Effect of copper ion implantation on the optical properties and low-temperature conductivity of carbon films

Abstract

The optical and electrical properties of diamond-like carbon films implanted with copper ions with energy 40 keV and implantation doses ranging from 3 × 1014 to 3 × 1017 ion/cm2 are studied. The effect of postimplantation thermal annealing on the properties is examined. It is established that the copper atoms implanted with doses below 6 × 1015 ion/cm2 have no effect on the properties of the carbon films. Post-implantation thermal annealing at temperatures below 500°C does not induce any activation of the copper impurities. However, the formation of copper nanoparticles brings about specific changes in the optical and electrical properties of the carbon films. It is found that for the composite films, the effective optical gap determined from the Tauc plot is a function of the filling factor of the metal phase and can take negative values. It is shown that the optical absorption of the synthesized copper-carbon films in the visible and near-infrared spectral regions can be adequately described using a two-layer model. The formation of copper nanoparticles in the carbon matrix modifies the temperature dependence of the conductivity; however, the hopping mechanism of charge transport remains unchanged.