Tin oxide thin films prepared by laser-assisted metal–organic CVD: Structural and gas sensing properties

Amorphous and polycrystalline tin oxide (SnOx) thin films were grown by ArF excimer laser-induced metal–organic chemical vapour deposition (L-MOCVD) from tetramethyltin (TMT) and oxygen as precursors. The films structure and composition were investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The deposition temperature and the ratio of the TMT and oxygen flow rates have been optimised in order to minimise the residual carbon content and to achieve stoichiometric SnO2 films. The films deposited at room temperature were amorphous, strongly substoichiometric [O]:[Sn] = 1.3 and with a high residual carbon content depending on the TMT and oxygen ratio. Films grown at 300 °C were polycrystalline with [O]:[Sn] ratios up to 1.8 and with a much lower carbon content. The tin oxide films were subsequently used as sensing layers for gas detection. A satisfactory sensor performance was obtained for the oxidising NO2 and the reducing N2O, CH4, SO2, CO, CO2, H2 gases.