Kamil Postava, H. Sueki, Mitsuro Aoyama, Tomuo Yamaguchi, C. Ino, Y. Igasaki, M. Horie
Spectroscopic ellipsometry of epitaxial ZnO layer on sapphire substrate
Journal of Applied Physics 87 (2000) 7820–7824
Optical properties of epitaxial ZnO layers have been studied in the spectral region from 1.5 to 5.4 eV using four-zone null spectroscopic ellipsometry. An existing model dielectric function based on excitonic structure near direct band gap has been improved by including a high-energy absorption term. Surface layer, corresponding to the surface roughness, was found to be essential to fit the spectroellipsometric data obtained. Two kinds of samples have been studied: ZnO layers prepared on (0001) and (11overbar20)- oriented sapphire substrates. The surfaces of the first ones were found to be more rough.
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