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We describe the growth of intact D2O monolayer and multilayer structures on Ru(0001) using LEED, RAIRS, He scattering and gas adsorption to probe water crystallisation and the structures formed. Monolayer water forms a hexagonal √3 overlayer, containing flat and H-down water, which compresses at saturation. Density functional calculations suggest the monolayer does not adopt an ice bilayer structure, instead forming chains of flat and H-down water within the honeycomb structure. This arrangement leads to disorder in the O height and proton orientation, which is reflected in the LEED and He scattering. At low temperatures, where water mobility is limited, multilayer adsorption forms continuous, amorphous solid water films. These films are unstable, roughening on annealing to form multilayer ice crystallites and expose regions of water monolayer. Nucleation of multilayer ice clusters occurs above a critical coverage and temperature, and is followed by a rapid increase in thickness to expose more monolayer water. The ice clusters are stabilised by hydrogen bonding within the 3D structure and minimise their contact to the water monolayer. This behaviour is attributed to the strong interaction between first layer water and Ru(0001), which pins the monolayer into a structure that is unfavourable for bonding to a multilayer ice film. No ordered multilayer ice structures were seen by LEED, even at high coverage (~100 layers), indicating that the wetting layer will not reconstruct to accommodate an incommensurate ice Ih(0001) film to the metal surface. |