0000000000122308
AUTHOR
A Steinbrunn
Molybdenum deposition on TiO2 (110) surfaces with different stoichiometries
Abstract The deposition of ultra thin molybdenum films has been carried out on three different TiO 2 surfaces: a stoichiometric and flat one obtained after annealing, a non stoichiometric and rough surface made by Ar + bombardment and a stoichiometric and rough surface obtained by oxygen bombardment. Whatever the substrate preparation, in situ AES and XPS studies and ex situ AFM and RHEED characterizations have revealed a Stranski–Krastanov growth mode: the completion of three monolayers followed by island growth is observed in any case. The three monolayers are composed of amorphous molybdenum oxide with a molybdenum oxidation state between III and IV. The oxidation of the molybdenum layer…
Characterization of deuteride titanium targets used in neutron generators
Abstract The study of the physicochemical characteristics of titanium thin films and the corresponding deuterium absorption/desorption kinetics was performed. In order to optimize the production of high-energy neutrons the behaviour of deuteride titanium targets has been studied experimentally by bombardment with 120 and 350 kV deuterons by means of electrostatic accelerators. The importance of the deposit evaporation conditions on the efficiency of neutron emission is clearly demonstrated as well as the thermomechanical stability of the Ti thin film by deuteron bombardment. The main parameters involved in the targets behaviour have been discussed from a thermodynamical approach.
Trivalent cation substitution of pulverulent cobalt—iron molybdates Co1 − xFexMoO4
Abstract Different mixed cobalt—iron molybdates Co1 − xFexMoO4 (0 ≤ x ≤ 1) have been prepared by means of a ceramic process. The oxidation of pulverulent samples leads to ferric molybdate Fe2(MoO4)3, spinelle Co3O4 and cobalt molybdate CoMoO4. After a strong grinding which reduces the grain size (about 0.1 μm) and induces crystallographic defects in the grains, the cobalt—iron molybdates can be partially oxidized into cation-deficient phases. This oxidation corresponds to an isostructural substitution of part of the Fe2+ and Co2+ ions by Fe3+ and Co3+ ions and the creation of cation vacancies. The concomitant presence of trivalent cations and associated cation vacancies in the lattice stabi…
Superficial defects induced by argon and oxygen bombardments on (110) TiO2 surfaces
Abstract Compositional and chemical changes of titanium dioxide monocrystalline surfaces induced by bombardment with 4 keV argon and oxygen ions have been studied by AES, XPS and AFM. Argon ion bombardment induced strong changes in the composition and chemical state of the surface: loss of oxygen due to preferential sputtering occurred, and, related to this, Ti4+ species were reduced to Ti3+ and Ti2+. During oxygen bombardment, competition between preferential sputtering of oxygen ions of the oxide surface and oxygen implantation was observed. This phenomenon was found to be strongly dependent upon the incidence angle of the oxygen ions. Moreover, an oxygen bombardment with normal incidence…