Nano-scale STM observation of dioctyl diselenide self-assembled monolayers on Au(111)

Abstract

Dioctyl diselenide (DODSe) self-assembled monolayers (SAMs) on Au(111) were investigated by scanning tunneling microscopy (STM), cyclic voltammetry (CV) and contact angle measurement. Compared to the formation of well ordered SAMs on Au(111) by octanethiol (OT), DODSe SAMs are composed of disordered phase and a number of vacancy island (VIs) with a higher VIs fraction. By varying immersion time, we observed the phase transition of DODSe SAMs from aggregated low surface phase to saturated missing-row ordered phase. In addition, we found that the fraction of VIs of DODSe SAMs are strongly influenced by solution concentration, which may be due to a strong adsorption of selenium headgroup on gold. It was also found that DODSe SAMs were formed unique VIs with a straight-line shape after annealing at elevated temperature which are never reported in other SAMs system. In this presentation, we will discuss about the unique surface characteristics of DODSe SAMs on Au(111).