Invited speaker - Gaetano Granozzi (Italy)

 

TiOx Nanostructures on Metallic Substrates: 
A Combined Spectroscopic and Theoretical Investigation
 
Gaetano Granozzi
Department of Chemical Sciences and CNR-INFM Research Unit, University of Padova
Gaetano.granozzi@unipd.it
 
Abstract

     Nanolayers of ordered TiOx films on Pt(111) and Pt(110) surface are prepared by reactive evaporation of Ti in oxygen. In the case of the Pt(111) substrate, varying the Ti dose and the annealing conditions (i.e. temperature and oxygen pressure), several different long-range ordered phases were obtained (see Table below) [1]. They were characterized by means of LEED, synchrotron based valence and core photoemission experiments and STM [1-4]. 

     

     The experimental analysis show that these wide range of structures can be rationalized in two main groups i.e. three stoichiometric phases with an O-Pt interface and four substoichiometric one-monolayer phases, with Ti at the interface with the substrate. For six of these seven phases a structural model, in agreement with the experimental result and supported by DFT calculation, has been proposed [5-7].
     In the case of the Pt(110) substrate, a stoichiometric TiO2 nanolayer has been prepared and it has been found that the model which best fits all the experimental LEED, XPD and STM data can be obtained from an anatase (001) bilayer by sliding the upper monolayer by half a unit cell along the [1-10] substrate direction. The principal interest of stoichiometric phases is related to their structure that is the same of some TiO2 nanosheets obtained by exfoliation of 3D stacked titanates. These nanosheets show innovative properties and are presumably the building blocks of titania nanotubes [8].
    On the other hand three different substoichiometric TiOx phases have been used as templates for growing ordered and monodispersed Au nanocluster arrays [9].
 

 
[1] F.Sedona, G.A. Rizzi,S. Agnoli, F. X. Llabrés i Xamena, A. Papageorgiou, D. Ostermann, M. Sambi, P. Finetti, K. Schierbaum and G. Granozzi, J. Phys. Chem. B 109 (2005) 24411.
[2] F. Sedona, S. Agnoli and G. Granozzi, J. Phys. Chem. B 110 (2006) 15359.
[3] P. Finetti, F. Sedona, G.A. Rizzi, U. Mick, F. Sutara, M. Svec, V. Matolin, K. Schierbaum and G. Granozzi, J. Phys. Chem. C 111 (2007) 869.
[4] F. Sedona, M. Sambi, L. Artiglia, G. A. Rizzi, A. Vittadini, A. Fortunelli, G. Granozzi, J. Phys. Chem. C 112 (2008) 3189.
[5] G. Barcaro, F. Sedona, A. Fortunelli and G. Granozzi, J. Phys. Chem. C 111 (2007) 6095.
[6] F. Sedona, G. Granozzi, G. Barcaro and A. Fortunelli, Phys. Rev. B 77 (2008) 115417. 
[7] Y. Zhang, L. Giordano, G. Pacchioni , A. Vittadini, F. Sedona, P. Finetti and G. Granozzi, Surf. Sci. 601 (2007) 3488. 
[8] T. Sasaki et al., J. Am. Chem. Soc. 118 (1996) 8329. 
[9] F. Sedona, S. Agnoli, M. Fanetti, I. Kholmanov, E. Cavaliere, L. Gavioli and G. Granozzi, J. Phys. Chem. C 111 (2007) 8024.