Mechanisms of Reduced Surface Mobility in Liquid Silicon

JP Luo and JH Pei and JF Xiang and ZY Li and JH Choi and LJ Liu, JOURNAL OF PHYSICAL CHEMISTRY B, 129, 6944-6953 (2025).

DOI: 10.1021/acs.jpcb.5c02295

The surface diffusion properties of liquid silicon play a critical role in applications, such as semiconductor manufacturing and nanotechnology. Using molecular dynamics (MD) simulations based on two different popular empirical potentials, this study investigates the surface and bulk diffusion coefficients of liquid silicon. First-principle molecular dynamics simulation is also applied to provide validations. Results reveal that the size effect of the diffusion coefficient in the cubic system with surfaces will deviate from the theoretical relation (i.e., it decreases linearly with 1/L) to lower values. This effect is caused by an unusual phenomenon: the surface diffusion coefficients are lower than the bulk diffusion coefficients in liquid silicon, contrary to typical trends in other materials. This phenomenon is explained by analyzing the microstructure of the liquid surface including coordination number (CN) distributions and atomic mobility heterogeneity.

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