Spontaneous Oxidation of Ni Nanoclusters on MgO Monolayers Induced by Segregation of Interfacial Oxygen.
We report the study of Ni nanoclusters deposited on MgO/Ag(100) ultrathin films (one monolayer) at T = 200 K. We show by STM analysis and DFT calculations that in the limit of low Ni coverage the formation of nanoclusters of four to six atoms occurs and that these aggregates are flat rather than 3D, as expected for Ni tetramers, pentamers, or hexamers. Both the shape of the clusters and the interatomic distance between neighboring Ni atoms are indicative that the nanoparticles do not consist of pure metal atoms but that a NiyOx structure has formed thanks to the availability of atomic oxygen accumulated at the MgO/Ag interface, with Ni clusters acting as oxygen pumps. Besides being of relevance in view of the use of metal nanoclusters in catalysis and other applications, this finding gives a further proof of the peculiar behavior of ultrathin oxide films.
†IMEM-CNR, U.O.S. Genova, Via Dodecaneso 33, 16146 Genova, Italy.
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Smerieri
†IMEM-CNR, U.O.S. Genova, Via Dodecaneso 33, 16146 Genova, Italy.|‡Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy.
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Pal
†IMEM-CNR, U.O.S. Genova, Via Dodecaneso 33, 16146 Genova, Italy.
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Savio
†IMEM-CNR, U.O.S. Genova, Via Dodecaneso 33, 16146 Genova, Italy.|‡Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy.
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Vattuone
†IMEM-CNR, U.O.S. Genova, Via Dodecaneso 33, 16146 Genova, Italy.|§Dipartimento di Chimica e Chimica Industriale, Università di Genova, Via Dodecaneso 31, 16146 Genova, Italy.
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Ferrando
∥Dipartimento di Scienza dei Materiali, Università Milano Bicocca, via R. Cozzi 55, 20125 Milano, Italy.
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Tosoni
∥Dipartimento di Scienza dei Materiali, Università Milano Bicocca, via R. Cozzi 55, 20125 Milano, Italy.
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Giordano
∥Dipartimento di Scienza dei Materiali, Università Milano Bicocca, via R. Cozzi 55, 20125 Milano, Italy.
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Pacchioni
†IMEM-CNR, U.O.S. Genova, Via Dodecaneso 33, 16146 Genova, Italy.|‡Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy.
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Rocca
D008277:Magnesium Oxide / Q000737:chemistry*; D008962:Models, Theoretical; D049329:Nanostructures / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*
D008277:Magnesium Oxide; D009532:Nickel; D010100:Oxygen
DFT; MgO thin film; Ni clusters; NiO clusters; STM; morphology