A density functional theory study on the lattice trapping of (1 1 1) [1 [formula omitted]0] crack system of silicon implanted by different impurities

Abstract

Doped silicon (Si) is commonly applied in semiconductor industries. Different impurities impose different effects on the mechanical performance of Si micro/nano structures. In this work, we employ density functional theory (DFT) to investigate the influences of three typical substitutional impurities, boron (B), germanium (Ge) and arsenic (As) on the crack stability, characterized by lattice trapping, of (1 1 1) [1 1¯0] system. The impurities are located at the crack front. The simulations reveal that different impurities result in quite different crack advancing/healing behavior. The impurity B can greatly enhance the difficulty for crack propagation and healing. Therefore, the lattice trapping range is markedly expanded, indicating the elevated crack stability. In sharp contrast to B, when implanted with As, the crack tip advances under a notably lower load and heals more easily. The effects of Ge lie between B and As, i.e., the increased difficulty for crack propagation is close to B and that for crack healing is close to As. These impurities affect the lattice trapping mainly in two manners. The range and strength of interatomic interactions largely depend on the orbital hybridization when Si atoms bond with foreign atoms. Further, this can change the reconstruction pattern of the fractured surfaces near the crack front. Impurities B and Ge are more likely to promote Pandey reconstruction which is more stable than Haneman reconstruction, so that the cracks are more difficult to propagate or heal, while As has no such effect. Interestingly, the B doped system exhibits plasticity during healing process.