Surface Mobility of Copper Ions on Cuprous Oxide

This paper reports on the motion of ${\mathrm{Cu}}^{+}$ 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 ${\mathrm{Cu}}^{+}$ vacancies was made by means of a "time of flight" procedure. The formation of luminescent centers is the unique property of ${\mathrm{Cu}}^{+}$ vacancies that makes them directly observable. The mobility of the ${\mathrm{Cu}}^{+}$ vacancies at room temperature is about ${10}^{-11\mathrm{}}$ ${\mathrm{cm}}^2$/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 $D=D_0\exp \left(\frac{\Delta H}{\mathrm{RT}}\right)$ are computed. $D_0=5\mathrm{}\times {10}^{-7\mathrm{}}$ ${\mathrm{cm}}^2$ sec, $\Delta H=8100\mathrm{}$ 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.