ELLIPSOMETRIC SPECTROSCOPY OF THE ZNO NONPOLAR (1100) SURFACE

Ellipsometric spectroscopy has been performed on nonpolar ZnO {Mathematical expression} surfaces in the spectral range 1.5 eV<h{combining short stroke overlay}ω<4.0 eV. Absolute measurements with two different crystal orientations in air allow the determination of the optical constants n ∥, k ∥ and n ⊥, k ⊥ for light polarized parallel and perpendicular to the c-axis. The ellipsometric angles Δ and ψ are changed remarkably on ultrahigh vacuum cleaved surfaces near the band gap energy of ∼3.4eV when oxygen or atomic hydrogen is adsorbed or when the crystal is annealed. This observation is interpreted in terms of a field effect on the optical constants in the space charge layer. © 1979 Springer-Verlag.