Fabrication and characteristics of transparent conducting In2O3-ZnO thin films by ultrasonic spray pyrolysis

Transparent conducting In2O3-ZnO thin films were prepared by ultrasonic spray pyrolysis technique. Indium nitrate trihydrate (In(NO3)3·3H2O) and zinc acetate dihydrate (Zn(CH3COO)2.2H2O) were used as precursors and a solvent was 2-methoxyethanol. The thin films, as a function of Zn/(Zn + In) atomic ratio (abbreviated to x), were annealed at 550 °C. Oxygen gas was used as both carrier and reactor gas. From analyzing X-ray diffraction patterns, In2O3 phase and ZnO phase were formed at x = 0.11 and 0.89, respectively, while homologous phases of In2O3-ZnO were observed between x = 0.5 and 0.67. The resistivity of the thin film increased until x = 0.33 and then decreased to be the lowest value (1.47 * 10^-2 (omega)cm) at x = 0.5. In the range of x = 0.6-1, the resistivity increased again with x. The highest carrier concentration and the highest Hall mobility were 2.02 * 10^19 cm^-3 at x = 0.6 and 15.89 cm^2/V s at x = 0.5, respectively. The optical transmittance in the visible region at x = 0.5 was 88-92%.