Experimental realization of hysteresis free mode of vanadium reactive magnetron sputtering in Ar/O2 mixtures has
allowed, for the first time, a detailed measurement of discharge current- voltage characteristics (CVC). They appear to be
not smooth but with a kink, which was not observed earlier. It is shown, that the existing model of reactive sputtering can
describe only part of the observed CVC, the one above a certain ratio of a discharge current to oxygen partial pressure.
The experimental data at smaller currents can be interpreted assuming the target oxidation to a depth not smaller than
two monolayers, therefore sputtering does not result in the metal base exposure. The mechanisms of oxidation can be
recoil implantation of surface oxygen atoms and probably radiation-enhanced thermal diffusion.