RECONSTRUCTION AT ORDERED AU(110)-AQUEOUS INTERFACES AS PROBED BY ATOMIC-RESOLUTION SCANNING TUNNELING MICROSCOPY

Atomic-resolution scanning-tunneling-microscopy images of ordered Au(110) in aqueous 0.1 M HClO4, reported as a function of electrode potential, provide an unusually detailed picture of surface reconstruction. Lowering the potential of a freshly annealed surface to -0.3 V versus saturated calomel electrode (SCE) yield images consisting primarily of domains having (1 x 2) symmetry. While the (1 x 2) structure exhibits an atomic density commensurate with the usual "missing-row" model, the images suggest that significant relaxation of both top- and second-layer atoms occurs. Three-atom-wide ribbons, lying along the [110BAR] direction, are seen to provide the basic building blocks of the reconstruction; these units also yield "added-row" domains of (1 x n) symmetry, with n = 3 or higher. The reconstruction is lifted, yielding the (1 x 1) Au(110) surface, rapidly (within approximately 2 s) upon altering the potential to 0 V vs SCE, yet reappears immediately upon returning to -0.3 V.