Epitaxial Nature and Transport Properties in (LaBa)Co2O5+δ Thin Films

Epitaxial (LaBa)Co2O5+delta thin films were grown on (001) LaAlO3 single-crystal substrates using pulsed laser deposition. Microstructure characterizations from X-ray diffraction and electron microscopy indicate that the Films are highly c-axis oriented with cube-on-cube epitaxy. Transport property measurements indicate that the films have typical semiconductor behavior with a novel phase transition and hysteresis phenomena at 540 K. The chemical dynamic studies reveals that the resistance of the film changes drastically with the change of redox environment, i.e., the magnitude of resistance changes, Delta R = 1 x 10(2)double left right arrow 1 x 10(6) Omega, is found within a short response time (similar to 700 ms). These phenomena suggest that the as-grown (LaBa)Co2O5+delta film have extraordinary sensitivity to reducing-oxidizing environment and the exceedingly fast surface exchange rate.