POTENTIAL DEPENDENCE OF THE SURFACE SELF-DIFFUSION COEFFICIENT ON AU(100) IN SULFURIC-ACID-SOLUTION MEASURED BY ATOMIC-FORCE MICROSCOPY

We have measured the surface self-diffusion coefficient, D-s values on Au(100) in aqueous 50mM H2SO4 by using electrochemical atomic force microscopy (ECAFM). It was found that the D-s minimum appears around the potential of zero charge for the Au(100)-(1X1) surface (E(PZC(1X1)) is approximately equal to 270 mV versus NHE). The minimum D-s value of 10(-15) cm(2) s(-1) around the E(PZC(1X1)) agrees well with the extrapolated D-s value under the vapor phase. The results have shown that the potential dependence of the D-s values can be explained by considering not only the anion adsorption but also the role of excess charge densities at the Au(100) surface in altering the interatomic Au-Au bonds.