Surface reconstructions on gold in contact with solution

The low index planes of Au display a number of reconstructions when prepared in vacuum. UHV studies have established that the (100) surface relaxes to a (1 × 1) surface structure with the adsorption of very small amounts of ad-atoms. This (1 × 1) surface has been referred to as a metastable surface, and it quickly reverts to the reconstructed surface on heating to mild temperatures (200°C) in vacuum. Early reports indicated that this surface also reverted to a (1 × 1) if brought into contact with water, though more recent work suggests that this is not necessarily the case. We have just completed construction of a UHV system, equipped with AES, LEED and STM, designed to track changes in surface structure due to reactions in solution. The sample can be brought into contact with a solution without exposure to air, and we have used this to study the effect of exposing the (100) and (110) surfaces of Au to pure H₂O. The LEED and STM measurements from these surfaces suggest that they revert to the (1 × 1), even though the AES indicates that the surface is clean. Whether or not the surface reconstruction is induced by contact with water and not the adsorption of very small amounts of specific ions which are subsequently desorbed, is however, not resolved by these experiments.