Structure and optical properties of M/ZnO (M=Au, Cu, Pt) nanocomposites

Metal (Au, Cu, Pt)/zinc oxide nanocomposite films were prepared with different metal contents by radio frequency co-sputtering technique. The films were annealed at different temperatures in an argon atmosphere for 2 h. Formation of metal nanoparticles was studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD). UV-Vis optical absorption spectroscopy was used for optical characterization of the samples. With the increase of annealing temperature, the size of the metal particles in the ZnO matrix varied. Surface plasmon resonance bands were observed in the Au/ZnO and Cu/ZnO composite films due to the formation of nanometer-size Au and Cu particles in the matrix. However, a similar behavior was not seen with Pt/ZnO composites. Upon incorporation of Pt nanoparticles in the ZnO matrix, the optical band gap of the matrix was drastically reduced.