(2d) The Effect of Density On Silicon Nanowires Growth and Tapering

Silicon nanowires (Si NWs) have many potential device applications in areas such as nanoelectronics and nanoelectromechanical systems (NEMS), and thus it is important to be able to tightly control the growth of these nanowires. The effect of Au colloid catalyst density and temperature on Si NWs growth rate and tapering is studied. The densities examined are high (0.29 ? 1.95 wires/µm²) and low (0.07 - .27 wires/µm²) while the temperature range is 780°C ? 900°C. The SiNWs are grown using the vapor-liquid-solid (VLS) mechanism in a chemical vapor deposition reactor with silicon tetrachloride as precursor. Scanning electron micrographs are analyzed to characterize the growth rate and tapering of the resulting Si NWs. Growth rate and tapering trends are found to differ for low and high wire densities. At higher wire densities, growth rate is found to increase as temperature increases, then decrease after a certain temperature. Tapering decreases dramatically as temperature increases. At lower wire densities, neither growth rate nor tapering changed significantly across the temperature range studied.