Two-dimensional overgrowth in the low submonolayer range: the case of

Beauvais, C. de; Rouxel, Didier; Michailov, Michail; Mutaftschiev, B.

doi:10.1016/0039-6028(94)00709-8

Cited by 25 publications

(12 citation statements)

References 18 publications

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“…The significant reduction of the local forces as a result of broken symmetry strongly affects the atomic vibrations of surface atoms. Extensive experimental studies reveal a larger mean-square displacement of surface atoms compared to the bulk [9,10]. Therefore, the heat capacity of clusters with a comparable number of surface and bulk atoms should deviate from that of the large systems.…”

Section: Introductionmentioning

confidence: 99%

Specific heat of nanocrystals

Avramov

Michailov²

2008

J. Phys.: Condens. Matter

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The present study extends the Einstein model for heat capacity of solids to nanoclusters. In the case of small phases the contribution of surface energy to overall thermodynamic properties of the system is essential. On that physical background, the heat capacity depends on the size of cluster through its interface energy. Employing the same relation between Einstein temperature and the cluster melting point as that for the infinitely large phase, we derive a simple expression for the heat capacity, C V (n), dependence on the number of atoms in the cluster, n. We explain the experimentally observed increase of C V (n) compared to C V (∞) of an infinitely large homogeneous phase, with lowering of the Einstein temperature due to the contribution of the cluster interface energy. The heat capacity in the model presented scales at high T with the classical Dulong and Petit 3R limit and tends to zero for T → 0 as required by the third law of thermodynamics. The model reported could be applied to various systems with nanoparticles, where the knowledge of specific heat is important; for example formation of nanocomposite materials, the initial stages of formation of fogs, smog and clouds, etc.

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Section: Introductionmentioning

confidence: 99%

Specific heat of nanocrystals

Avramov

Michailov²

2008

J. Phys.: Condens. Matter

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“…Increasing the concentration of adsorbed atoms, at coverage 0.5 ML, a reversible effect of demixing has been observed both experimentally and by Monte Carlo simulations. 4,7,12 The surface alloying process on the most densely packed Cu͑111͒ surface is rather different. At 0.1 ML coverage and T Ͻ 400 K, the time evolution snapshots data show absence of Pb atoms inside the Cu͑111͒ substrate matrix.…”

Section: Resultsmentioning

confidence: 99%

“…As a model for studying surface alloying we choose Pb adsorption on Cu single-crystal surfaces because of the large number of experimental data collected in the last two decades. [3][4][5][6][7][8] Although Pb and Cu are volume immiscible, it has been shown that at low coverage, , the formation of 2D surface alloy is an energetically favorable process. [4][5][6][7] As a result, stable mixed equilibrium phases are formed with embedded Pb atoms inside the Cu top surface layer.…”

Section: Introductionmentioning

confidence: 99%

“…[3][4][5][6][7][8] Although Pb and Cu are volume immiscible, it has been shown that at low coverage, , the formation of 2D surface alloy is an energetically favorable process. [4][5][6][7] As a result, stable mixed equilibrium phases are formed with embedded Pb atoms inside the Cu top surface layer. Whereas surface alloying on the less densely packed Cu͑110͒ and Cu͑100͒ surfaces is a well-studied phenomenon, the atomistic mechanism of formation of surface alloy on the most compact Cu͑111͒ crystal orientation is not clear in detail.…”

Section: Introductionmentioning

confidence: 99%

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Computational study of stripe alloy formation on stepped surfaces

Michailov

2009

Phys. Rev. B

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The present study deals with two-dimensional ͑2D͒ surface alloy formation on stepped crystal surfaces. In specific temperature range, the high diffusion barrier for direct atomic exchange between adsorbed layer and substrate, completely block 2D intermixing on smooth, step-free surface domains. Hence, in a given energy gap the diffusion takes place exclusively via step terrace mechanism. In such systems, the dynamic competition between energy gain by mixing and substrate strain energy results in diffusion scenario where adsorbed atoms form alloyed stripes in the vicinity of terrace edges. The stripe width, L S , is step-anisotropy dependent and correlates with the relaxation ability of the terraces in specific direction. Atomic terraces having a critical width L T Ͻ 3L S are completely transparent for the adsorbed atoms. This phenomenon, considered as incomplete 2D alloying, opens up a way various surface pattern to be configured at different atomic levels on the crystal surface. Refining important details of diffusion behavior of adsorbed atoms and accounting for the energy barriers at specific atomic sites ͑smooth domains, terraces, and steps͒ located on the crystal surface, the presented computational model reveals a classification order of surface alloying: blocked, incomplete, and complete. Being in agreement with experimental findings, the observed stripe alloy formation could be applied to nanoscale surface design in volume-immiscible systems.

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“…The experimental observations of this phenomenon, occurring despite the large difference (37%) in 'atomic diameters' of Pb and Cu, is an additional motivation for the present study. Both STM and TEAS experiments of Pb/Cu(100), Pb/Cu(110) and Pb/Cu(111) demonstrate that Pb atoms preferentially replace Cu atoms in the substrate lattice matrix, overcoming the strain energy of the topmost layer [1,5,11]. Recently it was shown that the large variety of ordered lead alloys on the (110) face of copper can be explained by the delicate competition between the strain energy and the energy gain due to mixing in the layer [14].…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo simulations of the interface layer in Pb/Cu(110); a tight-binding-model calculation

Michailov

Georgiev

1999

J. Phys.: Condens. Matter

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Monte Carlo simulations with energies computed via the tight-binding model are applied in studying the equilibrium properties of the interface layer in the system Pb/Cu(110). In a submonolayer range below 0.5 ML (ML monolayer), the model based on the coverage-dependent interactions reveals a lattice-gas random adsorption, an equilibrium adatom-substrate intermixing and formation of a centred c(2 × 2) phase. The process of intermixing is found to be coverage and temperature dependent. At high adatom concentration, 0.75-0.80 ML, as a result of very subtle competition between the strain energy and the energy gain due to mixing, the system forms a succession of commensurate unidimensional p(n × 1) structures. The results are in line with those recently obtained from scanning tunnelling microscopy and thermal energy atom scattering observations.

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Two-dimensional overgrowth in the low submonolayer range: the case of

Cited by 25 publications

References 18 publications

Specific heat of nanocrystals

Specific heat of nanocrystals

Computational study of stripe alloy formation on stepped surfaces

Monte Carlo simulations of the interface layer in Pb/Cu(110); a tight-binding-model calculation

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