Thin films of vanadium oxide with thickness of 0.1 to 0.2 Am were deposited on Si3N4/Si substrate by reactive rf magnetron sputtering. The oxide films were sputtered using a vanadium metal target in various ratios of Ar and O-2 gases. The O-2 content in the mixed atmosphere has a significant influence on the metal-insulator transition characteristics of the oxide films. The oxide film deposited in an Ar/O-2 ratio of 98/2 exhibited high optical transmission of 70% to 80% in wavelength from 2 to 10 mum in insulating state while very low transmission of less than 5% in metallic state. Films prepared with higher O-2 Concentration showed no metal-insulator transition. In low O-2 concentration, films showed characteristics of having both a broader transition region spanning over 30 degreesC and a lowered transition temperature which are similar to those of doped vanadium oxide films. (C) 2004 American Vacuum Society.