The optical properties of Ag/ZnO nanocomposite thin films with different thickness

In recent years, it has attracted much interest to tailor the optical properties of metal oxides by metal nanoparticles. Many studies have found that the presence of Ag nanoparticles is beneficial to improve the ultraviolet (UV) emission of ZnO. In this investigation, Ag/ZnO nanocomposite thin films were prepared by sol-gel method. The effect of the film thickness on the optical properties of the samples was studied. The X-ray photoelectron spectroscopy (XPS) showed that Ag was present in ZnO in the form of simple substance, and Ag nanoparticles were observed by transmission electron microscope (TEM). A strong absorption originating from the surface plasmon resonance of Ag nanoparticles was also seen in the transmittance spectra of the samples. The photoluminescence spectra showed that the UV emission of the Ag/ZnO nanocomposite thin film was first improved with the increase of the film thickness; however, the UV emission was decreased again when the thickness of the film was more than 6 layers. This suggests that the thickness is an important factor which influences the photoluminescnece of the Ag/ZnO nanocomposite films.