Confined polaronic transport in (LaFeO3)(n)/(SrFeO3)(1) superlattices

Abstract

Functional oxide superlattices offer new and exciting possibilities for the exploration of emergent properties at the nanoscale. While the behavior of La1-xSrxFeO3 films has been extensively investigated at low temperatures, few studies have been carried out at high temperatures, particularly for LaFeO3/SrFeO3 superlattice systems. Here, we investigate the transport behavior and optical properties of (LaFeO3)(n)/(SrFeO3)(1) superlattices at 373 K and above. Using optical spectroscopy, we observe a low energy excitation at similar to 1 eV, attributable to charge transfer between the O 2p and Fe 3d states of the delta-doped single SrFeO3 layer. From in-plane conductivity measurements on the superlattices, we determine activation energies that are much lower than those of alloyed samples and vary with the total number of SrFeO3 layers. This suggests that polaronic transport is confined near the SrFeO3 regions, permitting mobilities significantly enhanced over those in alloyed thin films.