Nonlinear positive temperature coefficient of resistance of BaTiO3 film

Conductance decreasing with increasing temperature (T) above a characteristic T (T-0) is found in the reverse-diode characteristics of metal contacts on strained BaTiO3 epitaxial films. The conduction mechanisms below and above T-0 near the Curie temperature of the bulk BaTiO3 are distinctly different. Marked similarities to these characteristics are found in the surface conduction on BaTiO3 single crystal in a high vacuum. By comparing the observations with the positive temperature coefficient of resistance (PTCR) effect in ceramics, we suggest that the anomaly is regarded as a PTCR effect at metal/ferroelectric contact, and discuss the origin of the effect in thin films and single crystals. (C) 2003 American Institute of Physics.