Critical Excitation Energy-Based Method for Chemical Bonding State Analysis Using SEM-EDS.

In this study, we investigate the feasibility of evaluating the chemical bonding states using an electron-beam-based spectroscopic method implemented on a conventional scanning electron microscope and energy dispersive X-ray spectroscopy (SEM-EDS) system. The widely used surface-sensitive techniques such as X-ray absorption spectroscopy (XAS) often require synchrotron facilities and are not suitable for localized measurements. The critical excitation energies of silicon and silicon oxide featuring distinct absorption edge energies in XAS were determined by measuring the onset of characteristic X-ray emission as a function of incident electron energy. The observed difference in the critical excitation energy is consistent with the reported chemical shifts in the Si 1s binding energies and Si-K absorption edge energies. Systematic evaluations confirmed that variations in the beam current, instrumental instability, and surface charge-up did not significantly affect the measured thresholds. These results indicate that the proposed method captures chemically sensitive information related to the core-level electronic structure. The proposed approach provides a simple and accessible alternative to probe chemical bonding states and offers potential advantages for localized analysis because of the small probe size achievable with electron beams.