Improvement of gas-sensing properties of SnO 2 by surface chemical modification with diethoxydimethylsilane

Abstract

SnO 2 powder was subjected to repeated surface chemical modification with diethoxydimethylsilane (DMES) through condensation reaction with hydroxyl groups on the surface Sn 4+ sites, followed by calcination at 600°C, in order to investigate the effects of the incorporation of the SiO 2 component on the gas-sensing properties of a partially sintered SnO 2 sensor. Secondary ion mass spectroscopy and elemental analysis confirmed the incorporation of the SiO 2 component on the SnO 2 surface. The amount of the Si atoms introduced with a single time modification was about 25% of the surface Sn 4+ sites. Temperature programmed desorption peaks of oxygen adsorbates and surface hydroxyl groups on the SnO 2 surface apparently disappeared with the repeated modification, but it was suggested that the surface was not completely covered with a monolayer of SiO 2, suggesting that the SiO 2 component aggregated to some extent into fine particles. Gas sensitivity to H 2 was found to be markedly enhanced by the surface chemical modification, though the recovery rate became very slow. In contrast, sensitivity to CH 4 and C 3H 8 increased up to two cycles of modification. The variations in the gas-sensing properties are discussed in terms of the variations in the potential barrier height at the grain boundaries or necks.