Growth characteristics of silicon nanowires synthesized by vapor–liquid–solid growth in nanoporous alumina templates

Abstract

The fabrication of Si nanowires has been demonstrated using a combination of template-directed synthesis and vapor–liquid–solid (VLS) growth. The use of nanoporous alumina membranes for VLS growth provides control over nanowire diameter while also enabling the production of single crystal material. An investigation of the growth characteristics of Si nanowires over a temperature range from 400°C to 600°C, and over a SiH 4 partial pressure range from 0.13 to 0.65 Torr was carried out. The length of Si nanowires was found to be linearly dependent on growth time over this range of conditions. The nanowire growth rate increased from 0.068 μm/min at 400°C to 0.52 μm/min at 500°C at a constant SiH 4 partial pressure of 0.65 Torr. At temperatures greater than 500°C, Si deposited on the top surface and pore walls of the membrane thereby reducing the nanowire growth rate. The growth rate versus temperature data was used to calculate an activation energy of 22 kcal/mol for the nanowire growth process. This activation energy is believed to be associated with the decomposition of SiH 4 on the Au–Si liquid surface, which is considered to be the rate-determining step in the VLS growth process.