Synthesis, control, and characterization of surface properties of Cu₂O nanostructures.

The ability to control nanostructure shape can strongly affect the overall properties of that system. Here we report the ability to deterministically control nanostructure shape, surface facet orientation, and surface potentials of the oxide semiconductor Cu(2)O. Epitaxial Cu(2)O nanostructures with different shapes and geometries-from boxes to pyramids to huts-have been grown via pulsed laser deposition. By varying the adatom energy and flux per laser pulse we can tune the nature of the nanostructure geometry, the total density of features, the relative surface area to volume ratio, and can create polar, nonequilibrium surfaces. In addition to detailed structural analysis of the nanostructures, high-resolution Kelvin probe force microscopy has been used to systematically analyze the surface potential and electronic structure of the (100), (110), and (111) surfaces of Cu(2)O. These studies suggest that each surface, possessing a unique atomic structure, gives rise to different surface energy levels of conduction and valence bands and the formation of electronic surface junctions. The implication of these findings in terms of a range of applications is discussed.