Download or read book Etude en microscopie par effet tunnel des premiers stades de croissance de l interface pb si 111 temp rature ambiante written by Frank Palmino and published by . This book was released on 1992 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: CETTE ETUDE PORTE SUR L'ELABORATION ET LA CARACTERISATION SOUS ULTRA-VIDE DE L'INTERFACE PB/SI(111)-77 A TEMPERATURE AMBIANTE PAR MICROSCOPIE A EFFET TUNNEL. LA PREMIERE PARTIE FAIT LE POINT SUR LES CONNAISSANCES ACTUELLES EN MICROSCOPIE PAR EFFET TUNNEL, EN PARTICULIER SUR LES ASPECTS THEORIQUES DU COURANT TUNNEL ET L'INTERPRETATION DES IMAGES. LA DESCRIPTION DU MICROSCOPE EST ENSUITE ABORDEE. ELLE CONSTITUE AVEC LA PRESENTATION DE SON ENVIRONNEMENT ET DES DIFFERENTES AMELIORATIONS APPORTEES A L'ENSEMBLE EXPERIMENTAL, LE DEUXIEME CHAPITRE DE CE MEMOIRE. LA TROISIEME PARTIE EST CONSACREE A L'ETUDE EN MICROSCOPIE PAR EFFET TUNNEL, EN RESOLUTION MOYENNE ET ATOMIQUE, DES CONDITIONS DE PREPARATION DU SI(111) AFIN D'OBTENIR SYSTEMATIQUEMENT DES SUBSTRATS A TRES FAIBLE RUGOSITE ET RECONSTRUITS 77 SUR DE GRANDS DOMAINES. L'ETUDE DE L'INTERFACE PB/SI(111)-77 A TEMPERATURE AMBIANTE EST ABORDEE DANS LE DERNIER CHAPITRE. NOUS AVONS MIS EN EVIDENCE LES DIFFERENTES ETAPES DU MODE DE CROISSANCE TYPE STRANSKI-KRASTANOV (MONOCOUCHE+CRISTALLITES) DE CETTE INTERFACE, ENTRE 0 ET 2 MONOCOUCHES. A LA SOUS-MONOCOUCHE, NOUS AVONS MONTRE QUE LA PERIODICITE 77 DU SUBSTRAT INITIAL EST PRESERVEE. AU-DELA DE LA MONOCOUCHE, NOUS AVONS OBSERVE DES CRISTALLITES DE PB DE FAIBLES DIMENSIONS DONT LA CROISSANCE EST FORTEMENT INFLUENCEE PAR LA TOPOGRAPHIE DE LA SURFACE (NOMBRE ET HAUTEUR DES MARCHES). DE PLUS, CES CRISTALLITES EPITAXIEES PARALLELEMENT AVEC LE SUBSTRAT POSSEDENT UNE SYMETRIE D'ORDRE 3

Download or read book Microscopie par effet tunnel et application l tude de surfaces ordonn es de silicium 111 written by Franck Thibaudau and published by . This book was released on 1988 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt: LA MICROSCOPIE PAR EFFET TUNNEL FOURNIT UNE TECHNIQUE D'ETUDE LOCALE DES SURFACES A L'ECHELLE ATOMIQUE. PREMIERE PARTIE: EXPOSE DES PRINCIPALES INFORMATIONS QUE PEUT EN TRIER LE PHYSICIER. DEUXIEME PARTIE: RESULTATS CONCERNANT LES DIFFERENTES INTERFACES DE SI(111): AU/SI, B/SI ET SN/SI. DANS LE CAS DE AU/SI(111), BON ACCORD AVEC LES MODELES STRUCTURAUX RECEMMENT PROPOSES. L'EXODIFFUSION DU BORE AVEC DES ECHANTILLONS FORTEMENT DOPES EST UNE PARTIE IMPORTANTE DE CE TRAVAIL. OBTENTION D'UN MODELE DE STRUCTURE A PARTIR DE RENSEIGNEMENTS SPECTROSCOPIQUES SUR LA SURSTRUCTURE OBSERVEE. L'ETUDE PRELIMINAIRE DANS LE CAS DE SN CONFIRME LE MODELE T4 POUR LES SITES D'ABSORPTION DES ELEMENTS DU GROUPE IV

