Probing low-temperature water ice phases using electron-stimulated desorption

Low-energy electron-stimulated desorption (ESD) of D+ from D2O has been used to examine the phase and growth behavior of nanoscale vapor-deposited ice films grown on Pt(111) between 90–155 K. The D+ yield from porous amorphous solid water (deposited at 90 K) shows evidence for sintering near 120 K, increases between 120 and 140 K, and then drops at the amorphous–crystalline phase transition near 155 K. Ice deposited at 155 K forms an epitaxial crystalline film, with a D+ yield nearly one-third larger than the yield from crystalline films prepared by annealing the amorphous phase. This suggests that the film formed by annealing may have a different crystalline ordering or morphology than the epitaxial film deposited between 150 and 155 K. Ice deposited at 90 K on top of the epitaxial film is amorphous, but it crystallizes to a form similar to that of the underlying crystalline ice substrate. This suggests that, in this case, the buried two-dimensional interface nucleates the crystallization.