Using first-principles density-functional theory calculations, an investigation was made of the influence of both biaxial and uniaxial strain (−4%≤ε≤4%) on the stability and structure of small, neutral vacancy clusters (Vn, n≤12) on Si (100). A thorough understanding of vacancy clusters under strain was an important step toward elucidation of the evolutionary life cycle of native defects, especially during semiconductor manufacturing. Fourfold-coordinated structures were more favourable than so-called partial hexagonal ring structures in the size regime of this study under strain-free conditions. However, fourfold-coordinated structures were also more rigid and consequently more sensitive to strain. The calculated results indicated that partial hexagonal ring structures could be thermodynamically more favourable than fourfold-coordinated structures in the presence of specific strain conditions. In addition, orientation effects were identified in which the cluster symmetry and its alignment within the strain field dictated cluster stability; in consequence, both configuration and orientation were essential factors in the identification of minimum-energy vacancy structures in strained Si. Furthermore, highlights of the simulation results suggested that minimum-energy cluster configurations formed under strain were often different than minimum-energy cluster configurations formed in the absence of strain.

Strain Effects on the Stability and Structure of Vacancy Clusters in Si - a First-Principles Study. R.J.Bondi, S.Lee, G.S.Hwang: Physical Review B, 2010, 81[24], 245206