Copper-silicon dioxide nanocomposites: Structure and electron transport

We investigated correlation between structure and electron transport properties of composite films synthesized by the ion-beam sputtering of Cu + SiO2 target. Photoluminescence (PL) spectra testify to an oxygen deficiency in the silicon dioxide matrix in agreement with the Raman spectroscopy, which reveals the presence of Cu2O phase along with elemental copper. For the nanocomposites with copper atomic fraction x < 0.64, the temperature dependence of conductivity obeys ln(σ) ∼ T−0.5 law at low temperatures (electron tunneling between size distributed copper nanoparticles) replacing with the Mott Variable Range Hopping (VRH) with the temperature increase. Electron transport properties of the studied nanocomposites are significantly affected by matrix defectiveness, which increases with metallic phase content according to PL study. The increasing matrix defectiveness results in decrease of crossover temperature from tunneling to VRH conductivity, as well as growth of matrix permittivity due to an enhanced contribution of electrons localized at defects.