The influence of Al doping on the electrical, optical and structural properties of SnO2 transparent conducting films deposited by the spray pyrolysis technique

In this study, the influence of increasing the Al concentration on the electrical, optical and structural properties of spray-pyrolysis-deposited SnO2 films has been investigated. The SnO2 : Al films were deposited at a substrate temperature of 480degreesC using a hydro-alcoholic solution consisting of tin and aluminium chlorides with various Al-doping levels from 0 to 30 wt% in solution. The [Al]/[Sn] atomic ratios were from 0 to 12.1 in films. The results of x-ray diffraction have shown that the deposited films are polycrystalline without any second phases with preferential orientations along the (110), (211) and (30 1) planes and an average grain size of 28.7 rim. Also, the Hall effect and resistivity measurements of the films show that for a specific acceptor dopant (Al) concentration (8.0 at% in film), majority carriers convert from electrons to holes and p-conductivity dominates. The optical absorption edge for undoped SnO2 films lies at 4.105 eV, whereas for high acceptor-doped films it shifts towards lower energies (longer wavelengths) in the range of 4.105-3.604 eV.