Structure and photoluminescence of ultrathin films of SnO2 nanoparticles synthesized by means of pulsed laser deposition
Bibliographic record
Abstract
Tin oxide (SnO2) ultrathin films were deposited by pulsed laser deposition (PLD) onto SiO2/Si and quartz substrates, at various nominal thicknesses ranging from isolated nanoparticles (NPs) to ∼300 nm-thick films, under an oxygen background pressure of 10 mTorr. The microstructural and surface morphologies of the NP-based SnO2 films were characterized by x-ray diffraction and atomic force microscopy, as a function of their nominal film thickness. The PLD-SnO2 films were found to be composed of NPs (in the 1–6 nm range), whose size increases with the film thickness. The energy band gap, as determined from the absorption edge, was found to shift to higher values with decreasing the film thickness (i.e., decreasing the NPs size). It was found that an annealing at 700 °C under O2 ambient is a prerequisite to get a photoluminescence (PL) emission from the PLD-SnO2 films. The PL of the annealed SnO2 films was found to consist of two broad emission bands, regardless of the SnO2 film thickness. The first band is composed of 3 PL subbands peaking at 3.20, 3.01, and 2.90 eV, while the second one is centered on 2.48 eV. In spite of the observed band-gap widening (as confirmed by theoretical calculation), we show that surface state (e.g., oxygen vacancies) dominate completely the PL emission of SnO2 NPs, which becomes more luminescent as the NPs size decreases while the PL energy remains unchanged. The PL properties of the PLD-SnO2 NPs are discussed in terms of defects and/or oxygen vacancies related transitions.
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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".