Department of Chemistry, The University of Georgia, Athens, Georgia 30602, USA.
Langmuir. 2010 Feb 16;26(4):2877-84. doi: 10.1021/la902929j.
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.
在水溶液中，通过循环伏安法、俄歇电子能谱和原位扫描隧道显微镜（STM）研究了锗在 Au(111) 上的电沉积。数据提供了锗沉积的图像，该沉积始于两种有序的氢氧化物相的形成，初始还原 Ge(IV) 物种（可能在 pH 4.7 时为 H(2)GeO(3)）时，其覆盖度分别为 1/3 ML 和 4/9 ML。这些结构似乎是由三电子还原形成的，形成表面受限结构，分别具有 (sqrt(3) x sqrt(3))R30 度或 (3 x 3) 单位细胞。进一步的还原，可能是从氢氧化物结构的两电子过程，导致锗氢化物结构，再次是表面受限的，覆盖度接近 0.8 ML。尽管具有莫尔图案的周期性调制特征，但氢化物结构非常平坦。在某些情况下，较长的沉积时间和较低的电势会导致 Ge 覆盖率增加，但随着 pH 值的增加，覆盖率似乎有限。使用 pH 9.32 的沉积溶液观察到最大 Ge 覆盖率约为 4 ML。在 Moiré 图案负电位下，约 -850 mV 相对于 Ag/AgCl，光滑的 Moiré 图案发生“腐蚀”。这种粗糙化似乎标志着 Au-Ge 合金的初始形成，这解释了在某些 pH 值下观察到超过形成 Moiré 图案所需的覆盖率的原因。
