Optical and electrical properties of amorphous Sb-Sn-O thin films

The physical properties of tin oxide thin films containing Sb (Sb-Sn-O) have been investigated. The films were prepared by spray pyrolysis at a temperature of 350 degrees C. While the undoped tin oxide (SnO2) thin film is polycrystalline, the Sb-Sn-O thin films are amorphous. All the films in this study have absorption edges at a wavelength of around 300 nm and are transparent in the wavelength range 400-2600 nn. An explanation is given as to why the amorphous Sb-Sn-O thin films retain transparency although polycrystalline Sb-Sn-O thin films prepared at 500 degrees C are deeply coloured as reported by Kojima et al. in 1993. The resistivity of the undoped film is 0.23 Omega cm and the addition of Sb causes the resistivity to rise significantly. From the temperature dependence of the film resistivity, a change in the electronic conduction is found; in the undoped polycrystalline film the electron transport mechanism is band conduction while in the amorphous Sb-Sn-O films it is variable-range hopping.