Optical and electrical properties of the copper-carbon nanocomposites

摘要

We prepared copper-carbon nanocomposite films by co-deposition of RF-Sputtering and RF-PECVD methods at room temperature. These films contain different copper concentration and different size of copper nanoparticles. The copper content of these films was obtained from Rutherford Back Scattering (RBS) analyze. We studied electrical resistivity of samples versus copper content. A metal-nonmetal transition was observed by decreasing of copper content in these films. The electrical conductivity of dielectric and metallic samples was explained by tunneling and percolation models respectively. In the percolation threshold conduction results from two mechanisms: percolation and tunneling. In the early stage of nonmetal-metal transition a reverse effect of metallic to nonmetallic state occurs by increasing metal content. We also study the effect of percolation on Surface Plasmon Resonance (SPR) peak of Cu nanoparticles in visible spectra. The width of this peak is raised by increasing number of percolated nanoparticles. Also position of this peak is shifted to the larger wavelength by decreasing resistivity of film. Mie theory was used for the dielectric sample. Using Mie theory, the size of copper core and copper oxide shell, the dielectric constant of shell and carbon host are estimated from SPR peak. The activation tunneling energy that was obtained from estimated value of Mie theory is consistent with that one obtained from temperature dependence of electrical resistivity. Atomic Force Microscopy (AFM) image shows particle size and coalescence of the nanoparticles.