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Physique des Solides et Morphologie des Surfaces

100%
Rousseau J., Mathia T. G.
Acta Physica Polonica A
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1993
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vol. 83
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issue 5
535-550
EN
PHYSICS OF SOLIDS AND MORPHOLOGY OF SURFACES: The morphology of surfaces is now an important field of research because of its direct connection with the industrial activity like manufacturing and optimising of functional criteria through complicated interfacial phenomena. Presently, characterization of the surface morphology, via the profile metrology, is well modelled by a statistical description. The use of shape morphological parameters allows to identify features of the surface structures generated by the process techniques and the emergence of the different phases of the condensed matter. Starting from the solid state background knowledge, prediction of the surface morphology appears as a tedious way. However, progress in the science of the solids formation and industrial requirements promises the best future for the physicists in such a new technological activity. Philosophy and basic formalism of that approach is presented here.
2
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Topological Correlations in a Layer Adsorbed on a Crystal Surface

71%
Wojtczak L., Zasada I., Bosse Le J. C., Lopez J., Rousseau J., Institute of Physics U. o. Ł., Laboratoire de Physique des Interfaces B.
Acta Physicae Superficierum
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1990
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vol. 1
EN
The incoherent scattering of electrons by a layer adsorbed at a single crystal surface is determined by the topological correlations of elements forming the adsorbed layer. The model for the description of atoms or molecules adsorbed on the surface is formulated in terms of occupation operators which are expressed in terms of pseudospin operators with a given spin value. The correlations can be determined by the fluctuation dissipation theorem in connection with the susceptibility or given directly by means of the Green functions properly chosen. An example of the topological or chemical disorder of two components is considered in detail. The calculations of the topological correlations allow us to find the incoherent scattering amplitude as a function of the surface coverage which can be experimentally detected.
3
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Monte Carlo Simulation of Partially Ordered Atomic Layers Adsorbed on the Monocristalline Surfaces

71%
Wiatrowski G., Le Bossé J., Lopez J., Rousseau J., Zasada I.
Acta Physica Polonica A
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1993
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vol. 83
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issue 5
587-596
EN
The calculations of the correlations functions and structure factors are performed by means of the Monte Carlo simulation. The results for O/Ni(001) system are presented and compared with those obtained using self-consistent molecular field approximation and cumulant expansion method. The simulation for more complex system CO/Pt(111) is also performed. The calculations of the topological correlations allow us to find the coverage dependence of the incoherent scattering amplitude which can be experimentally detected.
4
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Caracterisation de l'ordre par diffraction d'electrons

71%
Le Bosse J., Lopez J., Hansali G., Wiatrowski G., Rousseau J.
Acta Physica Polonica A
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1993
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vol. 83
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issue 5
567-580
EN
CHARACTERIZATION OF THE ORDER BY ELECTRON DIFFRACTION: In the case of a solid with a local atomic order, we can consider only a statistical description of atomic positions. For a homogeneous phase, this description is given by the two-site occupancy correlation function, the three-site occupancy correlation function, ... etc. The local atomic order is investigated by experiments in which the solid is bombarded with a well-collimated monoenergetic beam of particles (here electrons). Starting from a model describing the force law between an electron and an atomic scatterer and from a model of the solid describing the distribution of atoms in space, a computation of elastically backscattered intensities can be carried out. The latter depends on geometrical parameters which are determined in such a way that one gets the best agreement between the results of calculation and the measurements. This work aims to provide the way of proceeding to calculate the diffuse intensity. The main difficulty in this task appears when we undertake to treat the problem of multiple scattering. We provide here a detailed description of a calculation corresponding to the case of the backscattering of electrons at a single crystal surface covered with a partially disordered atomic layer. Assuming that the coverage in adatoms is small and these adatoms are weak scatterers, we can neglect the multiple scattering events inside the layer. This simplifying assumption leads to an expression of the diffuse intensity in terms of: the Fourier transform on the 2D surface lattice of the pair correlation function; the renormalized transition matrices of the different kinds of adatoms.
5
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Two-Site Correlations in a Surface Layer Adsorbed on the Crystal

71%
Wojtczak L., Zasada I., Le Bossé J., Lopez J., Rousseau J.
Acta Physica Polonica A
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1991
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vol. 80
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issue 5
631-648
EN
The incohorent scattering of electrons by layer adsorbed at a single crystal surface is determined by the Fourier transform of correlation functions of elements forming this layer. The model of the description of atoms or molecules adsorbed on the surface is formulated by the occupation operators which are represented by the pseudospin operators. The calculations of the correlation functions are performed by means of methods which consider a given pair of elements embedded in the effective field of remaining elements of the system while the interaction between the elements of the pair are taken in its exact form. Two approaches are presented here, i.e. the cumulant average and constant coupling approximations, and the case of binary chemisorption is considered in detail. The problem of the correlation symmetry is also discussed.
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