Size Dependence of Si Nanocrystals Infrared Spectra: A Density Functional Theory Study

作者：Abdulsattar Mudar A^*

来源：Silicon, 2013, 5(3): 229-237.

DOI：10.1007/s12633-013-9152-4

• Nanocrystals
• ab initio calculations
• Infrared spectroscopy

Infrared vibrational modes were calculated using ab initio density functional theory and coupled perturbed Hartree-Fock equations for Si nanocrystals of approximately 1.57 nm length. Frequencies of modes were analyzed against intensities, reduced masses and vibrational force constants. The present calculations were able to reproduce the red shift associated with size reduction from the original 521 cm(-1) of the bulk optical Si-Si vibrations to the present nanocrystal 493 cm(-1) high intensity mode. In order to investigate size dependence of infrared spectra a comparison is given with bulk silicon crystals and sila adamantane. A comparison revealed several changes as the nanocrystal size goes from bulk to the molecular limit. This includes a blue shift of radial breathing mode which is an acoustical mode and red shift of the optical modes. Different surface SiH2 and SiH3 vibrational modes were matched with experimental symmetric, asymmetric, wagging, scissor, rocking and twisting modes.

• 出版日期2013-7