AVS 45th International Symposium
    Surface Science Division Friday Sessions
       Session SS2-FrM

Paper SS2-FrM2
Crystallization Kinetics of Amorphous Solid Water: The Effect of Underlying Substrate

Friday, November 6, 1998, 8:40 am, Room 309

Session: Water and Ice Interfaces
Presenter: Z. Dohnálek, Pacific Northwest National Laboratory
Authors: Z. Dohnálek, Pacific Northwest National Laboratory
G.A. Kimmel, Pacific Northwest National Laboratory
K.P. Stevenson, Pacific Northwest National Laboratory
R.S. Smith, Pacific Northwest National Laboratory
B.D. Kay, Pacific Northwest National Laboratory
Correspondent: Click to Email
Thermally induced crystallization of ultra-thin amorphous solid water (ASW) films grown from a directed H@sub 2@O(g) beam is investigated. The temperature programmed desorption (TPD) spectra of N@sub 2@(g) physisorbed on ASW and crystalline ice (CI) surfaces exhibit striking differences in their lineshapes. The spectroscopic sensitivity of the N@sub 2@(g) TPD provides a unique opportunity to study the ASW crystallization with high sensitivity at temperatures well below H@sub 2@O desorption. The ASW crystallization kinetics are followed isothermally on Pt(111) and CI substrates as a function of temperature and ASW film thickness. The crystallization kinetics are strongly substrate dependent. On Pt(111), the data is consistent with the 3-dimensional crystallization model with the nucleation occurring in the bulk of the ASW film as shown previously.@footnote 1@ In contrast, on the CI substrate we observe that the CI surface serves as a 2-dimensional nucleation center and the crystallization proceeds from the ASW/CI interface towards the ASW surface. The activation barrier of the crystallization process on the CI substrate is significantly lowered as compared to the Pt(111) due to the presence of the crystalline template. @FootnoteText@ Pacific Northwest National Laboratory is operated for the Department of Energy by Battelle under Contract DE-AC06-76RLO 1830. @footnote 1@ R. S. Smith, C. Huang, E. K. L. Wong, and B. D. Kay, Surf. Sci. 367 (1996) L13.