Effect of substrate temperature on the surface structure, composition and morphology of indium–tin oxide films

Surface properties of indium–tin oxide (ITO) films are sensitive to substrate temperature. ITO films have been produced by reactive thermal evaporation (RTE) of an indium–tin alloy in the presence of oxygen at different substrate temperatures. The surface chemical composition and structure of the deposited films have been examined by X-ray photoelectron spectroscopy (XPS). The surface morphology has been investigated by atomic force microscopy (AFM). XPS results indicate that all the examined ITO films contain amorphous and crystalline phases. The best ITO films for optoelectronic applications show the smallest percentage of oxygen and indium atoms in an amorphous phase, AFM shows that these films have reduced surface roughness (6.265 nm) and grains with almost uniform size and shape. The ITO films deposited on substrates in the lower temperature range are darkened and show an increase in the amount of surface tin associated with a decrease in the amount of indium, leading to the formation of the SnO2-rich surfaces.