X-ray photoelectron spectroscopic and ion scattering study of the SrTiO 3(0 0 1) surface

Abstract

The chemical and structural properties of several as-received (unspecified and TiO 2 terminated) SrTiO 3(0 0 1) surfaces have been analyzed prior to and following UHV and O 2 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 TiO 2 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 TiO 2 terminated surface reconstructed following O 2 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 TiO 2 terminated surface. Valence band XPS spectra reveal the presence of surface states and Ti 3d sub-band states.