Impurity effects in crystal growth from solutions: Steady states, transients and step bunch motion

Ranganathan, Madhav; Weeks, John D.

doi:10.1016/j.jcrysgro.2013.11.018

Cited by 13 publications

(17 citation statements)

References 29 publications

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“…Once fcc-Al nucleates at/or near interface, it will consume the excess Al, which in turn will promote diffusion of excess Al to the interface. The for mation Al clusters at the interface will also locally block the propagation of ε-phase [35][36][37][38][39][40][41]. Growth of ε-phase can only proceed from regions without excess Al until the next nucleation and growth event of Al nanocrystal happens.…”

Section: Discussionmentioning

confidence: 99%

An abnormal meta-stable nanoscale eutectic reaction revealed by in-situ observations

et al. 2019

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Phase selection and growth of materials far from equilibrium provides fertile ground for novel phases and morphologies since a multitude of different pathways may be energetically accessible. In this study, a complex metastable devitrification of Al60Sm11 (ε-phase) from its amorphous precursor is discovered using a combination of in-situ high-energy X-ray diffraction (HEXRD), providing insight into the average bulk behavior, and in-situ aberration corrected scanning transmission electron microscopy, revealing the atomic scale mechanisms of growth and their dynamics. We have found that non-equilibrium chemical partitioning disrupts the nominal planer growth by formation of nanoscale Al enriched regions inhomogeneously segregated at the ε/glass interface, to locally balance the compositionally dependent driving force and the associated diffusional burden imposed on its grain growth. These Al-rich regions form fcc-Al-rich nanocrystallites epitaxially with the ε-phase, modifying ε/glass interface mobility and creating a crenulated growth front. This new mechanism offers a pathway for fabricating alloy structures with nanoprecipitate dispersions through a meta-stable phase transition.

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Section: Discussionmentioning

confidence: 99%

An abnormal meta-stable nanoscale eutectic reaction revealed by in-situ observations

et al. 2019

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“…In reality, steps do not display the smooth curvatures as assumed in their simplified model, but rather are discrete, atomistic objects subject to fluctuations. This was already realized by Frank [12] and explored further by van Enckevort and van den Berg [9] and more recently by Ranganathan and Weeks who developed a coarse grained terrace-step-kink model to study impurity induced step bunching [10,11].…”

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confidence: 90%

“…Such a dead zone occurs for a specific class of impurities, namely, those that are firmly adsorbed onto the surface with (near-) infinite residence times (Dynamic residues with finite residence times can in extreme cases lead to kinetic arrest, but only at very high concentrations.) The moments leading up to this growth cessation event have been the subject of intense study [4][5][6][7][8][9][10][11] and are thought to be well understood. The first theoretical description was developed as early as 1958 by Cabrera and Vermilyea (CV) [3], whose core views on the subject still persist today.…”

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confidence: 99%

Mesoscopic Impurities Expose a Nucleation-Limited Regime of Crystal Growth

et al. 2015

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Nanoscale self-assembly is naturally subject to impediments at the nanoscale. The recently developed ability to follow processes at the molecular level forces us to resolve older, coarse-grained concepts in terms of their molecular mechanisms. In this Letter, we highlight one such example. We present evidence based on experimental and simulation data that one of the cornerstones of crystal growth theory, the Cabrera-Vermilyea model of step advancement in the presence of impurities, is based on incomplete physics. We demonstrate that the piercing of an impurity fence by elementary steps is not solely determined by the Gibbs-Thomson effect, as assumed by Cabrera-Vermilyea. Our data show that for conditions leading up to growth cessation, step retardation is dominated by the formation of critically sized fluctuations. The growth recovery of steps is counter to what is typically assumed, not instantaneous. Our observations on mesoscopic impurities for lysozyme expose a nucleation-dominated regime of growth that has not been hitherto considered, where the system alternates between zero and near-pure velocity. The time spent by the system in arrest is the nucleation induction time required for the step to amass a supercritical fluctuation that pierces the impurity fence.

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“…From Monte Carlo simulations, Weeks and co-workers [5,8,9] were able to study twodimensional step motion and showed that mesh-like step bunch patterns are formed by step bunching. In their model, the effect of impurities is taken into account as a reduction in the probability of step advancing.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Surface Diffusion and Evaporation of Impurities on Step Bunching Induced by Impurities

Sato

2019

J. Phys. Soc. Jpn.

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We consider a vicinal face, where atoms and impurities impinge and evaporate to a vapor phase, to study how the surface diffusion and evaporation of impurities affect step bunching induced by impurities. When the lifetime of impurities on the vicinal face τ imp is long and the surface diffusion of impurities is neglected, the step bunches induced by impurities are tight. When τ imp decreases, the size of the step bunches, which means the number of steps in the bunches, decreases but the separation of single steps from bunches does not occur. When we take into account fast surface diffusion of impurities, the separation and collision between single steps and step bunches occur repeatedly.

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Impurity effects in crystal growth from solutions: Steady states, transients and step bunch motion

Cited by 13 publications

References 29 publications

An abnormal meta-stable nanoscale eutectic reaction revealed by in-situ observations

An abnormal meta-stable nanoscale eutectic reaction revealed by in-situ observations

Mesoscopic Impurities Expose a Nucleation-Limited Regime of Crystal Growth

Effect of the Surface Diffusion and Evaporation of Impurities on Step Bunching Induced by Impurities

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