Atomic and electronic structures of Si[0 0 1] (1 3 0) symmetric tilt grain boundaries based on first-principles calculations

We have established two patterns of the Si[0 0 1] (1 3 0) symmetrically-tilted grain boundaries through two procedures: One is atomic relaxation at 0 K, and the other is high-temperature treatments plus 0 K relaxation. The relaxation and subsequent electronic calculations are based on the density functional theory (DFT) method, while the empirical Tersoff potential was employed to conduct the high-temperature equilibration. The results show that the high-temperature preprocessing is indispensable to avoiding local minima, and the two resultant configurations agree well with those in the literature. We adopted electron localization functions to revise the conventional Si–Si bond-length criterion, refreshing the distortion details. Bandgap structures of the two systems are completely different, and absence of gap states is confirmed in the more stable one. Potential barriers are found to be quite high at the grain boundaries in both structures, and defect-related localized states are reckoned to account for such facts besides gap states though maybe in weaker way.

► High-temperature treatments are essential to achieving more stable grain boundaries. ► The conventional limit of Si–Si bond length does not hold for strong distortions. ► The structure containing straight 5–3 units is semi-metallic. ► The structure containing zigzag 5–3 units is electrically inactive. ► Apparent potential barriers exist even in the absence of gap states.