Download or read book Etude en microscopie par effet tunnel de surfaces ordonn es written by Philippe Dumas and published by . This book was released on 1988 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: CETTE THESE EST CONSACREE A L'ETUDE DE SURFACES ORDONNEES DE SILICIUM (111) ET DES SURSTRUCTURES INDUITES PAR LA PRESENCE D'ATOMES D'OR ET DE BORE EN SURFACE. LA PREMIERE PARTIE TRAITE DU PRINCIPE DE LA MICROSCOPIE PAR EFFET TUNNEL ET DE LA REALISATION D'UN MICROSCOPE (STM). ELLE DECRIT ENSUITE LES RENSEIGNEMENTS QUE CETTE TECHNIQUE PEUT APPORTER AU PHYSICIEN DES SURFACES. DANS LA SECONDE PARTIE, APRES QUELQUES RAPPELS SUR LA DIFFRACTION D'ELECTRONS LENTS (LEED) ET LA SPECTROSCOPIE AUGER, NOUS ETUDIONS PAR CES TECHNIQUES CONJOINTES (STM, LEED, AUGER) LES SYSTEMES SUIVANTS: LE SILICIUM (111) RECONSTRUIT 7 X 7, L'INTERFACE AU/SI(111) RAC3 X RAC3 R30**(O) ET LE B-SI(111) RAC3 X RAC3 R30**(O). CES ETUDES NOUS PERMETTENT DE CONFRONTER NOS RESULTATS AUX MODELES EXISTANTS ET DE PROPOSER, POUR LE DERNIER SYSTEME, UN NOUVEAU MODELE DE LA STRUCTURE RAC3

Download or read book A Sub Kelvin Scanning Tunneling Microscope and Its First Application of Spectroscopy on Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: La compréhension de la supraconductivité à haute température critique (T[c souscrit]) est un défi majeur de la physique du solide. Dans le but d'étudier la densité d'états électroniques des supraconducteurs à l'échelle nanoscopique, nous avons développé un système de mesure unique : un microscope à effet tunnel opérant entre 275mK et température ambiante, sous ultra-haut vide et dans des champs magnétiques atteignant 14Tesla. Ce système a permis l'étude spectroscopique de deux supraconducteurs : Bi2Sr2CaCu2O et Bi2Sr2CuO6. Pour le premier, nous avons examiné l'état mixte, caractérisé par la présence de "vortex" magnétiques, et étudié la distribution spatiale de leurs coeurs, leur forme et l'évolution détaillée de leur densité d'états dans l'espace. Pour le second, nous avons mesuré le comportement de la densité d'états en fonction de la température. L'observation d'un "pseudogap" au-dessus de T[c souscrit] et sa relation avec le "gap" supraconducteur, permettent de conclure que l'origine du "pseudogap" est liée à la supraconductivité.

