Alkylation of Si Surfaces Using a Two-Step Halogenation/Grignard Route

Abstract

Despite the fact that H-terminated, HF-etched Si crystals are the starting point for construction of most contemporary electronic devices, little is known about the chemical reactions of H-terminated Si surfaces under ambient temperature and pressure. Functionalization of Si without partial oxidation and/or formation of electrical defects is potentially important in fabricating improved electronic devices as well as in measurement of charge transfer rate constants at semiconductor/liquid contacts. One recently described approach involves the reaction of HF-etched Si(111) with olefins and organic diacyl peroxides, in which formation of a self-assembled (near)-monolayer of Si-alkyls was hypothesized. We report here an alternative strategy to functionalize HF-etched Si surfaces involving halogenation and subsequent reaction with alkyl Grignard or alkyl lithium reagents. We report vibrational spectroscopic and temperature programmed desorption data which confirm that the alkyl groups are bonded covalently to the Si surface, and we demonstrate that such overlayer formation can impede the undesirable oxidation of Si in a variety of environments while providing surfaces of high electrical quality.

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