Extrinsic origin of giant permittivity in hexagonal BaTiO3 single crystals: Contributions of interfacial layer and depletion layer

Three dielectric relaxations in hexagonal (h)-BaTiO3 single crystals exhibiting giant permittivity were detected in a frequency range of 100Hz–3GHz and analyzed by an equivalent circuit with three parallel RC elements. A best-fit result indicated that the three dielectric relaxations were the responses of bulk crystal with a capacitance of 1pF, an interfacial layer with a capacitance of 1.4nF, and a depletion layer with a capacitance of 1nF. We confirmed that a giant permittivity exceeding 105 could be achieved by the interfacial layer in the h-BaTiO3 crystal. In addition, a Schottky barrier height at the contacting interface between Cu electrodes and the h-BaTiO3 surface was estimated as 1.56eV from the voltage dependence of capacitance.