Fabrication and characterization of silicon nanowires for electromechanical and gas sensing application

(eng) When dimensions of material approach nanoscale, it often reveals startling properties which pave way to innovative functionality. These unique properties when compared to bulk material make them interesting candidates for new technologies. In a race to sustain Moore’s Law, silicon nanowires which possess remarkable properties diverse from bulk-silicon have gained notable attention. With advancement in technology engineers have mastered the art of fabrication of nanowires, but there exists a big gap in understanding various phenomena at this scale. The aim of this thesis is to bridge the gap and give an insight into some interesting properties and application of silicon nanowires. Top-down method with electron beam lithography is used to fabricate silicon nanowires. The nanowires are released with various methods to determine their mechanical properties such as maximum release length without stiction, residual stress and stress gradient. Followed by this, a novel method to determine fracture strain based on “internal stress relaxation” method is presented. Fracture strain of 5% is measured in silicon nanowires when compared to 0.3% for bulk-silicon. Very large piezoresistance is observed in nanowires although the detailed mechanism behind this is not yet well understood. Finally, the use of functionalized silicon nanowires for gas detection is demonstrated with very large sensitivity and detection window reported for the first time.