We have investigated the electronic and optical properties of epitaxial La1-xSrxFeO3 for 0 = x = 1 prepared by molecular beam epitaxy. Core-level and valence-band x-ray photoemission features monotonically shift to lower binding energy with increasing x, indicating downward movement of the Fermi level toward to the valence band maximum. Both Fe 2p and O 1s spectra broaden to higher binding energy with increasing x, consistent with delocalization of Sr-induced holes in the Fe 3d – O 2p hybridized valence band. Combining X-ray valence band photoemission and O K-edge x-ray absorption data, we map the evolution of the occupied and unoccupied bands and observe a narrowing of the gap, along with a transfer of state density from just below to just above the Fermi level, resulting from hole doping. In-plane transport measurements confirm that the material becomes a p-type semiconductor at lower doping levels and exhibits a insulator-to-metal transition at x = 1. Sub-gap optical transitions revealed by spectroscopic ellipsometry are explained based on insight from theoretical densities of states and first-principles calculations of optical absorption spectra.
Revised: February 4, 2021 |
Published: February 4, 2019
Citation
Wang L., Y. Du, P.V. Sushko, M.E. Bowden, K.A. Stoerzinger, S.M. Heald, and M. Scafetta, et al. 2019.Hole-Induced Electronic and Optical Transitions in La1-xSrxFeO3 Epitaxial Thin Films.Physical Review Materials 3, no. 2:Article Number 025401.PNNL-SA-139953.doi:10.1103/PhysRevMaterials.3.025401