Prediction of the formation of stable periodic self-interstitial cluster chains [(I4)m,m=1-4] in Si under biaxial strain

Using density functional theory calculations, we examined the structure and stability of extendable self-interstitial cluster configurations (I-n,n=12,16) with four-atom periodicity in crystalline silicon under biaxial strain (-4%<epsilon < 4%) on Si(100). In the absence of strain, the ground state configurations of I-12 and I-16 share a common structure (I-12-like) with C-2h symmetry and a four-atom repeating unit; however, we identified an extended configuration based on I-4 (D-2d symmetry) cluster aggregates [(I-4)(m)(m=3,4)] along << 110 >> that is more favorable under certain magnitudes of strain. While both the I-12-like and (I-4)(m) configurations exhibit relative stabilities that are a function of both strain and orientation, the larger (I-4)(m) orientation effect is the primary reason that these structures are preferred in both highly tensile and highly compressive environments. This suggests that I-4 derivatives may participate in the growth transition of Si self-interstitial clusters in the compact-to-extended size regime (10 < n < 20) under strain.