Molecular-level imaging of ice crystal structure and dynamics by atomic force microscopy

The atomic force microscope (AFM) was used to obtain molecular-level images of the structure and dynamics of ice crystals formed from vapor phase on a mica surface. The images show epitaxial growth of ice to form monolayers. Under contact force from the AFM tip, motion of these monolayers was observed. One of the interesting observations made in this study is that the adsorbed water layer freezes to form a polycrystalline structure consisting of a single monolayer. Detailed imaging of the grain boundaries shows highly disordered percolation structure with short-range alignment along crystallographic directions. It is proposed that the percolation grain boundaries are formed because of phase segregation during freezing of an ionic solution in the water monolayers.