Quantitative Evaluation of the Carbon Hybridization State by Near Edge X-ray Absorption Fine Structure Spectroscopy

Abstract

The characterization of the local bonding configuration of carbon in carbon-based materials is of paramount importance since the properties of such materials strongly depend on the distribution of carbon hybridization states, the local ordering, and the degree of hydrogenation. Carbon 1s near edge X-ray absorption fine structure (NEXAFS) spectroscopy is one of the most powerful techniques for gaining insights into the bonding configuration of near-surface carbon atoms. The common methodology for quantitatively evaluating the carbon hybridization state using C1s NEXAFS measurements, which is based on the analysis of the sample of interest and of a highly ordered pyrolytic graphite (HOPG) reference sample, was reviewed and critically assessed, noting that inconsistencies are found in the literature in applying this method. A theoretical rationale for the specific experimental conditions to be used for the acquisition of HOPG reference spectra is presented together with the potential sources of uncertainty and errors in the correctly computed fraction of sp 2 -bonded carbon. This provides a specific method for analyzing the distribution of carbon hybridization state using NEXAFS spectroscopy. As an illustrative example, a hydrogenated amorphous carbon film was analyzed using this method, and showed good agreement with X-ray photoelectron spectroscopy (which is surface sensitive).Furthermore, the results were consistent with analysis from Raman spectroscopy (which is not surface sensitive), indicating the absence of a structurally different near-surface region in this particular thin film material. The present work can assist surface scientists in the analysis of NEXAFS spectra for the accurate characterization of the structure of carbon-based materials.3

Silicon Oxide‐Rich Diamond‐Like Carbon: A Conformal, Ultrasmooth Thin Film Material with High Thermo‐Oxidative Stability

“…Most importantly, NEXAFS spectroscopy allowed the quantification of carbon atoms in the sp 3 hybridization state and the variation of this quantity upon annealing under HV and aerobic conditions . For the as‐grown film, the sp 3 fraction is calculated to be 78 ± 3%, indicating that PIIID‐grown a‐C:H:Si:O films have a significant diamond‐like character.…”

Hard carbon spheres prepared by a modified Stöber method as anode material for high-performance potassium-ion batteries

“…The % sp 2 ratio of SSAC is only 54.85%, reecting that SSAC has a large number of amorphous structures and defects. [31][32][33] From the elemental analysis results in Table S1, † it can be seen that SSAC contains a large amount of non-carbon elements, while HSGC is almost pure carbon, which is due to the element loss caused by the high-temperature carbonization process.…”

Cross‐sectional structural characterization of the surface of exfoliated HOPG using HRTEM‐EELS

“…6 HOPG substrates have been used for coatings of various substances and materials including DNA, 7 palladium nanowires, 8 oligomers, 9 metallothionein, 10 Fe 2 O 3 films, 11 phenyl-C61-butyric acid methyl ester (PCBM), 12 and gold nanoparticles coating. 13 Furthermore, HOPG substrates have been used as reference compounds in near-edge X-ray absorption fine structure (NEXAFS) measurements 14 and test electrodes for electrochemical reactions in a study on lithium-ion batteries. 15 The freshly prepared surfaces of HOPG substrates were used for coatings during the above-mentioned studies.…”