Dielectric functions of Si nanocrystals embedded in a SiO2 matrix -: art. no. 153301

Knowing the dielectric functions of semiconductor nanocrystals isolated in a dielectric matrix is important to both solid-state physics and applications. In this work, we have developed an approach to determine the dielectric function of Si nanocrystals embedded in a SiO2 matrix synthesized with Si ion beams. The approach is based on the effective medium approximation, and appropriate models are developed to simulate the secondary ion mass spectroscopy and spectroscopic ellipsometry measurements on the material system. The energy gap expansion of the Si nanocrystals due to the nanocrystal size effect has been obtained by modeling the real part of the dielectric function with the single-oscillator model. From the energy gap expansion, the nanocrystal size can be also obtained with two independent models including the phenomenological model based on quantum confinement and the bond contraction model. The results from the two models are similar and are also consistent with transmission electron microscope and x-ray diffraction measurements.