Methyl termination of Si(110) surface for an improved stability against oxidation

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Gupta, Ankit
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Conversion and storage of solar energy in the form of hydrogen fuel using a solar water splitting device is one approach to meet increasing energy demands. Silicon microwires that serve as the light absorbing elements in the proposed design of the device, consist of different facets with an orientation along {110} direction. Oxidation of the microwire surface adversely affects the performance of the device by limiting the available photovoltage to drive the water splitting reactions. Functionalization of the silicon surface with an organic group can improve the oxidative stability of the surface. In this work, methyl substitution on a (110)-oriented monohydride terminated silicon surface using a chlorination/alkylation procedure was studied. Transmission infrared spectroscopy (TIRS), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used for characterizing different surfaces. TIRS observations indicated presence of coupled monohydride chains along [-1 1 0] direction on the hydrogen terminated silicon surface which was also supported by AFM images. XPS studies revealed a surface coverage of 0.83 ML for a methyl-terminated surface. The methyl-terminated surface was found to be stable when exposed to air, only 0.2 ML of surface oxide was observed even after a month from sample preparation. Thus, this surface preparation strategy can be implemented for the functionalization of the microwire surface.
Methyl, Functionalization, Si(110), oxidation, silicon