Effect of tin doping on optical properties of nanostructured ZnO thin films grown by spray pyrolysis technique

Sn-doped ZnO thin films with 0%, 0.5%, 1%, 1.5% and 2% Sn were grown by spray pyrolysis method on glass substrates under optimized conditions. High resolution Field Effect Scanning Electron Microscopy characterization showed that the films consist of hexagonal-like grains. A comprehensive study of the optical properties was performed and the dispersion constants were determined. The effect of Sn content on the optical band gap and the optical constants (refractive index, extinction coefficient, dielectric constants, and dispersion parameters) was studied. These Sn-doped ZnO thin films are highly transparent (73-93%) in the visible region. A blue shift of the optical band gap, attributed to the Burstein Moss effect, was observed for the Sn-doped films. All the optical dispersion parameters depend on the Sn content of the films, but were found to reach threshold values at a Sn content of 0.5%. These optical parameters are discussed in terms of the single oscillator model. This study demonstrated that this 0.5% Sn-doped ZnO thin film has enhanced physical properties, allowing its better integration in optoelectronic devices. (C) 2014 Elsevier B.V. All rights reserved.