Study of Optical Properties of Au Nanoparticle Embedded Zinc Oxide Thin Film

Abstract

Au embedded ZnO thin films were grown by Sputtering technique. ZnO thin films were grown on soda lime glass substrates, the deposition time is set at 60 min leading to a thickness of approximately 150 nm. A thin Au layer by varying thickness was then deposited onto the ZnO/glass substrates by an Au target. A sandwich structure was completed by depositing a top ZnO layer. The structural and optical properties of the resulting thin films were characterized by various techniques such as X-Ray diffraction (XRD), Scanning electron Microscopy (SEM), UV-Visible absorption spectroscopy. The formation of Bragg’s peak reveals the presence of wurtzite ZnO. Additional peaks are also formed showing the presence of FCC Au. SEM micrography suggests that deposition of the Au layer followed by annealing leads into incongruent covering of the surface on which the top ZnO layer is deposited. Au nanoparticles show strong absorption peak(s) that can be tuned by the size and shape of the nanoparticles due to the surface plasmon effect. A sharp fall in the transmittance corresponds to the band edge that was observed in the UV region. However, as the Au layer was deposited, the optical transmittance continuously decreased and absorbance increased continuously with increasing Au thickness. These peaks are also attributed to the SPR in the Au nanoparticles.