Surface Mobility of Copper Ions on Cuprous Oxide

This paper reports on the motion of Cu⁺ ion vacancies on the surface of cuprous oxide at room temperature under the application of an electric field. The measurement of the mobility of the Cu⁺ vacancies was made by means of a "time of flight" procedure. The formation of luminescent centers is the unique property of Cu⁺ vacancies that makes them directly observable. The mobility of the Cu⁺ vacancies at room temperature is about 10^-11 cm²/volt-sec. The variation of the mobility with temperatures between 28^∘{}C to 55^∘{}C is observed. From these data the constants of the diffusion equation D=D₀exp(ΔHRT) are computed. D₀=5×10^-7 cm² sec, ΔH=8100 calories. The low values obtained for these constants shows that the ionic current follows low-resistance paths formed by the crystal grain boundaries or along the surface of the crystal.