Formation of Sulfur Atomic Layers on Gold from Aqueous Solutions of Sulfide and Thiosulfate: Studies Using EC-STM, UHV-EC, and TLEC

Abstract

The formation of S atomic layers on Au from alkaline solutions of sulfide and thiosulfate is described. These studies are relevant to the formation of self-assembled monolayers (SAMs), as sulfide can be thought of as the simplest thiol and, thus, S atomic layers as the shortest chain SAM. S atomic layers are also of interest as precursors for the electrochemical formation of compound semiconductor thin films such as ZnS, CdS, and PbS. The deposition of S was investigated using electrochemical scanning tunneling microscopy (EC-STM), thin layer electrochemistry (TLEC), and ultrahigh vacuum electrochemical techniques (UHV-EC). UHV-EC studies included analysis with Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS). EC-STM and LEED revealed a 1/3 coverage (√3 × √3)R30°-S structure, previously observed by a number of workers, formed from both sulfide and thiosulfate solutions. From sulfide solutions, EC-STM showed that the (√3 × √3)R30°-S struc...