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

Low-energy electron-stimulated desorption (ESD) of D+ from D2O has been use d 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 amorphou s 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-crystallin e phase transition near 155 K. Ice deposited at 155 K forms an epitaxial cr ystalline 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 orderin g or morphology than the epitaxial film deposited between 150 and 155 K. Ic e deposited at 90 K on top of the epitaxial film is amorphous, but it cryst allizes to a form similar to that of the underlying crystalline ice substra te. This suggests that, in this case, the buried two-dimensional interface nucleates the crystallization. (C) 2000 Elsevier Science B.V. All rights re served.