Nucleation with a critical cluster size of zero: Submonolayer Fe inclusions in Cu(100)

Chambliss, D. D.; Johnson, Kevin E.

doi:10.1103/physrevb.50.5012

Cited by 150 publications

(85 citation statements)

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“…However, in the metal͑111͒ systems, the island size distribution at low T does not have a monotonically decreasing form. 28 Finally, it should be noted that monotonically decreasing island size distributions have been observed in models for ͑i͒ nucleation mediated by irreversible exchange of single adatoms with the substrate ͑a process sometimes described as having a critical size i =0͒; 29,30 ͑ii͒ nucleation under conditions of strongly incomplete condensation ͑i.e., deposition when desorption is active͒, 31,32 and which is described by Avrami-type adsorption kinetics; 32 and ͑iii͒ postdeposition nucleation for critical size i =1. 33 There has, however, been no previous comprehensive analysis of these models, or comparison with more traditional models, to determine whether there is some generic feature producing monotonically decreasing size distributions ͑or, more generally, producing a higher population of smaller islands͒.…”

Section: Figmentioning

confidence: 99%

“…In this regime, the island size distribution has a monotonically decreasing form with many small islands. 29,30 Analysis of the rate equations for these models reveals an initial "transient" regime for t ഛ t * where the adatom density, n Ϸ Ft, increases from its initial zero value due to deposition, followed by a steady-state regime where the gain in adatom density due to deposition is roughly balanced by the loss due to either nucleation or aggregation. Table II summarizes the behavior of n and N isl for the above models in the transient ͑tr͒ and steady-state ͑ss͒ regimes, as well as the behavior of K nuc and K agg at crossover ‫͒ء͑‬ when t Ϸ t * .…”

Section: Appendix: Correlation Between Nucleation Behavior and Islandmentioning

confidence: 99%

“…32 ͑iv͒ Heterogeneous nucleation by exchange of deposited adatoms with substrate atoms ͑so-called i =0͒. 29,30 Here, a single exchanged atom forms a stable nucleus for island growth. The nucleation rate satisfies K nuc = h ex n = h 0 n, where h ex = h 0 is the exchange rate.…”

Section: Appendix: Correlation Between Nucleation Behavior and Islandmentioning

confidence: 99%

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Monotonically decreasing size distributions for one-dimensional Ga rows on Si(100)

et al. 2005

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Deposition at room temperature of Ga on Si(100) produces single-atom-wide metal rows orthogonal to the Si-dimer rows. Detailed analysis using scanning tunneling microscopy reveals a monotonically decreasing size (i.e., length) distribution for these rows. This is unexpected for homogeneous nucleation without desorption, conditions which are operative in this system. Kinetic Monte Carlo simulation of an appropriate atomistic model indicates that this behavior is primarily a consequence of the feature that the capture of diffusing atoms is greatly inhibited in the Ga∕Si(100) system. The modeling also determines activation barriers for anisotropic terrace diffusion, and recovers the experimental distribution of metal rows. In addition, we analyze a variety of other generic deposition models and determine that the propensity for a large population of small islands in general reflects an enhanced nucleation rate relative to the aggregation rate. Disciplines Chemistry CommentsThis article is from Physical Review B 72 (2005) Deposition at room temperature of Ga on Si͑100͒ produces single-atom-wide metal rows orthogonal to the Si-dimer rows. Detailed analysis using scanning tunneling microscopy reveals a monotonically decreasing size ͑i.e., length͒ distribution for these rows. This is unexpected for homogeneous nucleation without desorption, conditions which are operative in this system. Kinetic Monte Carlo simulation of an appropriate atomistic model indicates that this behavior is primarily a consequence of the feature that the capture of diffusing atoms is greatly inhibited in the Ga/ Si͑100͒ system. The modeling also determines activation barriers for anisotropic terrace diffusion, and recovers the experimental distribution of metal rows. In addition, we analyze a variety of other generic deposition models and determine that the propensity for a large population of small islands in general reflects an enhanced nucleation rate relative to the aggregation rate.

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Section: Figmentioning

confidence: 99%

Section: Appendix: Correlation Between Nucleation Behavior and Islandmentioning

confidence: 99%

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Monotonically decreasing size distributions for one-dimensional Ga rows on Si(100)

et al. 2005

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“…(1), this temperature dependence reflects the mobilities of both the deposited and the displaced substrate atoms. Although these studies capture different aspects of heteroepitaxial growth with intermixing, none provides a comprehensive picture integrating all aspects of this complex process over a wide range of growth conditions, e.g., Miranda and Gallego neglect adatom pinning at substitutional sites [13], while other groups do not consider the effect of substrate adatoms ejected onto the surface [4,10]. Further, because diffusion barriers of two-component systems are difficult to obtain in experiments, these approaches rely on rather rough estimates of the diffusion parameters.…”

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confidence: 99%

“…However, to date, only a few studies have attempted this [4,10 -13]. Chambliss and Johnson proposed that substitutional Fe atoms constitute stable nuclei for the growth of Fe on Cu(001) [4]. By accounting for monomer stability [i 0 in Eq.…”

