Structural and electronic properties of 90 degrees dislocations in silicon nanorods: A first-principles calculation

摘要

Dislocation as a topological line defect plays a key role in electronic devices made of crystalline silicon (Si). In this work, using the first-principles calculations we have systematically investigated the atomic structures and electronic properties of 90 degrees dislocation in Si nanorods, including the cases of glide and shuffle perfect dislocations, as well as single-period and double-period reconstruction partial dislocations. Our results show that the dislocations strongly influence the valence and conduction bands near the Fermi level, inducing a narrower band gap. Especially for glide and double-period reconstruction dislocations, the transition from indirect gap of bulk Si to direct gap is achieved. The analysis of the band structures and partial charges reveals the existence of defect levels in the band gap. More interestingly, the defect level of shuffle dislocation crosses the Fermi level, resulting in one-dimensional metallic chain along the dislocation line, which can be related to experimental observations.