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The new carbon allotropes “between diamond and graphite” have come under intensive examination during the last decade due to their numerous technical applications. The modification of energy gap in thin films of these allotropes was studied experimentally using optical methods. The proposed simple model of carbon clusters with variable lengths of chemical bonds allows us to imitate the transfer from diamond and diamond-like to graphite-like structures, as well as the corresponding modification of hybridization sp3/sp2 for diamond-like and spz for graphite-like phases. This enables us to estimate various allotropes parameters, like the gap Eg, energies of valence Ev, and conduction Ec band edges, and the value of electronic affinity, i.e., optical work function X, which are all of practical importance. The obtained estimations correspond to the experimental data.

Mechanisms of adsorption-catalytic activation of composites fabricated on the basis of porous silicon with incorporated nanoparticles of transition metals (Pd, W, Cu) and their oxides have been analyzed theoretically. The influence of adsorbed atoms of acceptor elements (O, S, F, Cl) on the catalytic activity of transition metals during the formation of surface nanoclusters of transition metal oxides is revealed. The enhancement of the catalytic activity of transition metals with the completely filled-band may consist in a change of the filling of-states with electrons (the appearance of holes above the Fermi level) at the formation of surface nanoclusters of transition metal oxides. The results of experimental researches of the adsorption-electric effect in gas-sensitive structures with Schottky barriers obtained within the method of highfrequency volt-farad characteristics are presented. The experimental adsorption isotherms of hydrogen and hydrogen sulfide on the surface of nanostructured silicon composites with copper, tungsten, palladium, and their oxides in the pores are analyzed. An increased adsorption sensitivity of those composites to various gases (H2, H2S, H2O) in comparison with an ordinary porous silicon layer is found. It is established that the mechanism of physical adsorption is realized at low gas pressures (≤ 25 ppm) and/or short times of the adsorbate-substrate interaction, and the chemisorption mechanism at higher pressures and in the course of long-term processes. This conclusion agrees with the theoretical data calculated for the adsorption heat from experimental isotherms (0.3-0.5 eV).

Abstract. Review of original results concerning electrochemical formation of porous Si layers and investigation of properties inherent to the formed layers has been presented. The results related with observation of changes in pores' morphology depending on the etching conditions, correlation of morphology of the porous layers with their surface composition, photoluminescence and structural characteristics, catalytic activity of porous Si based MIS structures as well as theoretical modeling of the kinetics and mechanisms of the porous Si growth have been described.

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