1,720,995 research outputs found
Deuterium scattering from Rh(110) surface
No full textThermal energy deuterium beam scattering (TEDS) from Rh(110) surface is reported and compared to helium atom scattering (HAS). Unlike for He, we find quite strong D-2 off-specular diffraction. The D-2 diffraction intensities are fairly isotropic along the [001] and [1 (1) over bar 0], reflecting the presence of a finite dissociation barrier in the potential energy surface (PES) rather than the anisotropic corrugation of the relevant Rh(110) surface electron density. Inelastic D-2 scattering with strong J=0-->2 kinetic-to-rotational energy conversion is also presented and discussed
Disorder-order evolution of InSb(110) studied by He scattering
No full textThe evolution of surface defects created by low energy ion bombardment on InSb(110) is studied by He beam scattering experiments. At surface temperatures above 500 K the ion erosion is found to proceed layer-by-layer without changing the stoichiometric composition of the surface. This indicates that the nucleation of surface islands driven by vacancy diffusion is faster than the ion erosion. After different doses of Ar+ ion bombardment, the surface is left in a non-equilibrium state whose time evolution is monitored by measuring the profiles of the He diffraction peaks. It is seen that the coalescence of islands proceeds with anisotropic island size distributions
Surface burgers vectors and surface defects
No full textAlthough extended surface defects are often described as dislocations, they are less commonly associated with Burgers vectors. The concept of linear surface dislocations and their associated surface Burgers vectors is defined and discussed in an introductory way and the main properties are summarised. The definition of the Burgers vector differs from that used in the bulk, as a closed path integral is not used. The Burgers vector is a quantity which is conserved, modulo a surface unit vector, and which adds vectorially; and a surface dislocation must form either a closed loop on a surface, or else begin and terminate at a bulk dislocation. The utility of this approach is illustrated by considering a number of applications in real space, in particular imaging with topographic or diffraction contrast, where the concept allows a general means of classifying defects. In diffraction, the surface Burgers vector provides a convenient way of quantifying the effect of defects on peak profiles
Disordering of the Ge(001) surface studied by He atom scattering
No full textThe Ge(001) surface is known to undergo phase transitions from c(4 x 2) to (2 x 1) at low temperature and from (2 x 1) to (I x 1) at high temperature. In the former case the phase transition is shown to occur at 240 K and to fall into the 2D Ising universality class. The high temperature phase transition takes place above 900 K and is characterized by (2 x 1) domain wall proliferation, thus indicating an order-disorder character. We have also observed an increase in the density of steps, but these are shown to be only partially involved in the disordering of the (2 x 1) phase
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Step height oscillations during layer-by-layer growth of Pb on Ge(001)
No full textHeteroepitaxial growth of Pb on the Ge(001) surface has been studied by He atom scattering. For low substrate temperatures, Pb is found to grow layer by layer with (111) orientation. A detailed analysis of the specular peak profile as a function of the He wave vector reveals that the step height of the growing monatomic terraces oscillates with the him thickness. This variation, initially as large as +/-15% around the value of the Pb(Ill) bulk interlayer spacing, gradually dampens out after the deposition of a dozen monolayers. This is direct evidence of quantum size effects affecting the interlayer distance of a growing metal film
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