An aluminum doped zinc oxide (ZnO:Al) thin film is prepared on soda lime glass by radio frequency (RF) magnetron sputtering. Optical properties of ZnO: Al in the form of complex dielectric function (epsilon = epsilon(1) + i epsilon(2)) spectra are studied from 0.4 to 6 meV and 0.035 to 5.89 eV using spectroscopic ellipsometry. The film is found to have an optical band gap of 3.62 perpendicular to 0.01 eV and an extrapolated DC dielectric constant of 9.072. Resistivity, scattering time, mobility, and carrier concentration are found to be (2.250 +/- 0.007) x 10(-3) Omega cm, 5.1 +/- 0.7 fs, 20.8 cm(2)V(-1)s(-1), and 1.3 x 10(20) cm(-3) respectively. Resistivity and scattering time resulting from fitting to measurements are found to depend on the spectral range modeled, such that the inclusion of increasingly longer wavelengths results in a convergence to direct electrical property measurements. (C) 2017 Elsevier B.V. All rights reserved.