A material for room temperature FET sensor to detect ammonia and hydrocarbon gases

Abstract

336-339<span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">Cobalt oxide has been reported as a new material for room temperature FET gas sensor. Thin films of cobalt oxide have been prepared by DC magnetron sputtering on oxidized silicon substrates and used as gas sensitive layers in a capacitively controlled field effect transistor (CCFET) structures. CCFET is a MOSFET with an extended gate electrode. Gas sensing behaviour of these films has been investigated at room temperature for different gases of varying concentrations, ranging from 10 ppm to <span style="font-size:15.5pt;mso-bidi-font-size:8.5pt;font-family: " times="" new="" roman","serif""="">10,000 <span style="font-size:15.0pt; mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">ppm. Gases such as CH<span style="font-size:13.0pt;mso-bidi-font-size:6.0pt; font-family:" times="" new="" roman","serif""="">4<span style="font-size: 13.0pt;mso-bidi-font-size:6.0pt;font-family:" times="" new="" roman","serif""="">, C3H8, NH3, CO, NO and H2 have been used to study the sensor performance. Since the measured sensor signal is not amplified, it is a direct measure of sensitivity of the film to a gas to which it is exposed. The CCFET structure, preparation of sensitive films and measurements are described in this paper. The results indicate that cobalt oxide is selectively sensitive to ammonia and hydrocarbon gases only with a little or negligible response to other gases. Signals of 5 mV and <span style="font-size:15.5pt;mso-bidi-font-size: 8.5pt;font-family:" times="" new="" roman","serif""="">30 <span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">mV for 10 ppm of the hydrocarbons and ammonia respectively have been observed. </span