Ellipsometry in a Uniaxial ZnO Thin Film

Abstract

In this work, the indexes of refraction of a uniaxial anisotropic, inhomogeneous thin film of ZnO grown on a glass substrate are determined in the transparent region using spectroscopic four-modulator generalized ellipsometry (4-MGE). Three different points of the sample are studied at three angles of incidence and the real and imaginary parts of the coefficient 𝜌=𝑡𝑝𝑝/𝑡𝑠𝑠 are ob-tained and fitted from 450 to 800 nm assuming zero absorption. The results lead to very accurate values of the parameters used for the model, which include the thickness of the film and the reso-nant wavelengths with nanometer precision. The obtained functions are then compared to the tabu-lated data of the bulk material, showing a clear reduction of the refractive indexes of roughly 0.15 in the whole range. The effects of the inhomogeneity of the sample are reflected in the dispersion of the obtained refractive index values from point to point