Evidence of Stranski-Krastanov growth at the initial stage of atmospheric water condensation.

The precipitation products (rain, snow and so on) of atmospheric water vapour are widely prevalent, and yet the map of its initial stage at a surface is still unclear. Here we investigate the condensation of water vapour occurring in both the hydrophobic-hydrophilic interface (graphene/mica) and the hydrophilic-hydrophilic interface (MoS2/mica) by in situ thermally controlled atomic force microscopy. By monitoring the dynamic dewetting/rewetting transitions process, the ice-like water adlayers, at the hydrophobic-hydrophilic interface and not at the hydrophilic-hydrophilic interface, stacked on top of each other up to three ice-Ih layers (each of height 3.7 ± 0.2 Å), and the transition from layers to droplets was directly visualized experimentally. Compared with molecular dynamics simulation, the Stranski-Krastanov growth model is better suited to describe the whole water condensation process at the hydrophobic-hydrophilic interface. The initial stage of the hydrometeor is rationalized, which potentially can be utilized for understanding the boundary condition for water transport and the aqueous interfacial chemistry.