Download or read book Propri t s Optiques Des Couches Minces de Dichalcog nures de M taux de Transition written by Maciej Koperski and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The research reported in the thesis entitled 'Optical properties of thin layers of transition metal dichalcogenides' focuses on physical phenomena which emerge in the limit of two-dimensional (2D) miniaturisation when the thickness of fabricated films reaches an atomic scale. The importance of such man-made structures has been revealed by the dynamic research on graphene: a single atomic plane of carbon atoms arranged in honeycomb lattice. Graphene is intrinsically gapless and therefore mainly explored with respect to its electric properties. The investigation of semiconducting materials which can also display the hexagonal crustal structure and which can be thinned down to individual layers, bridges the concepts characteristic of graphene-like systems (K-valley physics) with more conventional properties of semiconductors. This has been indeed demonstrated in a number of recent studies of ultra-thin films of semiconducting transition metal dichalcogenides (sc-TMD). Particularly appealing, from the point of view of optical studies, is a transformation of the bandgap alignment of sc-TMD films, from the indirect bandgap bulk crystals to the direct bandgap system in single layers. The presented thesis work provides a comprehensive optical characterisation of thin structures of sc-TMD crystals. The manuscript is divided into five parts: three main chapters with a preceding introduction and the appendix reporting the supplementary studies of another layered material: hexagonal boron nitride.Introduction. The fundamental properties of the investigated crystals are presented, especially those which are important from the point of view of optical studies. The discussion includes information on the crystal structure, Brillouin zone and electronic band structure. Also, the general description of the samples' preparation process and experimental set-up is provided.Chapter 1. Basic optical characterisation of excitonic resonances in mono- and multi-layers of sc-TMDs. The optical response, as seen in the reflectance and luminescence spectra of thin sc-TMDs is analysed (mostly for MoSe2 and WSe2 materials). The impact of the number of layers and temperature on the optical resonances is studied and interpreted in details. The complementary time-resolved study is also presented.Chapter 2. Zeeman spectroscopy of excitonic resonances in magnetic fields. The evolution of the optical resonances in an external magnetic field, applied perpendicularly to the layers of sc-TMD materials is investigated. Based on these results, a phenomenological model is developed aiming to describe the linear with magnetic field contributions to the energy of individual electronic states in fundamental sub-bands of sc-TMD monolayers. Furthermore, the effects of optical pumping are investigated in WSe2 monolayers, which can be tuned by tiny magnetic fields.Chapter 3. Single photon sources in thin sc-TMD flakes. The discovery of localised narrow lines emitting centres has been in thin sc-TMD flakes is presented. An investigation of their fundamental properties is discussed. This includes the measurements of temperature and magnetic field evolution of the photoluminescence lines, and the analysis of the polarisation properties and the excitation spectra as well as photon correlation measurements.Appendix A. Single photon emitters in boron nitride crystals. Hexagonal boron nitride also belongs to the family of layered materials, but it exhibits much larger band gap than semiconducting transition metal dichalcogenides. A narrow lines emitting centres has been observed in boron nitride structures, which reveal multiple similarities to defect centres in wide gap materials. They are characterised in a similar manner as the emitting centres in WSe2.
Download or read book Sur les propri t s optiques des couches minces des m taux alcalino terreux written by Robert Blanc and published by . This book was released on 19?? with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Contribution l tude des propri t s optiques des m taux de transition et du b ryllium dans l ultra violet lointain written by André Seignac (auteur d'une thèse de sciences.) and published by . This book was released on 1978 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Contribution l tude des propri t s optiques anormales de certains m taux pris en couche mince written by Jacques Richard (metallurg.) and published by . This book was released on 1964 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Contribution l tude des propri t s optiques anormales de certains m taux pris en couche mince written by Jacques Richard (auteur d'une thèse en sciences physiques en 1964).) and published by . This book was released on 1964 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Propri t s optiques d agr gats mixtes de m taux de transition en matrice d alumine written by Mélanie Gaudry and published by . This book was released on 2002 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt: La réponse optique des petites particules de métaux nobles (Au, Ag, Cu) se manifeste essentiellement par une bande de résonance plasmon de surface dont la position et la largeur dépendent notamment de la taille des agrégats et du milieu environnant. Ce travail présente l'étude des propriétés optiques d'agrégats mixtes AuM (M=Ag, Ni, Co et Pt) de 1,5 à 6 nm de diamètre, en matrice d'alumine. La technique de préparation des films minces de nanoparticules en matrice d'alumine ainsi que les différentes techniques de caractérisation et d'étude de leurs propriétés optiques sont présentées d'abord. Puis les modèles théoriques qui permettent d'interprèter ces propriétés sont introduits : un modèle semiquantique, mettent en évidence l'influence des électrons de coeur, de la matrice et de sa porosité, mais qui n'est pas adapté à tous les systèmes; un modèle classique dans les autres cas. L'influence de la taille et de la composition des agrégats mixtes or-argent est étudiée ensuite. Les spectres d'absorption montrent une résonance plasmon de surface intermédiaire par rapport à l'argent et l'or purs, et le blue-shift odservé quand la taille diminue est d'autant plus important que la proportion d'or est grande. Ces résultats expérimentaux sont comparés avec ceux d'un calcul semi-quantique, en utilisant deux modèles pour la fonction dialectique du mélange AuAg. Il semble que ces agrégats forment plutôt des alliages. Enfin, les systèmes NiAg et CoAg forment des "core-shell" : un coeur de nickel ou de cobalt, entouré d'argent et leurs spectres d'absorption présentent une bande plasmon de surface conformément aux prévisions théoriques classiques. A l'inverse, les agrégats (PtxAg1-x)n présentent expérimentalement une résonnance plasmon de surface très fortement atténuée, contrairement aux prévisions classiques si l'agrégat est sous forme "core-shell" ou a une structure pour laquelle la fonction diélectique dépend simplement de celles de se constituants.
Download or read book Magnetism and Superconductivity written by Laurent-Patrick Levy and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: This up-to-date work presents a modern vision of magnetism and superconductivity covering both microscopic and phenomenological aspects. The basic information is illustrated with the help of current research topics such as the quantum Hall effect or mesoscopic aspects of superconductivity.
Download or read book Physical Properties of Amorphous Materials written by David Adler and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Institute for Amorphous Studies was founded in 1982 as the international center for the investigation of amorphous mate rials. It has since played an important role in promoting the und er standing of disordered matter in general. An Institute lecture series on "Fundamentals of Amorphous Materials and Devices" was held during 1982-83 with distinguished speakers from universities and industry. These events were free and open to the public ,and were attended by many representatives of the scientific community. The lectures themselves were highly successful inasmuch as they provided not only formal instruction but also an opportunity for vigorous and stimulating debate. That last element could not be captured within the pages of a book I but the lectures concentrated on the latest advances in the field I which is why their essential contents are he re reproduced in collective form. Together they constitute an interdisciplinary status report of the field. The speakers brought many different viewpoints and a variety of back ground experiences io bear on the problems involved I but though language and conventions vary I the essential unity of the concerns is very clear I as indeed are the ultimate benefits of the many-sided approach.
Download or read book The Electron Glass written by M. Pollak and published by Cambridge University Press. This book was released on 2013 with total page 307 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presenting an up-to-date report on electronic glasses for researchers in condensed matter physics.
