Fast atom diffraction inside a molecular beam epitaxy chamber, a rich combination

Two aspects of the contribution of grazing incidence fast atom diffraction (GIFAD) to molecular beam epitaxy (MBE) are reviewed here: the ability of GIFAD to provide \emph{in-situ} a precise description of the atomic-scale surface topology, and its ability to follow larger-scale changes in surface roughness during layer-by-layer growth. Recent experimental and theoretical results obtained for the He atom beam incident along the highly corrugated $[ 1\bar{1}0 ]$ direction of the $\beta_{2}$(2$\times$4) reconstructed GaAs(001) surface are summarized and complemented by the measurements and calculations for the beam incidence along the weakly corrugated [010] direction where a periodicity twice smaller as expected is observed. The combination of the experiment, quantum scattering matrix calculations, and semiclassical analysis allows in this case to reveal structural characteristics of the surface. For the in situ measurements of GIFAD during molecular beam epitaxy of GaAs on GaAs surface we analyse the change in elastic and inelastic contributions in the scattered beam, and the variation of the diffraction pattern in polar angle scattering. This analysis outlines the robustness, the simplicity and the richness of the GIFAD as a technique to monitor the layer-by-layer epitaxial growth

Ab initio potential for the He-Ag(110) interaction investigated using grazing-incidence fast-atom diffraction

Experimental diffraction patterns produced by grazing scattering of fast helium atoms from a Ag(110) surface are used as a sensitive tool to test an ab initio potential model derived from accurate density-functional theory (DFT) calculations. The scattering process is described by means of the surface eikonal approximation, which is a distorted-wave method that includes the quantum interference between contributions coming from different projectile paths, taking into account the complete corrugation of the three-dimensional projectile-surface potential. A fairly good agreement between the theoretical and experimental momentum distributions is found for incidence along different low-indexed crystallographic directions. This agreement is indicative of the quality of the DFT potential. The effective corrugation of the interaction potential across the incidence channel is also investigated.Fil: Rios Rubiano, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio(i); Argentina. Universidad de Buenos Aires; ArgentinaFil: Bocan, Gisela Anahí. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); ArgentinaFil: Gravielle, Maria Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio(i); Argentina. Universidad de Buenos Aires; ArgentinaFil: Bundaleski, N.. Universidade Nova de Lisboa. Faculdade de Ciencias e Tecnologia. Department of Physics; PortugalFil: Khemliche, H.. Centre National de la Recherche Scientifique; Francia. Universite Paris Sud; FranciaFil: Roncin, P.. Centre National de la Recherche Scientifique; Francia. Universite Paris Sud; Franci

Auger rates on NaCl(001), effect of the final state and modeling via an effective length

International audienceNeutralization of keV He+, Ne+ and F+ ions colliding on NaCl(001) at grazing incidence is studied by energy loss in coincidence with emitted electrons. Three closely related Auger-like mechanisms are identified. In all processes, two electrons are removed from the valence band, one is captured on the ground state of the neutral projectile whereas the remaining electron is found either in the electron continuum, in the conduction band or in a surface excited state. To help comparing the three different processes, a procedure is proposed that allows a first order correction of so-called trajectory effect's on the observed neutralization fraction without a priori knowledge of the detailed trajectory