Coarsening Mechanisms in a Metal Film: From Cluster Diffusion to Vacancy Ripening

Wen, Jianming; Evans, James W.; Bartelt, M. C.; Burnett, Joseph W.; Thiel, Patricia A.

doi:10.1103/physrevlett.76.652

Cited by 186 publications

(164 citation statements)

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“…One of the widely used model systems for such investigations is the decay of two-dimensional ͑2D͒ metal islands on metal substrates. [2][3][4][5][6][7][8][9][10][11] The thermal decay of such islands was found to reduce the island area with time t proportional to (t 0 Ϫt) 2␤ , where t 0 is the time at which the island is fully dissolved. 12 The value of the exponent ␤ is a signature of the dominant microscopic mechanism governing the rate of decay.…”

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confidence: 99%

Decay characteristics of two-dimensional islands on strongly anisotropic surfaces

Yao

Ebert

et al. 2002

Phys. Rev. B

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We investigate analytically the decay characteristics of two-dimensional islands on strongly anisotropic surfaces. We show that a generic scaling law can always be established in describing the dynamical evolution of such islands, given by Lϰ(t 0 Ϫt) ␤ , where L is the island width, and t 0 is the lifetime of the islands. The value of the scaling exponent ␤ in the fast-decay direction is always 1/2 in the low-temperature regime where the decay is quasi-one-directional, irrespective of the specific dominant decaying mechanism involved. At higher temperatures where the decay proceeds effectively in both directions, ␤ is again a good measure of the dominant microscopic decaying mechanism involved, just like the isotropic case. We discuss these results in connection with recent experiments. There has been an overwhelming wealth of research activity on fabricating various nanostructures that may possess unique physical properties. Nevertheless, the stability of nanostructures, once formed, often poses a limiting factor for their practical applications. 1,2 Therefore, understanding the physical mechanisms involved in the stability and the dynamical evolution of nanostructures after their formation is both scientifically intriguing and technologically significant, and has been receiving increasing attention in recent years. One of the widely used model systems for such investigations is the decay of two-dimensional ͑2D͒ metal islands on metal substrates. [2][3][4][5][6][7][8][9][10][11] The thermal decay of such islands was found to reduce the island area with time t proportional to (t 0 Ϫt) 2␤ , where t 0 is the time at which the island is fully dissolved. 12 The value of the exponent ␤ is a signature of the dominant microscopic mechanism governing the rate of decay. In the case where attachment and detachment of atoms from the island edges dominate the rate of decay, ␤ equals 1/2 whereas for the diffusion-limited case, i.e., where diffusion of adatoms on the terrace limits the decay rate, ␤ is 1/3. These results very well describe the decay of islands on isotropic surfaces, which in fact has attracted most of the attention so far. However, the decay of islands on anisotropic substrates, i.e., surfaces with different energy barriers along the nonequivalent crystallographic directions, is expected to be more complex and may provide additional insight into the physical nature of island dissolution. Indeed the larger complexity was substantiated by the observation of a transition from a 2D decay mode at high temperatures to a quasi-onedimensional ͑1D͒ decay mode at low temperatures for the anisotropic system of Ag islands on Ag͑110͒. 11 Several more recent studies have also studied the evolution of islands and voids on other metal ͑110͒ surfaces, 13-15 but to date, the theoretical basis for description of island decay on anisotropic substrates is still lacking.In this paper we develop a comprehensive analytical description of the decay of two dimensional islands on highly anisotropic surfaces. We find that even for highl...

