Electrical-transport characteristics of as-grown and oxygen-reduced LaCeMnO films: calculation of hopping energies, Mn valences, and carrier localization lengths
arXiv:1408.4569 · doi:10.1016/j.jpcs.2014.12.014
Abstract
Presently, cerium-doped LaMnO is vividly discussed as an electron-doped counterpart prototype to the well-established hole-doped mixed-valence manganites. Here, LaCeMnO thin films of different thicknesses, degrees of CeO phase segregation, and oxygen deficiency, grown on SrTiO single crystal substrates, are compared with respect to their resistance-vs.-temperature (R vs. T) behavior from 300~K down to 90~K. While the variation of the film thickness (and thus the degree of epitaxial strain) in the range between 10~nm and 100~nm has only a weak impact on the electrical transport, the degree of oxygen deficiency as well as the existence of CeO clusters can completely change the type of hopping mechanism. This is shown by fitting the respective \textit{R-T} curves with three different transport models (adiabatic polaron hopping, Mott variable-range hopping, Efros-Shklovskii variable-range hopping), which are commonly used for the mixed-valence manganites. Several characteristic transport parameters, such as the hopping energies, the carrier localization lengths, as well as the Mn valences are derived from the fitting procedures.
9 pages, 3 figures