Influence of hole depletion and depolarizing field on theBaTiO3/La0.6Sr0.4MnO3interface electronic structure revealed by photoelectron spectros

Abstract

The effects of the bonding mechanism and band alignment in a ferroelectric (FE) BaTiO 3 /ferromagnetic La 0.6 Sr 0.4 MnO 3 heterostructure are studied using x-ray photoelectron spectroscopy and first-principles calculations. The band lineup at the interface is determined by a combination of band bending and polarization-induced modification of core-hole screening. A Schottky barrier height for electrons of 1.22 ± 0.17 eV is obtained in the case of downwards FE polarization of the top layer. The symmetry of the bonding states is emphasized by integrating the local density of states ±0.2 eV around the Fermi level, and strong dependence on the FE polarization is found: upwards, polarization stabilizes Ti t 2g (xy) orbitals, while downwards, polarization favors Ti t 2g (yz) symmetry. It is predicted that the abrupt (La,Sr)|TiO 2 interface is magnetoelectrically active, leading to a A-type antiferromagnetic coupling of the first TiO 2 interface layer with the underlying manganite layer through a superexchange mechanism.

Ce0.8Sr0.2CoxFe1‐xO3‐δ (x=0.2, 0.5, 0.8) – A Perovskite‐type Nanocomposite for Application in the Oxygen Evolution Reaction in Alkaline Media

“…The line shape shows only a marginal change between the samples, and it is reflected in the slight variations in the fitted parameters shown in Table 6. Given the BE and the energy difference between Sr1 and Sr2, we can ascribe Sr2 to Sr ions at the surface of these materials, while Sr1 is the bulk component for Sr ions in a 2+ oxidation state, consistently with what was reported in the literature [74].…”

Impact on Ferroelectricity and Band Alignment of Gradually Grown Au on BaTiO3

“…All BE of the substrate are featured by gradual shifts toward HBE with increasing metal thickness, up to 0.9 eV at 100 Å Au (Figure c and d). The values of the core levels obtained for the main component of the clean surface ( for Ba 3 d 5/2 , for Ti 2 p 3/2 ) are in reasonable agreement with previous data. For more details about the Au and O 1 s evolution during layer growth see the Supporting Information.…”

“…The resulting Schottky barrier has the height , where is the modification of the ‘apparent built‐in potential‘ at the FE interface and . According to the mechanism suggested in Figure derived from our experimental data, the apparent BE shift of the Au covered surface by 0.9 eV toward HBE, allows to extract the ferroelectric term = 1.2 eV with and effective dielectric constant and, deduce that . This is larger by a factor of 2‐3 compared to PZT …”

“…When the polarization is oriented inwards, the bands bend upwards and the signature is seen in photoemission as shifts toward lower binding energies (LBE) near surfaces, while in the outwards polarization case they bend downwards accompanied by shifts toward higher binding energies (HBE) . Core levels shift rigidly with respect the vacuum level together with the valence band maximum (VBM), following the band alignment direction . X‐ray Photoelectron Spectroscopy (XPS) emerges as the tool to directly extract such signatures close to the surfaces and their corresponding interfaces with different electrodes .…”

AMnO3 (A = Sr, La, Ca, Y) Perovskite Oxides as Oxygen Reduction Electrocatalysts

“…This broad peak contains contributions from Mn 3+ (641.9 eV) and Mn 4+ (642.2 eV) states [30], which are rather difficult to deconvolute. The Sr 3d line shows two components; the one at lower BE corresponds to the Sr in the perovskite lattice (132.0 eV), whereas the one at higher BE is attributed to the formation of SrO/Sr(OH) 2 at the surface (133.8 eV) [31,32]. Two components are also observed in the Y 3d region, one at 156.2 eV, associated with the formation of Y 2 O 3 , and the another at 158.5 eV Fig.…”