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 0.1M ${\mathrm{HClO}}_4$, 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 versus saturated calomel electrode (SCE) yield images consisting primarily of domains having (1×2) symmetry. While the (1×2) 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 occurss. Three-atom-wide ribbons, lying along the [11¯0] direction, are seen to provide the basic building blocks of the reconstruction; these units also yield ‘‘added-row’’ domains of (1×n) symmetry, with n=3 or higher. The reconstruction is lifted, yielding the (1×1) Au(110) surface, rapidly (within ∼2 s) upon altering the potential to 0 V vs SCE, yet reappears immediately upon returning to -0.3 V.