Preparation of High quality Cu2O crystal and its opto-electronic properties

The growth condition, including annealing temperature, annealing time and cooling ambient on the crystal structure and opto-electronic properties of thermally oxidized polycrystalline Cu2O plate are systematically investigated. High vacuum cooling is efficient to eliminate the CuO impurity to improve the bulk mobility. Both high temperature and longtime annealing lead to preferential grow of (311) surface. Orientation dependent conductivity in a single grain is observed. Surface potential measurement reveals that the dependence is originated from the facet-dependent work function. The facet-dependent work function is also suggested to induce an energy barrier of tens of meV between grains, which explain the positive dependence of mobility on the grain size.