One dimensional silicon nanostructures prepared by oxidized porous silicon under heat treatment

Abstract

One dimensional high aspect ratio Si nanostructures were prepared by using oxidized sponge like nanostructured porous silicon (pSi) as a seed material. This can be considered as a complementary technique to synthesize silicon nanowires such as vapour–liquid–solid method (VLS). One dimensional silicon nanostructures were fabricated by subjecting pSi to heat treatment without metal assistance. It is shown that the aspect ratio can be tuned by controlling the concentration of oxygen (SiO2) and the porosity of the seed material (pSi). The atomic percentage of oxygen incorporated into pSi was estimated by Energy Dispersive X-ray Spectroscopy (EDS). Field Emission Scanning Electron Microscope (FESEM) confirms unambiguously the formation of silicon nanowires. The broad peak observed around 490cm−1 in Raman spectra further confirms the formation of Si NWs. At higher oxygen concentration, narrower (∼20nm) and longer (∼1μm) silicon nanowires have been achieved. The observed change in photoluminescence (PL) peak position towards lower wavelength as a function of the aspect ratio of Si NWs is in good agreement with quantum confinement effects. This work demonstrates a new oxide assisted method to prepare high aspect ratio silicon nanowires without using any metal catalysts.