The factors controlling low frequency (1 MHz) dielectric losses of textured SrTiO3 thin films deposited by radio-frequency magnetron sputtering on platinized sapphire substrates were investigated. In particular, the influence of film texture, phase transformations, applied bias field, temperature and annealing atmospheres was studied. Films that were (111) textured showed a phase transformation at ~ 150 K, whereas films that were predominantly (110) oriented did not exhibit a phase transformation in the measured temperature range (100 K – 300 K). Two major contributions to the dielectric losses were identified: a low temperature loss increase for the (111) oriented film, which could be suppressed by an applied bias field, and a loss peak at ~ 250 K (at 1 MHz), which was strongly frequency dependent and likely associated with a relaxing defect. The low temperature loss mode was related to the appearance of a phase transformation and contributed to the dielectric losses even at temperatures that were more than 100 K above the phase transformation. In contrast to the leakage properties of the films, which were strongly dependent on annealing atmospheres, annealing under reducing conditions had no significant influence on any of the observed loss modes. Possible origins of the different loss contributions are discussed.
