Imaginary Part of the Dielectric Function of Sintered and Microcrystalline Cubic Boron Nitride

The optical reflectance of cubic boron nitride (c-BN) was measured for sintered and microcrystalline samples at room temperature in the photon energy range 5–25 eV. Kramers-Kronig analysis was performed to determine the real ε 1 and imaginary ε 2 parts of the dielectric function. The spectrum of ε 2 for sintered c-BN shows peaks at 9.05 eV and 11.7 eV and shoulders at 10 eV, 13.2 eV and 16.7 eV. This spectrum was compared with the one theoretically obtained by Tsay et al. and assignment of the structure was made. The ε 2 for microcrystalline c-BN has a broad structure with a peak at 11.7 eV.