| AVS 64th International Symposium & Exhibition | |
| Surface Science Division | Thursday Sessions |
| Session SS+EM+HC+MI-ThM |
| Session: | Oxides: Structures and Reactions |
| Presenter: | Sandamali Halpegamage, University of South Florida |
| Authors: | S. Halpegamage, University of South Florida L. Bignardi, Elettra-Sincrotrone Trieste, Italy P. Lacovig, Elettra-Sincrotrone Trieste, Italy A. Kramer, University of South Florida Z. Wen, East China University of Science and Technology, PR China X. Gong, East China University of Science and Technology, PR China S. Lizzit, Elettra-Sincrotrone Trieste, Italy M. Batzill, University of South Florida |
| Correspondent: | Click to Email |
Ternary oxide monolayers supported on or intermixed with a second oxide surface have attracted great interest in designing new materials with unique chemical functional properties including selective heterogeneous catalysts and nanocatalysts. Due to the complexity of the structure and composition, it is challenging to discover and characterize such phases. Here we synthesized an ordered mixed oxide monolayer of FeTi2O5 on rutile-TiO2(011) via two different experimental pathways; firstly, by annealing the clean TiO2(011) in 1x10-7 mbar of O2 at ~450 0C and secondly, by physical vapor depositing Fe on clean TiO2(011) in 1x10-7 mbar of O2 at ~450 0C.In both procedures the Fe atoms intermixe with Ti atoms in the surface layer of the substrate and form an ordered mixed-oxide monolayer with FeTi2O5 composition. High resolution and fast X-ray photoemission spectroscopy (XPS) reveals that Fe and Ti are in 2+ and 4+ charge states respectively. The structure of this mixed oxide monolayer was predicted by a combination of atomically-resolved STM (Scanning Tunneling Microscopy) and DFT-based calculations and further confirmed by synchrotron based angle scanned x-ray photoelectron diffraction (XPD) studies. Multiple electron scattering simulations implemented in the Electron Diffraction in Atomic Clusters (EDAC) package were performed for comparing experimental XPD patterns with structural models. Judged by the reliability factor (Rp), the experimentally determined XPD patterns are in good agreement with the simulated XPD patterns. The study has been extended to a few of the other transition metals namely, V, Cr, and Ni. Due to the similarities in the bulk oxide structures of these transition metals they all are capable of forming similar intermixed monolayer oxide surfaces with the composition MTi2O5 (M=V,Ni,Cr). For all these monolayers, the valance band maximum (VBM) is above the VBM for TiO2, suggesting that these monolayers may trap holes at the surface efficiently and thus may modify the photocatalytic activity of TiO2.