SE ADLATTICES FORMED ON AU(100), STUDIES BY LEED, AES, STM AND ELECTROCHEMISTRY

Ordered selenium atomic layers have been formed electrochemically on A u(100) at a series of coverages. Cyclic voltammetry and coulometry wer e used to study the deposition process, and to determine the correspon ding coverages of a number of Se structures. Structures, with Se cover ages of 0.25, 0.33, 0.5, and 0.89 monolayers, were identified using ul tra high vacuum - electrochemical techniques as well as scanning tunne ling microscopy. The corresponding unit cells of those structures were : p(2 x 2), (2 x root 10), c(2 x 2), and a mostly (3 x root 10), compo sed of close-packed Se, rings. Pit formation, associated with the form ation of the densely packed Se-8 ring structure, was observed. They ar e 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(2x2), via anodic stripping. Se atomic layers were for med electrochemically in three ways: direct reduction from a HSeO3- so lution; anodic stripping of previously formed bulk Se; or cathodic str ipping of previously formed bulk Se. All three resulted in equivalent atomic layer structures on the Au(100) surface, but with some variatio n in the homogeneity and distribution of particular structures. (C) 19 97 Elsevier Science B.V.