Se adlattices formed on Au(100), studies by LEED, AES, STM and electrochemistry

Abstract

Ordered selenium atomic layers have been formed electrochemically on Au(100) at a series of coverages. Cyclic voltammetry and coulometry were used to study the deposition process, and to determine the corresponding coverages of a number of Se structures. Structures, with Se coverages of 0.25, 0.33, 0.5, and 0.89 monolayers, were identified using ultra high vacuum — electrochemical techniques as well as scanning tunneling microscopy. The corresponding unit cells of those structures were: p(2 × 2), (2 × √10), c(2 × 2), and a mostly (3 × √10), composed of close-packed Se 8 rings. Pit formation, associated with the formation of the densely packed Se 8 ring structure, was observed. They are reminiscent of pits observed in self-assembled monolayers of alkane thiols on Au surfaces. The pits disappeared as the structure, composed of Se rings, was converted to lower coverage structures, such as the 0.25 monolayer p(2 × 2), via anodic stripping. Se atomic layers were formed electrochemically in three ways: direct reduction from a HSeO − 3 solution; anodic stripping of previously formed bulk Se; or cathodic stripping of previously formed bulk Se. All three methods resulted in equivalent atomic layer structures on the Au(100) surface, but with some variation in the homogeneity and distribution of particular structures.