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Thermal Faceting of Clean and Oxygen-Covered Ir Nanocrystals

par Bryl, Robert ;Olewicz, Tomasz;Visart de Bocarmé, Thierry ;Kruse, Norbert
Référence The Journal of Physical Chemistry Part C: Nanomaterials and Interfaces
Publication Publié, 2010-09-30

Article révisé par les pairs

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Résumé :

Thermal faceting of a clean and oxygen-covered iridium nanosized crystal was studied by field ion microscopy for oxygen exposures up to 6 langmuirs (1 langmuir = 1.3 * 10-4 Pa 3 s) and annealing temperatures of 300-1100 K. The clean Ir specimen (the “tip”), originally hemispherically shaped, started to facet upon annealing to at least 850 K, exposing only {111} and {001} facets in the final cuboctahedral form. Even small amounts of adsorbed oxygen caused changes in the Ir tip morphology. An oxygen exposure of 0.3 langmuir caused {113} facets to develop at 700 K. For larger (1 to 6 langmuirs) exposures, well characterized {111}, {001}, {113}, and {011} facets were observed to develop when annealing to at least 650 K. The recorded micrographs suggest (1 * 3) or, to a lesser extent, (1 * 4) missing row reconstructions of the {011} facets, while other facets do not exhibit any clear evidence of reconstruction.