Energy Level Alignment and Cation Charge States at the LaFeO3/LaMnO3 (001) Heterointerface

The electronic properties of LaFeO3/LaMnO3 epitaxial heterojunctions are investigated to determine the valence and conduction band offsets and the nominal Mn and Fe valence states at the interface. Studying a systematic series of (LaFeO3)(n)/(LaMnO3)(m) bilayers (m approximate to 50) epitaxially grown in the (001) orientation using molecular beam epitaxy, layer-resolved electron energy loss spectroscopy reveals a lack of significant interfacial charge transfer, with a nominal 3+ valence state observed for both Mn and Fe across the interface. Through a combination of variable angle spectroscopic ellipsometry and hard X-ray photoelectron spectroscopy, type I energy level alignments are obtained at the LaFeO3/LaMnO3 interface with positive valence and conduction band offsets of (1.20 +/- 0.07) eV and (0.5-0.7 +/- 0.3) eV, respectively, with minimal band bending. Variable temperature resistivity measurements reveal that the bilayers remain insulating and that the presence of the heterojunction does not result in a conducting interface.