Non-uniform SiO2 membranes produced by ion beam-assisted chemical vapor deposition to tune WO3 gas sensor microarrays

Ion beam-assisted chemical vapor deposition (IBAD) has been applied to prepare non-uniform SiO2 layers to adjust the gas selectivity of metal oxide gas sensors integrated in a microarray of 40 WO3 individually addressable gas sensor elements. SiO2 membranes with a thickness gradient in one direction are applied on microarrays to differentiate initially identical sensor elements with respect to their gas response. The analysis with X-ray photoelectron spectroscopy (XPS) and secondary neutral mass spectrometry (SNMS) showed the coating of the microarray by a SiO2 layer with a thickness gradient across the microarray to be successful. The gas-detecting properties were examined by exposing the SiO2-coated microarray to model gas atmospheres. A different gas response for each sensor element was obtained due to the non-uniform SiO2 coating resulting in decisive conductivity patterns of the microarray to be used for gas recognition. (C) 1998 Elsevier Science S.A. All rights reserved.