Energetic negative ions in titanium oxide deposition by reactive sputtering in Ar/O2

The flux of energetic negative ions was measured during the preparation of TiO2 in Ar/O2 as a function of oxygen partial pressure. The Ti surface was so active that the small amount of O2 contained in Ar was sufficient to oxidize the target surface. Ti target is also oxidized as similarly to the other metals such as Zr and Zn. Oxide islands form, which coalesce and cover the target surface with an oxide layer. The thickness of the Ti oxide layer on the target surface increased with increasing target current and Ar/O2 gas pressure, which increased the oxygen flux incident on the target. This is due to the high reactivity of the Ti surface with oxygen. The data revealed that the flux of energetic negative ions in reactive sputtering of Ti in Ar/O2 is fairly small compared with the sputtering of Zr and Zn. This indicates that the generation rate of negative ions on the Ti target during the reactive sputtering is very small.