The Influence of F-Doping in SnO2 Thin Films

Abstract

Transparent conductive oxide (TCO) films are widely used in many consumer products. The properties of the TCO can critically affect the efficiency of the application. With this in mind the surface morphological, optical and electrical properties have been targeted by systematic exploration of the Atmospheric Pressure Chemical Vapour Deposition (APCVD) growth parameters and in this work particularly the effect of dopant concentrations. APCVD processes are particularly suited to use in industry due to the high volume, continuous growth processes and fast growth rates achievable. Using the APCVD process, F-doped SnO2 has been deposited on glass using monobutyl tin trichloride with trifluoro-acetic acid as the dopant source. The deposited films were characterised for crystallinity, morphology, optical haze and electrical properties. Additionally, the stability of the films to post growth annealing were studied, as this is an important factor as most TCO’s will need further processing for the production of consumer products. It has been shown that increasing the dopant levels led to a decrease in surface roughness along with a reduction in feature size. The surface features also showed a decrease in the average angle, although with a broader distribution. As expected increased doping gave increased carrier concentration and mobility, with a non-linear decrease in resistivity. The polycrystalline structure became less selective in orientation on doping, but no further change was seen on increasing the dopant level. The samples tested showed only marginal changes in electrical and optical properties at elevated temperatures, confirming their thermal stability.