ZnO:Ga (GZO) thin films were deposited by dc-magnetron sputtering on glass and polyethylene naphthalate (PEN) substrates, under an Ar atmosphere with a base pressure of 2 × 10-4 Pa, from a GZO target (zinc oxide/gallium oxide, 95.5/4.5 wt.%) of 2" diameter. A target current density of 0.6 mA/cm2 was applied, and a deposition rate of 21 nm/min was obtained. No bias was applied to the substrate holder during the depositions, which took place at room temperature. The working pressure (Pw) was varied from 0.41 to 0.86 Pa, with the target-to-substrate distance kept at a constant 8 cm. The crystallinity and crystal orientation was studied using a Bruker AXS Discover D8 (Madison, USA) for X-ray diffraction (XRD). Glass substrates were used to avoid the presence of polymer substrate peaks. The electrical resistivity, carrier concentration and Hall mobility of the coatings on glass substrates were all measured using Van der Pauw geometry under a magnetic field of 1 Tesla. The electromechanical tests were carried out on 10 × 40 mm2 samples using a computer-controlled tensile testing machine (Minimat, Polymer Labs, Loughborough, UK), which was mounted on an optical microscope stage (Nikon Optiphot-100, Tokyo, Japan). One of the grips of the instrument was displaced at a constant speed of 0.2 mm/min. The applied load and stage displacement values were recorded at 1-s intervals. Crack development was recorded through a CCD camera connected to the microscope, with the evolution of the crack density obtained by the subsequent video analysis. The thickness of the polymer substrates was measured using a Fischer Dualscope MP0R instrument (Sindelfingen, Germany).