Change of conduction mechanism by microstructural variation in Pt/(Ba,Sr)TiO3/Pt film capacitors

The effects of microstructure on the leakage current behaviors in Pt/(Ba,Sr)TiO3/Pt thin film capacitors prepared by a radio-frequency magnetron sputtering technique were studied. Both applying an epitaxial seed layer and controlling post-annealing processes enabled us to obtain (Ba,Sr)TiO3 films of three different microstructures (granular, columnar, and epitaxial) but possessing an identical interface state with the Pt electrode. The Schottky emission dominates in the film composed of granular grains. In contrast, the Fowler-Nordheim tunneling governs in the epitaxial film with much elevated leakage current levels. In the case of the columnar film, at low temperatures the tunneling dominates, while at high temperatures the Schottky emission governs with intermediate leakage levels. An energy band model accounting for the change of leakage current mechanisms by microstructure variation is presented. (C) 2002 American Institute of Physics.