Thin films of amorphous and polycrystalline indium zinc oxide (IZO) having various In/(In + Zn) nominal compositions from 0.3 to 0.9 were grown by the pulsed laser deposition technique at room temperature or at 400 degrees C on oxidized Si and quartz substrates. After deposition, the films were gamma irradiated at doses of 10, 20 and 30 kGy under Ar atmosphere. Grazing incidence X-ray diffraction investigations could not find measurable changes of the structure after irradiation. Simulations of the X-ray reflectivity (XRR) and diffuse scattering curves acquired from the films showed a small density decrease after irradiation, accompanied by an increase of the thickness and surface roughness. Spectroscopic ellipsometry investigations confirmed the increase of the IZO films' thickness after irradiation, being in agreement with the XRR results. Small changes in the refractive index, most probably caused by changes in the film density were also observed. Four point probe measurements showed very small resistivity increases after irradiation, with the films containing higher In concentration presenting negligible changes. (C) 2016 Elsevier B.V. All rights reserved.