Solntsev V. Electrophysical properties of multilayered structures on the base of modified porous silicon during gas adsorption.

The thesis is devoted to the investigation of the electrophysical properties of multilayered structures based on the porous silicon during the adsorption of hydrogen containing gases (hydrogen, water, and hydrogen sulphide) as well as of the influence on the properties of such structures of the modification of porous silicon by Cu microparticles and of the modification of catalytically active Pd films by WO3 microparticles. The influence of the adsorption of hydrogen containing gases on the electrophysical properties of multilayered structures based on the porous silicon of different modifications with the catalytically active Pd and Pd/WO3 electrodes was investigated. The morphological features of the structure and the composition of porous silicon in dependence on the regimes of anode electrochemical etching (current density, etching time, electrolyte concentration) were investigated. The technology of the formation of porous silicon layers with reproducible parameters (layer thickness, porosity, pore size, surface area) was optimized. The modifications of the chemical composition of porous silicon surface during the growth and as a result of oxidation (chemical, electrochemical, thermal oxidation) were in detail investigated by IR spectroscopy. The adsorption heat of gas molecules was calculated. The physical model of the adsorption on the multilayered gas sensitive structures was proposed. This model takes into account the peculiarities of the porous silicon layer with the catalytically active Pd and WO3/Pd electrodes. The structures based on the active porous silicon layers with Cu microparticles (0.1 - 1.2 µm) and catalytically active Pd films modified by WO3 microparticles (0.3 - 0.7 µm) having a high sensitivity to hydrogen sulphide gas were demonstrated for the first time. The laboratory sample of hydrogen, water vapor and hydrogen sulphyde sensor was fabricated.