Prediction of the formation of stable periodic self-interstitial cluster chains [(I_4m,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%ε4%) on Si(100). In the absence of strain, the ground state configurations of I12 and I16 share a common structure (I12 -like) with C2h symmetry and a four-atom repeating unit; however, we identified an extended configuration based on I₄ (D2d symmetry) cluster aggregates [(I4 _m (m=3,4)] along 〈 110 〉 that is more favorable under certain magnitudes of strain. While both the I12 -like and (I4_m configurations exhibit relative stabilities that are a function of both strain and orientation, the larger (I4_m orientation effect is the primary reason that these structures are preferred in both highly tensile and highly compressive environments. This suggests that I₄ derivatives may participate in the growth transition of Si self-interstitial clusters in the compact-to-extended size regime (10n20) under strain.