Influence of Sn content on properties of ZnO:SnO2 thin films deposited by ultrasonic spray pyrolysis

The present work is devoted to the preparation of zinc oxide (ZnO): tin oxide (SnO2) thin films by ultrasonic spray technique. A set of films are deposited using a solution formed with zinc acetate and tin chloride salts mixture with varied weight ratio R=[Sn/(Zn+Sn)]. The ratio R is varied from 0 to 100% in order to investigate the influence of Sn concentration on the physical properties of ZnO:SnO2 films. The X rays diffraction (XRD) analysis indicated that films are composed of ZnO and SnO2 distinct phases without any alloys or spinnel phase formations. The average grain size of crystallites varies with the ratio R from 17 to 20 nm for SnO2 and from 24 to 40 nm for ZnO. The obtained films are highly transparent with a transmission coefficient equal to 80%. An increase in Sn concentration increases both the effective band gap energy from 3.2 to 4.01 eV and the photoluminescence intensity peak assigned defects to SnO2. The films electrical characterization indicated that films are resistive. Their resistivities vary between 1.2×102 and 3.3×104 (Ω cm). The higher resistivity is measured in film deposited with a ratio R equal to 50%.