Step effects on surface diffusion of H on stepped Pt(111) were studied by linear optical diffraction technique at 90 to 150K. Diffusion anisotropy on stepped Pt(111) surfaces was observed: the unexpected enhanced diffusion perpendicular to steps cannot be explained within the lattice gas model on stepped substrates, indicating a non-local and directional step effect. The coverage-dependent diffusion coefficient on flat Pt(111) surface was also measured over a wide coverage range from 0.1 to 0.8ML. They were analyzed within the framework of the lattice gas model using quasichemical approximation, indicating that H-H repulsive interaction could significantly affect the energy of saddle point as well as that at the adsorption sites.

Step Effects and Coverage Dependence of Hydrogen Atom Diffusion on Pt(111) Surfaces. C.Z.Zheng, C.K.Yeung, M.M.T.Loy, X.Xiao: Physical Review B, 2004, 70[20], 205402 (7pp)