Silicon nanowires based resistors as gas sensors

Silicon nanowires (SiNWs) are synthesized following two methods: (i) the VLS (Vapor–Liquid–Solid) growth technique (bottom up approach) and (ii) the sidewall spacer fabrication (top-down approach) commonly used in microelectronic industry. The VLS growth technique uses gold nanoparticles to activate the vapor deposition of the precursor gas and to initiate 100 nm diameter SiNWs network growth. In the case of the sidewall spacer method, a polysilicon layer is deposited by LPCVD (Low Pressure Chemical Vapor Deposition) technique on SiO2 wall patterned by conventional UV lithography technique. Polysilicon film is then plasma etched. Accurate control of the etching rate leads to the formation of spacers with a 100 nm curvature radius that can be used as polysilicon NWs. Each kind of nanowires is integrated into resistors fabrication. Electrical measurements show the potential use of these SiNWs based resistors as gas sensors for ammonia (NH3) and smoke detection.