Silicon nano-wire fabrication and its applications

This thesis focuses on the fabrication of silicon nanowires and their applications in MOS capacitors. Silicon nanowires (SiNWs) were fabricated using the metal-assisted chemical etching method (MACE) and AgNO3, HF, and H2O2 were used as the precursors during the process. Silicon nanowires were fabricated by using three different samples of silicon substrates and were etched in HF/H2O2/H2O for 10 min, 30 min, and 60 min. Subsequently, SiO2 was grown onto n-Si (100) and SiNWs/n-Si (100) substrates by using both dry and wet oxidation methods in a diffusion furnace at 1000℃ for 30min. The crystalline structures and surface morphologies of SiNWs and SiO2/SiNWs were investigated by x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. To investigate the electrical characteristics of the capacitors, the capacitance-voltage(C-V) measurements were performed at 1MHz for the MOS capacitor without SiNWs and the length of 1µm, 2µm, and 4µm SiNWs capacitors. MOS capacitor without SiNWs was found to have the highest capacitance value and the highest calculated dielectric constant value of about 4.18. However, the value of the oxide capacitance in the accumulation region decreased with an increase in the length of the SiNWs capacitor. The 1µm SiNWs capacitor was chosen as the optimum because this capacitor had the highest oxide capacitance and highest k- value compared to other SiNWs capacitors. Therefore, this capacitor was irradiated by using a gamma-ray source at different doses ranging from 1Gy to 40Gy. It was found that the capacitance value increased with an increase in the radiation dose. Moreover, the results demonstrated that interface states density(D_it ), oxide trap(〖∆N〗_ot ) and interface trap charges ∆N_it were induced during gamma irradiation.