Photostimulated Near-Resonant Charge Transport over 60 nm in Carbon-Based Molecular Junctions
Bibliographic record
Abstract
The bias and temperature dependence of both dark and photoinduced currents in carbon-based molecular junctions were examined over a wide range of oligomeric layer thickness ( d ) values from 4 to 60 nm. The dark current density versus bias ( JV ) response of nitroazobenzene molecular junctions exhibits the exponential thickness dependence consistent with coherent tunneling when d < 5 nm, but becomes weakly dependent on d and temperature ( T ) for d = 15–60 nm. The photocurrent ( PC ) response is orders of magnitude higher than the dark current for the same d and bias, with very different curve shape and much earlier onset with bias. Although the dark and PC differed greatly in magnitude for d > 14 nm, they both exhibit near zero attenuation coefficients (β < 0.05 nm –1 ) and are activationless ( E act < 5 meV) below ∼200 K. For d > 14 nm, both dark and PC become electric field ( E ) dependent and exhibit approximate overlap of J versus E response for d = 14–60 nm. The value of ln J versus E 1/2 is linear for both PC and dark current, with very different magnitudes and slopes. We propose an orbital mediated transport for PC, which involves sequential tunneling of photogenerated electrons and holes between frontier orbitals of adjacent, weakly interacting oligomeric subunits. Such transport is “bulk-limited”, E dependent, and nearly activationless due to small tunneling barriers and short distances between adjacent molecular orbitals. In contrast, the dark current is activated and injection limited due to an interfacial energy barrier much larger than that for bulk transport in the junction interior. Rapid, low-barrier transport between orbitals in adjacent molecules should significantly extend the “range” of molecular electronics to >50 nm and avoid the usually strong temperature dependence observed in thicker organic films.
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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".