Structural Dynamics of Adsorption Equilibrium for Iodine Adsorbed on Au(111)

The structural dynamics of an iodide layer adsorbed on Au(111) were investigated using X-ray photon correlation spectroscopy (XPCS), electrochemical scanning tunneling microscopy (STM), and time-resolved X-ray diffraction. At the adsorption equilibrium of iodide at a constant electrode potential, the STM images captured at regular intervals show the migration of atomic vacancy sites in the ordered adsorbed iodide layer. The results indicate that reversible adsorption/desorption and site conversion continuously occur at the equilibrium state. Although the transitions occur at various time scales according to the STM images, the time decay of the autocorrelation function at the specular position is estimated to be 127 s according to the XPCS measurement. The dynamics observed using XPCS suggest that the vertical relaxation of the surface layers is associated with the adsorption of iodide.