Defining the nature of adventitious carbon and improving its merit as a charge correction reference for XPS
Bibliographic record
Abstract
The chemical nature of adventitious carbon (AdC), a thin layer of carbonaceous material that deposits on the surface of most air-exposed samples and is widely used for charge correction of insulating materials in X-ray photoelectron spectroscopy (XPS), has been investigated by XPS and time-of-flight secondary ion mass spectrometry (ToF-SIMS) on a variety of air-exposed samples from various material classes. The results from this case study show that on average AdC is aliphatic in nature with ∼25% of carbon species having bonds to oxygen. D-parameter and ToF-SIMS results show that AdC is not graphitic in nature, as had been suggested in earlier studies. Using assumptions about volatile organic compounds (VOC) in air that contribute to AdC accumulation, a peak-fitting model for the C 1s XPS spectrum of AdC including beta shifted carbon peaks was developed. This model is shown to increase accuracy of the positioning of the aliphatic peak. Using this model and data from 117 samples an AdC C 1s aliphatic peak binding energy of 284.81 eV (+/-0.25 eV) was found. Average XPS and ToF-SIMS AdC spectra are presented. The average AdC XPS spectrum has been utilized to model the C 1s spectrum of complex organic compounds with AdC present.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".