Moiré Structure of the 2-Mercaptobenzothiazole Corrosion Inhibitor Adsorbed on a (111)-Oriented Copper Surface

The adsorption of 2-mercaptobenzothiazole (2-MBT) vapor on a Cu(111) surface under ultra-low pressure was investigated. For an exposure of 45 L at 150°C, a Moiré pattern was observed as a result of the superposition of an underlying (SQRT3xSQRT3)R30°structure and an outer layer compressed by 18% and rotated by 1.2°. The Moiré pattern was rich in S bonded to Cu as a result of molecular decomposition and partial desorption and was transformed to a (SQRT7×SQRT7)R19.1°structure when the sample temperature was increased above 250°C during deposition. This pre-adsorbed Moiréstructure led to the sharp decrease of the oxidation kinetics, which better protects copper against corrosion than the non-ordered 2-MBT monolayer formed at room temperature. Upon further exposure to 2-MBT at room temperature, an equivalent monolayer of the molecule was adsorbed on the Moiré structure at saturation whereas a multilayer was formed for the direct deposition on Cu(111) at room temperature.