Effect of depletion layers on scaling effect in barium strontium titanate epitaxial film

The influence of different work functions of metal electrodes on (Ba,Sr)TiO3 thin film capacitor was investigated. We fabricated BST film parallel plate capacitor with top electrodes of Pt, Au, Ag, and In. The apparent dielectric permittivity increased depending on the work function of the electrodes. We measured the complex impedance of the capacitors and separated the capacitance of the low permittivity layers from that of BST. We concluded that the scaling effect of the BST films is negligible, and the origin of the low permittivity layer is the internal bias electric field in the interface.