Carbon monoxide response of molybdenum oxide thin films deposited by different techniques

MoO3 thin films have been deposited on alumina substrates by radio frequenc y (RF) sputtering from a metallic molybdenum target in a reactive atmospher e and by the sol-gel (SG) technique using molybdenum ethoxide solutions. Th e as-deposited RF films have been annealed at 500 degrees C for 1 h, while the SG films have been annealed at temperature range between 400 degrees C and 700 degrees C for 1 h. The formation of a well-developed nanoparticle s tructure for the RF films with respect to the SG ones was suggested by scan ning electron microscopy (SEM) characterisation, X-ray diffraction (XRD) ha s confirmed the formation of crystalline orthorhombic MoO3 structures (JCPD S 5-508) for both the RF and SG films after annealing. The gas sensing prop erties towards CO have been examined. MoO3-based gas sensors developed are capable of CO down to few ppm with a very fast response. (C) 2000 Elsevier Science S.A. All rights reserved.