Core Hole Effects on Eels Near-Edge Fine Structure in Semiconductors and Insulators

Abstract

Electron energy-loss spectroscopy (EELS) is now a standard tool to investigate the local chemistry and bonding of defects in solids. to first order, the energy thresholds of the ionization edges in EELS spectra are determined by the identity of the element [1], while small shifts are induced by different bonding coordination and charge states [2]. The shapes of ionization edges in EELS spectra reflect the local bonding environments. We present first-principles calculations that incorporate electron-hole interactions and are in excellent agreement with experimental data obtained with X-ray absorption spectroscopy (XAS) and EELS. The superior energy resolution in XAS spectra and the new calculations make a compelling case that core-hole effects dominate core-excitation edges in all of the materials investigated: Si, SiO2, MgO, SrTiO3 and SiC. These materials differ widely in their dielectric constants leading to the conclusion that core-hole effects dominate all core-electron excitation spectra in semiconductors and insulators.