APPLICATION OF THIN-FILM MATERIALS IN SOLID-STATE GAS SENSORS

The mode of operation of metal-insulator-semiconductor (MIS) hydrogen sensors, which contain Langmuir-Blodgett solid ultrathin films as the insulator layer, has been examined. The device response to low concent rations (0-6 ppm) of hydrogen in nitrogen at 373 K was observed to cor relate with analyte concentration according to the Lundstrom model, wh ile at lower temperatures or in the presence of air, no such correlati on was evident. Results from transient response and operating stabilit y tests, taken together with previously reported analyses using X-ray photoelectron spectroscopy, indicate significant differences, compared with conventional (oxide I-layer) MIS devices, in the mechanism of in teraction of hydrogen with the sensor. The palladium M-layer in the pr esent device does not appear to be porous, according to carbon monoxid e interference tests and it is proposed that there is no significant p ermeation of oxygen through the device.