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.