Metallic conductivity and the role of copper in ZnO/Cu/ZnO thin films for flexible electronics

Abstract

ZnO/Cu/ZnO multilayer structures are obtained with the highest conductivity of dielectric-metal-dielectric films reported in literature with a carrier concentration of 1.2×1022 cm−3 and resistivity of 6.9×10−5 Ω-cm at the optimum copper layer thickness. The peak transmittance, photopic averaged transmittance, and Haacke figure of merit are 88%, 75%, and 8.7×10−3 Ω−1, respectively. The conduction mechanism involves metal to oxide carrier injection prior to the formation of a continuous metal conduction pathway. Optical transmission is elucidated in terms of copper’s absorption due to d-band to Fermi surface transitions at short wavelengths and reflectance combined with scattering losses at long wavelengths.