The plasma oxidation of stainless steel using water vapor plasmas was studied. The plasma oxidation was compared with thermal oxidation. The enhancement effect of oxidation using plasma was almost constant regardless of temperature. Study of the bias potential effect revealed that the oxide thickness drastically increases with positive bias potential. The bias effect on the OH emission intensity has a similar tendency to the bias effect on plasma oxidation. Investigation on the relation between OH emission intensity and the oxide thickness confirmed that the oxide thickness was proportional to the amount of OH radicals. (c) 2005 Elsevier B.V. All rights reserved.