Influence of microstructure on local conductivities in La_0.7Ce_0.3MnO₃ thin film

Abstract

We report on scanning tunneling microscopy and spectroscopy (STM/S) studies of electron doped La_0.7Ce_0.3MnO₃/LaAlO₃ thin films grown by pulsed laser deposition. Atomic force microscopy of these films reveals an average grain size of ~100 nm. Spatially resolved STS maps in the metallic state, i.e., well below the metal-insulator transition temperature, show phase separation on a length scale of several nanometers. The conductance maps indicate a correlation between the phase separation and the microstructure of the films. The results demonstrate that the local strain as well as the morphology of thin films have a strong influence on the local conductivities which complicates the search for an intrinsic phase separation in manganite thin films.