title: Aqueous electrodeposition of Ge monolayers.
abstract: The electrodeposition of germanium on Au(111) in aqueous solutions has been investigated by means of cyclic voltammetry, Auger electron spectroscopy, and in situ scanning tunneling microscopy (STM). The data yield a picture of germanium deposition, which starts with the formation of two well-ordered hydroxide phases, with 1/3 ML and 4/9 ML coverages upon initial reduction of the Ge(IV) species (probably H(2)GeO(3) at pH 4.7). Those structures appear to result from a three-electron reduction to form surface-limited structures with (square root(3) x square root(3))R30 degrees or (3 x 3) unit cells, respectively. Further reduction, probably in a two-electron process from the hydroxide structures, resulted in a germanium hydride structure, again surface-limited, with a coverage of close to 0.8 ML. The hydride structure is very flat, though with the periodic modulation characteristic of a Moiré pattern. Longer deposition times and lower potentials resulted in increased coverage of Ge in some cases, but with apparently limited coverage as a function of pH. The maximum Ge coverage, about 4 ML, was observed using a pH 9.32 deposition solution. At potentials negative of the Moiré pattern, about -850 mV versus Ag/AgCl, a "corruption" of the smooth Moiré pattern occurred. This roughening appears to mark the initial formation of a Au-Ge alloy, accounting for the observation of coverage in excess of that needed to form the Moiré pattern at some pH values.
authors.affiliation: Department of Chemistry, The University of Georgia, Athens, Georgia 30602, USA.
authors.forename: Xuehai
authors.initials: X
authors.lastname: Liang
authors.forename: Youn-Geun
authors.initials: YG
authors.lastname: Kim
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Gebergziabiher
authors.forename: John L
authors.initials: JL
authors.lastname: Stickney