A simple route for spray deposition of ZnO thin films embedded with Ag nanoparticles: influence of Ag concentration on the structural, morphological, optical, and photoluminescence properties

Ag nanoparticles (NPs) were embedded in the spray-deposited ZnO thin films by simply adding AgNO₃ to the stating solution. The Ag concentration was varied by adding 0, 2, 4, 6, and 10 wt% of AgNO₃ to the precursor. The X-ray diffraction (XRD) pattern of the prepared films indicates the presence of both the Ag NPs with cubic structure and the ZnO thin films with hexagonal wurtzite structure. According to the field emission scanning electron microscopy (FESEM) of the surface and cross-section images, the Ag NPs are almost spherical with the average diameter of 65 nm to 99 nm depending on the Ag concentration. The ZnO thin films embedded with Ag NPs exhibit absorption peak around 500 nm, which is related to the Ag NPs surface plasmon (SP). There are two absorption edges in the transmittance spectra of the embedded films, which correspond to the bandgap of ZnO (~ 3.26 eV) and SP of Ag NPs. The photoluminescence (PL) spectra reveal that as the Ag concentration increases, the 395 nm emission related to the Zn vacancies reduces, whereas the yellow emission (570 nm) results from the coupling of ZnO excitons and Ag NPs SP increases.