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Séminaire général

The surface structure of titanate crystals, thin films and monolayers

Martin R. Castell

In this presentation I will first discuss the surface structure and origin of the many reconstructions of SrTiO3 crystals [1]. I will then show how with an increasingly Ti-rich surface environment there is an evolution of epitaxial titanate nanostructures [2] that eventually result in TiO2 anatase thin films on the surface [3]. These reconstructed and nanostructured surfaces can be used as templates to self-assemble molecules such as fullerenes into patterns that differ significantly from the close-packed structures that are usually observed on metal surfaces. I will also show some results of epitaxial film growth of TiOx on Au (111) [4]. This work demonstrates that due to the variable oxidation states of titanium, and the nature of the interface, it is possible to create titanate structures in an ultra-thin film form that are not stable as a bulk termination.

The main experimental techniques that are used to produce the results in this presentation are UHV scanning tunnelling microscopy (STM), photoemission (XPS), and Auger spectroscopy (AES). Modelling the surface structures and STM image simulation is performed with density functional theory (DFT).s

References : [1] J.A. Enterkin, A.K. Subramanian, B.C. Russell, M.R. Castell, K.R. Poeppelmeier and L.D. Marks,
Nature Mat., 9, 245 (2010). [2] M.S.J. Marshall, A.E. Becerra-Toledo, L.D. Marks and M.R. Castell, Phys. Rev. Lett., 107, 086102 (2011). [3] M.S.J. Marshall and M.R. Castell, Phys. Rev. Lett., 102, 146102 (2009). [4] C. Wu, M.S.J. Marshall and M.R. Castell, J. Phys. Chem. C, 115, 8643 (2011).