Deposition of ZnO and Al-doped ZnO thin films using pressed-sintered targets

Abstract

Zinc oxide (ZnO) and aluminum-doped ZnO (AZO) thin films were deposited using a custom-built deposition system operated by a radio frequency power supply. The targets used for the deposition process were made from custom-made pressed-sintered targets. Sputter deposition was carried out using argon gas only at 9.5 Pa and 50 W power. Growth of ZnO and AZO films with a preferred orientation along the c-axis was confirmed. Microscopy images revealed the growth of uniformly distributed grains that are dense and void-free with a columnar structure. Visible light transmittance ranged from 70 to 80%. For AZO films, the Al doping level was 0.64 at.%, the sheet resistance was at 560.3 $\Omega$/sq, carrier concentration at -2.65 × 10²⁰ cm⁻³, and mobility at 14.50 cm${}^2$V⁻¹s⁻¹. The figure of merit is 1.2 × 10⁻⁴ ${\Omega }^{-1}$. This work demonstrated the feasibility of preparing powder-based targets with a tunable composition to deposit transparent thin films under low vacuum conditions.