Microstructure and optical properties of Cu@Ni nanoparticles embedded in a-C:H

Cu@Ni core-shell nanoparticles on a-C:H thin film were prepared by co-deposition of RF-sputtering and RF-PECVD. Samples having different Cu nanoparticle sizes were grown and then Ni layers of different thicknesses were grown over these Cu nanoparticles. Atomic force microscopy indicated that the thin film consisted of nanoparticles 6-14 nm in size. Also, in the present work the RMS roughness and PSD spectra computed from atomic force microscopy (AFM) data were used for studying the morphology of thin films. X-ray diffraction (XRD) profiles show that the Cu nanocrystal core and Ni nanocrystal shell have formed in the film and that the surfaces of these core-shells oxidize when exposed to air. The surface plasmon resonance peak of the Cu nanoparticles can be observed at about 600 nm in a region damped by the increased thickness of the Ni layer. Absorbance in the near-IR region increased as the thickness of the Ni layer increased. The edge of strong absorption observed near the IR region varied with the thickness of the Ni layer.