Multilevel computer-generated holograms for reconstructing 3-D images in combined optical-digital security devices

Computer-generated holograms (CGHs) integrated within combined optical-digital security devices (CO/DSDs) are described in this work. They can restore the monochrome and color 3D images in white light. To record them, the Electron Beam Lithography (EBL) is used. Our investigations on optimization of synthesis and recording the CO/DSDs with the integrated in it multilevel CGHs of 3D images possessed horizontal parallax only (HPO) are presented here. The CGH fabrication process is mainly composed of two parts: calculation of the interferogram data (ID) and their recording. Calculation of the ID is done as follows: firstly, the geometrical and optical constants of recording scheme and the object surface represented by the elemental self-radiating areas, are determined, secondly, the basic parameters accounting for discretization of ID in hologram plane is defined. The ID values can be derived by calculation of the necessary elemental object areas bipolar intensities sum. Next, over suitable quantization of ID, recording the rectangle data appropriate for EBL onto glass coated with non-organic photoresist based on As₄₀S₄₀Se₂₀ is performed. We have also investigated reciprocal influence of an optical part of the CO/DSD and a digital one

Tin doping effect on crystallization of amorphous silicon obtained by vapor deposition in vacuum

The influence of tin impurity on amorphous silicon crystallization was investigated using the methods of Raman scattering, Auger spectroscopy at ion etching, scanning electron microscopy and X-ray fluorescence microanalysis in thin films of Si:Sn alloy manufactured by thermal evaporation. Formation of Si crystals of the 2 to 4- nm size has been found in the amorphous matrix alloy formed at the temperature 300 C. Total volume of nanocrystals correlates with the content of tin and can comprise as much as 80% of the film. The effect of tin-induced crystallization of amorphous silicon occurred only if there are clusters of metallic tin in the amorphous matrix. The mechanism of tin-induced crystallization of silicon that has been proposed takes into account the processes in eutectic layer at the interface metal tin – amorphous silicon

Tin-induced crystallization of amorphous silicon assisted by a pulsed laser irradiation

The process of tin-induced crystallization of amorphous silicon under the influence of different types of laser irradiation was investigated using the method of Raman scattering by thin-film Si-Sn-Si structures. The dependences of the size and concentration of Si nanocrystals on the power of laser radiation was experimentally evaluated and analyzed. As sources of excitation pulse laser radiation with the pulses duration equal to 20 ns and 150 s and wavelengths equal to 535 and 1070 nm was used. The possibility of efficient tin-induced transformation of silicon from amorphous phase to crystalline one in the 200-nm thick layers of a-Si under the action of laser pulses with duration equal to 20 ns was shown. The spatial and temporal distributions of laser induced temperature rise was calculated to interpret experimental results