Selective Adsorption and Thermal Evolution of Bifunctional Carboxylic Acids: Competition of O—H Dissociation and Other Reaction Products in Acrylic Acid and Propanoic Acid on Si(100)2×1
Bibliographic record
Abstract
The dissociative adsorption of acrylic acid on Si(100)2×1 at room temperature has been investigated by X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD), as well as density-functional theory (DFT) calculations. Three C 1s features can be attributed to the carboxyl C of bidentate acrylate (at 286.8 eV) and unidentate acrylate (at 289.3 eV), both resulting from O—H dissociation upon adsorption, and to their corresponding ethenyl C atoms (at 285.0 eV). The formation of bidentate acrylate at a low exposure is followed by that of unidentate acrylate at a higher exposure, with approximately equal populations for both adstructures at the saturation exposure. DFT calculations confirm that the bidentate acrylate adstructure gives the most stable adsorption structure configuration. The combined temperature-dependent XPS and TPD studies provide strong evidence for the formation of CO, ethylene, acetylene, and propene, with 60% of the C moiety from the adsorption configurations converted to SiC with increasing annealing temperature to 1050 K. A companion study on propanoic acid on Si(100)2×1 shows similar formation of bidentate and unidentate propanoate adsorption configurations and thermal evolution to only CO and ethylene. In both acrylic acid and propanoic acid, the respective O—H dissociation products appear to be preferred over the other reaction products, such as [O, C] bidentate formation, C—OH dissociation, C═C cycloaddition, C═O cycloaddition, and ene formation. The unreacted backbone of the acrylate adsorption configuration provides a reactive site for further functionalization by other molecules.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".