Anisotropic Optical Spectra of α-Al_2O_3 Single Crystals in the Vacuum Ultraviolet Region.II. Spectra of Optical Constants

概要

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The spectra of optical constants of α-Al_2O_3 single crystals at 297 K and 10 K are presented over the range of photon energies from 6 eV to 120 eV for the electric fields of incident light parallel to optic axis <c> and normal to it. The optical constants include the complex index of refraction, conductivity, complex dielectric constant, loss functions and effective number of electrons per unit cell. The spectra in E≲78 eV are interpreted in terms of the interband transitions from the O 2p and 2s bands to the Al conduction bands and the free electron-like absorption of photons by the O 2p band electrons. The volume energy loss function has a prominent peak at E〜26. 4 eV for the plasma oscillation dominantly of the 2p electrons. The spectral features in E≳78eV resulting from electronic transitions from the Al L_<2,3> levels are presented with the L_<2,3> exciton doublet, e.g., at 78.72 eV and 79.15 eV for ε_<2⫽>.
社団法人日本物理学会の論文
1993-04-15