Conduction mechanisms in barium tantalates films and modification of interfacial barrier height

nThe leakage current-voltage characteristics of rf-magnetron sputtered BaTa 2O6 film in a capacitor with the top aluminum: and the bottom indium-tin-ox ide electrodes have been investigated as a function of applied field and te mperature. In order to study the effect of the surface treatment on the ele ctrical characteristics of as-deposited film we performed an oxygen plasma treatment on BaTa2O6 surface. The de current-voltage, bipolar pulse charge- voltage, de current-time, and small ac signal capacitance-frequency charact eristics were measured to study the electrical and the dielectric propertie s of BaTa2O6 thin film. All of the BaTa2O6 films in this study exhibited a low leakage current, a high breakdown field strength (3-4.5 MV/cm), and a h igh dielectric constant (20-30), From the temperature dependence of the lea kage current, we could conclude that the dominant conduction mechanism unde r high electrical fields (>1 MV/cm) is ascribed to the Schottky emission wh ile the ohmic conduction is dominant at low electrical fields (<1 MV/cm). F urthermore, the oxygen plasma treatment on the surface of as-deposited BaTa 2O6 resulted in a lowering of the interface barrier height and thus, a redu ction of the leakage current at Al under a negative bias. This can be expla ined: by the formation of Ba-rich metallic layer by surface etching effect and by filling the oxygen vacancies in the bulk.