Surface Flatness of Transparent Conducting ZnO:Ga Thin Films Grown by Pulsed Laser Deposition

Abstract

ZnO films doped with 4, 7 and 13 wt% Ga2O3 (GZO films) have been deposited on glass and quartz substrates using a pulsed laser deposition technique with an ArF laser (λ=193 nm). In all experiments, a repetition rate of 10 Hz, an energy density of 1 J/cm2, and an irradiation time of 20-30 min (12000-18000 shots) were used. An optical transmittance of more than 90% was obtained in the visible region of the spectrum for 150-200-nm-thick GZO (7 wt%) films deposited at substrate temperatures of 200-300° C. The lowest resistivity of 2.08×10-4 Ω⋅cm and the lowest sheet resistance of 14.5 Ω/sq were obtained for GZO (7 wt%) films grown at a substrate temperature of 200° C. It was found from AFM images that there were minute irregularities (50-70 nm in size, average roughness 0.8 nm) on the surfaces of GZO (7 wt%) films grown at substrate temperatures of 25-300° C.