First-principles calculations of optical energy loss functions for 30 compound and 5 elemental semiconductors

The energy loss function (ELF) describes the interaction be-tween electrons and matter in solids. Electron inelastic mean free paths (IMFPs), which are important and basic parameters for describing electron inelastic scattering in matter, have been cal-culated theoretically from the ELFs of materials. These are es-sential for understanding quantitative surface spectroscopies, such as Auger electron and X-ray photoelectron spectroscopy. However, the optical constants or the ELFs of most compounds are unknown in the 10-50 eV energy range, where electron-solid interactions are strong, owing to experimental difficulty. In this study, the ELFs and the optical constants were calculated for 35 inorganic semiconductors [AgBr, AgCl, AgI, AlAs, AlN, AlSb, cubic-BN (c-BN), hexagonal-BN (h-BN), CdS, c-CdSe, h-CdSe, CdTe, C (diamond), GaAs, GaN, GaP, GaSb, GaSe, Ge, InAs, InP, InSb, PbS, PbSe, PbTe, Se, Si, c-SiC, h-SiC, SnTe, Te, c-ZnS, h-ZnS, ZnSe, and ZnTe] in a wide energy range (from 0.1 eV to 1 MeV) using first-principles calculations with FEFF and WIEN2k. The resulting 35 ELFs were evaluated using two sum rules, the f-sum rule and the Kramers-Kronig sum rule, resulting in average relative errors of 1.6% and 0.05%, respectively. The calculated ELFs for InAs, GaAs and InSb agreed well with the experimental ELFs obtained from the transmission electron energy loss spectroscopy (EELS) experiments and the reflection EELS experiments. The resulting database of the ELFs and the optical constants for 35 compound semiconductors was con-cluded to be accurate and useful for understanding the inelastic scattering processes of semiconductors with respect to IMFPs and electron stopping powers. All detailed data are available in the materials data repository provided by the National Institute for Materials Science (https://doi.org/10.34968/nims.1434). © 2021 The Japan Society of Vacuum and Surface Science. All rights reserved.