Investigation on local structures of Si-Cr-based solvents via ab initio molecular dynamics

Abstract

For the top-seeded solution growth (TSSG) method, an emerging technique for SiC single crystal fabrication, the high-temperature behavior of Si-Cr-based solvents after dissolving carbon (C) is critical for designing and optimizing the growth process. However, atomic-scale study of the local structures of Si-Cr-based solvents is still lacking. In this work, ab initio molecular dynamics (AIMD) method was employed to investigate the local structures and C diffusion behavior in Si-Cr-based solvents. It is revealed the addition of Ce or Al strengthens the Cr-C interactions while weakening the Si-C. Remarkably, C atoms in the Si-Cr solvent tend to aggregate, forming C-C dimers, whereas the addition of Ce/Al effectively suppresses this aggregation. The diffusion coefficients further indicate enhanced C migration in the Si-Cr-Ce and Si-Cr-Al solvents compared to the Si-Cr binary system. Moreover, the local structures of solvents are influenced by the crystalline facets of seed, with the C diffusion occurring more rapidly in the solvents in contact with the Si-face. Our work provides the first atomic-scale analysis of local structures of solvents and the diffusion behavior of the solute C atoms, which provides a new perspective for understanding the regulation mechanism of SiC high temperature solution growth.