Analysis of Atomic and Electronic Structures on CSL Boundary in Silicon

Σ3 CSL grain boundaries in poly-crystalline silicon were investigated by high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS) and ab initio calculations. A {112} Σ3 CSL boundary consisted of two segments which differed in atomic structure. The segment near the corner and connected to {111} Σ3 CSL boundary showed symmetric structure while the other long segment, which was the distant one and away from the corner, showed asymmetric structure. Ab initio calculations revealed that the asymmetric structure is more stable than the symmetric one. A pronounced pre-edge shoulder was detected only in Si-L23 electron energy-loss near-edge structure (ELNES) acquired from the symmetric segment of the {112} and {111}Σ3 CSL boundaries. It was indicated that the shoulder in the ELNES acquired from the CSL junction resulted from the formation of the deep gap state originated by the 5-fold-coordinated silicon atom