[[alternative]]Adsorption and Thermal Reactions of Alkanethiols on GaAs(100)

[[abstract]]Organothiols and related organosulfur compounds hold promise for using as self-assembled ultra-thin electron beam resists and monolayer passivation layers. We report the results of temperature-programmed desorption (TPD) and X-ray photoemission spectroscopy (XPS) studies of the surface chemistry of alkanethiols (CH3SH, C2H5SH, C4H9SH and CH3SSCH3) on GaAs(100). Dissociation of sulfhydryl hydrogen (RS-H) of alkanethiol results in the formation of alkanethiolate at adsorption temperature 115 K. All of these alkanethiolates can decompose to evolve hydrocarbon via scission of the C-S bond, resulting in deposition of sulfur on Ga and As sites of surface. The dissociation of surface alkanethiolates is accompanied by the recombinative desorption of alkanethiol and hydrogen. The thermal reaction of methanethiolate appears to desorb methyl radical, while neither hydrogenation of CH4 nor coupling reaction of C2H6 undergo dissociative chemisorption. The surface of C2H5S and C4H9S undergo exclusively elimination of β-hydride to form C2H4 and C4H8 with desorption of H2. At a large coverage, most of dimethyl disulfides carry out the same passways as methanethiol reaction. The rests dissociate to form CH3SS of chemisorbed intermediates, and then react with segregation of methyl group to gaseous CH3SCH3. This paper discusses the surface reaction mechanisms of alkanethiols through products formed on GaAs(100).