Optical constants and band gap expansion of size controlled silicon nanocrystals embedded in SiO2 matrix |
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Authors: | X Yu RJ Zhang ZJ Xu DX Zhang HB Zhao YX Zheng LY Chen |
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Institution: | Key Laboratory of Micro and Nano Photonic Structures, Ministry of Education, Department of Optical Science and Engineering, School of Information Science and Engineering, Fudan University, Shanghai 200433, China |
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Abstract: | Silicon nanocrystals (Si-NCs) with different sizes embedded in SiO2 matrix were synthesized by phase separation and thermal crystallization of SiOx/SiO2 supperlattice approach. The optical constants and band gap expansion of Si-NCs have been investigated by spectroscopic ellipsometry, based on the Maxwell–Garnett effective medium approximation and the Forouhi–Bloomer optical dispersion model. Similar spectra shapes but smaller values of Si-NCs optical constants with respect to bulk crystalline Si is observed. With the size of Si-NCs decreasing from 6 nm to 2 nm, the band gap increases from 1.64 eV to 2.56 eV. The band gap expansion, as compared to bulk crystalline Si, which agrees with the prediction of first-principles calculations based on quantum confinement effect, is presented in this paper. |
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