Doped nano–phase tin oxide thin films for selective gas sensing

The paper deals with the development of ethanol gas sensing films of tin oxide nano–particles which are insensitive to saturated aliphatic hydrocarbons, such as gasoline vapours. Stannous alkoxide (particularly iso–propoxide) and tin 2–ethyl hexanoate in solution have been used for fabrication of tin oxide films on alumina substrates with two pre–fabricated gold electrodes. For achieving selectivity, attempts have been made to stabilise the desirable composition of tin oxide by addition of bivalent and trivalent dopants such as cadmium, lanthanum, molybdenum, zinc, aluminium, etc. in low concentrations (of the order of 0.5–2 mol %). The sensing behaviours of various tin oxide films so produced are studied in terms of resistance vs. time. Film morphology was studied using FESEM. XRD analysis was done for compositional characterisation.