Vertically Aligned Silicon Nanowire Mid-Infrared Carbon Monoxide Gas Sensor

Recently, semiconductor nanowires (SCNWs) have received much attention due to their crucial role in physiochemical science and their high prospect for essential applications in advanced devices such as solar cells, light-emitting-diodes, transistors and bio/chemical sensors. Vertically-aligned silicon nanowires (SiNWs) platform is considered as a strong candidate for advanced devices because of the high volume-to-surface area ratio as well as the high aspect ratio originating from the vertical structure. The CMOS compatibility of such a platform allows for cheap commercial manufacturing of nanophotonic integrated circuit. Nanowire diameter is usually on the order of several nanometers and is comparable to the Debye length and this often results in much larger sensitivity than their thin film.In this work, we design a vertically-aligned SiNW gas sensor optimized to detect carbon monoxide (CO) gas at the midinfrared (MIR) range. SiNWs of diameters of only 200 nanometers are grown on Si wafers. According to Liao et al, thin nanorods have a significantly better sensing performance than thick nanorods in the detection of C2H5OH and H2S (100 ppm) in air. In addition, (MIR) gas sensing is very useful and user friendly as the gases are directly detected when they flow through the active sensing region of the sensor with no required human interaction with the dangerous gases.Finite difference time domain (FDTD) simulations are performed to verify the results and a comparison between the FDTD results and the experimental ones are held.