The influence of O-2 concentration on metal-insulator transition (MIT) of vanadium oxide (VOx) thin films was studied in terms of structural and electrical properties. The VOx films were prepared by varying O-2 concentration using reactive radio frequency magnetron sputtering with a vanadium target. As the O-2 concentration in O-2/Ar gas increased from 1% to 7%, the deposition rate of VOx films abruptly decreased and the crystalline phases of the films were transformed from V2O3 to V2O5. The VOx films deposited at 2% O-2 mainly consisted of the VO2 phase and showed better crystallinity than those deposited at other O-2 concentrations. From the current-voltage measurements of Pt/VOx/Pt capacitors, the VOx films deposited at 2% O-2 showed excellent MIT properties which can be applied to memory devices. (C) 2007 Elsevier B.V. All rights reserved.