Growth of AZO/Cu/AZO multilayer structures by confocal RF magnetron sputtering and their microstructural and optoelectronic properties before and after annealing

The impacts of Cu thickness and annealing temperature on microstructure and optoelectronic properties of AZO/ Cu/AZO multilayer structures grown by confocal sputtering are investigated. X-ray diffraction (XRD) analysis reveals that heat treatment affects film orientation and crystallite sizes. Atomic force microscopy (AFM) analysis shows lower surface roughness and larger grain size after annealing. The optical measurements indicate that all multilayer films are transparent in the visible-NIR range and the average transmission depends on Cu thickness and annealing (68.38-84.54 %), while the optical bandgap energy decreases with temperature in the range 3.45-3.42 eV. The photoluminescence spectra of all samples show a dominant ultraviolet emission that is significantly influenced by annealing and Cu thickness. Hall-effect measurements demonstrate that annealing in air deteriorates electrical properties. Figures of merit of as-deposited films are better than those of annealed ones, with a highest value of 1.97 x 10- 3 ohm- 1 at 13 nm Cu thick.