Robust p -type doping of copper oxide using nitrogen implantation

We demonstrate robust p -type doping of Cu₂O using low/medium energy ion implantation. Samples are made by controlled oxidation of annealed Cu metal foils, which results in Cu₂O with levels of doping close to intrinsic. Samples are then implanted with nitrogen ions using a kinetic energy in the few keV range. Using this method, we are able to produce very high levels of doping, as evidenced by a 350 meV shift in the Fermi level towards the VB maximum. The robustness of the nitrogen implanted samples are tested by exposing them to atmospheric contaminants, and elevated temperatures. The samples are found to survive an increase in temperature of many hundreds of degrees. The robustness of the samples, combined with the fact that the materials used are safe, abundant and non-toxic and that the methods used for the growth of Cu₂O and N⁺ implantation are simple and cheap to implement industrially, underlines the potential of Cu₂O:N for affordable intermediate band photovoltaics. (paper)