We report on the thickness d dependences of the Seebeck coefficient, electrical conductivity, and Hall coefficient of PbTe and PbS epitaxial thin films (d=5–200 nm), prepared by thermal evaporation in vacuum and deposition on (001) KCl substrates. The oxidation of the films in air at 300 K leads to a sign inversion of the carrier type from n to p in films with d⩽125 and 110 nm for PbTe and PbS, respectively. The observed d dependences are interpreted in terms of compensating acceptor states created by oxygen on the film surface.

Extrema were observed in the film thickness d dependence of various thermoelectric parameters (Seebeck coefficient S, electrical conductivity σ, Hall coefficient RH, charge carrier mobility μ, and power factor P) of epitaxial PbTe/(001) KCl thin films prepared by thermal evaporation in vacuum and protected from oxidation by an EuS layer. We attribute the observed extrema in properties and the high values of μ and P at d≈50 nm to the percolation transition from an island-like to a continuous film and to the self-organization of the islands, which can occur not only in quantum dot superlattices but also in an individual layer.

A non-monotonous character of the concentration dependence of properties in the region of small impurity contents has been detected in a number of semiconducting solid solutions based on AIVBV' compounds [l to 31. This note presents results on the concentration dependences of microhardness H , coefficient of thermal expansion CI, Hall coefficient RH, and electrical conductivity cr in Pb,-,Mn,Te solid solutions (x = 0 to 0.0175) belonging to the class of semimagnetic semiconductors [4].The measurements of H , CI, R,, and cr were performed on samples prepared from polycrystalline bulks by hot pressing and annealing at 820 K during 200 h. All the samples were of p-type. The value of Hall mobility ,uH was calculated as p, = R,a. The error in the measurement of H and CI was less than 2%, the error for R , and cr did not exceed 5%. The linear change of the unit cell parameter with increasing x (Fig. 1) evidenced that the concentration range under consideration corresponded to solid solution formation.As is seen from Fig. 2 and 3, three subregions with different characters of concentration dependences of properties can be distinguished within the investigated interval of x: 1) 0 to 0.0075; 2) 0.075 to 0.0125;3) 0.0125 to 0.0175. Fig. 1. Unit cell parameter a as a function of x I I I I . in Pb, -,Mn,Te solid solutions at 300 K 0 0.m 0.02 X -I) 21, Frunze St., 310001 Kharkov, Ukraine. ') 4, Svoboda Sq., 310077 Kharkov, Ukraine. 45*

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