Highly flexible Al-doped ZnO/Ag/Al-doped ZnO multilayer films deposited on PET substrates at room temperature

We investigated the effects of the Ag layer thickness on the electrical and optical properties of AZO (36 nm)/Ag/AZO (36 nm) multilayer films that were deposited on polyethylene terephthalate (PET) substrates using a radio frequency magnetron sputtering method. The AZO/Ag/AZO films had transmittances over 74–89% at 550 nm. The relationship between the transmittance and the Ag layer thickness was investigated with three-dimensional finite-difference time-domain (3D FDTD) simulations to understand high transmittance. As the Ag layer thickness increased from 15 to 23 nm, the carrier concentration increased from 5.84×1021 to 9.66×1021 cm−3, while the sheet resistance decreased from 10.15 to 3.47 Ω sq−1. The Haacke figure of merit (FOM) was calculated for the samples with various Ag layer thicknesses; it was a maximum at 19 nm (43.9×10−3 Ω−1). The resistance change for the 100 nm-thick ITO only films was unstable even after 5 cycles, while that of the AZO (36 nm)/Ag (19 nm)/AZO (36 nm) film remained constant up to 1000 cycles.