X-ray photoelectron spectroscopic and ion scattering study of the SrTiO3(0 0 1) surface

The chemical and structural properties of several as-received (unspecified and TiO2 terminated) SrTiO3(0 0 1) surfaces have been analyzed prior to and following UHV and O2 annealing using X-ray photoelectron spectroscopy (XPS), time-of-flight scattering and recoiling spectrometry (TOF-SARS), and low energy electron diffraction (LEED). Well resolved 1×1 LEED patterns were noted for the TiO2 terminated surface. Simulations of the TOF-SARS azimuthal scans indicate that the O atoms are situated 0.1 Å above the Ti layer (surface plane). This TiO2 terminated surface reconstructed following O2 annealing resulting in the loss of the azimuthal TOF-SARS features and the LEED pattern. This disordered surface also exhibited a stronger Sr TOF-SARS signal, and a high binding energy (HBE) component in the Sr 3d, 3p and 4p XPS spectra similar to that observed in the unspecified surfaces. Cleaning with organic solvents and exposure to air further enhanced the HBE components, suggesting Sr–C formation. No HBE components were observed in the Sr spectra from the TiO2 terminated surface. Valence band XPS spectra reveal the presence of surface states and Ti 3d sub-band states.