Dynamics of irreversible island growth during submonolayer epitaxy

Bales, G. S.; Chrzan, D. C.

doi:10.1103/physrevb.50.6057

Cited by 425 publications

(369 citation statements)

References 36 publications

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“…Computer simulations : Monte-Carlo simulations of the growth of thin films by a continuous flux have been independently implemented by several groups with small variations [11][12][13]. To simulate the growth in the presence of a chopped flux, we introduce the four following physical processes :…”

Section: Measuring the Evaporation Timementioning

confidence: 99%

The effect of a modulated flux on the growth of thin films

Jensen

Niemeyer

1997

Surface Science

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Thin films are usually obtained by depositing atoms with a continuous flux.We show that using a chopped flux changes the growth and the morphology of the film. A simple scaling analysis predicts how the island densities change as a function of the frequency of the chopped flux in simple cases where aggregation is irreversible. These predictions are confirmed by computer simulations.We show that the model can be used to obtain information on the diffusion or the evaporation of the adatoms. The model is also useful to understand the growth of thin films prepared by pulsed sources.Typeset using REVT E X 1 One of the main interests of usual deposition techniques such as Molecular Beam Epitaxy [1] is that the structure of the deposited films is to a large extent determined by kinetic factors, as opposed to thermodynamic equilibrium. This allows to "play games" [2] with the different growth parameters (incident flux of particles, diffusion coefficient of an adatom . . . ) in order to obtain different film morphologies. A simple example is given by the quantity of islands grown on a substrate at low enough temperatures : it is known that the number of islands at saturation is given by (F/D) 1/3 [3][4][5] where F is the incident flux and D the diffusion coefficient. Then, by increasing the flux or decreasing the diffusion constant (by lowering the substrate temperature), one can adjust the saturation number of islands grown on the substrate. In this sense, each kinetic factor is a "handle" on the system, allowing to control the morphology of the films. We introduce in this Letter a new kinetic handle, which should enable a larger control over film growth : the chopping of the incident flux. We note that this flux modulation is intrinsic to other deposition techniques such as cluster laser vaporization (the laser is pulsed [6]). It is therefore important to understand how growth proceeds in the presence of a modulated flux if one is to be able to interpret experiments performed in these conditions. For example, one may wonder whether the usual growth theories [3][4][5] can be used by replacing the continuous flux by the average value of the chopped flux over a cycle. In the following, we will show that this is not the case, and that the growth of the film is profoundly changed by the modulation of the incident flux for the case of growth with irreversible aggregation (critical island size 1, see [3][4][5][7][8][9]. Conversely, we show what kind of information can be derived from experiments carried under these conditions.The basic idea of our method is that if instead of using a continuous flux we use a chopped flux to grow a film, the number of islands formed on a substrate will depend on the chopping frequency f and on d, the fraction of the period the flux is "on" (see Fig. 1).This dependence is due to the fact that the free particle concentration on the surface does not reach its steady state concentration instantaneously, but only after a time which we will call τ m . Then, if the timescale of the chopping (...

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Section: Measuring the Evaporation Timementioning

confidence: 99%

The effect of a modulated flux on the growth of thin films

Jensen

Niemeyer

1997

Surface Science

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“…Furthermore, dendrite formation is not limited to bulk alloy systems. Under certain kinetic constraints, two-dimensional island growth on metal surfaces during deposition can result in dendritic structures [8]. Also, dendrites have been observed during the formation of cubically ordered silica micelle structures [9] and during the growth of bacterial colonies [10].…”

Section: Introductionmentioning

confidence: 99%

Atomistic and continuum modeling of dendritic solidification

Hoyt

2003

Materials Science and Engineering: R: Reports

397

220

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“…is the adatom capture number as derived in [5,45]. Without the factor σ 1 , (4) describes the rate of collisions for a system of uniformly distributed particles that do not stick together; the factor σ 1 provides the leading order correction for particles that stick together.…”

Section: Nucleation and Submonolayer Growthmentioning

confidence: 99%

Growth, Structure and Pattern Formation for Thin Films

Caflisch¹

2008

J Sci Comput

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An epitaxial thin film consists of layers of atoms whose lattice properties are determined by those of the underlying substrate. This paper reviews mathematical modeling, analysis and simulation of growth, structure and pattern formation for epitaxial systems, using an island dynamics/level set method for growth and a lattice statics model for strain. Epitaxial growth involves physics on both atomistic and continuum length scales. For example, diffusion of adatoms can be coarse-grained, but nucleation of new islands and breakup for existing islands are best described atomistically. In heteroepitaxial growth, mismatch between the lattice spacing of the substrate and the film will introduce a strain into the film, which can significantly influence the material structure, for example leading to formation of quantum dots. Technological applications of epitaxial structures, such as quantum dot arrays, require a degree of geometric uniformity that has been difficult to achieve. Modeling and simulation may contribute insights that will help to overcome this problem. We present simulations that combine growth and strain showing the structure of nanocrystals and the formation of patterns in epitaxial systems.

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Dynamics of irreversible island growth during submonolayer epitaxy

Cited by 425 publications

References 36 publications

The effect of a modulated flux on the growth of thin films

The effect of a modulated flux on the growth of thin films

Atomistic and continuum modeling of dendritic solidification

Growth, Structure and Pattern Formation for Thin Films

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