Morphological change of D2O layers on Ru(0 0 0 1) probed with He atom scattering

The morphological change of D2O layers on a Ru(0 0 0 1) surface has been investigated on the basis of He atom scattering. With the increase of D2O exposure on Ru(0 0 0 1) at 111 K, the intensity of a specularly reflected He beam continuously decreases up to the exposure of 1.0 L (Langmuir). At the D2O coverage of 1.0 adsorbed layer (∼1.5 L), which is characterized by temperature-programmed desorption measurements, the formation of the (√3 × √3)R30° superstructure as a result of the diffusion of D2O on the surface was confirmed by He atom diffraction. With the further increase of D2O exposure, at 2–3 adsorbed layers, the disordered structure was found to be on the surface at 111 K. The morphological change of the disordered layers was observed during annealing, and discussed in detail.