Atomic signatures of local environment from core-level spectroscopy inβ−Ga2O3

Abstract

We present a joint theoretical and experimental study on core-level excitations from the oxygen K-edge of β-Ga 2 O 3 . A detailed analysis of the electronic structure reveals the importance of O-Ga hybridization effects in the conduction region. The spectrum from O 1s core electrons is dominated by excitonic effects, which overall red-shift the absorption onset by 0.5 eV, and significantly redistribute the intensity to lower energies. Analysis of the spectra obtained within many-body perturbation theory reveals atomic fingerprints of the inequivalent O atoms. From the comparison of energy-loss near-edge fine-structure (ELNES) spectra computed with respect to different crystal planes, with measurements recorded under the corresponding diffraction conditions, we show how the spectral contributions of specific O atoms can be enhanced while quenching others. These results suggest ELNES, combined with ab initio many-body theory, as a very powerful technique to characterize complex systems, with sensitivity to individual atomic species and to their local environment.

P-type β-gallium oxide: A new perspective for power and optoelectronic devices

“…The covalent bonding interaction is due to the symmetry of the Ga4s states which enables a more energetically favorable bonding with the p-states of the oxygen. Several theoretical [54][55][56] and experimental studies [50][51][52]56] suggest that the partial density of states for the valence band is predominantly of O2p character while the conduction band states are predominantly derived from Ga4s and Ga4p states mixed with some contributions of O2p.…”

Addressing electron-hole correlation in core excitations of solids: An all-electron many-body approach from first principles

“…3c), is confined within the layer of the absorbing atom. Its extension beyond the size of the unit cell of the material is a signature of the electron-hole correlation, which is typical of bound excitons in the core [17,18,23,56], as well as in the valence region (see, e.g., [8,57]). It is worth noting that the first core exciton in PbI 2 is much more localized than its counterpart in the optical region [55].…”

Ab Initio Quantum-Mechanical Predictions of Semiconducting Photocathode Materials

“…In that work, we noticed that the local environment of the individual Cs atoms strongly impacts the X-ray spectral features. This is expected based on the knowledge over even more complex systems, such as Ga 2 O 3 , where crystallographically inequivalent atoms are also chemically inequivalent and exhibit different coordination [103,130]. In Ref.…”

“…This is straightforward in the all-electron implementations of DFT and MBPT where core electrons are explicitly accounted for [95][96][97]. In this scenario, the GW step is typically omitted, and the QP correction to the gap is included in the applied scissors operator [96,[98][99][100][101][102][103][104]. Either way, the BSE is cast into the effective Schrödingerlike equation as follows:…”