Site occupancy pair correlation functions and structure factors of partially ordered overlayers

Wiatrowski, G.; Bosse, J.; López, Jesús María Rincón; Zasada, I.

doi:10.1016/0039-6028(92)90503-x

Cited by 13 publications

(7 citation statements)

References 20 publications

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“…A correlation function for Cl sites is required to describe the partially ordered adsorbate layer. 3,36 For this aim, 20 sites that surround a centered ad- sorption site ͑labeled 0͒ on a Si͑100͒ lattice with a dimerized structure are first numbered using an integer s, as shown in the inset of Fig. 4͑a͒.…”

Section: B Correlation Of CL Occupancy Between Two Adsorption Sitesmentioning

confidence: 99%

Determination of dissociative fragment-adsorbate interaction energy during chemisorption of the diatomic molecule HCl on Si(100)

et al. 2010

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This study investigates the surface chemistry and the ordering characteristics of coadsorbed hydrogen and chlorine atoms, generated by the exposure of the Si͑100͒ surface to gas-phase HCl molecules at various substrate temperatures, by scanning tunneling microscopy ͑STM͒, core-level photoemission spectroscopy, and Monte Carlo simulation. Experimental results show that saturation exposure to HCl causes all surface dangling bonds to be terminated by the two fragments H and Cl atoms and that the number of H-terminated sites exceeds that of Cl-terminated ones by more than 10%. This finding suggests that, in addition to the dominant dissociative chemisorption, atomically selective chemisorption or atom abstraction occurs. STM images reveal that some Cl-terminated sites form patches with a local 2 ϫ 2 structure at 110 K and that the degree of ordering is reduced as the substrate temperature increases. Results of Monte Carlo simulations demonstrate the importance of including dissociative fragment-adsorbate interactions during the random adsorption of diatomic molecules. Comparing the correlations between Cl-terminated sites identified from STM images and those predicted by simulation reveals two effective interaction energies of 8.5Ϯ 2.0 and 3.5Ϯ 2.0 meV between a dissociative fragment Cl atom and a nearest neighboring Cl adsorbates in the same dimer row and in the adjacent row, respectively.

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Section: B Correlation Of CL Occupancy Between Two Adsorption Sitesmentioning

confidence: 99%

Determination of dissociative fragment-adsorbate interaction energy during chemisorption of the diatomic molecule HCl on Si(100)

et al. 2010

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“…to the local order of the site occupancy in its top or bridge position with respect to the basic lattice. The diffuse LEED investigations can verify the reported theories and test the topological correlations [7]. From the theoretical point of view we consider the experimental conditions for two different cases determined by the grand canonical or canonical ensemble for the statistical operator.…”

Section: Introductionmentioning

confidence: 76%

A Simple Model for the Surface Phenomena

Wojtczak

1993

Acta Phys. Pol. A

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The simplicity of the present model consists in the construction of the Hamiltonian based on the models of quasi-harmonic oscillators coupled to quasi-free electrons with the effective parameters which are estimated by means of the pseudoharmonic approach and coherent potential approximation, respectively. The geometry of a sample is determined by the topological disorder at the surface reflecting the surface roughness. The model is discussed in connection with the friction related to the melting and pre-melting phenomena. The backscattering of electrons seems to be a testing tool useful not only for decorated surfaces but also for quasi-liquid 1ayers.PACS numbers: 68.15.+t, 68.45.-v In troductionThe surface phenomena constitute one of the largest areas of interdisciplinary sciences such as physics, chemistry and mechanics, i.e. sciences representing different approaches to the description of the considered surface effects. The physical picture seems to be the leading one in the considerations which give in consequence the complete model constructed on the basis of complementary pictures obtained from the different approaches. Although the great number of papers dealing with the above problems resulted in the emergence of several specialized journals, many problems, however, remain still unsolved. The field is open for investigations and for new aspects of the surface properties to be discovered.The present contribution is devoted to the model describing the friction related to the melting and pre-melting phenomena as well as applicable to the diffuse low energy electron diffraction (diffuse LEED) which seems to be particularly interesting as the backscattering by a quasi-liquid layer growing on the surface. The coincidence of these two aspects is not only due to the common aspect of the research but, first of all, to the same background of these phenomena, namely, the behaviour of topological correlations at the surface.The role of tw osite occupancy was discussed in several papers in connection with a general treatment of the correlation problem [1,2] as well as in the "Permanent address:

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“…Si la couche est partiellement ordonnée, il faut alors calculer les fonctions de corrélation de la couche adsorbée. Ce type de calcul, qui peut être effectue par différentes méthodes (méthodes des cummulants, du champ moyen, de Monte Carlo), nécessite la connaissance des interactions entre adsorbats [17].…”

Section: Fonction D'onde De Diffusionunclassified

Caracterisation de l'ordre par diffraction d'electrons

et al. 1993

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CHARACTERIZATION OF THE ORDER BY ELECTRON DIFFRAC-TION:In the case of a solid with a local atomic ordér, 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 wełl-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 calcułation 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 ełectrons 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 mułtiple 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.

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Site occupancy pair correlation functions and structure factors of partially ordered overlayers

Cited by 13 publications

References 20 publications

Determination of dissociative fragment-adsorbate interaction energy during chemisorption of the diatomic molecule HCl on Si(100)

Determination of dissociative fragment-adsorbate interaction energy during chemisorption of the diatomic molecule HCl on Si(100)

A Simple Model for the Surface Phenomena

Caracterisation de l'ordre par diffraction d'electrons

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