Carrier freeze-out induced metal-insulator transition in oxygen   deficient SrTiO3 films
  We report the optical, electrical transport, and magnetotransport properties of high quality oxygen deficient SrTiO3 (STO) single crystal film fabricated by pulsed laser deposition and reduced in the vacuum chamber. The oxygen vacancy distribution in the thin film is expected to be uniform. By comparing the electrical properties with oxygen deficient bulk STO, it was found that the oxygen vacancies in bulk STO is far from uniform over the whole material. The metal-insulator transition (MIT) observed in the oxygen deficient STO film was found to be induced by the carrier freeze-out effect. The low temperature frozen state can be re-excited by an electric field, Joule heating, and surprisingly also a large magnetic field. 
Z. Q. Liu (Zhiqi, Liu), D. P. Leusink, X. Wang, W. M. L\"u, K.   Gopinadhan, A. Annadi, Y. L. Zhao, X. H. Huang, S. W. Zeng,...
cond-mat.mtrl-sci