POSTDEPOSITION ANNEALING EFFECTS IN ELECTRON-BEAM-EVAPORATED INDIUM TIN OXIDE THIN-FILMS

Transparent and conductive electrodes are required in various multilayer thin film sensors using light incidence for stimulation. Indium tin oxide (ITO) (In:Sn = 90:10 (atomic per cent)) reactively evaporated onto hot substrates (Corning 7059, T = 250°C) had good properties (d = 290 nm; Rs = 69 ω/□; relative transmittance, about 90%), but films deposited on cold substrates and post-oxidized for 1 h at 475°C in air were found to be superior (Rs = 10 ∓ 5 ω/p[; transmittance, about 90%). In contrast to the monotonic variation in transmittance with annealing temperature and time, the temperature dependence of the sheet resistance is critically determined and time, the temperature dependence of the sheet resistance is critically determined by the quenching rate after annealing: mechanical stress is considered to be responsible for those strange effects such as bumps in the Rs vs. T curve observed during long-term annealing (10 h). In situ R(T, t) measurements were used to resolve the rapid post-deposition resistivity changes preceding the oxidation process during annealing. Further, the suitability of different metallic thin films as contact materials on ITO films is discussed. © 1990.