Physical properties of arsenic-doped tin oxide thin films

Abstract

Transparent conducting arsenic-doped tin oxide films were fabricated on a soda glass substrate by a chemical vapour deposition technique with an oxidation of SnCl 2. At 0.15 wt.% of arsenic doping the minimum resistivity and the maximum carrier concentration were found to be 1.5 × 10 −6 ωm and 9.0 × 10 26 m −3 respectively. The direct band gap was found to be 3.87 eV, transmittance of the film was about 90% and the maximum figure of merit at wavelength of 600 nm was found to be 13.1 × 10 −3 ω −1. The variation of thermoelectric power (TEP) with temperature for different concentrations has also been studied. The variation of conductivity with temperature indicates two donor activation energies for the films. X-ray diffraction studies demonstrate that SnO 2/As films deposited at lower temperature have poor crystallinity, but when deposited at 673 K, the films are polycrystalline. Scanning electron microscopic studies of these films indicate that the mean grain size varies from 0.20t to 0.45 ωm. It was found that the uniformity of the films and the mean grain size increases with deposition temperature.