Structure of Silver (100) and (111) Single-Crystal Surfaces Obtained by Chemical Polishing.

In single-crystal electrochemical studies, various researchers have prepared the electrode surfaces by mechanical polishing followed by chemical polishing without further cleaning or high temperature annealing in vacuo. The quality of such single-crystal surfaces is in question. The present work has involved the use of LEED Low Energy Electron Diffraction and Auger electron spectroscopy AES to examine the order and purity of the silver 111 and 100 surfaces after preparation with such procedures with the chemical polishing carried out in a cyanide-hydrogen peroxide solution. For both surfaces the LEED patterns have surprisingly well-defined spots indicating a high two-dimensional periodicity, although not as ordered as the UHV cleaned and annealed surfaces. Highly diffuse background and weak fractional-order spots are present in the LEED pattern of the chemically polished surfaces, probably due to random and order impurity adsorption during transfer to the vacuum chamber. The Auger electron spectra before sputtering indicate the main impurity to be carbonaceous with no nitrogen detected. Voltammetry curves in 0.1M HF in a thin-layer cell are generally featureless over the potential range -0.1 to 0.45V vs RHE. These data indicate that chemical polishing can yield silver single-crystal surfaces of sufficient quality to produce LEED patterns but still short of the quality for UHV cleaned and annealed surfaces. Author