Epitaxial growth of copper oxide films by cross-beam pulsed-laser deposition
Résumé
Epitaxial cuprite (Cu2O) and tenorite (CuO) films are grown on (0 0 1)-oriented MgO single crystal by reactive cross-beam pulsed-laser deposition assisted by radio-frequency plasma discharge in oxygen atmosphere. X-ray diffraction (XRD) shows that the films are single phased and well crystallized. The Cu2O films grow according to two directions with their (2 0 0) and (1 1 0) planes parallel to the (0 0 1) MgO basal plane, while the CuO films show a single main axis growth along the [1 1 1] direction. The precise in-plane orientations on the (0 0 1) MgO plane are determined by XRD measurements in asymmetric mode. As the cuprite phase is cubic, the (2 0 0) Cu2O crystallites grow according to a simple cube-on-cube growth mode, i.e. View the MathML source[100]Cu2O‖[100]MgO relationships, while the (1 1 0) crystallites display the View the MathML source[100]Cu2O‖[110]MgO in-plane orientation. Despite its large differences in structure and crystallographic symmetry with the cubic MgO substrate, the monoclinic CuO phase grows with the (1 1 1) planes parallel to the (0 0 1) MgO planes and the [1¯ 1 0]CuO∥[1 1 0]MgO in-plane orientations are observed. This last feature is explained by the low lattice misfit between the film and the substrate in this orientation, the large atomic density of the (1 1 1) CuO plane, and the minimizing of interface energy by electrostatic interactions between the (0 0 1) MgO and (1 1 1) CuO planes.