SnO2 thin films were deposited on alumina substrates by R.F. magnetron sputtering to fabricate a sensor for ethylene gas detection. Two deposition parameters, the argon-to-oxygen ratio in sputter gas and post-annealing, were controlled to investigate the effects on the structural and gas sensing properties of SnO2 thin films. Argon-to-oxygen ratios ranging from 15:15 to 27.3:2.7 and post-annealing was performed at 650 C in air. The microstructure and crystalline phase of sputtered tin oxide are more influenced by post-annealing than the argon-to-oxygen ratio. In ethylene gas detection, post-annealed SnO2 films showed more highly improved sensitivity than as-deposited films, but the effect of the argon-to-oxygen ratio during SnO2 sputter deposition on ethylene gas sensing was not evident. (C) 2010 Elsevier B.V. All rights reserved.