We report the formation of silicon oxide thin films at room temperature obtained by Ar+ ion bombardment of Si(100) wafers in partial oxygen atmosphere. Samples have been prepared at several ion beam energies (0 less than or equal to E(b) less than or equal to 400 eV) and characterized by x-ray photoelectron spectroscopy. The oxidation rate, as well as the SiO2/SiOx (x = 0.5, x = 1, and x = 1.5) ratio, have been found to increase with the ion beam energy. For the highest energy bombardment, E(b) = 400 eV, we observed the formation of a uniform, electrically insulating, SiO2 top layer about 37 Angstrom thick. (C) 1995 American Institute of Physics.