Thermally stimulated polarization and depolarization processes inAl2O3:Mg

Thermally stimulated polarization (TSP) and depolarization current measurements in as-cut as well as in oxidized magnesium-doped aluminum oxide show a huge peak at around 265 K, another one at 245 K, and a broadband at higher temperatures. They are related to the presence of ${\mathrm{Mg}}_{\mathrm{Al}}^{\mathit{x}}$ centers (substitutional magnesium ions with a hole trapped at a neighboring oxygen ion) and originate from the thermally activated ionization of these centers, which release holes. The current-voltage curves and the TSP results related to the main polarization process show that this is due to the formation of blocking contacts at the sample-electrode interfaces.