Phase stability and oxygen doping in the Cu-N-O system

A growth stability diagram for the Cu-N-O system has been determined in the temperature range 250-500 degrees C for a thermally activated CVD process, based on copper (II) hexafluoroacetylacetonate (Cu(hfac)(2)), NH3 and H2O. Without any addition of water only Cu3N was obtained. Addition of water introduces oxygen into the Cu3N structure to a maximum amount of 9 at% at a water/nitrogen molar ratio of 0.36 at 325 degrees C. Above this molar ratio Cu2O starts to deposit, in addition to an oxygen doped Cu3N phase. Only Cu2O is deposited at large excess of water. XPS and Raman spectroscopies indicated that the additional oxygen in the doped Cu3N structure occupies an interstitial position with a chemical environment similar to that of oxygen in Cu2O. The oxygen doping of the Cu3N phase did not influence the lattice parameter, which was close to the bulk parameter value of 3.814 angstrom. The film morphology varied markedly with both deposition temperature and water concentration in the vapour during deposition. Increasing the water concentration results in less faceted and textured films with smoother and more spherical grains. The resistivity of the Cu3N films increased with increased oxygen content of the film and varied between 10 and 100 Omega cm (0-9 at% O). The optical band gap increased from 1.25 to 1.45eV as the oxygen content increased (0-9 at%). (C) 2010 Elsevier B.V. All rights reserved.