Nothing Moves a Surface: Vacancy Mediated Surface Diffusion

Gastel, Raoul van; Somfai, Ellák; Albada, S.B. van; Saarloos, Wim van; Frenken, J.W.M.

doi:10.1103/physrevlett.86.1562

Cited by 140 publications

(129 citation statements)

References 12 publications

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“…We have used first-principles densityfunctional theory to calculate E f and E m for vacancies and adatoms on the pure Cu surface. Our results, consistent with other previous reports 3,4, [16][17][18] , show that island ripening on the pure Cu surface is mediated by surface vacancies. In order to understand the slowing effect of Pd in the limit of dilute alloys ( < ∼ 0.20 ML Pd), we have explored the interaction of vacancies with isolated buried Pd atoms.…”

Section: Discussionsupporting

confidence: 83%

“…In this work, we use Cu-adatom island-ripening measurements to show that Cu(001) surface diffusion is slowed by the presence of buried Pd atoms near the surface. Previous studies 3,4, [16][17][18] found that Cu(001) surface diffusion is mediated by surface vacancies, and we propose that the alloy slows surface diffusion by increasing the energetic barrier to vacancy diffusion. Using first-principles density-functional theory calculations, we find that Cu surface vacancies are attracted to buried Pd atoms, which inhibits vacancy migration on alloyed terraces.…”

Section: Introductionmentioning

confidence: 99%

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Buried Pd slows self-diffusion on Cu(001)

et al. 2011

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Using low-energy electron microscopy, we determine that self-diffusion of the Cu(001) surface is slowed by the presence of a c(2 × 2)-Pd buried surface alloy. We probe surface diffusion using Cu-adatom island-ripening measurements. On alloyed surfaces, the island decay rate decreases monotonically as the Pd concentration is increased up to ∼ 0.5 ML, where the 2 × 2 buried alloy is Pd saturated. We propose that the Pd slows island ripening by inhibiting the diffusion of surface vacancies across terraces. For dilute alloys ( < ∼ 0.2 ML Pd), this conclusion is supported by densityfunctional theory calculations which show that surface vacancies migrate more slowly owing to an attraction to isolated buried Pd atoms. The results illustrate a fundamental mechanism by which even a dilute alloy thin-film coating may act to inhibit surface-diffusion-mediated processes, such as electromigration.

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Section: Discussionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Buried Pd slows self-diffusion on Cu(001)

et al. 2011

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“…The freezing of i=4 processes marks a violation of detailed balance (since such a vacancy, if it existed, could be filled by a roving adatom); however, given the negligible occurrence of such vacancies in our simulations, the violation should be insignificant. In some physical systems, motion of surface vacancies does evidently dominate mass transport [21]. Again, our goal in these calculations is not to account generally for experiments but to create a fully-controlled data set to see how well the dynamics can be described using our Fokker-Planck formalism.…”

Section: Modelmentioning

confidence: 99%

Relaxation of terrace-width distributions: Physical information from Fokker–Planck time

2008

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Recently some of us have constructed a Fokker-Planck formalism to describe the equilibration of the terrace-width distribution of a vicinal surface from an arbitrary initial configuration. However, the meaning of the associated relaxation time, related to the strength of the random noise in the underlying Langevin equation, was rather unclear. Here we present a set of careful kinetic Monte Carlo simulations that demonstrate convincingly that the time constant shows activated behavior with a barrier that has a physically plausible dependence on the energies of the governing microscopic model. Furthermore, the Fokker-Planck time at least semiquantitatively tracks the actual physical time.

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“…Vacancy attachment has an additional barrier compared with vacancy diffusion because it requires the concerted motion of two atoms. Vacancy motion has been confirmed for this system by tracing the displacement of substitutional In atoms on Cu(100) [246,247]. The experiments for Ag/Ag(111) have been repeated for adatom and vacancy islands placed within a big vacancy island (Figure 20.20c,d) [112].…”

Section: The Ostwald Ripeningmentioning

confidence: 99%

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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Nothing Moves a Surface: Vacancy Mediated Surface Diffusion

Cited by 140 publications

References 12 publications

Buried Pd slows self-diffusion on Cu(001)

Buried Pd slows self-diffusion on Cu(001)

Relaxation of terrace-width distributions: Physical information from Fokker–Planck time

Epitaxial Growth of Thin Films

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