Spectroscopic ellipsometry studies of Mg-doped ZnO thin films prepared by the sol-gel method

Abstract

Zn1–x Mgx O (ZMO) thin films with x = 0, 0.1, 0.2, and 0.3 were prepared on Si(100) substrates by the sol–gel method. The influence of Mg content on the structural and the optical properties was studied by X-ray diffraction and spectroscopic ellipsometry (SE) in the UV–visible region. The measured SE spectra were analyzed with an appropriate procedure to accurately determine the thickness and the optical constants of the thin films. It was found that the optical constants of the ZMO films are functions of the film composition. The refractive indices of the ZMO films decrease with increasing Mg content, and the optical bandgap energy exhibits nonlinear behavior or a bowing effect with the change of Mg mole fraction. A maximum band gap of ∼3.91 eV was achieved at x = 0.3. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)