Crystal, optical, and electrical characteristics of transparent conducting gallium-doped zinc oxide films deposited on flexible polyethylene naphthalate substrates using radio frequency magnetron sputtering

Gallium-doped zinc oxide (GZO) thin films were deposited on flexible polyethylene naphthalate substrates using radio frequency (RF) magnetron sputtering. The resulting GZO thin films were polycrystalline, displaying a hexagonal wurtzite-type crystal structure with a preferred grain orientation in the (002) direction. The covalent bond length of the films decreased as the RF deposition power increased, an inverse trend to that of the residual stress. In the transmission spectra, the absorption edge was about 380 nm, and the optical transmittance decreased from 93.2% to 88.6% in the visible range as the RF deposition power increased from 75 to 150 W. A minimum resistivity of 2.994 × 10^-3 Ω-cm was obtained for the film deposited at 125 W, with a Hall mobility of 8.652 cm² V s^-1 and a carrier concentration of 6.3417 × 10¹⁹ cm^-3. The figure of merit results indicated that the film deposited at 125 W possessed satisfactory optical and electrical properties for potential applications.