Interface Response Functions for Amorphous and Crystalline Si and the Implications for Explosive Crystallization

Abstract

Interface response functions (IRFs) for amorphous and crystalline forms of Si have been determined for several empirical atomic-scale models using Molecular Dynamics and compared to available experimental results fitted to a Wilson-Frenkel equation form. Stillinger–Weber (SW), the environment-dependent intermolecular potential (EDIP), and a version of the modified embedded atom method (MEAM) models were found to produce unacceptable representations of the IRFs of both solid phases; they were either unable to predict the amorphous melting point and/or the maximum solidification velocity. The best of these models was judged to be the SW potential, known to produce a very accurate IRF for crystalline silicon. Increasing the strength of the three-body term by up to 25% above that of the original SW potential improves the prediction of the melting characteristics of the amorphous phase. Above this limit, liquid phase properties are impaired. The resultant IRFs provide an important backdrop to understand the kinetics of explosive crystallization (EC) processes, as we shall show in comparison to recent experimental data on the EC of amorphous Ge. [A. Chojnacka and M.O. Thompson, in Growth, Evolution and Properties of Surfaces, Thin Films and Self-Organized Structures, edited by S.C. Moss, D.B. Poker, D. Ila, (Mat. Res. Soc. Symp. Proc. 648, Warrendale, PA 2001) p. P11.12.1–8]. We also provide evidence that homogeneous melting within the bulk of the amorphous material competes with heterogeneous melting at the planar amorphous/liquid interface.