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Current issue   Ukr. J. Phys. 2017, Vol. 62, N 7, p.605-614


Lytovchenko V.G., Gorbanyuk T.I., Solntsev V.S.

V.E. Lashkaryov Institute of Semiconductor Physics, Nat. Acad. of Sci. of Ukraine
(41, Prosp. Nauky, Kyiv 03028, Ukraine; e-mail: lvg@isp.kiev.ua)

Mechanism of Adsorption-Catalytic Activity at the Nanostructured Surface of Silicon Doped with Clusters of Transition Metals and Their Oxides

Section: Solid Matter
Original Author's Text: Ukrainian/English

Abstract: echanisms 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 infuence 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 flled �-band may consist in a change of the flling of �-states with
electrons (the appearance of holes above the Fermi level) at the formation of surface nanoclus-
ters of transition metal oxides. The results of experimental researches of the adsorption-electric
efect in gas-sensitive structures with Schottky barriers obtained within the method of high-
frequency volt-farad characteristics are presented. The experimental adsorption isotherms of
hydrogen and hydrogen sulfde on the surface of nanostructured silicon composites with copper,
tungsten, palladium, and their oxides in the pores are analyzed. An increased adsorption sen-
sitivity 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 inter-
action, 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).

Key words: nanostructured silicon, nanoparticles, transition metals and their oxides, adsorption sensitivity, hydrogen sulfde, gas sensor.