The Influence of Al and Zn Co-Doping on Optical and Structural Properties of Transparent and Conducting SnO2 Thin Films Prepared by Spray Pyrolysis Technique

Abstract

ABSTRACT The influence of increasing Al concentration on the electrical, optical and structural properties of transparent and conducting S 2nO : Al films has been investigated. The films were deposited on glass substrates at a temperature of 480°C using a hydro-alcoholic solution consisting of S 4 2 nCl .5H O and A 3 2 lCl .6H O with various Al-doping levels from 0 to 0.53 being spray ratios of A 3 lCl : S 2nO in solution. The effect of changing the aluminum-to-tin spray ratio, [ Al ]/[ Sn ], from 0 to 0.53 was investigated. The optical properties were studied in the UV/VIS/NIR region. The optical band gap for undoped S 2nO films lay at 3.9 eV, whereas for high Al -doped films it shifts towards lower energies in the range of 3.9 – 3.61 eV. The results of x-ray diffraction have shown that the deposited films are polycrystalline without any second phases with preferential orientations along the (110), (101), (200) and (211) planes and an average grain size of 25.7 nm. It has been shown that increasing Al doping concentration lowers both the grain size and electrical conductivity of tin oxide significantly. ©