High transparent and conductive ZnO/Ag/ZnO film structure

ZnO(45-nm)/Ag/ZnO(45-nm) film structures with different Ag-film sputtering time were fabricated in this work. The electrical measurement demonstrates that the electrical property of the ZnO/Ag/ZnO film structures with thick Ag films (Ag-film sputtering time over 103 s) is dominated by the Ag films and behaves like the typical Ag film. With thinner Ag films (Ag-film sputtering time less than 82 s), the resistivity of the ZnO/Ag/ZnO structures drops exponentially with sputtering time. The electrical conduction mechanism for ZnO/Ag/ZnO structures with thinner Ag films can be explained by tunneling conduction mechanism among discrete Ag clusters in the thin Ag films. The admittance calculation results show that the transmittance of Ag nano-scale films can be greatly improved by sandwiching nano-Ag film with two anti-reflection 45-nm ZnO layers. The calculated transmittance of the ZnO(45-nm)/Ag/ZnO(45-nm) film structures with thicker Ag films (Ag-film sputtering time over 103 s) match well with the measured results. Yet, for thinner Ag films (Ag-film sputtering time less than 82 s), their average measured transmittance is much lower than the calculated transmittance by admittance model. This discrepancy attributes to the light scattering among Ag clusters in the thinner Ag films, which causes lower measured transmittance. The best measured transmittance structures occur at the Ag film prepared with 82-s sputtering time (about 8 nm), which has average transmittance of 90.83 % in visible range. The highest F_TC (5.5×10⁻² Ω⁻¹) of the ZnO/Ag/ZnO film structures occurs at the sample of ZnO₄₅/Ag₁₀/ZnO₄₅, which is larger than the lower bound of the reported acceptable range (1.77×10⁻³ Ω⁻¹).