Effect of silver thickness and annealing on optical and electrical properties of Nb₂O₅/Ag/Nb₂O₅ multilayers as transparent composite electrode on flexible substrate

Multilayer structures of Nb₂O₅/Ag/Nb₂O₅ have been deposited onto flexible substrates by sputtering at room temperature to develop indium free composite transparent conductive electrodes. The optical and electrical properties of the multilayers are measured by UV-Visible spectroscopy, Hall measurement and four point probe and the effect of Ag thickness has been studied. The critical thickness of Ag to form a continuous conducting layer is found to be 9.5 nm and the multilayer stack has been optimized to obtain a sheet resistance of 7.2 Ω/sq and an average optical transmittance of 86 % at 550 nm. The Haacke figure of merit (FOM) has been calculated for the films, and the multilayer with 9.5 nm thick Ag layer has the highest FOM with 31.5 x 10^-3 Ω/sq, which is one of the best FOM reported till date for room temperature deposition on flexible substrates. The multilayered samples are annealed in vacuum, forming gas, air and O₂ environments and the optical and electrical properties are compared against the as-deposited samples.