Monolayer and multilayer adsorption of water on Ru(001)

Abstract

The properties of H2O adsorbed on Ru(001) at 95 K have been studied using a variety of techniques. The geometrical properties of the overlayer, deduced from low-energy electron diffraction and electron stimulated desorption ion angular distributions, indicate that layered, hydrogen-bonded clusters of H2O molecules form which have specific orientation with respect to the hexagonal metallic substrate. The vibrational, electronic, and thermodynamic properties of the first two layers of H2O admolecules are distinct from the properties of ice multilayers. At an adsorption temperature of 165 K, only the first two layers adsorb, and the H2O lattice is more ordered than at 95 K, which is an effect analogous to the irreversible vitreous-to-cubic phase transition which occurs at approximately this temperature in bulk ice. Off-specular scattering measurements have resolved overlapping vibrational features with different angular distributions of intensity.