Epitaxial thin films oxides on Fe: what happens when a low dimensional oxide grows on a highly reactive metal substrate?

The investigation of oxide films with a thickness of a few nanometers or below grown on another substrate is a scientific topic that has recently attracted a huge amount of experimental and theoretical research work [1]. In this contribution we shall focus on some of the recent advances in understanding the formation of transition metal oxide/Fe interfaces [2,3]. Fe can be considered on the one hand as a prototypical example of ferromagnetic material, and on the other hand as an example of a highly reactive metal. The former characteristic makes it particularly appealing for spintronic applications and magnetic storage media, while the latter makes the preparation of well-defined oxide/metal interfaces a difficult task. For this reason, despite the large body of literature focusing on the preparation and characterization of ultra-thin oxide films on inert materials such as noble and quasi noble metals, comparatively little is known about the atomic scale mechanisms driving the formation of the transition metal oxide/Fe interfaces. In the first part of the talk we shall discuss the stabilization of single-layer-thick oxide films on Fe, by using selected examples involving the deposition of transition metals on the well-ordered and defect-free Fe(001)-p(1 × 1)O surface. This is characterized by one oxygen atom per surface unit cell which can be used as a reservoir for the stabilization and investigation of Fe-supported twodimensional transition metal oxides [4,5], avoiding at the same time the Fe oxidation occurring when more traditional preparation procedures (such as for instance metal deposition in a reactive oxygen atmosphere) are employed. In the second part we shall discuss the growth of oxide films out of the interfacial layer, with particular emphasis on the growth mode leading at the same time to sharp interfaces, useful to correctly modeling the interfacial physical phenomena, and atomically flat surfaces, crucial to allow scanning probe microscopy studies down to the atomic scale. References: [1] See e.g. S.Valeri and G. Pacchioni, eds., Oxide Ultrathin Films (Wiley-VCH Verlag, Weinheim,2011). [2] M. Finazzi, L. Duò, and F. Ciccacci, Surf. Sci. Rep. 64, 139 (2009). [3] M. Finazzi, L. Duò, and F. Ciccacci, eds., Magnetic Properties of Antiferromagnetic Oxide Materials: Surfaces, Interfaces and Thin Films (Wiley-VCH Verlag, Weinheim, 2010). [4] A. Picone, G. Bussetti, M. Riva, A. Calloni, A. Brambilla, L. Duò, F. Ciccacci, and M. Finazzi, Phys. Rev. B 86, 075465 (2012). [5] A. Picone, G. Fratesi, M. Riva, G. Bussetti, A. Calloni, A. Brambilla, M.I. Trioni, L. Duò, F. Ciccacci, M. Finazzi, Phys. Rev. B 87 (2013) 085403.