In-situ Investigation of the Early Stage of TiO2 epitaxy on (001) SrTiO3

We report on a systematic study of the growth of epitaxial TiO2 films deposited by pulsed laser deposition on Ti-terminated (001) SrTiO3 single crystals. By using in-situ reflection high energy electron diffraction, low energy electron diffraction, x-ray photoemission spectroscopy and scanning probe microscopy, we show that the stabilization of the anatase (001) phase is preceded by the growth of a pseudomorphic Sr-Ti-O intermediate layer, with a thickness between 2 and 4 nm. The data demonstrate that the formation of this phase is related to the activation of long range Sr migration from the substrate to the film. The role of interface Gibbs energy minimization, as a driving force for Sr diffusion, is discussed. Our results enrich the phase diagram of the Sr-Ti-O system under epitaxial strain opening the roudeficient SrTiO phase.Comment: 8 pages, 7 figure

Electronic phase separation near the superconductor-insulator transition of Nd1+xBa2−xCu3O7−δ thin films studied by an electric-field-induced doping effect

We report a detailed study of the transport properties of Nd(1+x)Ba(2-x)Cu(3)O(7-delta) thin films with doping changed by field effect. The data cover the whole superconducting to insulating transition and show remarkable Similarities with the effect of chemical doping in high critical temperature superconductors. The results suggest that the add-on of carriers is accompanied by an electronic phase separation, independent on the details of the doping mechanism

Maria, Mari! : My Marie

https://digitalcommons.library.umaine.edu/mmb-ps/1247/thumbnail.jp

Role of interband scattering in neutron irradiated MgB2_2 thin films by Scanning Tunneling Spectroscopy measurements

A series of MgB$_2$ thin films systematically disordered by neutron irradiation have been studied by Scanning Tunneling Spectroscopy. The c-axis orientation of the films allowed a reliable determination of local density of state of the $\pi$ band. With increasing disorder, the conductance peak moves towards higher voltages and becomes lower and broader, indicating a monotonic increase of the $\pi$ gap and of the broadening parameter. These results are discussed in the frame of two-band superconductivity.Comment: The text will be submitted in Latex format, and the corresponding pdf file should take 6 pages. There are 5 figures (eps files submitted) and 1 tabl

A teaser made simple: a didactic measurement of the spectral answer of a human-eye-calibrated lux meter

A simple didactic experiment has been designed and realized, in order to illustrate to undergraduate students in scientific faculties some basic concepts lying behind the fundamentals of geometrical optics. The spectral response of a human-eye-calibrated lux meter was measured using a very trivial experimental arrangement. The white light of a halogen lamp was decomposed into its spectral components through a diffraction grating, so that collecting the radiation at different dispersion angles allowed one to measure the intensity as a function of wavelength. The experiment can be used to effectively illustrate the concepts of spectral distribution, the radiometry versus photometry conversion and photopic response, and the famous historical experience by Herschel on the 'temperature of colours'

First results from an aging test of a prototype RPC for the LHCb Muon System

Recent results of an aging test performed at the CERN Gamma Irradiation Facility on a single--gap RPC prototype developed for the LHCb Muon System are presented. The results are based on an accumulated charge of about 0.45 C/cm$^2$, corresponding to about 4 years of LHCb running at the highest background rate. The performance of the chamber has been studied under several photon flux values exploiting a muon beam. A degradation of the rate capability above 1 kHz/cm$^2$ is observed, which can be correlated to a sizeable increase of resistivity of the chamber plates. An increase of the chamber dark current is also observed. The chamber performance is found to fulfill the LHCb operation requirements.Comment: 6 pages, 9 figures, presented at the International Workshop on Aging Phenomena in Gaseous Detectors'', DESY-Hamburg (Germany), October 200

Preliminary results of an aging test of RPC chambers for the LHCb Muon System

The preliminary results of an aging test performed at the CERN Gamma Irradiation Facility on a single--gap RPC prototype developed for the LHCb Muon System are presented. The results are based on an accumulated charge density of 0.42 C/cm^2, corresponding to about 4 years of LHCb running at the highest background rate. We observe a rise in the dark current and noise measured with source off. The current drawn with source on steadily decreased, possibly indicating an increase of resistivity of the chamber plates. The performance of the chamber, studied with a muon beam under several photon flux values, is found to still fulfill the LHCb operation requirements.Comment: 4 pages, 6 figures, presented at RPC2001, VIth Workshop on Resistive Plate Chambers and Related Detectors, November 26-27 2001, Coimbra, Portuga