Influence of oxygen flow ratio on properties of Zn2SnO4 thin films deposited by RF magnetron sputtering

Zinc stannate (Zn2SnO4) 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 degrees 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 degrees 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 105 Q-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 41 x 10(-2) Omega(.)cm was observed.