Effect of oxygen stoichiometry on the electrical property of thin film La0.5Sr0.5CoO3 prepared by pulsed laser deposition

A measurement of electrical conductivity and Hall effect has been made for thin film La0.5Sr0.5CoO3-delta (LSCO) prepared on (001) SrTiO3 substrates by pulsed laser deposition under reduced oxygen pressures. A considerable effect of oxygen stoichiometry on electrical resistivity of LSCO thin films has been observed. The semiconducting behavior was observed as long as the sample was slightly oxygen deficient. The Hall effect measurements revealed a change ranging from four to six orders of magnitude in the carrier density, from 10(19) to 10(15) cm(-3) at room temperature, and 10(20)-10(12) cm(-3) at similar to 80 K for the films prepared inbetween 1 bar and 1 mu bar O-2. A chemical equilibrium approach of the interaction between oxygen vacancies and hole carriers was used to explain the measured data. The results were compared with the microstructural measurements, yielding an empirical relation between the lattice expansion along c-axis and oxygen vacancies for LSCO films. (C) 1998 American Institute of Physics. [S0021-8979(98)08121-3].