Self-Directed Growth of Aligned Adenine Molecular Chains on Si(111)7×7: Direct Imaging of Hydrogen-Bond Mediated Dimers and Clusters at Room Temperature by Scanning Tunneling Microscopy
Bibliographic record
Abstract
The early stage of adsorption of adenine on Si(111)7×7 is studied by scanning tunneling microscopy (STM). Bright protrusions are observed in both empty-state and filled-state STM images, indicative of molecular adsorption of adenine through dative bonding. The majority of these bright protrusions appear as dimer pairs formed by hydrogen bonding at the initial adsorption stage. The formation of dative bonds between the substrate and adenine and the feasibility of the H-bond mediated dimers are supported by ab initio DFT/B3LYP/6-31G++(d,p) calculations, and are in excellent accord with our recent X-ray photoemission data. Remarkably, these dimers are found to undergo self-organization into aligned superstructures, evidently with common link arrangements, including straight, offset, and zigzag chains, square quartets, double quartets, and other multiple dimer structures. As the exposure of adenine increases, the populations of dimers as well as the self-organized double dimer and other higher-order structures also increase. The end-to-end dimer links are found to be most prominent in the growth of adenine molecular chains, most notably aligned along the Si dimer-wall or [-1 1 0] direction of the 7×7 unit cell. The self-aligned adenine dimer molecular chains offer a natural template for catch-and-release biosensing, lithography, and molecular electronic applications.
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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) | 0.001 | 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".