Observation of negative capacitances in metal-insulator-metal devices based on a-BaTiO3: H

We study capacitance dispersion in hydrogen-doped amorphous barium titanate (a-BaTiO3: H). Negative values of capacitance are observed at very low frequencies (<10 Hz). This behavior is shown to be related to proton and oxygen vacancy conductions. A qualitative model is proposed to explain negative capacitances. It involves the modification of the Schottky barrier at the metal-dielectric interface upon accumulation of mobile protons and oxygen vacancies at electrodes. (C) 2008 American Institute of Physics.