Low-temperature electrical transport properties of La doped BaSnO₃ films

Abstract

A series of Ba<sub>0.94</sub>La<sub>0.06</sub>SnO<sub>3</sub> thin films were deposited on MgO (001) single crystal substrates by RF magnetron sputtering method, and their structure and electrical transport properties were systematically investigated. All films reveal degenerate semiconductor (metal) characteristics in electrical transport properties. In the high-temperature region (<i>T</i>><i>T</i><sub>min</sub> with <i>T</i><sub>min</sub> being the temperature at which the resistivity reaches the minimum), the resistivity of the films increases with temperature, and exhibits a linear relationship with the square of the temperature. In the low-temperature region (<i>T</i><<i>T</i><sub>min</sub>), the resistivity increases with decreasing temperature and varies linearly with ln<i>T</i>. This temperature dependent behavior of resistivity cannot be explained by the general electron-electron interaction or weak localization effects in homogeneous disordered conductors and cannot be explained by Kondo effect either. After quantitative analysis, it is found that the ln<i>T</i> behavior of resistivity at low temperatures can be explained by the electron-electron Coulomb interaction effects in the presence of granularity. In additional, it is found that the Hall coefficient <i>R</i><sub><i>H</i></sub> also varies linearly with ln<i>T</i> for the Ba<sub>0.94</sub>La<sub>0.06</sub>SnO<sub>3</sub> films, which also quantitatively agrees with the theory prediction of the electron-electron Coulomb interaction effects in the granular metals The cross-sectional high-resolution transmission electron microscopy results indicate that although the films exhibit epitaxial structure overall, there are many strips amorphous region in films, which makes the films similar to metallic granular films in electrical transport properties. Our results provide strong support for the validity the theory concerning the influence of Coulomb interaction on conductivity and Hall coefficient in granular metals.