Download or read book tude par microscopie en champ proche et diffraction d lectrons rapides des premiers stades de croissance de syst mes m talliques written by Frédéric Dulot and published by . This book was released on 2000 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ce mémoire est consacré à l'étude des premiers stades de croissance de systèmes métalliques à partir de deux techniques d'analyse de surface complémentaires : la diffraction d'électrons rapides (RHEED) et la microscopie à effet tunnel (STM). Dans une première partie, nous avons pu dégager pour le système FE/CU(100) à température ambiante quatre par bicouche stades de croissance correspondant à : I. l'incorporation du fer dans le substrat de cuivre par mécanisme d'échange. II. la nucléation des premiers ilots de fer sur les inclusions de fer préalablement formées. III. la nucléation du cuivre contre ces ilots de fer. IV. la nucléation du second plan atomique avec un transfert de matière entre les deux premiers plans. Nous avons mis en évidence une croissance alternée entre le premier plan et le second plan atomique pour des dépôts inferieurs a 1.2 MC puis bicouche par bicouche jusqu'a 2 MC. Au delà, la croissance est de type couche par couche. Ces mesures nous ont permis de conclure à une ségrégation du cuivre par mécanisme d'échange entre les plans de croissance jusqu'a 4 MC. Dans une seconde partie, nous nous sommes intéressés à l'origine physique de la largeur des raies de diffraction RHEED et des oscillations de largeur observées lors de la croissance 2d de systèmes épitaxies. Un travail expérimental combinant RHEED et STM sur les systèmes CU/FE(100) et FE/FE(100) ainsi que la simulation numérique des cliches de diffraction a partir d'images STM échantillonnées, nous ont permis de mettre en lumière le rôle de la contribution diffuse liée a un ordre local entre ilots de nucléation. Cette contribution diffuse donne lieu à des structures satellites qui, lorsqu'elles ne sont plus résolues expérimentalement, contribuent à un élargissement des raies de diffraction. Le transfert d'intensité entre la contribution diffuse et le pic de BRAGG en cours de croissance est à l'origine des oscillations de largeur de raies observées sur certains systèmes.

Download or read book Plant Response to Climatic Factors written by R. O. Slatyer and published by . This book was released on 1973 with total page 586 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Review of Research on Laterites written by Roger Maignien and published by . This book was released on 1966 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Background, definition and scope of the problem; Morphological and analytical characteristics of laterites; Global distribution of laterites; Origin of laterites; Classification of laterites.

Download or read book Radioactive Aerosols written by Constantin Papastefanou and published by Elsevier. This book was released on 2011-07-28 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt: Whenever radioactivity is released to the atmosphere, for example by the detonation of nuclear weapons or the testing of nuclear weapons or from nuclear reactor accidents that fraction of it which remains airborne for more than a few hours is liable to be attached to aerosol particles. The resulting radioactive aerosols are carried by atmospheric mixing processes until they settle out or are scavenged by precipitation. The radiation exposure pathway of maximum concern to humans is by inhalation of aerosols and their deposition in the respiratory tract. In this context, it is important to note that radioactive aerosols are commonly of natural origin alos. In particular, the associated radionuclides can be of natural terrestrial origin, such as the decay products of radon gas, or they can e cosmogenic, such as beryllium-7. The exposure of miners of uranium and other ores and minerals to radon and its aerosol-borne decay products is of major significance. The book describes the formation of aerosols, their aerodynamic size distribution, their atmospheric residence time, their sampling and measurement, the range of radioactive aerosols found and studied thus far, including man-made nuclides and radon decay products and their interaction with man, including deposition in the lung and subsequent health effects. - Advanced level science handbook for researchers, scientists and academics - Covers all aspects of radiation exposure in humans, including subsequent health implications - Presents the latest findings and analysis in this highly topical area

Download or read book The Problems of the Arid Zone written by Unesco and published by paris. This book was released on 1962 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Metallic Magnetism written by I. A. Campbell and published by Springer. This book was released on 1987 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Translating the Paris Agreement into Action in the Pacific written by Anirudh Singh and published by Springer Nature. This book was released on 2020-01-20 with total page 323 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an insight into how a country contributes to the GHG emissions reductions required to keep global warming within the limits set by the Paris Agreement arrived at COP21 in 2015. It shows what actions are needed for the implementation plan that Fiji will use to satisfy its quota (i.e. its Nationally Determined Contribution or NDC) of the total GHG emissions reductions. It is a primary resource material for those who wish to obtain an understanding of the science behind climate change mitigation. It reveals the behind-the-scenes action that takes place to convert the rhetoric of climate change into the action on the ground that actually reduces the GHG emissions and global warming. The book also presents a critique of methods adopted by nations in meeting their NDCs to emissions reductions as agreed at the Paris Agreement, and suggests improvements.

