Enhancement of Field Emission from Silicon Nanowires Treated with Carbon Tetrafluoride Plasma

Abstract

In this study, a simple method using carbon tetrafluoride (CF4) plasma to functionalize the surface and to modify the structures of silicon nanowires (SiNWs) grown on silicon substrates is presented. A layer of nickel was evaporated onto a (100) silicon substrate to induce the growth of SiNWs at 1000 °C for 2 h. Oxygen derived from native oxide lying on the silicon substrate was incorporated into SiNWs resulting in silica nanowires. Due to its high resistivity, the emitted currents from SiNWs are much lower than those emitted from carbon nanotubes. After 4 min of CF4 plasma treatment, a large increase (more than two orders of magnitude) in the emitted current is observed. It is found that conglomeration of SiNWs is found after CF4 plasma treatment which increases the surface density of emission sites. Furthermore, the SiO2 layer covering the surface of SiNWs has been removed by CF4 plasma etching. These two factors combined to obtain the enhanced field-emission characteristics of SiNWs. However, nonvolatile fluorocarbon polymers may form on the sidewall of SiNW after prolonged CF4 plasma treatment and thus field-emission current is lowered. These results clearly manifest the potential of using SiNWs in field emitter applications.