SrTiO3 (x) thin films with various oxygen vacancies were fabricated by laser molecular beam epitaxy. The out-of-plane and in-plane lattice constants of the films increase with increasing oxygen vacancies, which was attributed to the increase of Ti3+ ions in the films. Ti3+ ions are formed only in the film inner which is revealed from X-ray photoemission spectroscopy (XPS). With varying the oxygen content, a metal-to-semiconductor transition was observed. The oxygen contents in the films, determined from lattice parameters and XPS are very consistent with each other, which shows quasi-quantitative methods to measure oxygen content in thin films. (c) 2008 Elsevier B. V. All rights reserved.