Surface layers and their conductivity on high-resistance Cu2O

Abstract

The surface and bulk conductivities of high-resistance Cu2O crystals were measured on natural and etched samples over a temperature range from 230 to −145 °C in vacuum and in air. The total conductivity measured from high temperatures in vacuum was found not to be influenced by the surface conductivity. The bulk conductivity followed the simple exponential temperature dependence with a single activation energy of about 0.61 eV over the entire range. Exposure to air caused the formation of conducting surface layers which changed over several days. The surface conductivity of samples could be detected by a change in activation energy at 20 °C. The elimination of surface layers was only possible by heat treatment in vacuum. The temperature behavior of the surface conductivity is explained on the assumption that absorption and desorption of oxygen and diffusion of copper ions take part in the formation of the surface layers.