Ag thickness and substrate effects on microstructural and optoelectronic properties of AZO/Ag/AZO multilayer structures deposited by confocal RF magnetron sputtering

AZO/Ag/AZO multilayer structures were grown at room temperature on glass and quartz substrates with different Ag layer thicknesses using confocal RF magnetron sputtering. Microstructural, morphological and optoelectronic properties of the AZO/Ag/AZO multilayer structures were studied as a function of Ag thickness and substrate type. Grazing incidence X-ray diffraction (GIXRD) analysis shows that the AZO/Ag/AZO structures for both substrates are polycrystalline and have preferential growth of ZnO (002) and Ag (111). In addition, the thickness of the Ag layer and the nature of substrate affect crystallinity and crystallite size. Atomic force microscopy (AFM) studies show that the structures on quartz substrate have reduced surface roughness and increased crystallite size, with the smoothest surface at 7 nm Ag thickness. The optical measurements show that the multilayer structures deposited on glass substrate have better transmission than those on quartz and the average transmission strongly depends on the Ag thickness, while the optical bandgap increases with Ag thickness in the range of 3.56–3.65 eV for both substrates. The photoluminescence (PL) spectra of all samples show a decrease in UV emissions with increasing Ag thickness. Hall Effect measurements show that the electrical properties of AZO/Ag/AZO structures on both substrates are improved by increasing the Ag thickness. The multilayer structures on glass substrate demonstrate a better figure of merit for the considered thickness, with a best value of 1.34 × 10–3 Ω−1 achieved with 10 nm Ag thickness and a low resistivity of 7.98 × 10–5 Ω cm and a good average transmittance of 61.5%.