Synthesis of well aligned silicon nanowire arrays by reflow of photoresist techniques

Well aligned Si nanowires (SiNWs) by Vapor-Liquid-Solid growth process are presented. Instead of using H₂, the current work uses N₂ as carrier gas. The growth conditions of SiNWs are controlled by the ratio of nitrogen versus silane gas. Tapering of nanowires was found at T=620degC and P=333 m torr, and the tapering parameter was reduced by increasing the N₂ gas. Tapering of nanowires is attributed to volume reduction of Au catalyst which diffuses onto the side wall of nanowires. However, it is found that the N₂ gas has a similar effect of O₂ gas which can reduce diffusion of Au catalyst so that volume reduction of Au catalyst is not so significant and nanowire growth becomes untapered. By adopting reflow of photoresist techniques, the size of metal catalyst for SiNWs growth can be significantly reduced, and the growth location of SiNWs can be defined. Well aligned Si nanowires can be obtained. However, aspect ratio of the nano size hole in the photoresist after reflow has a significant effect on the amount of the Au in the nanoparticles and thus the quality and growth of the nanowires.