| dc.description.abstract | In this study, large area well-aligned silicon nanowire (SiNW) arrays were successfully synthesized on (001)Si substrates by redox reaction of Ag+ and Si in the aqueous solution containing silver nitrate (AgNO3(aq)) and hydrofluoric acid (HF(aq)). The growth kinetics of the SiNWs formed by redox reaction has been investigated. The lengths of the SiNWs were found to increase linearly in samples synthesized at 0–50 °C. By measuring the growth rate at different reaction temperatures, the activation energy for linear growth of the SiNWs was found to be 0.41 eV. In addition, by varying the concentrations of AgNO3 and HF solutions, the orders of reaction with respect to the reactants and the rate equation for the growth of SiNWs have been obtained. From TEM, SAED, and HRTEM analysis, the SiNWs are about 30-200 nm in width with aspect ratios of about 900-6000. The axial orientation of the SiNWs was identified to be along the [001] direction, which is the same as that of the initial (001)Si wafer. The possible mechanisms for the growth of SiNW arrays are discussed in the context of the localized electrochemical redox reaction processes and the oxidation and etching rates of different Si crystal planes.
For the evaporated Ni thin films on SiNWs samples after different heat treatments, the epitaxial NiSi2 phase was observed to form at an annealing temperature as low as 300 ℃. The formation temperature of NiSi2 phase is about 400-450 ℃ lower than what is usually needed for the NiSi to NiSi2 transformation. In addition, the effect on the enhanced formation of epitaxial NiSi2 is apparently more pronounced with a decrease in the width of SiNWs. Based on the SAED and TEM analysis, the epitaxial orientation relationships between the NiSi2 and SiNWs were identified to be [100]NiSi2//[100]Si, (002)NiSi2//(004)Si and [110]NiSi2//[110]Si, (1-11)NiSi2//(1-11)Si. The observed result could be attributed to the small lattice mismatch (－0.4 %) between NiSi2 and Si at room temperature, and the fast diffusion of Ni atoms via the surface of Ni films to the NiSi2/Si interface since the surface/volume ratio is higher for the one-dimensional (1D) nanowire structures. | en_US |