Effect of Gold Thickness and Annealing on Optical and Electrical Properties of TiO<inf>2</inf>/Au/TiO<inf>2</inf> Multilayers as Transparent Composite Electrode on Flexible Substrate

Multilayer structures of TiO<inf>2</inf>/Au/TiO<inf>2</inf> have been deposited onto flexible substrates by room temperature sputtering to develop indium-free transparent composite electrodes (TCEs). The effect of Au thicknesses on optical, electrical properties and the mechanism of conduction have been discussed. The electrical conductivity of the TCEs is solely contributed by the middle metal layer. The critical thickness (t<inf>c</inf>) of the Au mid-layer to form a continuous conducting layer is 10 nm, and the multilayer has been optimized to obtain a sheet resistance of 12.2 Ω/sq and an average optical transmittance of 86% at 590 nm. The Haacke figure of merit (FOM) for t<inf>c</inf> has one of the highest FOM with 18 × 10⁻³ Ω⁻¹. The samples were annealed in various environments for 24 h up to 150°C.