Self-activated ultrahigh chemosensitivity of oxide thin film nanostructures for transparent sensors

One of the top design priorities for semiconductor chemical sensors is developing simple, low-cost, sensitive and reliable sensors to be built in handheld devices. However, the need to implement heating elements in sensor devices, and the resulting high power consumption, remains a major obstacle for the realization of miniaturized and integrated chemoresistive thin film sensors based on metal oxides. Here we demonstrate structurally simple but extremely efficient all oxide chemoresistive sensors with similar to 90% transmittance at visible wavelengths. Highly effective self-activation in anisotropically self-assembled nanocolumnar tungsten oxide thin films on glass substrate with indium-tin oxide electrodes enables ultrahigh response to nitrogen dioxide and volatile organic compounds with detection limits down to parts per trillion levels and power consumption less than 0.2 microwatts. Beyond the sensing performance, high transparency at visible wavelengths creates opportunities for their use in transparent electronic circuitry and optoelectronic devices with avenues for further functional convergence.open181

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

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

LPCVD and PECVD silicon nitride for microelectronics technology

303-309<span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">Silicon nitride deposition by chemical vapour deposition (CYD) based techniques like low pressure CYD (LPCYD) and plasma enhanced CYD (PECYD) is described in this paper. The technological advantages of silicon nitride deposition by these two techniques, developed at CEERI, are discussed in detail. Applications of LPCYD nitride films for LOCOS, <span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">composite gate structures for MNOS and MOS devices are highlighted. The importance of PECYD nitride films for diffusion masking of compound semiconductors, and for passivation in Si, GaAs, and InP devices are demonstrated. Process parameters of LPCYD and PECYD nitride deposition have been optimized for various substrate conditions depending on the technological requirements. Material properties are being explored for various micromachining activities, which includes diaphragm , cantilever, and beam formations. </span