Catalyst-adsorptive oxide-semiconductor gas sensors

Abstract

The demand for better environmental control and safety has increased research activities in solid state gas sensors. One of the research trends exploits the silicon microfabrication technique to produce small, rugged and low cost gas sensors. Silicon based gas sensors utilizing catalytic metals such as palladium, platinum or other noble metals as the gate material for an MOS capacitor, transistor or Schottky barrier diode have been extensively studied for detection of hydrogen, hydrocarbon, alcohol vapor, hydrogen sulfide, ammonia and carbon monoxide [l-5]. We have recently explored a new family of device structures utilizing a catalyst-adsorptive oxide-semiconductor MIS structure for gas detection. The first prototype device fabricated in the MIS configuration of Pd-SnO,Si,N,-SiO&-Al, with resistive SnO, as the oxygen adsorption agent and Pd as catalyst, for the detection of oxygen at room temperature has been reported by Kang et al. [6]. In this report we present data on device characteristics of a family of gas detectors with Pd, Pt or Ag as catalyst and SnO, or ZnO as the adsorptive oxide in the MIS configuration for the detection of 02, H2 and CO. AV,, in the C-V plot was measured. The following parameters characterizing the device were determined: (a) shift in flat-band voltage as a function of gas partial pressure and temperature, (b) adsorption and desorption rates and device response time constant as a function of temperature and gas partial pressure and (c) gas adsorption activation energy of the device at a fixed gas partial pressure.