Tuning the electronic and optical properties of hydrogen-terminated Si nanocluster by uniaxial compression

The structural, electronic, and optical properties of hydrogen-terminated Si nanocluster (Si₆₆H₆₄) with a diameter of 1.3 nm under uniaxial compression have been investigated by means of density functional theory calculations. The structural deformation of silicon nanoparticle under axial strain manifests as reduction of cluster symmetry, contraction of bond length, and broadening of bond angle distribution. Such strain-induced distortion modifies the highest occupied molecular orbital (HOMO) the lowest unoccupied molecular orbital (LUMO) eigenvalues, HOMO–LUMO gap, and isosurfaces of HOMO and LUMO wavefunctions, that is, the HOMO–LUMO gap diminishes as strain increases and isosurface of HOMO and LUMO wavefunctions redistributes along the strain orientation. Moreover, uniaxial compression has a strong influence on the optical absorption spectra of the Si₆₆H₆₄ cluster. With increasing strain, the onset of absorption spectra red shifts. Interestingly, the strain-tunable photoluminescence in Si nanoparticle (Si₆₆H₆₄) can cover a broad spectrum (i.e., from visible light to ultraviolet), implying an exciting possibility for optical devices.