MODULATION OF FLAT-BAND POTENTIAL AND INCREASE IN PHOTOVOLTAGE FOR N-SI ELECTRODES BY FORMATION OF HALOGEN ATOM TERMINATED SURFACE BONDS

The flat-band potential (U-FB) of n-Si electrodes in concentrated hydr ogen halide (HX) solutions, as determined from Morr-Schottky plots and the onset potential of photocurrent, shifts largely toward the negati ve with the decreasing electronegativity of halogen atoms. XPS studies have shown the presence of halogen atoms on the Si electrodes which w ere beforehand immersed in the HX solutions. The shift in U-FB can be explained as due to changes in surface potential by formation of Si-ha logen surface termination bonds.