BLACKENING OF TIN OXIDE THIN-FILMS HEAVILY-DOPED WITH ANTIMONY

The electrical and optical properties of tin oxide (SnO2) thin films h eavily doped with antimony (Sb) have been investigated. The films were prepared by spray pyrolysis at a temperature of 500-degrees-C. An und oped SnO2 film is transparent and its resistivity is 4 x 10(-3) OMEGAc m. With increase in antimony content the resistivity initially decreas es 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 subs titutional doping by trivalent antimony Sb3+. The films become opaque with increasing antimony content and finally turn black. The interacti on between antimony in the two different oxidation states in the SnO2 lattice is responsible for the blackening of the films.