First-principles investigation of strain effects on the energy gaps in silicon nanoclusters

Abstract

First-principles density functional calculations were performed to study strain effects onthe energy gaps in silicon nanoclusters with diameter ranging from 0.6 to 2 nm.Hydrostatic and non-hydrostatic strains have been found to affect the energy gapsdifferently. For the same strain energy density, non-hydrostatic strain leads toa significantly larger change in the energy gap of silicon clusters compared tothat of the hydrostatic strain case. In contrast, hydrostatic and non-hydrostaticstrain effects on the energy gaps of bulk Si or larger size Si quantum dots arecomparable. Non-hydrostatic strains break the tetrahedral bonding symmetry in silicon,resulting in significant variation in the energy gaps due to the splitting of thedegenerate orbitals in the clusters. Our results suggest that the combination ofenergy gaps and strains permits the engineering of photoluminescence in siliconnanoclusters and offers the possibility of designing novel optical devices and chemicalsensors.