Thickness dependence of leakage current behavior in epitaxial (Ba,Sr)TiO3 film capacitors

Abstract

Thickness dependence of leakage current behavior in Pt/(Ba,Sr)TiO3/Pt film capacitors was investigated by fabricating epitaxial (Ba,Sr)TiO3 thin films having different thicknesses of 55–225 nm but with an identical interface state on Pt(001)/MgO(001) substrates by a radio-frequency magnetron sputtering technique. In the 55-nm-thick film, the Schottky emission is found to be a main leakage mechanism over a wide electric field range. In sharp contrast, instead of the Schottky emission, the Fowler–Nordheim tunneling dominates particularly in the thicker films (⩾90 nm) at high electric fields. According to the energy band model proposed to explain these results, the major leakage conduction mechanism is likely to be associated with overlapping of the depletion layers formed at the top and bottom interfaces.