X-ray diffraction, XPS, and Raman spectroscopy of coated ZnO:Al (1−7 at%) nanoparticles

Abstract

Group III elements doping for zinc oxide is currently attracting much attention for the study of absorber layer in nano-optoelectronic and photovoltaic devices as an alternative route to indium tin oxide (ITO) due to their optimized properties. In this report, Al-doped ZnO (AZO, Al: 1−7 at%) nanoparticles have been successfully deposited onto glass substrates using sol-gel process, and investigated by techniques such as X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The coated ZnO:Al nanoparticles at Al concentration up to 5 at% showed a nanosized polycrystalline structure with a c-plane preferred orientation. In AZO (7 at%), lower diffraction peaks were observed. The crystallite size calculated from XRD was ranged 38.7−43.5 nm. SEM showed spherical nanoparticles in shape with a smooth surface. The Raman results provided peaks located at 434, 435, 559, 851, and 1090 cm−1. According to XPS, the as-grown nanoparticles present the most intense peak located at about 1021.8 eV, assigned to the Zn 2p3/2 corresponding to zinc oxide. It was concluded that the structural properties of AZO thin films were improved with Al (5 at%), and these samples may be considered as an alternative of costly ITO in thin-film photovoltaic applications.