Electronic states in tin oxide thin films upon photo and electrochemical analysis

Abstract

Sb-doped SnO2 thin films have been deposited by the dip-coating technique. The morphology analysis revealed that the surface is granular, crack-free and the average roughness varies with Sb-doping. The sub–band gap electronic transitions were successfully probed using the optical and Mott-Schottky measurements. Therefore, the energetic band diagrams were established to locate the conduction band (3.85 eV) and valence band (7.69 eV) below vacuum. The concentrations of shallow and deep donors were determined from the pseudo-slopes. The charge transport was achieved with bulk-localized states which mediate the carriers tunneling. The electrical conductivity above 1 V, involves electrons hopping between tail states and the current increases exponentially (I∼ ea.V). The ac-conductivity is enhanced with increasing the thermal energy, which promotes the carriers hopping. The photoconductivity revealed that the tunneling mechanism is sensitive to the localized states overlapping, thus generating donor and/or traps levels within the forbidden band.