Precise control of time-varying effusion cell flux in molecular beam epitaxy
Bibliographic record
Abstract
We outline a method to control time-varying effusion cell flux in molecular beam epitaxy. This can be used to grow 2D nanostructures with precise continuously graded alloys, and we explore the specific case of controlling an Al cell for the growth of continuously graded Al xGa 1 − xAs parabolic quantum wells. We develop a simple model of the Al cell’s thermal dynamics, including the effects of shutter transients. This model’s parameters can be empirically derived using a beam flux monitoring ion gauge. Though simple, this model can already be used to generate near-arbitrary time-varying fluxes (within the physical limits of the cell). For growths that require higher precision than the simple model can achieve, we introduce an iterative correction scheme to eliminate any lingering errors. Using this method, we control the composition in a 3 THz Al xGa 1 − xAs parabolic quantum well array to a root mean squared error of just ± 0.18 %Al. This accuracy is achieved at the standard growth rates necessary for thick structures (0.15–0.25 nm/s). The approach is quite generally applicable to other composition profiles or other situations where time-dependent flux control is necessary, and it could be extended to other effusion cells.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 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".