Electrical transport properties of La_1-xSr_xCoO₃ thin films

The electrical transport properties of La_1-xSr_xCoO₃ (LSCO) thin films were investigated in this paper. As x increased up to 0.3, the electrical transport mechanism transferred from variable range hopping to double-exchange and the film simultaneously turned from an insulator into a conductor. Different from the bulk materials, the maximum conductivity of the film appeared at x = 0.3. A novel electrical transport model was proposed to explain this unconventional phenomenon. Besides, the effects of doped Sr and oxygen vacancies on the electrical transport properties were clarified by investigated the transport behaviors of the LaCoO₃, La_0.7S_0.3CoO₃, and La_0.7S_0.3CoO_3-δ films. We found that, when Sr was doped into the LaCoO₃ film, the insulating film turns into a conductor; when oxygen atoms were removed from the La_0.7S_0.3CoO₃ film, the conducting film goes back to an insulator. Our work could shed light on the electrical transport mechanism of the LSCO films.