Oxide based materials are often used for relevant technological applications in fields as catalysis, corrosion protection, micro- and nano-electronics, sensoristics, spintronics, drug delivery, etc. The ability to engineer nearly perfect ultrathin oxide layers, up to the limit of monolayer thickness, is a key issue for nano-technological applications [1].Here we face the difficult and important case of ultrathin MgO films on Ag(100), for which no extended and well-ordered layers could so far be produced in the monolayer limit. We demonstrate [2] that their final morphology depends not only on the usual growth parameters (crystal temperature, metal flux and oxygen partial pressure) but also on after-growth treatments controlling so far neglected thermodynamics constrains. We succeed thus in tuning the shape of the oxide films from irregular, nm-sized, monolayer thick islands (panel a), to slightly larger, perfectly squared bilayer islands (panel b), to extended monolayers (panel c) limited apparently only by substrate steps.Panels (a-c): STM Images of MgO films of 0.7 ML nominal thickness grown under different conditions. SC and FC indicate slow and fast cooling, respectively. For all panels, image size 21x21 nm2; I=0.2 nA. The combination of these parameters can be relevant not only for the production of oxide thin films but also for many other layered systems. Since the film structure influences both chemical and electronic properties of the layers, a full control of all experimental parameters opens important perspectives for applications in catalysis and for the use of ultrathin oxide films as support for the further deposition of organic and inorganic nano-objects.[1] G. Pacchioni, H.J. Freund, Chem. Rev. 113, 4035 (2013).[2] J. Pal, M. Smerieri, E. Celasco, L. Savio, L. Vattuone, M. Rocca, Phys. Rev. Lett., in press (2014).

Morphology of monolayer MgO films on Ag(100): Switching from corrugated islands to extended flat terraces

248th National Meeting (2014)

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