Formation of Si nanowires by the electrochemical reduction of SiO2 with Ni or NiO additives

Abstract

Various morphologies of silicon nanowires (SiNWs) were successfully prepared by the electrochemical reduction of silica mixed with different additives (Au, Ag, Fe, Co, Ni, and NiO, respectively). Straight SiNWs were extensively obtained by the electro-reduction of porous Ni/SiO₂ blocks in molten CaCl₂ at 900 °C. The SiNWs had a wide diameter distribution of 80 to 350 nm, and the Ni–Si droplets were found on the tips of the nanowires. The growth mechanism of SiNWs was investigated, which could reveal that the nano-sized Ni–Si droplets formed at the Ni/SiO₂/CaCl₂ three-phase interlines. Based on the mechanism proposed, NiO particles with sub-micrometer size were selected as the additive, and straight SiNWs with diameters of 60 to 150 nm were also prepared via the electrochemical process.