Influence of the DC magnetron sputtering parameters on copper oxide thin film characteristics

Copper oxide thin films have been synthesized by reactive magnetron sputtering from a copper target using an Ar-O2 gas mixture. The films have been analyzed by X-ray diffraction, scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy and four probes method. We show that the composition, the structure and the morphology of the films can be tailored by tuning the plasma parameters. Various parameters have been selected: the oxygen flow rate, the power dissipated in the discharge, the working pressure and the target-to-substrate distance. By increasing the oxygen flow rate (and keeping the total flow rate constant), all copper oxide phases can be obtained: Cu2O, Cu4O3 and CuO. The oxygen flow rate also influences the morphology of the films: we found a dense and columnar structure for Cu2O films, granular structure in the case of Cu4O3 and a porous columnar structure for CuO. The porosity of the films was also influenced by the power dissipated in the discharge, the working pressure and the target-to-substrate distance. These parameters influence the energy of particles reaching the growing film and thus the film morphology. Furthermore, we demonstrate that the electrical resistivity of copper oxide thin films is highly influenced by the growth conditions. The influence of chemical and structural properties will be discussed in detail. By increasing the pressure from 10 mTorr to 20 mTorr and the target-to-substrate distance from 4 cm to 7 cm, lead to an increase in the CuO resistivity from 10-3 O.m to 10-1 O.m and for Cu2O, from 10-5 O.m to 10-3 O.m. The Cu4O3 is the most resistive phase that we obtained with a resistivity of about 1 O.m likely due to intrinsic properties.