In situ electrochemical ATR-FTIR spectroscopic investigation of hydrogen-terminated Si(111) surface in diluted NH4F solution

In situ real-time and electrochemical attenuated total reflection Fourier t ransform infrared (ATR-FTIR) spectroscopy has been employed to study the de pendence of hydride structures of an Si(111) surface in diluted NH4F soluti on on etching time and applied potential. The in situ real-time ATR-FTIR re sult shows that the Si(111) surface remains H terminated in diluted NH4F so lution, and the hydride on Si(111) has a strong interaction with water mole cules under cathodic potential control. Potential dependence of the in situ electrochemical ATR-FTIR spectra reveals that Si(111) surface is free of o xide at the open circuit potential (OCP) and SiHO3 is formed only at potent ials positive of the OCP. Infrared roughness factors, defined as the ratio of monohydride at steps or dihydride over the monohydride on the (111) plan e, suggest that monohydride chain steps are the dominating defects on the S i(111) surface in NH4F at cathodic electrode potential. Horizontal (D') and vertical (D) dihydrides are predominant on the Si(111) surface leading to roughened morphology via oxidation at anodic potential. (C) 2001 The Electr ochemical Society.