ESR study of impurities in strontium titanate films

The paper reports on an ESR study of Cr- and Ca-codoped SrTiO3 films, 1700 and 350 nm thick, before and after UV irradiation (lambda = 365 nm). The spectrum of the thick film (1700 nm) exhibits two ESR lines with g factors of 1.977 and 1.974, which belong to the Cr3+ centers. In the spectrum of the thin film (350 nm), one observes only one line, which is due to the chromium center with a g factor of 1.974. Calculations showed that the line with the smaller g factor belongs to the Cr3+ center located close to the film surface. The weak line observed in the spectrum after UV irradiation (g factor = 2.012) is most likely due to the O- center. The regions of thermal stability of the observed centers were studied. A comparative analysis of the characteristics of impurities in bulk samples and films was carried out. (C) 2001 MAIK Nauka/Interperiodica.