Formation and Structure of Dialkyl Diselenide Self-Assembled Monolayers on Au(111)

Abstract

Self-assembled monolayers (SAMs) of organic thiols prepared by solution deposition on gold are one of the most extensively studied system for obtaining well-ordered SAMs with high structural reproducibility and chemical stability.1,2 But, there has been a few works regarding organoselenide self-assembled monolayers on gold and ambient vapor deposition technique.3 In this study, dialkyl diselenides (DADSe) prepared by both ambient vapor deposition and solution deposition. The surface structures and phase transitions of DADSe SAMs prepared by ambient vapor deposition technique on Au(111) were investigated by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Compare to the solution deposition of disordered DADSe SAMs on Au(111), vapor deposited DADSe SAMs are composed of well ordered phase and less number of vacancy islands (VIs). We revealed the phase transitions of DADSe SAMs from molecular aggregations to disordered dense phases via less dense missing-row phases. We also found that deposition time and temperature are critical factors for determining the surface structures of DADSe SAMs in ambient vapor-pressure deposition.