The objective of curve-fitting high-resolution core XPS spectra with a set of component peaks is to separate the photoemission signal originating from distinct elemental or chemical states. Curve/peak fitting is often the only way to extract quantitative information from these spectra.
The resulting data can be analyzed by curve fitting.
In the core region, chemical shifts in the BEs yield a series of typically overlapping peaks when the sample has atoms in different chemical environments, e.g., oxidation states. The spectral features of both the core and valence regions are sensitive to the chemical environments of the atoms in a sample. Grant, Surface Analysis by Auger and X-Ray Photoelectron Spectroscopy ( IM Publications, Chichester, UK, 2003). In contrast, the features in the valence band region arise from photoelectrons generated from energy levels that typically involve the chemical interactions between the atoms in chemical bonding (the molecular orbitals). In the core region, the spectral features arise from photoelectrons generated from core energy levels (atomic orbitals), which are characteristic of the individual atoms in the sample. In XPS, it is convenient to identify two spectral regions, namely, the core region (electrons with binding energies, BEs, greater than 30 eV) and the valence band region (BE < 30 eV). This guide is intended to help address this important problem. Furthermore, errors, misconceptions, and bad curve-fitting practices accounted for most of the serious problems in both the measured XPS data and the spectral analysis that were identified in more than 30% of the papers analyzed. it was observed that roughly 70% of the papers using XPS analyzed the data using some type of curve fitting. In an ongoing study of XPS data in three high profile journals, 3 3. The absence of a distinct theoretical description of XPS fitting has led to the publication of erroneous conclusions about surface chemistry. Despite computational advances and higher accessibility of software resources, it has been challenging to develop a chemically and physically meaningful approach to curve fitting. Curve fitting has been widely used for more than 50 years for extracting chemical information from the overlapping features in high-resolution XPS spectra. Over the past 30 years, x-ray photoelectron spectroscopy (XPS) has become the most widely used surface analysis tool and has been an essential component of many research studies.
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