Direct Electrodeposition of Crystalline Si Nanowires at Low Temperatures

Crystalline Si nanowires (SiNWs) were synthesized through an electrochemical liquid-liquid-solid (ec-LLS) deposition process from dissolved SiCl₄ in propylene carbonate at 90 °C using Ga nanoelectrodes. Scanning electron micrographs showed controlled growth of nanowire structured deposits from an array of Ga nanoelectrodes after the ec-LLS process. Energy dispersive X-ray spectroscopy indicated that the chemical composition of as deposit nanowires was Si with low Ga incorporation. X-ray diffraction and Raman spectroscopy separately indicated that the film of as-deposited SiNWs were crystalline. Electron beam diffraction of a single SiNW was taken within a transmission electron microscope and patterns for a diamond cubic crystal structure was obtained. Scanning electron micrographs of the orientation of nanowires on Si(111) and Si(100) substrates with different crystalline orientations suggested that epitaxial nanowire growth was achieved under these conditions. Cyclic voltammogram of SiCl₄ electrolyte on Ga nanoelectrodes and potential response of the chronopotentiometry experiment that produced SiNWs indicated that the SiNW deposition is energetically favorable to other parallel processes in the deposition electrolyte. Temperature dependence study showed that SiNWs could be produced using ec-LLS at as low as 60 °C, at which temperature Si solubility in Ga and Si diffusivity in Ga is sufficient for heterogeneous nucleation to occur at Ga/substrate interface.