Interfacial reactions between vanadium and thermally grown SiO2films have been studied with Xe ions implanted in the SiO2as diffusion markers. After the sample is heated at temperatures from 700 to 900 °C, the SiO2decomposes and V3Si forms. A backscattering analysis of the marker displacement discloses that vanadium is the dominant moving species which diffuses through the V3Si to react with the SiO2, whereas the oxygen atoms generated as a result of the reaction outdiffuse and oxidize the outer vanadium layer. For a clear presentation of the reaction and marker motion, the usual energy spectra of backscattering have been converted to in‐depth compositional profiles.