Arsenic incorporation during Si(001):As gas-source molecular-beam epitaxy from Si2H6 and AsH3: Effects on film-growth kinetics
Bibliographic record
Abstract
The effects of As doping, at concentrations CAs⩽4.8×1018 cm−3, on the growth kinetics of Si(001):As layers deposited at temperatures Ts=575–900 °C by gas-source molecular-beam epitaxy from Si2H6 and AsH3 have been investigated. With constant AsH3 and Si2H6 fluxes, film deposition rates RSi increase while CAs decreases with increasing Ts. All incorporated As resides at substitutional electrically active sites for CAs up to 3.8×1018 cm−3 (Ts=800 °C), the highest value yet reported for Si(001):As growth from hydride source gases. Immediately following film growth or partial-monolayer As adsorption on clean Si(001), the samples were quenched to 300 °C and exposed to atomic deuterium (D) until saturation coverage. In situ D2 temperature-programmed desorption (TPD) spectra from both as-deposited Si(001):As and As-adsorbed Si(001) layers are composed of β1 and β2 peaks, due to D2 desorption from Si monodeuteride and dideuteride surface phases, together with a new peak β3 which we attribute to desorption from Si–As mixed dimers. Analyses of the TPD spectra show that, because of the lone-pair electrons associated with each As surface atom, the total dangling-bond coverage, and hence RSi, decreases with increasing incoming flux JAsH3 at constant Ts. From measurements of the steady-state As surface coverage θAs vs CAs and Ts, we obtain an As surface segregation enthalpy ΔHs=−0.92 eV. Dissociative AsH3 adsorption on Si(001) was found to follow second-order kinetics with a relatively Ts-independent reactive sticking probability of 0.3. Associative As2 desorption is also second order with a rate constant kd,As2=1×1013 exp(−3.0 eV/kTs). From the combined set of results, we develop a predictive model with no fitting parameters for CAs vs JAsH3, JSi2H6, and Ts.
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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".