Biaxial strain effects on the structure and stability of self-interstitial clusters in silicon

Using first-principles density-functional theory calculations, we examine variations in the structure and stability of small self-interstitial clusters (In, n≤10) in crystalline silicon across a range of biaxial strain conditions (-3%≤ε≤3%) on Si(100). Under the strain conditions considered, there is no significant deviation in the ground-state configuration of any cluster from the strain-free case. However, the relative stability of I4 and I8 is significantly increased under both compressive and tensile strain conditions, while other cluster sizes generally show less sensitivity to changes in strain. This suggests that I4 and I8 likely play an even larger role in the clustering/dissolution of interstitial defects in strained Si relative to strain-free Si. We find that the noteworthy strain dependence of I4 and I8 is attributed to the unique shape and symmetry of the I4 -like core which allows reorientation within the lattice that is dependent on the compressive/tensile nature of biaxial strain.