Surface quality studies of high Tc_{c} superconductors of the Hg , Tl and Hgx_{x}Tl1−x_{1-x}-families: RBS and resonant C and O backscattering studies

The composition, crystallinity, uniformity, purity, and thermal stability of cuprate superconductors have been studied by Rutherford backscattering and channeling spectrometry, and 3.045 MeV He$^{+}$ oxygen non-Rutherford resonant scattering. Further experiments have been performed with 1.75 MeV H$^{+}$carbon non-Rutherford resonant scattering. Three sets of samples were studied : HgBa$_{2}$CuO$_{(4+\delta)}$ (Hg1201), Hg$_{x}$T1$_{1-x}$Ba$_{2}$Ca$_{2}$Cu$_{3}$O$_{(2n+\delta)}$ (Hg,T1-1223) and T1$_{1.85}$Ba$_{2}$CuO$_{6}$/LaA10$_{3}$ (T1-2201), either in bulk or as an epitaxial thin film. It was observed that the superconductors exhibit a metal deficiency near the surface, which is largely compensated by excess oxygen. Moreover, the samples are significantly contaminated with carbon within the probing region of the H$^+$ beam. The thermal stability and surface degradation were studied in both oxidizing ambient and vacuum. As a general trend, the heavy metal deficiency — and consequently the compensating oxygen excess — is enhanced as the temperature increases

X-Ray Diffraction Studies of 2212-Type Superconductors in the Tl–Hg–Ba–Sr–Ca–Cu–O System

International audienc

Structural Anomalies Study of 1223 Hg(Tl)-Ba-Ca-Cu-O Superconductors in the Temperature Range 100-300 K

The crystal structure of Hg-based 1223 phases, Hg1-xTlxBa2Ca2Cu3O8+delta, with different oxygen content and Hg/Tl substitution having critical temperature from 114 to 133 K has been investigated by the X-ray powder diffraction technique over the temperature range from room temperature to 100 K. Rietveld analysis results indicate the presence of two different structure anomalies at temperatures 138 and 165 K, respectively. The changes in lattice parameters, fractional coordinates, and individual atom thermal parameters near the observed anomalies are discussed.</p

Structural Anomalies Study of 1223 Hg(Tl)-Ba-Ca-Cu-O Superconductors in the Temperature Range 100-300 K

The crystal structure of Hg-based 1223 phases, Hg1-xTlxBa2Ca2Cu3O8+delta, with different oxygen content and Hg/Tl substitution having critical temperature from 114 to 133 K has been investigated by the X-ray powder diffraction technique over the temperature range from room temperature to 100 K. Rietveld analysis results indicate the presence of two different structure anomalies at temperatures 138 and 165 K, respectively. The changes in lattice parameters, fractional coordinates, and individual atom thermal parameters near the observed anomalies are discussed.</p

Pressure effect in the Hg-based superconductors: A structural study

Energy-dispersive synchrotron x-ray-diffraction studies were performed on powder samples of Hg1212 and Hg1223 in a diamond-anvil cell at pressure up to 300 kbar. High compressibility was found. A reversible structural transition was observed, which is suggested to correspond to a pressure-induced ordering along the c axis. The accommodation of the Ba ion at high pressure is studied, and the effect it might have on the electronic structure of these materials is discussed by employing results from cluster calculations

Nanolithographie par anodisation locale en microscopie à force atomique sur le phosphore d'indium pour des applications optoélectroniques

Dans le cadre de cette thèse, nous examinons les possibilités offertes par la microscopie à force atomique (AFM) pour la nanolithographie de matériaux semi-conducteurs. Deux méthodes sont présentées sur phosphore d'indium (InP): le mode contact/tension continue et le mode contact intermittent/une tension alternative. La première méthode est caractérisée par une cinétique logarithmique et une dépendance linéaire en tension. Nous interprétons ces résultats par l'existence d'une charge d'espace limitant l'oxydation (homogénéité et résolution). Les améliorations de la méthode sont en résolution et homogénéité. Nous avons réalisé une caractérisation électrique par différents modes AFM. La qualité électronique de l'oxyde a été estimée par des mesures en Tunneling-AFM et phase (AFM). Les déchargements électriques de l'oxyde ont été étudiés par EFM et par SCM. Nous interprétons ainsi les mécanismes d''oxydation. Pour finir, nous montrons l'intérêt de ces méthodes pour l'organisation de boîtes quantiques.We study local anodisation using Atomic Force Microscopy on Indium Phosphite. We develop two methods: a standard AFM oxidation (contact mode and constant bias) and a non usual method (intermittent contact mode and a modulated voltage). The first method results are logarithmic growth kinetic and a linear variation with applied bias voltage. These results had been related to charging effect that limits the oxidation (homogeneity and resolution). To reduce these limits we develop the second method. We obtain an improvement for: resolution, homogeneity, control on oxide shape, and lithography velocity. Electrical characterisations by using different AFM mode measurements had been realised: Tunnelling-AFM and Phase measurement to probe the oxide quality and Scanning Capacitance Microscopy and Electrostatic Force Microscopy measurement to probe charge dissipation. These measurements had been used to understand the oxidation process. We study these methods for Quantum Dots localisation.VILLEURBANNE-DOC'INSA LYON (692662301) / SudocSudocFranceF