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Photocurrent relaxation was investigated in pure and Pr-doped amorphous As 2 S 3 films after constant illumination had been switched off. It is shown that, in the temperature range from 290 to 370 K and for the time interval 0.5-150 s, the photocurrent relaxation might be approximated as an algebraic function. An analytic model of the recombination-controlled photocurrent decay in amorphous semiconductors is formulated. For the As 2 S 3 samples with Pr impurity, the relaxation rate is lower and the form of the decay profile varies only lightly in comparison with non-doped samples. The results are discussed in terms of the band tails and deep acceptor-like centres present in a-As 2 S 3 films.

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Experimental data and mathematical models of the dependence of the yield strength of constructional steels on test temperature have been analyzed. Adequacy of the known models is evaluated, and recommendations are given for determining the yield strength of low-carbon and low-alloy constructional steels under the negative climatic temperature action.

The optical and photoelectrical characteristics of amorphous As 2 Se 3 :Sn and Sb 2 Se 3 :Sn prepared by vacuum evaporation on glass substrates are investigated. From the transmission spectra the changes of the refractive index under the light irradiation and heat treatment are calculated. The band gap for amorphous Sb 2 Se 3 was found to be E g =1.30 eV and decrease with increasing of the tin concentration up to E g =1.0 eV for Sb 2 Se 3 :Sn 10.0 . The kinetics of photoinduced absorption in the investigated thin films was studied. The relaxation of the photocurrent has been recorded in the wide times scale (from 0.05 up to 25 s) and was determined by capture on the deep acceptor-like traps. The photoconductivity spectra of amorphous Sb 2 Se 3 and Sb 2 Se 3 :Sn films in the photon energy range 1.0÷2.5 eV show the band connected with the presence of the defect states with the maximum located at 1.46 eV. The intensity of this band increases in the samples with tin impurity. The experimental data are discussed in framework of the model of the charged defects and nonequilibrium dielectric polarization in amorphous semiconductors.