Adsorption and thermal reactivity of dimethyl trisulfide on a Au(111) single-crystal surface

Abstract

We investigated the adsorption and thermal reactivity of dimethyl trisulfide (DMTS, CH3SSSCH3) on a Au(111) single-crystal surface. X-ray photoelectron spectroscopy results indicated that at exposure temperatures of 100–300 K, DMTS dissociatively adsorbed as CH3S and CH3SS. That the dissociative adsorption rate was independent of exposure temperature suggested that DMTS dissociation on Au proceeded without an energy barrier at >100 K. In contrast, the thermal reactions of the adsorbed CH3S and CH3SS varied strongly with formation temperature. Specifically, after CH3S and CH3SS formed on Au(111) at 100 K, increasing the temperature resulted in associative desorption of CH3S as dimethyl disulfide (CH3SSCH3) and coupling reaction of CH3SS to ethane and atomic sulfur. In contrast, after CH3S and CH3SS formed at 150 K, increasing the temperature resulted not only in these two reactions but also in production of dimethyl disulfide and atomic sulfur by reaction between CH3S and CH3SS. At formation temperatures of 200 and 300 K, the only reaction observed was that between CH3S and CH3SS. These results suggest that the surface structure of the adsorbed species formed by DMTS dissociation on Au(111) depended on formation temperature. Specifically, at 100 K, dissociation of DMTS resulted in formation of CH3S and CH3SS islands on the Au(111) surface, whereas the two species were randomly adsorbed at higher formation temperatures.