Blackening of tin oxide thin films heavily doped with antimony

Abstract

The electrical and optical properties of tin oxide (SnO₂) thin films heavily doped with antimony (Sb) have been investigated. The films were prepared by spray pyrolysis at a temperature of 500°C. An undoped SnO₂ film is transparent and its resistivity is 4 × 10⁻³ Ω cm. With increase in antimony content the resistivity initially decreases and then begins to increase. The decrease in the resistivity can be attributed to the substitutional doping by pentavalent antimony Sb⁵⁺, whereas the increase in the resistivity can be attributed to the substitutional doping by trivalent antimony Sb³⁺. The films become opaque with increasing antimony content and finally tum black. The interaction between antimony in the two different oxidation states in the SnO₂ lattice is responsible for the blackening of the films.