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Abstract
The investigation of the films with the thickness h=1700nm and 350nm doped by 0·1%Cr and 0·2%Ca on Al2O3 single crystal substrate was performed by ESR method. The spectra were recorded at T=18K with and without illumination of ultraviolet light (λ=365nm). Analysis of the observed spectra had shown that there were two Cr3+ ESR lines with g-factors 1·977 and 1·974 in the thick film whereas in thin film there was line with g=1·974 with higher intensity than that in thick film. Calculations lead to the conclusion that the line with smaller g-factor belongs to Cr3+centers nearby films surface. Small intensity broad line with g=2·011−2·021 which was revealed under light illumination in the films most probably belongs to O center. The influence of the revealed defects and impurities on the properties of the films is discussed.