Coherent island formation of Cu2O films grown by chemical vapor depositionon MgO(110)

Cuprous oxide (Cu2O) films have been grown on single-crystal MgO(110) subst rates by a chemical vapor deposition process in the temperature range 690-7 90 degreesC. X-ray diffraction measurements show that phase-pure, highly or iented Cu2O films form at these temperatures. The Cu2O films are observed t o grow by an island-formation mechanism on this substrate. Films grown at 6 90 degreesC uniformly coat the substrate except for micropores between grai ns. However, at a growth temperature of 790 degreesC, an isolated, three-di mensional island morphology develops. Using a transmission electron microsc opy and atomic force microscope, both dome- and hut-shaped islands are obse rved and are shown to be coherent and epitaxial. The isolated, coherent isl ands form under high mobility growth conditions where geometric strain rela xation occurs before misfit dislocation can be introduced. This rare observ ation for oxides is attributed to the relatively weak bonding of Cu2O, whic h also has a relatively low melting temperature.