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Non-Arrhenius Behavior of the Island Density in Metal Heteroepitaxy: Co on Cu(001)

et al. 2003

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We present a combined theoretical and experimental study of island nucleation and growth in the deposition of Co on Cu(001) -a prototype for understanding heteroepitaxial growth involving intermixing. Experimentally, ion scattering is employed. Using density-functional theory, we obtain energy barriers for the various elementary processes and incorporate these into a kinetic Monte Carlo program to simulate the heteroepitaxial growth. Both the simulations and the experiments show a unique N-shape dependence of the island density on temperature that stems from the interplay and competition of the different processes involved. DOI: 10.1103/PhysRevLett.90.076101 PACS numbers: 68.55.-a, 61.43.Hv, 68.35.Fx, 82.40.Bj Heteroepitaxial metallic structures, such as Co=Cu multilayers represent a new material that has high potential for the development of magnetoelectronic devices. In order to control the interfacial properties it is important to achieve a quantitative understanding of the morphology that develops during growth and its dependence on the growth conditions. A standard model for the initial stages of growth is given by nucleation theory [1], where the island density n x is expressed in terms of the deposition rate F, the adatom hopping rate D D 0 exp ÿE d =k B T , and the binding energy E b of the critical nucleus of size i,The linear dependence of lnn x on 1=T is widely used to deduce quantities such as activation barriers from islanddensity measurements, when adatoms form islands on top of the substrate [2]. However, in heteroepitaxial systems, deposited atoms may incorporate into the substrate displacing substrate atoms into the growing layer [3][4][5][6][7][8][9]. The effect of site exchange is not considered in Eq. (1). A prototypical system where intermixing takes place is Co on Cu(001). A broad [5,6] and bimodal [6] island-size distribution was observed in submonolayer growth studies using scanning-tunnelling microscopy (STM) -in contrast to a Poisson-like distribution anticipated in standard nucleation theory [1]. In addition Nouvertné et al. reported that the island density at 415 K is slightly higher than at 295 K [6], which is at variance with the predictions of Eq. (1). The island composition was found to depend on the growth conditions and to vary from mostly Co to mostly Cu. Moreover, a correlation has been observed between island composition and island size [5,6].From a fundamental standpoint, it is important to extend nucleation theories to account for intermixing. However, to date, only a few studies have attempted this [4,10 -13]. Chambliss and Johnson proposed that substitutional Fe atoms constitute stable nuclei for the growth of Fe on Cu(001) [4]. By accounting for monomer stability [i 0 in Eq. (1)] at substitutional Fe pinning sites, they found that the island density is independent of F=D. Meyer and Behm assumed irreversible pinning of adatoms at substitutional nucleation centers and found that the island density goes through a minimum with increasing temperature -consistent with that...

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Epitaxial Growth of Thin Films

Brune

2014

Surface and Interface Science

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This chapter gives an introduction to the epitaxial growth of thin films on solid substrates. The term epitaxy refers to the growth of a crystalline layer on (epi) the surface of a crystalline substrate, where the crystallographic orientation of the substrate surface imposes a crystalline order (taxis) onto the thin film. This implies that film elements can be grown, up to a certain thickness, in crystal structures differing from their bulk. If film and substrate have the same crystal lattices, but different lattice constants, the film will be under strain, that is, it will have a slightly different lattice constant than in its own bulk. Both effects, together with the electronic hybridization at the interface, lead to novel properties.One distinguishes homo-and heteroexpitaxy, where the former refers to the growth on one element on a crystal surface of its own and the latter refers to the more general case, where film and substrate materials are different. Note that the first distinguishes itself from crystal growth, as we will see in more detail later.We start this chapter by giving examples from technology, illustrating where thin epitaxial films are used and outlining potential applications that become reality once we are able to grow the respective thin film sequences. We then contrast thin film and crystal growth, respectively, with kinetics and thermodynamics of growth. We introduce the deposition techniques used in epitaxial thin film growth and then discuss the classical thermodynamic approach, which led to the definition of the growth modes. These modes refer to the morphology taken on by a system grown close to thermodynamic equilibrium. Often films are grown far away from equilibrium and their morphology is determined by kinetics, that is, it is the result of the microscopic path taken by the system during growth. This path is determined by the hierarchy of rates of the single atom, cluster or molecular precursor displacements as compared to the deposition rate. Owing to the importance of kinetics, we focus in the rest of the chapter on the kinetic description of growth. In order to simplify the topic, we start with coverages below one atomic layer that is referred to as a monolayer. The first submonolayer part will be on nucleation, followed by a discussion of island shapes that, very much like snowflakes, tell us about the elementary processes that took place during their formation. We then discuss island coarsening, either by evaporation of atoms from their edges, referred to as the Ostwald ripening, or by the diffusion and subsequent coalescence of entire islands, referred to as the

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Nucleation with a critical cluster size of zero: Submonolayer Fe inclusions in Cu(100)

Cited by 150 publications

References 10 publications

Monotonically decreasing size distributions for one-dimensional Ga rows on Si(100)

Monotonically decreasing size distributions for one-dimensional Ga rows on Si(100)

Non-Arrhenius Behavior of the Island Density in Metal Heteroepitaxy: Co on Cu(001)

Epitaxial Growth of Thin Films

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