PNNL

Abstract

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 120-140 K, and then drops at the amorphous-crystalline phase transition near 155 K. Ice deposited at 155 K forms at 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 150-155 K. Ice deposited at 90 K on-top of the expitaxial film is amorphous but 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.