Anomalous leakage current characteristics of Pt/(Ba0.75,Sr0.25)Ti1+yO3+z/Pt thin films grown by metalorganic chemical vapor deposition

The leakage and dielectric properties of a thickness series (90-480 nm) of {100} fiber-textured metalorganic chemical vapor deposited (Ba0.75Sr0.25)Ti1+yO3+z (BST) thin films on Pt/SiO2/Si were investigated. The permittivity demonstrated a suppressed temperature and electric field response that transitioned to a more bulk-like response with increasing thickness, consistent with earlier observations. At low fields the leakage currents showed a weak-field dependence and a monotonic increase with increasing temperature. In contrast, a positive temperature coefficient of resistance (PTCR) was observed in the leakage current behavior at high-field. The PTCR behavior was more pronounced for thicker BST films. The observed effect is contrasted with PTCR behavior in bulk BaTiO3 ceramics. (C) 2003 American Institute of Physics.