Electrochemical Reduction of Silicon Tetrachloride in an Intermediate-Temperature Ionic Liquid

Electrochemical reduction of silicon tetrachloride has been investigated in an equimolar N-ethyl-N-methylpyrrolidinium chloride-zinc chloride melt at 423 K for low-cost production of silicon thin films. A dark-brown substance was formed preferentially on the Ni substrate near the electrode-gas-melt three-phase interface by potentiostatic electrolysis at 0 V vs Zn(II)/Zn. Both energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy suggested that some SiCl4 was electrochemically reduced to amorphous Si in the present system. Cross-sectional observation of electrodeposited films by scanning electron microscopy suggested that the deposition rate in the present system is about 100-fold higher than that in the room-temperature system investigated in our previous study. Contrivances of the electrode configuration and the SiCl4-supplying method enabled electrodepositing the Si-containing film on almost the whole Ni substrate.