Low temperature deposition of ITO thin films by ion beam sputtering

Abstract An ion beam sputtering system was used for the deposition of indium-tin-oxide (ITO) films at low temperatures (below 200°C). The electrical and optical properties and the microstructure were highly dependent on the growth temperature, the oxygen partial pressure and the ion beam energy. A reasonable resistivity (3.5×10 −4 Ωcm) was measured in the films deposited by Ar ion sputtering at as low as 50°C. In the films by Ar ion sputtering, the lowest resistivity was 1.5×10 −4 Ωcm at 100°C. Oxygen addition to the sputtering gas increased the resistivity, especially at low substrate temperatures. The addition of oxygen to the sputtering gas changed the microstructure from ‘domain’ (sub-grain) structure at 100°C to ‘grain’ structure. The oxygen addition induced the change in O/In ratios. The film composition also depended on the ion beam energy. The optical transmittance higher than 80% in the visible range was measured in the films deposited at above 100°C. The optical band gap calculated from the transmittance spectra was approximately 4.2 eV.