Electroluminescence materials ZnS:Cu,Cl and ZnS:Cu,Mn,Cl studied by EXAFS spectroscopy
Bibliographic record
Abstract
When a high-frequency ac voltage is applied to ZnS:Cu,Cl and ZnS:Cu,Mn,Cl devices, optical fluorescence, known as ac electroluminescence (EL), is observed; it depends on both the Cu (Mn) and Cl dopants. The local structure of these compounds was studied using the extended x-ray-absorption fine-structure (EXAFS) technique to understand the role of Cu and Mn. Data were taken at the $K$ edge of Zn, Cu, and Mn, for powder material and for both new and aged (degraded, low EL) devices. The EXAFS data show that Mn substitutes for Zn in the ZnS lattice, whereas Cu has a different local structure (it cannot be fit well with the ZnS structure). For all the Cu edge data, the first shell of neighbors is best fit using an experimental standard obtained from CuS, suggesting that almost all of the Cu resides in tiny CuS-like clusters. Since these clusters are dominant in both the new and degraded samples and do not change with aging, they likely do not contribute directly to the luminescence. Consequently, our results indicate that a very small fraction of the Cu atoms are EL-active; this is consistent with previous models for which the emission centers involve isolated Cu defects or Cu pairs. Thus, a possible explanation for the rapid degradation of a device is that the isolated Cu ions electrodiffuse to the CuS-like clusters, at which point they no longer produce EL. Based on these results, a low-temperature annealing experiment (200C) was carried out that shows that a degraded device can be nearly completely rejuvenated by heating.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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) | 0.000 | 0.001 |
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 teacher head, 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".