Revealing the role of Σ3{112} Si grain boundary local structures in impurity segregation

The interfacial structure of a silicon grain boundary (Si-GB) plays a decisive role on its chemical functionalization and has implications in diverse physical-chemical properties of the material. Therefore, GB interface is particularly relevant when the material is employed in high performance technological applications. Here, we studied from first principles the role of GB interface by providing an atomistic understanding of two different Σ3{112} Si-GB models. These models are (1×1) and (1×2) Σ3{112} Si-GBs which lead to different structural reconstruction. Starting from these two models, we have shown that geometry optimization has an important role on the structural reconstruction of the GB interface and therefore on its properties. For this reason, we discussed different methodologies to define an optimal relaxation protocol. The influence of the local structures in (1×1) and (1×2) models have also been investigated in the presence of vacancies where different light impurities of different valency (C, N, H, O) can segregate. We studied how local structures in (1×1) and (1×2) models are modified by the presence of vacancies and impurities. These structural modifications have been correlated with the changes of the energetics and electronic properties of the GBs. The behaviour of (1×1) and (1×2) models demonstrated to be significantly different. The interaction with vacancies and the segregation of C, N, H and O are significantly different depending on the type of local structures present in Σ3{112} Si-GB.