The atomic and electronic structure of a (001) tilt grain boundary in Si

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Abstract
The authors have examined the structural and electronic properties of a (001) symmetrical tilt grain boundary in Si the Sigma =5, (130) boundary, with a semi-empirical tight-binding model. Energy minimisation calculations have shown that the model of Bacmann (1985) and coworkers consisting of a zigzag arrangement of the 5-3 units is more energetically favoured than the model of Hornstra (1959) consisting of a straight arrangement of the 5-3 units. The optimum rigid-body translation of the stable configuration is consistent with the experiment on a Ge bicrystal. The calculated electronic structure has localised boundary states at the band edges and inside the valence band, which are caused by structural disorder such as the presence of odd-membered rings, the dihedral angle disorder and the bond length and bond angle disorder. However, there are no deep states inside the fundamental gap because of the absence of dangling bonds. Thus this boundary is considered to be electrically non-active intrinsically. The present results support the idea that the observed electrical activity of grain boundaries should be attributed to an intrinsic effect in the coincidence (001) tilt grain boundaries.