Concepts in Surface Physics

Desjonquères, M.C.; Spanjaard, D.

doi:10.1007/978-3-642-61400-2

Cited by 262 publications

(179 citation statements)

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“…6). The resulting cohesive energy is found to be ß0.34 eV per interface atom which is higher than what is typically expected for weak physisorption interactions (Desjonquères & Spanjaard, 1996). This value is however consistent with other modelling works on 2D heterostacks (Zhong et al, 2016) and points towards the presence of a strong interaction at the interface between the two phases (Lefebvre et al, 1998), which leads to a distortion in the atomic structure of the β-SnS layer, leading to the formation of the new β' phase.…”

Section: Fig 6 Evolution Of the Interaction Energy Per Surface Atomsupporting

confidence: 82%

Structural characterization of SnS crystals formed by chemical vapour deposition

Mehta

Zhang

Dabral

et al. 2017

Journal of Microscopy

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Summary The crystal and defect structure of SnS crystals grown using chemical vapour deposition for application in electronic devices are investigated. The structural analysis shows the presence of two distinct crystal morphologies, that is thin flakes with lateral sizes up to 50 μm and nanometer scale thickness, and much thicker but smaller crystallites. Both show similar Raman response associated with SnS. The structural analysis with transmission electron microscopy shows that the flakes are single crystals of α‐SnS with [010] normal to the substrate. Parallel with the surface of the flakes, lamellae with varying thickness of a new SnS phase are observed. High‐resolution transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), first‐principles simulations (DFT) and nanobeam diffraction (NBD) techniques are employed to characterise this phase in detail. DFT results suggest that the phase is a strain stabilised β’ one grown epitaxially on the α‐SnS crystals. TEM analysis shows that the crystallites are also α‐SnS with generally the [010] direction orthogonal to the substrate. Contrary to the flakes the crystallites consist of two to four grains which are tilted up to 15° relative to the substrate. The various grain boundary structures and twin relations are discussed. Under high‐dose electron irradiation, the SnS structure is reduced and β‐Sn formed. It is shown that this damage only occurs for SnS in direct contact with SiO2.

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Section: Fig 6 Evolution Of the Interaction Energy Per Surface Atomsupporting

confidence: 82%

Structural characterization of SnS crystals formed by chemical vapour deposition

Mehta

Zhang

Dabral

et al. 2017

Journal of Microscopy

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“…In thermodynamic equilibrium, the ratio between facet radius r and the distance h of the facet from the center of the crystal is equal to the ratio of step free energy b to surface free energy g of the facet [3,14]. With increasing temperature, steps lower their free energy by gaining configurational entropy due to kink formation [15] and by an excess vibrational free energy [5,16]. Since free energies for singular surfaces change much more slowly with temperature than step free energies [17], a temperature increase corresponds to shrinking (and decrease to expansion) of the equilibrium facet diameter.…”

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confidence: 99%

Step Dynamics in 3D Crystal Shape Relaxation

et al. 2001

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Three-dimensional relaxation of small crystallites was imaged in real time using variable-temperature scanning tunneling microscopy. The micron-sized Pb crystallites, supported on Ru(0001), were equilibrated at 500-550 K, and the volume-preserving shape relaxation was induced by a rapid temperature decrease to 353-423 K. The (111) facet at the top of the crystallite grows by sequential peeling of single atomic layers, which shrink like circular islands. The rate of layer peeling slows dramatically as a new final state is reached. DOI: 10.1103/PhysRevLett.87.186102 PACS numbers: 68.65. -k, 68.35.Fx, 68.35.Md, 68.37.Ef With the relentless drive toward solid state structures of ever decreasing size scales, the issue of the stability of such structures, especially in response to external perturbations, becomes increasingly important. Real-time experimental observations of the complete decay of unstable structures, e.g., patterned Si substrates [1], nanofabricated Si mounds [2], and homoepitaxial islands [3][4][5][6] have clearly shown the discrete single-layer mode of decay. However, in complete contrast to these examples, we discuss for the first time the volume-preserving relaxation of a heteroepitaxial 3D crystallite from one well-defined state to another stable state, in response to a sudden change in chemical potential, here induced by an abrupt change in temperature. In relaxation, the ratio of forward and reverse flux is constantly decreasing, reaching a value of one in the final, equilibrium structure. This results in qualitatively different behavior than a decay process, where the forward flux is strongly dominating. Figure 1 illustrates schematically the evolution of a facetted crystal from a stable high temperature state towards a low temperature state, causing the facet to grow. The thermodynamic driving force [7 -12] for this process is well understood in terms of the increasing density of monatomic steps in the rounded regions of the crystallite near the facet [13] (a step is the boundary of a change in height by an atomic layer). In thermodynamic equilibrium, the ratio between facet radius r and the distance h of the facet from the center of the crystal is equal to the ratio of step free energy b to surface free energy g of the facet [3,14]. With increasing temperature, steps lower their free energy by gaining configurational entropy due to kink formation [15] and by an excess vibrational free energy [5,16]. Since free energies for singular surfaces change much more slowly with temperature than step free energies [17], a temperature increase corresponds to shrinking (and decrease to expansion) of the equilibrium facet diameter. Using linear kinetics, the rate of motion of a step will be proportional to the chemical potential change involved in removing an atom from the step's edge [18,19]. Using this approach, we define the chemical potential of the step bounding the top layer of a facet of radius r, as illustrated in Fig. 1, in terms of the curvature FIG. 1. Schematic crystal shape evolution upo...

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“…This common property of this class of potentials has a clear physical origin: the energy E i of an atom i should decrease more and more slowly when its coordination increases towards the bulk coordination [59,65]. This clearly implies that F ′′ (ρ) must be positive.…”

Section: N-body Semi-empirical Potentialsmentioning

confidence: 90%

“…The step vibrational free energy of a given vicinal surface is of the order of a few meV and decreases with temperature, reaching a linear regime for T larger than 100K when the entropy contribution becomes the leading term (see ref. [59]). More interestingly F vib step (T ) can be plotted for a given temperature, as a function of the terrace width as shown in Fig.…”

Section: Vibrational Free Energy Of Stepsmentioning

confidence: 99%

On x-ray channelling in microcapillaries and nanocapillaries

Bellucci

Dabagov

2003

J. Phys.: Condens. Matter

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Abstract. The energetics of transition and noble metal (Rh, Pd, Cu) vicinal surfaces, i.e., surface energy, step energy, kink energy and electronic interactions between steps, is studied at 0K from electronic structure calculations in the tight-binding approximation using a s, p and d valence orbital basis set. Then, the surface phonon spectra of copper are investigated in the harmonic approximation with the help of a semi-empirical inter-atomic potential. This allows to derive the contribution of phonons at finite temperatures to the step free energy and to the interactions between steps. The last part is devoted to the stability of vicinal surfaces relative to faceting with special attention to the domain of orientations (100)-(111). Semi-empirical potentials are shown to be not realistic enough to give a reliable answer to this problem. The results derived from electronic structure calculations predict a variety of behaviors and, in particular, a possible faceting into two other vicinal orientations. Finally, temperature effects are discussed. Comparisons are made with other theoretical works and available experiments.

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Concepts in Surface Physics

Cited by 262 publications

References 0 publications

Structural characterization of SnS crystals formed by chemical vapour deposition

Structural characterization of SnS crystals formed by chemical vapour deposition

Step Dynamics in 3D Crystal Shape Relaxation

On x-ray channelling in microcapillaries and nanocapillaries

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