Electrodeposition of nanoscale silicon in a room temperature ionic liquid

In this letter we report for the first time that silicon can be well electrodeposited on the nanoscale in the room temperature ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide saturated with SiCl4. This liquid exhibits on highly oriented pyrolytic graphite (HOPG) an electrochemical window of 4 V, which is limited in the anodic regime by the degradation of HOPG, in the cathodic regime by the irreversible reduction of the organic cation. A silicon layer with a thickness of 100 nm exhibits a band gap of 1.0 +/- 0.2 eV, which is shown by in situ current/voltage tunneling spectroscopy, indicating that semiconducting silicon was electrodeposited. (C) 2004 Elsevier B.V. All rights reserved.