Effect of immersion temperature on structure of the self-assembled monolayer of 1,2-diphenyldiselenide on gold surface

Abstract

Self-assembled monolayers (SAMs) made from 1,2-diphenyldiselenide (DBSe) on gold surface at 345 K for different immersion times (ITs) were characterized using scanning tunneling microscopy (STM). After short IT (10 min) at room temperature (RT), the SAM surface was densely covered with very small gold islands and no structural order could be obtained. When SAMs were prepared at 345 K for the same IT, only a few large gold islands were present and two different closely packed phases, namely, α and γ were found. These phases were unstable with increasing the IT to 24 h at 345 K and a new phase labeled δ was formed. The δ-phase exhibited unusual order with domain sizes exceeding 400 nm. Moreover, the gold islands were completely left leaving a rough surface with multilayer gold steps. Further increasing the IT to 48 h at the same solution temperature resulted in the formation of orientated vacancy islands having uncommon shapes with straight edges intersecting at 60° or 120° rather than the usual rounded shape. The steps defining the borders of the vacancy islands were also found to run preferentially along the faceting of the Au(111) substrate edges.