The Preparation and Optoelectronic Properties of Symmetric and Asymmetric Multilayered Transparent Conductive Films with ZnS-TiO2-Ag Material System

Flexible transparent conductive films with symmetric and asymmetric multilayered structures are studied using the ZnS–TiO2–Ag material system, in order to capitalize on the divergent properties of the two dielectric layers for improved performance. The dielectric/metal/dielectric-structured films were deposited by magnetron sputtering sequentially, with high-purity targets. Multilayered films with various dielectric combinations and metallic layer thicknesses were prepared and analyzed. The surface morphology and phase structure were characterized by atomic force microscopy and scanning electronic microscopy. The optical properties were tested by spectrophotometry and analyzed by numerical simulation approach. The sheet resistance was measured via a four-point probe tester. Among the series of multilayers, asymmetric ZnS/Ag/TiO2 film with 35 nm thickness of dielectric layers and 8.5 nm of metallic layer possesses the optimum comprehensive optoelectronic performance. The average light transmittance reaches 90.72% in the visible spectrum, and the sheet resistance is 7.69 Ω/sq. The good result is ascribed primarily to the combined advantages of superior percolation effect of bottom ZnS layer on ultrathin Ag layer, beneficial impingement effect of top layer deposition on the metallic layer, and excellent surface smoothness of the top dielectric layer.