Preparation of RF sputtered AZO/Cu/AZO multilayer films and the investigation of Cu thickness and substrate effects on their microstructural and optoelectronic properties

Abstract

AZO/Cu/AZO multilayer films are deposited on glass and amorphous quartz substrates by RF magnetron sputtering in confocal configuration at room temperature. The effects of Cu thickness and substrate type on the microstructure and optoelectronics properties are investigated. The results show that the properties of the tri-layer films are strongly influenced by these parameters. For both substrates, all the films are polycrystalline and show an obvious ZnO (002) c-axis preferential growth. No diffraction peaks related to Cu are observed through X-ray diffraction analysis. The average transmittance in the visible region is in the range of 69–83%, while the optical band gap remains constant at 3.454 eV regardless of the Cu thickness and substrate type. With the increase of Cu thickness, the electrical properties of AZO/Cu/AZO tri-layer films on glass and quartz substrates are improved. The best figure of merit obtained is 1.97 × 10-3 Ω-1 for a Cu thickness of 13 nm on glass substrate with a low resistivity of 2.05 10-4 Ω cm and an acceptable average transmittance of 70%. These multilayer structures, with such good performances, are of great interest for potential thin film applications in optoelectronic devices in the visible and NIR region, in particular solar cells.