Epitaxial stabilization of orthorhombic cuprous oxide films on MgO(110)

Continuous epitaxial films of cuprous oxide (Cu2O) have been formed by the thermal oxidation of 1.5-mum-thick Cu metal films deposited on MgO(110) sub strates. These films melted at 1118 degreesC in air, in agreement with equi librium phase diagrams. Upon cooling from the liquid, a highly crystalline, epitaxial, 2.5-mum-thick Cu2O film was formed. X-ray diffraction spectrosc opy revealed that the Cu2O film crystal structure was orthorhombically dist orted from the bulk cubic crystal structure. High-resolution transmission e lectron microscopy showed that the film is coherent, and energy dispersive x-ray spectroscopy showed that interdiffusion is limited to the interface. These results suggest that a new epitaxially stabilized phase of Cu2O has b een formed.