Download or read book Radiation Protection Activities written by United States. Environmental Protection Agency. Office of Radiation Programs and published by . This book was released on 1976 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dormancy in Aquatic Organisms Theory Human Use and Modeling written by Victor R. Alekseev and published by Springer. This book was released on 2020-10-12 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the second volume on dormancy in aquatic organisms. The book is divided into three parts whereby the first part is devoted to several groups of aquatic organisms which are under-studied in terms of the dormancy’s role in the life cycle. The second part looks at the use of dormancy phenomena in science and potential human applications. Furthermore, part 3 comprises of examples of using modeling in relation to dormancy phenomenon and it opens with a theoretical analysis of studies of biological information, including seasonal information. This work can be used as a text book for students as well as a manual for science and practice purposes in ecology, aquaculture, nature protection and space researches with regards to creating ecological life supporting systems and discovering extraterrestrial life on other planets with harsh environmental conditions.

Download or read book Neutron Capture Gamma Ray Spectroscopy written by R. E. Chrien and published by Springer. This book was released on 2011-12-29 with total page 880 pages. Available in PDF, EPUB and Kindle. Book excerpt: The post World War II era witnessed a tremendous growth in the research carried out in neutron-induced reactions and especially in neutron capture y-ray studies. This growth was stimulated by the availability of neutron sources, such as reactors and accelerators, and by the development of high resolution y-ray and conversion electron detectors. Today the combination of high flux reactors and precise instrumentation has produced spectral data of exceptional quality, as the pages of these proceedings illustrate. The world-wide community of the practioners of the art of cap ture y-ray spectroscopy has met three times in the last decade: the first international symposium on this subject was held at Studsvik, Sweden in 1969, and the second at Petten, The Netherlands in 1974. A smaller meeting, of mostly u. S. and some European parti cipation, was held at Argonne National Laboratory in 1966. A perusal of the proceedings of these meetings shows the striking ad vances in this now mature field of physics over the last dozen years. Each meeting has seen a small but perceptible increase in the number of papers presented and the number of laboratories repre sented. More importantly, each meeting has documented the increasing impact of (n,y) reasearch, not only on other areas of basic physics, but also on commercial and medical applications of this technology. A total of 29 invited papers and 97 contributed papers were presented at this symposium.

Download or read book Basic Radiation Protection Criteria written by and published by . This book was released on 1971 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Geochemistry of Boron written by C. T. Walker and published by Dowden Hutchinson and Ross. This book was released on 1975 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Natural Radiation Environment VII written by S. E. Simopoulos and published by Elsevier Science Limited. This book was released on 2005 with total page 1191 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Natural Radiation Environment Symposium (NRE VII), the Seventh in the NRE series, which commenced forty years ago in 1963 at Rice University Texas, was held in Rhodes (Greece) in May 2002. During the intervening four decades the research work presented at these NRE Symposia has contributed to a deeper understanding of natural radiation and in particular of its contribution to human radiation exposures. It is clear from the quality and diversity of the 143 papers in this volume of Radioactivity in the Environment series that the study of the natural radiation environment is an active and continually expanding field of research. The papers in this volume fall into a number of main and topical research areas namely: the measurement and behaviour of natural radionuclides in the environment cosmic radiation measurement and dosimetry the external penetrating radiation field at ground level TENR (Technologically Enhanced Natural Radiation) and NORM (Naturally Occurring Radioactive Materials) studies assessment of the health effects of radon regulatory aspects of natural radiation exposures In these papers the results of many new surveys of natural radionuclide levels in the environment and of improved methods of detection are described. While some of the natural radiation sources investigated are unmodified by human activity, many accounts are given here of exposures to natural sources which have been enhanced by technology. Such TENR and NORM exposures are shown to range from activities such as mining, oil and gas exploitation, the use of industrial by-products as building materials, to space travel to name but a few. In several cases quite high doses to some individuals are shown to occur. Accounts are given here of methods to prevent and reduce exposures to such sources.