Atomic resolution chemical bond analysis of oxygen in La2CuO4

Abstract

The distorted CuO6 octahedron in La2CuO4 was studied using aberration-corrected scanning transmission electron microscopy at atomic resolution. The near-edge structure in the oxygen K-edge electron energy-loss spectrum was recorded as a function of the position of the electron probe. After background subtraction, the measured spectrum image was processed using a recently developed inversion process to remove the mixing of signals on the atomic columns due to elastic and thermal scattering. The spectra were then compared with first-principles band structure calculations based on the local-density approximation plus on-site Coulomb repulsion (LDA + U) approach. In this article, we describe in detail not only anisotropic chemical bonding of the oxygen 2p state with the Cu 3d state but also with the Cu 4p and La 5d/4f states. Furthermore, it was found that buckling of the CuO2 plane was also detectable at the atomic resolution oxygen K-edge. Lastly, it was found that the effects of core-hole in the O K-edge were strongly dependent on the nature of the local chemical bonding, in particular, whether it is ionic or covalent.

Nematicity in stripe-ordered cuprates probed via resonant x-ray scattering

“…At ∼528.5 eV, the electronic states are dominated by the O 2p states of the in-plane oxygen (39). In contrast, the peak at ∼532 eV, is characterized by apical oxygen, O(2), hybridized with La, Ba, Sr, Eu and Nd (20,23). (20,23).…”

“…In contrast, the peak at ∼532 eV, is characterized by apical oxygen, O(2), hybridized with La, Ba, Sr, Eu and Nd (20,23). (20,23). The measurements on the three samples have been normalized above and below the absorption edge.…”

Practical Aspects of Removing the Effects of Elastic and Thermal Diffuse Scattering from Spectroscopic Data for Single Crystals

“…As the effects of channeling and scattering are known to have a significant impact on the signal in atomic resolution STEM, either approach—and we suggest the method presented here is simplest—is preferable to the previously common practice of directly comparing experimental results and first principles calculations without accounting for channeling effects. Recent work using the inversion method to remove the effects of channeling allowed for a detailed analysis of the chemical bonding in the superconductor La 2 CuO 4 (Haruta et al, 2013).…”

“…A method has recently been developed to invert the effects of channeling and TDS and remove them from STEM EELS fine-structure experiments by effectively deconvolving the incident probe from the experimental signal (Lugg et al, 2012). In the context of EELS, this allows one to “unmix” the spectra recorded from inequivalently bonded atoms of the same species (Lugg et al, 2012; Haruta et al, 2013; Neish et al, 2013). Here we show how this method can also be used in the context of EDX simulations to correct for the “errors” introduced from the channeling of the incident probe.…”

Achieve atomic resolution in in situ S/TEM experiments to examine complex interface structures in nanomaterials

“…In high energy resolution configuration, e.g. when using a monochromator in combination very stable and sensitive spectrometers [24,54], EELS fine structure analysis gives additionally access to information about local electronic properties (atomic bonding state mapping, imaging plasmonic information, band gap measurements, etc.) [19,113,20,24,40,42,79,84,87,111,112,121].…”