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Paper   IPM / Nano-Sciences / 15308
School of Nano Science
  Title:   Rumpling and Enhanced Covalency at SrTiO3 (001) Surface
1.  Mohammad Saghayezhian
2.  Seyed Mojtaba Rezaei Sani
3.  Jiandi Zhang
4.  E. Ward Plummer
  Status:   Published
  Journal: J. Phys. Chem. C
  Vol.:  123
  Year:  2018
  Pages:   8086
  Supported by:  IPM
The TiO2 terminated surface of SrTiO3 (001) is considered to be weakly polar. It exhibits a surface structural distortion, quantified here using low energy electron diffraction at room temperature. Structural analysis shows the presence of strong surface rumpling in the TiO2 terminated surface with the oxygen atoms moving outward and Ti atoms moving inward. Density functional calculations confirm the measured rumpling, and experimental data show the distortion is localized at the surface. Angle dependent core-level X-ray photoemission spectroscopy (XPS) shows that the surface rumpling strongly impacts the electronic structure of the surface. This observation is reinforced by density functional theory, which demonstrates that the valence state of Ti at the surface is reduced while O is enhanced, where we found the Ti-O bonds are more covalent near the surface. Our calculated results show that surface rumpling is accompanied by change in the bond hybridization of Ti-O at the surface. Changes in the XPS satellite structures at the surface are consistent with this picture of the change in bonding, indicating that the (001) surface of SrTiO3 is not polar and charge rearrangement is a consequent rearranges as a ramification of surface reconstruction.

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