A loss for photoemission is a gain for Auger: Direct experimental evidence of crystal-field splitting and charge transfer in photoelectron spectroscopy

TL;DR

This study provides direct experimental evidence of crystal-field splitting and charge transfer in SrTiO₃ through the analysis of satellite features in Ti 1s photoelectron spectra, revealing new insights into electronic structure.

Contribution

It demonstrates that two satellite features in Ti 1s spectra are due to crystal-field splitting and charge transfer, supported by Auger decay analysis, which is a novel experimental confirmation.

Findings

Identification of a new 5 eV satellite in Ti 1s spectra.

Attribution of satellites to ligand-to-metal charge transfer and crystal-field effects.

Evidence linking satellite features to specific electronic excitations.

Abstract

We find a new 5 eV satellite in the Ti 1s photoelectron spectrum of the transition-metal oxide SrTiO$_3$. This satellite appears in addition to the well-studied 13 eV structure that is typically associated with the Ti 2p core line. We give direct experimental evidence that the presence of two satellites is due to the crystal-field splitting of the metal 3d orbitals. They originate from ligand 2p t$_{2g}$ $\rightarrow$ metal 3d t$_{2g}$ and ligand 2p e$_g$ $\rightarrow$ metal 3d e$_g$ monopole charge-transfer excitations within the sudden approximation of quantum mechanics. This assignment is made by the energetics of the resonant and high-energy threshold behaviors of the Ti K-L$_2$L$_3$ Auger decay that follows Ti 1s photo-ionization.