Schottky‐barrier diodes have been fabricated by evaporation of Pt on Si substrates followed by annealing at 500 °C to yield PtSi. Then V and Al were evaporated. The amount of oxygen intentionally incorporated in the V film during deposition was varied and the resulting effect on the diffusion barrier action of the vanadium film has been studied byI‐VandC‐Vmeasurements of the diodes and by backscattering spectrometry of simultaneously prepared test samples. It is found that for V films with low oxygen concentrations annealing in the range 400–600 °C leads to the formation of VAl3and subsequent barrier height change. For vanadium films containing 50‐at. % oxygen there is no observable reaction between V and Al and the barrier height is preserved for annealing between 400 and 600 °C.