Influence of Oxygen Flow Ratio on Properties of Zn₂SnO₄ Thin Films Deposited by RF Magnetron Sputtering

Abstract

Zinc stannate (Zn 2 SnO 4 ) thin films were deposited by RF magnetron sputtering on silica substrates at various [O 2 /(Ar+O 2 )] flow ratios. The influences of the [O 2 /(Ar+O 2 )] flow ratio on the crystalline structure, and the optical and electrical properties have been investigated. No sharp X-ray diffraction (XRD) peaks were observed in as-deposited thin films. After postdeposition annealing in air at 750°C, the thin films showed a preferred orientation of (111). The thin films exhibited a high transmittance in the visible spectrum irrespective of the [O 2 /(Ar+O 2 )] flow ratio or postdeposition annealing. The optical band gap was estimated to be 4.1 eV by analyzing the optical spectra of thin films annealed at 750°C. The composition ratio of Zn/Sn for thin films deposited in an Ar/O 2 mixture was 2.0 and their electrical resistivity was on the order of 10 5 Ω·cm. In contrast, the composition ratio of Zn/Sn for a thin film deposited in pure Ar was 1.5 and an electrical resistivity of 4.1 ×10 -2 Ω·cm was observed.