Molecular Self-Assembly of Organic Thiocyanates on Au(111)

Abstract

Organic self-assembled monolayers (SAMs) on gold have been extensively studied due to fundamental interests in surface science and various technological applications [1-3]. In this work, SAM prepared by spontaneous adsorption of alkythiocyanate (ATC) on Au(111) were formed by both solution and ambient-pressure vapor deposition methods at room temperature and 50 °C. STM imaging revealed for the first time that the adsorption of ATC on Au(111) in solution leads to the formation of partial ordered SAMs containing small ordered domains, whereas ATC SAMs formed by vapor deposition have a long-range ordered domains, which can be described as (√3 × √19)R5° or c(4 × 2) structure. Differently from alkanethiol SAMs, surface structure of ATC SAMs was strongly influenced by alkylchain length. From STM and x-ray photoelectron spectroscopy measurements, we found that vapor deposition is more suitable for the fabrication of high-quality thiocyanate SAMs on gold compared to solution deposition. The results obtained here will be very useful in understanding the SAM formation of organic thiocyanates on gold surfaces.