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

Comment on “Phase contribution of image potential on empty quantum well states in Pb islands on the Cu(111) surface”

1 página, 1 figura.-- PACS numbers: 68.37.Ef, 68.65.Fg, 73.21.FgThis work was partially funded by MCINN(FIS2010- 19609-C02-01) and G.V-UPV/EHU(IT-366-07).Peer reviewe

Effect of Raw Material Quality on Quality and Yield of Dried Fish Products

Dried fish products were prepared from siganid (Siganus sutor) and anchovy (Stolephorus sp.) using solar drying and from flounder (Paralichthys patagonicus) using atmospheric freeze-drying. Very good correlations were obtained between raw material quality and dried fish quality, in a dimensionless scale. A lower slope was obtained for flounder (R2= 0.971) when comparing with siganid and anchovy (R2= 0.892), indicating that raw material quality influences the quality of final products, being higher in fatty than in lean fish. This information is useful to reject unsuitable raw material before processing. A correlation between quality of raw material and process yield is presented

Environmental supply chain management in the seafood industry: past, present and future approaches

This review discusses and analyses previous results in identification, development and implementation of cleaner production strategies within the seafood industry. The relevant peer reviewed articles were identified from a structured keyword search and analysed by both supply chain stage (capture and aquaculture, transport, processing, storage and retail), and examination of the cleaner production strategies implemented. Results found entities along the seafood supply chain generally worked separately to improve cleaner production processes and outputs to grow their own businesses. Whilst this approach can be beneficial, it ignores the broader cleaner production potential benefits gained when applied across multiple supply chain entities. The most effective cleaner production strategies for improved environmental performance in each sector of the supply chain were identified with the potential to reduce unnecessary handling, energy usage, storage costs and waste production. To ensure the greatest reduction in environmental impact, a whole of supply chain management system that incorporates life cycle assessment modelling is recommended

Electronic structure, dynamics and spectroscopy of metallic nanosized systems: Pb thin overlayers and Na nanocontacts

Doctoral thesis submitted by Asier Zugarramurdi Camino for the degree of Doctor of Philosophy in Physics.This endeavor would not be possible without the financial support from Donostia International Physics Center (DIPC), during the first year, and that of Consejo Superior de Investigaciones Cientificas (CSIC) through the Centro de Fisica de Materiales (CFM) during the following four years, as well as the continuous support from various projects, and the support from the University of the Basque Country, at the Elektronika eta Elektrizitea Department.Peer reviewe

Theoretical study of constant current scanning tunneling spectroscopy in Pb overlayers

We present a theoretical study of the constant current scanning tunneling spectroscopy of quantum well states localized in Pb(111) overlayers on Cu(111) surfaces. The distance-voltage characteristic of the tunneling junction is obtained with a mixed approach. The wave packet propagation technique is applied to describe electron tunneling from the tip into the sample, and the density functional calculations provide the necessary inputs for the one-dimensional model potential representation of the system. The excited-state population decay mechanisms via inelastic electron-electron and electron-phonon interactions are taken into account with a bias-dependent absorbing potential introduced in the metal. Our results are in good agreement with recent experimental studies over the energy range where the free-electron description of the Pb overlayer used here applies. We find that at high bias the quantum well states experience a Stark energy shift and partially acquire a character of field emission resonances. The present model study also sheds light at the experimentally observed departure of the energies of the quantum well states from the particle-in-a-box prediction for the bias above 4 eV. The measured trend can be consistently explained as due to the departure of the realistic Pb band structure in the Γ-L direction from free-electron parabola when the electron momentum approaches the Γ point. © 2011 American Physical Society.Peer Reviewe

Lifetimes of quantum well states and resonances in Pb overlayers on Cu(111)

11 páginas, 8 figuras, 1 tabla.-- PACS number(s): 73.21.Fg, 73.50.Gr, 73.20.At, 78.47.-p.-- Trabajo presentado al "DIPC10 : Passion for Knowledge" celebrado en Donostia (España) del 27 de septiembre al 1 de octubre de 2010.We present results of calculations of the lifetimes of excited electrons (holes) in quantum well states and quantum well resonances in Pb overlayers supported on Cu(111). Many-body decay via inelastic energy relaxation and one-electron decay via energy-conserving one-electron transfer into the substrate are considered. One-electron energies and wave functions have been computed for different coverages of the Pb overlayer (from 1 to 18 monolayers) by using a one-dimensional pseudopotential for the entire overlayer-substrate system in the framework of density functional theory within the local density approximation. The elastic (energy-conserving resonant electron transfer) contribution to the total lifetime broadening of quantum well resonances has been calculated within the wave packet propagation method. The inelastic electron-electron (many-body) contribution to the lifetime broadening of both occupied and unoccupied quantum well states has been evaluated using GW approximation. The decay mechanisms of both quantum well states and quantum well resonances in thick overlayers are discussed.This work has been funded partially by the University of the Basque Country UPV/EHU (Grant No. GIC07IT36607), the Departamento de Educación del Gobierno Vasco, and the Spanish Ministerio de Ciencía y Technología (MCyT) (Grant No. FIS2007-66711-C02-01).Peer reviewe

Quantum-well states with image state character for Pb overlayers on Cu(111)

We study theoretically the quantum well states (QWSs) localized in Pb overlayers on Cu(111) surface. Particular emphasis is given to the states with energies close to the vacuum level. Inclusion of the long-range image potential tail into the model potential description of the system allows us to show the effect of hybridization between QWSs and image potential states (ISs). The particle-in-a-box energy sequence characteristic for QWSs evolves into the Rydberg series converging towards the vacuum level. The electron density of the corresponding states is partially moved from inside the metal overlayer into the vacuum. The decay rates due to the inelastic electron-electron scattering decrease with increasing energy, opposite to >conventional> QWSs and similar to the ISs. Many-body and wave packet propagation calculations of the inelastic decay rates are supplemented by simple analysis based on the phase accumulation model and wave-function penetration approximation. This allows an analytical description of the dependence of the QWS/ISs hybridization on different parameters and, in particular, on the overlayer thickness. © 2012 American Physical Society.This work was partially funded by MCINN(FIS2010-19609-C02-01) and G.V-UPV/EHU(IT- 366-07).Peer Reviewe