Low temperature formation of insulating layers on silicides by anodic oxidation

Abstract The anodic oxidation of the silicides CoSi, CoSi 2 , CrSi 2 , Ni 2 Si, NiSi, NiSi 2 , Pd 2 Si, PtSi, TiSi 2 and ZrSi 2 was studied by using Rutherford backscattering of 2MeV alpha particles. The room temperature oxidation was carried out at a constant current density of 8.9 mA cm −2 using n -methylacetamide (2% H 2 0 and 1% KNO 3 ) as electrolyte. No oxidation of Pd 2 Si and PtSi was detected. Pure SiO 2 layers were grown on CoSi, CoSi 2 , Ni 2 Si, NiSi and NiSi 2 at a much lower rate than on Si〈100〉 and with a thickness increase per volt of 0.6 ± 0.03 nm V −1 . Mixed layers of SiO 2 /metal oxide were grown on CrSi 2 , TiSi 2 and CrSi 2 . All oxidations occurred at the expense of the silicide layer. It is also shown how the purity of the SiO 2 layer formed can be predicted from thermodynamic considerations.