Thesis (Ph.D.) - Cairo University - National Institute of Laser Enhanced Sciences - Department of Laser Sciences and Interactions

A lot of attention has recently been paid to semiconductor nanowires (SCNWs) due to their crucial role in physiochemical science and their high potential for important applications in advanced devices such as solar cells, light-emitting diodes, transistors, and bio / chemical sensors. Vertical-aligned silicon nanowires SiNWs platform is considered a strong candidate for advanced devices due to their high volume-to-surface ratio as well as the high aspect ratio resulting from the vertical structure. The CMOS functionality of such a system allows for cheap commercial production of nano-photonic integrated circuits. Nanowire diameter is typically on the order of several nanometers and is equivalent to the length of Debye, which often results in a much greater resistance than its thin film. In this thesis, we design a vertically aligned SiNWs gas sensor optimized to detect carbon monoxide (CO) and ammonia (NH3) gas at the mid-infrared (MIR) range. SiNWs with a diameter of only 200 nanometers are grown on Si wafers. According to Liao et al, thin nanotubes have significantly better sensing efficiency than thick nanotubes when detecting C2H5OH and H2S (100 ppm) in water. Besides, (MIR) gas sensing is very useful and user-friendly; as gasses are detected directly as they pass through the active sensing area of the sensor without human interaction with hazardous gases. Finite difference time-domain (FDTD) simulations are conducted to check the results and to hold a correlation between the FDTD and the experimental results

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