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confidence: 99%

Decay characteristics of two-dimensional islands on strongly anisotropic surfaces

Yao

Ebert

et al. 2002

Phys. Rev. B

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“…The basic features of the coarsening kinetics due to diffusion and subsequent coalescence of (large) clusters are described by the Smoluchowski rate equation theory of coagulation, which has already been applied to cluster diffusion and coalescence. 6,21 The key result is that if the cluster diffusion coefficient scales like D ≈ D 0 S -R , then the mean island density decreases like N av ≈ N 0 (1 + t/τ) -, where…”

Section: Actual (Act) Values Of D(δt) Are Related By D(δt)mentioning

confidence: 99%

“…This behavior is reproduced by rate equation modeling if one first modifies the standard Smoluchowski equations to account for the finite extent of the islands. 6 Specifically, the rate of coalescence is increased since the cluster center of mass needs only to travel a distance ∼L edge , rather than ∼L av , before coalescence. The solid curves in Figure 5a are the results of such rate equation analyses 6 using the average value of D ) 2 × 10 -17 cm 2 /s for the cluster diffusion coefficient.…”

Section: Postdeposition Coarsening Of the Island Distributionmentioning

confidence: 99%

“…Our basic observation is surprising: coarsening for coverages below about 0.4 monolayer is dominated by diffusion and subsequent coalescence of (large) 2D clusters, rather than by "conventional" Ostwald ripening. 6 Only in the extreme regime of very low coverage (small islands and large separations) does Ostwald ripening account for a significant fraction of the reduction of island density. 6 Given this observation, we first discuss below the mechanisms and characteristics of cluster diffusion and then return to describe in more detail the coarsening kinetics.…”

Section: Postdeposition Coarsening Of the Island Distributionmentioning

confidence: 99%

“…5 However, in some homoepitaxial systems, it has been observed instead that coarsening is dominated by the diffusion and subsequent coalescence of (large) islands. 6,7 This unexpected role of large cluster diffusion in coarsening has prompted much recent experimental and theoretical interest in this issue. [8][9][10][11][12] Here we provide a comprehensive analysis of submonolayer nucleation and growth of 2D islands during deposition in Ag/Ag(100) homoepitaxy at 295 K, using a combination of scanning tunneling microscopy (STM) and high-resolution low-energy electron diffraction (HRLEED) techniques.…”

Section: Introductionmentioning

confidence: 99%

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Formation and Equilibration of Submonolayer Island Distributions in Ag/Ag(100) Homoepitaxy

et al. 1998

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We present an analysis both of the nucleation and growth of two-dimensional (2D) islands or clusters during deposition of Ag on Ag(100) at 295 K and of the subsequent postdeposition equilibration of such island distributions at coverages below about 0.25 monolayer. Island formation during deposition is shown to be effectively irreversible, and the island density and size and separation distributions are characterized using a combination of scanning tunneling microscopy (STM) and high-resolution low-energy electron diffraction. Postdeposition coarsening of the adlayer is monitored via STM and is shown to be dominated typically by diffusion and subsequent coalescence of large 2D clusters rather than by Ostwald ripening. Tailored studies of such coarsening elucidate both the kinetics and the underlying cluster diffusion process. KeywordsInstitute of Physical Research and Technology, coalescence, deposition, diffusion in solids, epitaxial growth, low energy electron diffraction, monolayers, nucleation, reaction kinetics, scanning tunneling microscopy, homoepitaxy We present an analysis both of the nucleation and growth of two-dimensional (2D) islands or clusters during deposition of Ag on Ag(100) at 295 K and of the subsequent postdeposition equilibration of such island distributions at coverages below about 0.25 monolayer. Island formation during deposition is shown to be effectively irreversible, and the island density and size and separation distributions are characterized using a combination of scanning tunneling microscopy (STM) and high-resolution low-energy electron diffraction. Postdeposition coarsening of the adlayer is monitored via STM and is shown to be dominated typically by diffusion and subsequent coalescence of large 2D clusters rather than by Ostwald ripening. Tailored studies of such coarsening elucidate both the kinetics and the underlying cluster diffusion process.

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Dynamics and Stability of Surface Structures

Giesen

Beltramo

2011

Catalysis in Electrochemistry

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Coarsening Mechanisms in a Metal Film: From Cluster Diffusion to Vacancy Ripening

Cited by 186 publications

References 14 publications

Decay characteristics of two-dimensional islands on strongly anisotropic surfaces

Decay characteristics of two-dimensional islands on strongly anisotropic surfaces

Formation and Equilibration of Submonolayer Island Distributions in Ag/Ag(100) Homoepitaxy

Dynamics and Stability of Surface Structures

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