Application of a cubic-like mesoporous silica film to a surface photovoltage gas sensing system

A self-ordered cubic-like mesoporous silica film has been successfully fabricated in a metal-insulator-semiconductor (=Au/SiO2 (cubic-like meso)/Si3N4/SiO2/Si) device based on the surface photovoltage (SPV) system and applied to an NO gas sensor. The self-ordered cubic-like mesoporous silica film is synthesized by using as a template in spin coating a nonionic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO100-PPO65-PEO100) type triblock copolymer surfactant. The sensing characteristics of the self-ordered cubic-like mesoporous SPV system have been investigated by repeated exposure to 100 ppm NO gas and standard air, as well as observation of the alternating (photo) current, which resulted from the physical adsorption and chemical interactions between detected NO gas and the self-ordered cubic-like mesoporous film. In sensing NO gas, this cubic-like mesoporous SPV system exhibits a response nearly five. times larger than that of a simple SPV sensor without mesoporous silica film. Even at room temperature, this mesoporous SPV system exhibits a recoverable response. These results can be explained by the characteristics of the cubic-like mesoporous silica film including large surface area and a bi-continuous mesopore structure. This kind of mesoporous film has a great potential for application to highly sensitive and responsive gas sensors. (C) 2002 Elsevier Science Inc. All rights reserved.