Doping of metastable Cu3N at different Ni concentrations: Growth, crystallographic sites and resistivity

Copper nitride, Cu3N, is a metastable material whose properties can be changed considerably by doping with metals which opens for a variety of applications in several areas (sensors, electrical connects, batteries, memories, etc.). The present work is a systematic study in the system Cu-Ni-N of preferences regarding occupation of interstitial and substitutional crystallographic sites in the Cu3N structure as the metal dopant level increases and how the occupation influences growth behavior, texture, microstructure and resistivity. Ni doped Cu3N films of different chemical composition were grown by a gas-pulsed Chemical Vapor Deposition technique. The occupation of the different crystallographic sites of the Cu3N by the Ni atoms was obtained from analysis of X-ray diffraction data. At low Ni content, less than about 21% in metal content, Ni replaced the Cu atoms in the structure. In the intermediate Ni metal content range from about 21 to 40% the vacant centre position became available. After filling the centre position, substitution of Cu for Ni occurred up to a Ni content of about 80% (Cu0.8Ni3.2N) which is the solid solubility limit of Ni in Cu3N. The film resistivity decreased rapidly by adding nickel to the Cu3N structure from about 109 μΩ·cm without any Ni doping to about 100 μΩ·cm with 80% Ni in the metal content. After filling the centre position the change in resistivity when Cu atoms were substituted for Ni was very small. Finally, the growth mechanism, texture and microstructure changed significantly with the uptake of Ni atoms in the structure.