High temperature electrical properties of highly epitaxial CaCu3Ti4O12 thin films on (001) LaAlO3

The high temperature electrical behavior of highly epitaxial CaCu3Ti4O12 thin films on (001) LaAlO3 have been systematically investigated with traditional four-probe dc and ac resistance measurement techniques and two-probe ac impedance spectroscopy. Both ac and dc resistance measurements reveal that the Arrhenius plot, ln(σ) vs (1/T), forms two linear sections with a transition temperature between them at 773 K, one with the activation energy Ea of ∼1.3 eV at low temperature, and the other with the activation energy Eb of ∼0.5 eV at high temperatures. The high temperature impedance spectra also confirm these phenomena and suggest that unlike in polycrystalline bulk material, the high frequency response is predominantly from grains rather than grain boundaries.