L. Barbier

Roughening of vicinal surfaces and step—step interactions: application to Cu(1,1,11) by means of statistical analysis of STM images

Abstract The surface morphology of vicinal surfaces is governed by thermal kink creation energies and step—step interactions. Kink creation energies Ek were measured first by means of the statistical analysis of STM images and within one-dimensional or free-step approximations. In the present paper a two-dimensional model is investigated where in addition to the simple no-crossing condition for steps, elastic like step—step interactions with A L 2 dependence are considered. In the framework of this model, novel analytical expressions are obtained for the correlation function, G(0,y) parallel to steps and G(m,0) perpendicular to steps, in terms of microscopic energetic parameters Ek and A. The good agreement observed between our approach, exact results (available for A = 0 and one peculiar A value) and Monte Carlo (MC) simulations confirms its validity. By statistical analysis of STM images of Cu(1,1,11), we have measured both G(0,y) and G(m,0) together with the terrace width distribution (TWD). All these measurements evidence a step—step interaction stronger than the mere no-crossing condition. This set of data can be consistently fitted within our approach with one couple of microscopic parameters Ek = 1430 K and A = 70 K.

Experimental study of Penning and Hornbeck-Molnar ionisation of rubidium atoms excited in a high s or d level (5d⩽nl⩽11s)

Rb+ and Rb2+ formation in a laser-excited Rb vapour is extensively studied for s and d levels ranging from 5d to 11s levels. Collisional ionisation with a ground-state atom leads to Rb2+ formation by Hornbeck-Molnar reaction with rate coefficients lying in the 10-10 cm3 s-1 range. This reaction is analysed theoretically. Penning ionisation occurs in collision with a resonant-state atom, Rb(5p), with a high efficiency (rate coefficient above 10-8 cm3 s-1). Associative ionisation between the 7s level and the 5p level is also observed (rate coefficient about 10-10 cm3 s-1). This reaction appears negligible for the neighbouring 5d level.

Vicinal surfaces: free energy, terrace width distribution and step correlation functions

Abstract The equilibrium morphology of vicinal surfaces is governed by thermal kink creation energies and step–step interactions. Such parameters can be determined within microscopic step models by means of the statistical analysis of surface images such as those provided by STM. A versatile multi-step transfer matrix (strip) method is introduced to calculate thermodynamical averages. The correlation function of step displacements along step edges, the terrace width distribution and the free energy are thus obtained. The applicability of various one-step and many-step formulae is discussed, and properties of the capillary wave approximation are given. Within this approximation, the width of the terrace width distribution at the roughening temperature is found to be universal.

Penning and associative ionisation of highly excited rubidium atoms

Highly excited and resonant states are created in a rubidium vapour in order to study the collisional ionisation with the ground state and between these different excited species. A mass analysis allows one to separate the atomic and molecular channels. Penning ionisation with a resonant state is shown to have a great efficiency (rate coefficient greater than 10-8 cm3 s-1) for all the highly excited levels under study (6d, 8s, 7d). The associative ionisation rate coefficient between these excited atoms and a ground-state atom lies in the expected range 10-10 to 5*10-10 cm3 s-1 and seems to be independent of l j and values.

Statistical analysis of STM images and measurement of the step-step interaction on Cu vicinal surfaces

Abstract The time and time-space correlation functions of the step positions as well as the terrace-width distribution are measured on STM pictures of the Cu(1111) surface. It is shown how the space-time correlation function can be interpreted. The kink energy together with the hopping frequency for atom diffusion along step edges are deduced. From measurements of the terrace-width distribution we estimate the strength of the repulsion between steps. The quantitative analysis is made in the framework of a two-dimensional model with an A / L 2 step-step repulsion.

Cleaved surface of i − Al Pd Mn quasicrystals: Influence of the local temperature elevation at the crack tip on the fracture surface roughness

Roughness of

Influence of an adsorbate on the morphology of a vicinal surface: sulfur on Cu(1 1 11), a STM and helium diffraction study

i\text{\ensuremath{-}}\mathrm{Al}\mathrm{Pd}\mathrm{Mn}

Step pairing and bulk chemical order at alloy vicinal surfaces

fracture surfaces are presently analyzed. From the atomic scale up to

Crackling versus continuumlike dynamics in brittle failure.

2\char21{}3\phantom{\rule{0.3em}{0ex}}\mathrm{nm}

Scaling and universality in the kinetic smoothening of interfaces: Application to the analysis of the relaxation of rough vicinal steps of an oxide surface

, they are shown to exhibit scaling properties hiding the cluster