PNNL

Abstract

We measure the isothermal crystallization kinetics of amorphous acetonitrile films using molecular beam dosing and reflection adsorption infrared spectroscopy RAIRS techniques. Experiments on a graphene covered Pt(111) substrate revealed that the crystallization rate slows dramatically at long times and that the overall kinetics cannot be described by a simple application of the Avrami equation. The crystallization kinetics also have a thickness dependence with the thinner films crystallizing much slower than thicker ones. Additional experiments showed that decane layers at both the substrate and vacuum interfaces can also affect the crystallization rates. A comparison of the crystallization rates for CH3CN and CD3CN films showed only an isotope effect of ~1.09. When amorphous films were deposited on a crystalline film, the crystalline layer did not act as a template for the formation of a crystalline growth front. These overall results suggest that the crystallization kinetics complicated indicating the possibility of multiple nucleation mechanisms. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. The research was performed using EMSL, a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory, which is operated by Battelle for the DOE.