PNNL

Abstract

LaCrO3 (LCO) / SrTiO3 (STO) heterojunctions are intriguing due to a polar discontinuity along (001), two distinct and controllable interface structures [(LaO)+/(TiO2)0 and (SrO)0/(CrO2)– ], and interface-induced ferroelectricity. In this study, we have used soft- and hard-x-ray standing-wave excited photoemission spectroscopy (SW-XPS) to generate a non-destructive determination of the elemental depth profile of the two interfaces, the layer-resolved valence electronic structure, and the depth distribution of interface-induced built-in potentials in the two constituent oxides. From the determined sample structure, an alternating charged interface configuration is observed: a positive charged 2-Å-thick (LaO)+/(TiO2)0 intermediate layer at the LCOtop/STObottom interface and a negative charged 2-Å-thick (SrO)0/(CrO2)– intermediate layer at the STOtop/LCObottom interface. SW-XPS also enabled us to deconvolute the LCO-contributed and STO-contributed matrix-element-weighted density of states (MEWDOSs) from the valence band (VB) spectra for the LCO/STO SL. Monitoring the VB edges of the deconvoluted MEWDOS shift with a change in probing profile, the alternating charged-induced built-in potentials are observed in both constituent oxides. Finally, with a two-step simulation, the built-in potentials across the SL are resolved in detail and represented by the depth distribution of VB edges.