Nanowire (NW) crystal growth via the vapour-liquid-solid mechanism is a complex dynamic process involving interactions between many atoms of various thermodynamic states. With increasing speed over the last few decades many works have reported on various aspects of the growth mechanisms, both experimentally and theoretically. We will here propose a general continuum formalism for growth kinetics based on thermodynamic parameters and transition state kinetics. We use the formalism together with key elements of recent research to present a more overall treatment of III-V NW growth, which can serve as a basis to model and understand the dynamical mechanisms in terms of the basic control parameters, temperature and pressures/beam fluxes. Self-catalysed GaAs NW growth on Si substrates by molecular beam epitaxy is used as a model system.
Nanowire (NW) crystal growth via the vapour-liquid-solid mechanism is a complex dynamic process involving interactions between many atoms of various thermodynamic states. With increasing speed over the last few decades many works have reported on various aspects of the growth mechanisms, both experimentally and theoretically. We will here propose a general continuum formalism for growth kinetics based on thermodynamic parameters and transition state kinetics. We use the formalism together with key elements of recent research to present a more overall treatment of III-V NW growth, which can serve as a basis to model and understand the dynamical mechanisms in terms of the basic control parameters, temperature and pressures/beam fluxes. Self-catalysed GaAs NW growth on Si substrates by molecular beam epitaxy is used as a model system.
“…The attractive interactions between the A and B species, that are responsible for the synergetic effect (see Refs. [26][27][28], lead to a B partial coverage larger than 1 − c 2 (value of θ B when θ = 1) for intermediate potentials. At larger chemical potentials θ B decreases with the increase of μ A .…”
Section: Determination Of the Total Density Of Clusters And Coveragementioning
We present a comprehensive study of the equilibrium properties of two codeposited species for an alloy that forms an ideal solution, on a one-dimensional chain. By use of a cluster description we provide exact formulae of the coverages, the total density of clusters, the cluster size distribution, and the chemical composition of each cluster. These analytical results, that are proved to be in agreement with Monte Carlo simulations, strongly differ from the ones derived in the mean-field framework. Indeed, we show by depicting the codeposit at the macroscopic, mesoscopic, and atomic scales, that its features are to be related to the chemical heterogeneities at the edges of the clusters.
“…The mean‐field approximation can be applied to mixed adsorption layers of two species on a foreign substrate . Isotherms of both partners may be obtained when one of them (e.g., B) is kept at constant super‐saturation, Δμ 2D,B and the super‐saturation, Δμ 2D,A of the other (A) is varied.…”
Section: Displacement and Mixing Of Condensed Layers On A Foreign Submentioning
confidence: 99%
“…Isotherms of isomorphic species A and B versus Δμ 2D,A at constant super‐saturation Δμ 2D,B = 0.5 of the species B; first nearest neighbor approximation; hexagonal symmetry; is the isotherm of A on a free substrate; super‐saturations are in units of k B T . Reprinted from B. Mutaftschiev, in “The Atomistic Nature of Crystal Growth” 368pp.…”
Section: Displacement and Mixing Of Condensed Layers On A Foreign Submentioning
confidence: 99%
“…Figure shows isotherms of co‐adsorption following the Mean‐field‐approximation . The component B is at a constant under‐saturation Δμ 2D,B = −0.5.…”
Section: Displacement and Mixing Of Condensed Layers On A Foreign Submentioning
It is shown all along this chapter that in the case of crystal growth governed by surface kinetics, foreign adsorption on the interface may intervene to a large extent in the overall process. Moreover, the mechanism of subsequent overgrowth can be gathered from the shape of the adsorption isotherms. The growth mode in a pure system depends of the thermal roughness which can be treated as self‐adsorption of molecules and molecular vacancies. Finally, foreign adsorption on a rough surface, just as strain due to structural misfit, may result in the formation of surface alloys.
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