Articles you may be interested inVisible to vacuum ultraviolet dielectric functions of epitaxial graphene on 3C and 4H SiC polytypes determined by spectroscopic ellipsometry Details of below band-gap uniaxial dielectric function of SiC polytypes studied by spectroscopic ellipsometry and polarized light transmission spectroscopy Spectroscopic rotating-analyzer ellipsometry employing a compensator and optical transmission were used to measure the dielectric functions of bulk 4H and 6H SiC from 0.72 to 6.6 eV for light propagating nearly parallel to the hexagonal axis. The measurements below the band gap show the presence of a thin surface layer, which was modeled as SiO 2 . The data are similar to results for cubic ͑3C͒ and 6H SiC from the literature, but differences are notable, particularly above 4 eV. At 5.56 eV, we observe a critical point in 4H SiC, which is assigned to direct interband transitions along the UϭM ϪL axis in the hexagonal Brillouin zone after comparison with band structure calculations. No evidence for direct transitions below 6.5 eV was found in 6H SiC. We apply our results to the analysis of a 4H SiC film on insulator ͑SiCOI͒ produced by high-dose hydrogen implantation and direct wafer bonding on Si. For comparison, we also studied a 1 m thick epitaxial layer of 3C SiC on Si, where the interference oscillations are influenced by surface and interface roughness.

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