Structure and chemistry of Pd(100)-p(2×2)-p4g–Al surface alloy

Abstract

Atomic structure and hydrogen adsorption on the Pd(100)-p(2×2)-p4g–Al surface alloy have been studied using scanning tunneling microscopy and electron energy loss spectroscopy. It was found that the topmost layer of this surface alloy is reconstructed into the p(2×2)-p4g structure, which is in good agreement with the recent crystallographic results based on low-energy electron diffraction and ion scattering. The initial hydrogen adsorption on this surface alloy gives rise to an unusual desorption peak, which does not shift with increasing coverage as reported previously. The vibrational spectrum for adsorbed hydrogen corresponding to this desorption state shows a peak at 77 meV, which is assigned to H at four-fold hollow sites on the clock-reconstructed p(2×2)-p4g–Pd layer.