VLS Silicon Nanowires based Resistors for Chemical Sensor Applications

Silicon nanowires (SiNWs) based resistors are fabricated in two different structures: i) inter-digital comb-shaped structure and ii) V-shaped groove structure. The SiNWs used are synthesized by VLS (Vapor-Liquid-Solid) mechanism using gold as metal catalyst and carried out by LPCVD (Low Pressure Chemical Vapor Deposition). For the former structure, tangled SiNWs network interconnects the inter-digital comb-shaped heavily doped electrodes. For the latter structure, tangled SiNWs network is locally synthesized inside a predefined V-shaped groove. Compared with the inter-digital structure, the V-shaped structure is more compatible with planar technology. Thanks to the high surface-to-volume ratio of SiNWs, high-efficiency surface modification can be obtained. The quantitative dynamic measurements under exposure to a wide range of gas (ammonia) concentration (from 175 ppm to 700 ppm) were performed and demonstrated high performance of the SiNWs based resistors as sensitive chemical sensors.