Structural changes during oxidation of Au(110)

Full text: We have constructed an Ultra High vacuum (UHV) system interfaced to an electro-chemical cell. The UHV system is equipped with Low Energy Electron Diffraction (LEED) and X-ray Photoelectron Spectroscopy (XPS). We have used these techniques to examine the oxidation of the Au(110) surface. The gold (110) single crystal exhibits a (2x1) surface structure when clean, but when immersed in 0.01 M HCIO4 under potential control, the structure has been found to change. Throughout the double layer region the structure remains as (2x1) but when the potential is increased above 0.9-1.0V vs Ag/AgCI, (the pre-oxidation region) the surface structure changes to a centred rectangular structure found to represent a c(2x2) over-layer. This structure is fairly stable and reproducible. After the initial oxidation the structure prevails until 1.2-1.3V whereupon oxidation occurs on a larger scale and the surface structure becomes (1x1). These structures return to (2x1) after the reduction of the oxide, proving that the structural changes are reversible. XPS of these regions has shown a difference in the chemical state of the oxygen. Adsorbed perchlorate ion is initially the only oxygen component but as the potential increases the peak shifts into the hydroxide region and finally it splits into a hydroxide peak and a metal oxide peak. This study indicates a new way of looking at the structure and composition of the gold surface and provides insight into the nature of the interaction between the surface and the solution