Dynamic electron scattering as the origin of forbidden reflections from black phosphorus
Bibliographic record
Abstract
Abstract Black phosphorus (BP) is a monoelemental two-dimensional semiconductor with exceptional electrical and optical properties including a widely tunable direct bandgap, high carrier mobilities, and in-plane anisotropy. Monolayer of BP, termed phosphorene, has been predicted to possess extremely high hole mobilities and excellent thermoelectric properties and thus holds great promise for applications in next-generation electronic, optoelectronic, and thermoelectric devices. Transmission electron microscopy (TEM) is most frequently used to determine if BP nanosheets prepared by liquid-phase exfoliation are composed of single or multiple layers. The presence of a strong (101) reflection in the electron diffraction pattern or in the fast Fourier transform of high-resolution TEM images of BP has been widely accepted as the signature of phosphorene since this reflection should be forbidden or negligible in bulk and multilayer BP. Here, we find that the presence of a strong (101) reflection is quite frequent for BP nanosheets prepared using of commonly used approach of liquid-phase exfoliation in N -methyl-2-pyrrolidone, but further investigation shows that the presence of monolayers is in fact extremely rare. In fact, this reflection vanishes when BP nanosheets are carefully aligned to the zone axis [010], but becomes visible once the nanosheet is slightly tilted away from the zone axis. The tilt-dependent forbidden reflection is attributed to the dynamic electron scattering, as supported by the simulated scanning TEM patterns of BP nanosheets with and without tilt using the multislice algorithm. Our findings contribute to a better understanding of the presence of forbidden reflections in BP and highlight the importance of careful alignment when employing TEM to identify phosphorene.
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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".