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Dielectric function and optical transitions of silicon nanocrystals between 0.6 eV and 6.5 eV

In this work, we report on the study of the dielectric function of nanocrystal silicon (nc‐Si) implanted in a SiO2 matrix on a silicon substrate by spectroscopic ellipsometry (SE). The formed nc‐Si have an average size around 4 nm. The SE measurements are performed at an angle of incidence of 70° in air at room temperature and in the spectral range of 0.6 eV to 6.5 eV. Two models are used to extract the optical responses of nc‐Si: Forouhi–Bloomer formalism and wavelength‐by‐wavelength inversion. The nc‐Si exhibits a significant reduction in the dielectric functions in comparison with the bulk Si. We have observed a reduction of the amplitude of the E1 transition with a very weak shift of its energy position. The transition E2 is characterized by a rather broad peak with an amplitude greater than that of E1. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)