Overcoming surface energy to control Cu3N epitaxial growth

Crystal orientation control during copper nitride (Cu3N) epitaxial growth was achieved using reactive DC magnetron sputtering. Both the (100)-orientation and (111)-orientation were observed readily from x-ray diffraction measurements for Cu3N thin films grown on single-crystal MgO(100), MgO(111), SrTiO3(100), and sapphire(0001) substrates. The Cu3N(111) surface energy is greater than that of Cu3N(100), suggesting that the Cu3N(111) orientation has a lower formation probability than the Cu3N(100) orientation. To control the influence of surface energy, thin film growth parameters related to the thermodynamics and kinetics of epitaxial thin film growth were tuned. The growth of single (111)-oriented Cu3N epitaxial thin films, which have a higher surface energy orientation, was achieved on MgO(111) substrates. The optical bandgaps of the single (111)-oriented Cu3N epitaxial thin film were 1.80 eV for direct transition and 0.82 eV for indirect transition, indicating the formation of a reasonable electronic structure in single (111)-oriented Cu3N epitaxial thin films with higher surface energy.