Surface morphology of GaAs during molecular beam epitaxy growth: Comparison of experimental data with simulations based on continuum growth equations
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Bibliographic record
Abstract
Using atomic force microscopy and in situ elastic light scattering we show that the surface of molecular beam epitaxy (MBE) grown GaAs tends towards an equilibrium roughness independent of the initial condition, as predicted by kinetic roughening theory. Two separate continuum growth equations are consistent with the observed equilibrium roughness, namely, the Kardar-Parisi-Zhang (KPZ) equation $\ensuremath{\partial}h/\ensuremath{\partial}t=\ensuremath{\nu}{\ensuremath{\nabla}}^{2}h+(\ensuremath{\lambda}/2)(\ensuremath{\nabla}{h)}^{2}+\ensuremath{\eta},$ where h is the surface height and $\ensuremath{\eta}$ represents nonconservative noise, and the MBE equation $\ensuremath{\partial}h/\ensuremath{\partial}t=\ensuremath{-}\ensuremath{\kappa}{\ensuremath{\nabla}}^{4}h\ensuremath{-}(\ensuremath{\Lambda}/2){\ensuremath{\nabla}}^{2}(\ensuremath{\nabla}{h)}^{2}+{\ensuremath{\eta}}_{c},$ where ${\ensuremath{\eta}}_{c}$ represents conservative noise. These equations represent different physical smoothing mechanisms, so to distinguish between them we have numerically solved both equations. A novel geometric implementation of the nonlinear terms avoids instabilities associated with stiffness of the equations. We find that the time and length scale dependence of the smoothing of initially rough substrates is consistent with the KPZ equation but not the MBE equation. As the growth temperature is increased the coefficient $\ensuremath{\nu}$ increases relative to $\ensuremath{\lambda},$ but the KPZ description remains valid over the entire measured temperature range of $550--600\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ Reducing the As overpressure increases the anisotropy of the surface morphology. We provide a physical interpretation of the KPZ equation in which the incorporation rate of mobile adatoms on the surface is governed by evaporation/condensation type dynamics. These results provide important insight into the MBE growth mechanism of GaAs.
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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 | 0.000 | 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) | 0.001 | 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 it