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Synthèse et propriétés de monocristaux, de poudres, films minces ou hétérostructures

Etudes à l'interface avec la matière biologique

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Nouvelle publication FM2N M. Le Gallic

Publié le 28 novembre 2015
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Communiqué 31 août 2015

Le papier "Particular structural defects in Ta2O5 from crystallisation of amorphous thin films in O2–H2O atmosphere" est apparu dans Acta Materiala

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Vous trouverez ici le papier de Marie Le Gallic. Voici l'abstract:

"Structural defects within Ta2O5 monoclinic structures were obtained by crystallisation at 850 C in atmosphere O2–H2O of amorphous thin films deposited by injection metal-organic chemical vapour deposition (i-MOCVD) on Si substrates. These defects, observed by high resolution transmission electron microscopy (HRTEM), contain alignments of Ta5+ vacancies along a crystallographic direction [001]. H2O gas of different partial pressures was obtained by bubbling O2 gas through deionised water or Na2CO3–K2CO3 aqueous solution maintained at different temperatures in a range of 25–45 C. The amount of structural defects increases dramatically with H2O partial pressure and annealing time from HRTEM observations and X-ray diffraction results. Such defects are thermally stable, at least up to 850 C. Using Na2CO3–K2CO3 aqueous solution, similar structural defects including mainly K+ species were formed. Na+ species contributes mostly to the formation of another phase of composition close to (Na0.8K0.2)2Ta4O11 of natrotantite type structure. Assuming that Ta5+ vacancies are occupied by H+ in a form of bridging hydroxyl groups Ta–OH–Ta in order to satisfy electrical neutrality, the presence of significant levels of hydrogen atoms within Ta2O5 concordant with H enrichment at defects was identified by time-of-flight secondary ion mass spectrometry (ToF-SIMS)."

DOI:10.1016/j.actamat.2015.04.041
 
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mise à jour le 16 octobre 2019

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