Abstract
It is interesting to examine facet-dependent electrical properties of single Cu 2 O crystals, because such study greatly advances our understanding of various facet effects exhibited by semiconductors. We show a Cu 2 O octahedron is highly conductive, a cube is moderately conductive, and a rhombic dodecahedron is nonconductive. The conductivity differences are ascribed to the presence of a thin surface layer having different degrees of band bending. When electrical connection was made on two different facets of a rhombicuboctahedron, a diode-like response was obtained, demonstrating the potential of using single polyhedral nanocrystals as functional electronic components. Density of state (DOS) plots for three layers of Cu 2 O (111), (100), and (110) planes show respective metallic, semimetal, and semiconducting band structures. By examining DOS plots for varying number of planes, the surface layer thicknesses responsible for the facet-dependent electrical properties of Cu 2 O crystals have been determined to be below 1.5 nm for these facets.