of these samples reveals that the transition from pure Ge and/or Si layers to GexSi1−x alloy becomes more pronounced as the annealing time and temperature increase.

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Si,Ge, strained layer superlattice (SLS) structures were grown by molecular beam epitaxy on Ge$ii --x buffer layers on (100) Si substrates to determine the effects of buffer layer composition, SLS thickness ratio, and superlattice periodicity, on the overall quality of these structures. X-ray diffraction methods were used to determine how closely actual periodicities and compositions met targeted values, and to evaluate the quality of these samples. In most instances the as-grown structures matched the targeted values to within lo%, though in some instances deviations of 20-25% in either the period or composition were observed. The quality of the SLS structures was greatly dependent on the composition of the buffer layer on which it was grown. Si,Ge, SLS structures grown on Si-and Ge-rich buffer layers were of much higher quality than Si,Ge, SLSs grown on Ge O,soSio~so layers, but the x-ray rocking curves of the Si,Ge, samples indicated that they were far from perfect and contained moderate levels of defects. These results were confirmed by cross sectional transmission electron microscopy, which showed that the Si,Ge, structures contained significant numbers of dislocations and that the layers were nonuniform in thickness and wavy in appearance. Si,Ge, structures, however, displayed fewer defects but some dislocations and nonparallelism of layers were still observed,

The demand for security is getting higher in these days due to easy reproduction of digitally created multimedia data especially in medicalfield. Digital watermark is the emerging technique to embed secret information into the original image to ensure the security of the medical data. In this paper, we present a multiple watermarking application in spatial domain to preserving the historic of the medical image by embedding medical diagnosis. This paper provides an overview of watermarking application and we present the used watermarking insertion domains. After that we proposed our method in spatial domain.