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O: Fachverband Oberflächenphysik
O 37: Metal Oxide Surfaces II: Structure, Epitaxy and Growth
O 37.2: Vortrag
Dienstag, 2. April 2019, 14:15–14:30, H16
Dopant-induced diffusion at metal-oxide interfaces studied for Fe- and Cr-doped MgO/Mo(001) films — Stefania Benedetti1, Sergio Tosoni2, Gianfranco Pacchioni2, and •Niklas Nilius3 — 1CNR, Instituto Nanoscienze, 41125 Modena, Italy — 2Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, 20125 Milano, Italy — 3Institute of Physics, Carl von Ossietzky University, 26111 Oldenburg, Germany
X-ray photoelectron spectroscopy reveals spontaneous atom diffusion from a Mo(001) support into a MgO thin film doped with transition-metal ions. The amount of interfacial mixing depends on the nature of the dopants and is larger for Fe than for Cr impurities. DFT calculations find the reason for Mo diffusion in the ability of the dopants to change oxidation state. Cr exclusively occurs as 3+ ion in MgO and charge mismatch with native ions is compensated for by Mg vacancies. Conversely, the Fe oxidation state depends on temperature, which enables Mo atoms from the support to move into Mg vacancies where they oxidize via electron transfer into the Fe dopants. The talk unravels a novel charge-compensation scheme in doped oxides that proceeds via chemical intermixing at a metal-oxide interface.