Determination of Diffusion Coefficient of Impurity Ions in a Crystal from their Drift Under Electric Field

We studied the drift of Cd interstitials in CdS single crystals at an electric field applied to the crystal. These atoms are totally ionized at moderate temperatures of the investigation (300 - 400 K). Mobile Cd ions drift from the anode to the cathode. A time-dependence was studied experimentally for the voltage dropped on the crystal at the constant value of the current passed through the sample. A non-stationary problem developed for the transient process allowed to derive the ion mobility in such a process from the experimental data. Concentration profiles and their time history were investigated in detail for the ions and free carriers.