Unique domain structure of π-conjugated tolanethioacetate self-assembled monolayers on Au(1 1 1)

Surface structures of tolanethioacetate (TTA) self-assembled monolayers (SAMs) on Au(1 1 1), formed in a 0.5 mM N,N′-dimethylformamide (DMF) solution, were investigated as a function of solution temperature by scanning tunneling microscopy (STM). The STM study revealed that thioacetyl-terminated TTA molecules on Au(1 1 1) did not form ordered SAMs at room temperature and 80 °C, whereas the adsorption of TTA molecules on Au(1 1 1) at a solution temperature of 50 °C led to the formation of two mixed phases: a disordered phase and a unique ordered phase, consisting rod-like domains, which can be described as a (√6×√13)15° superstructure. From this study, it was demonstrated that solution temperature is a key factor controlling the two-dimensional SAM structure of TTA molecules.