Abstract
AbstractUPS studies (21.2 and 40.8 eV) are performed on BaTiO3 (001) and SrTiO3 (100) surfaces. In both the compounds there is an enhanced emission at the top of the valence band for hv = 21.2 eV, which cannot be explained with the existing theoretical bulk densities of states. From the results of angle‐dependent UPS measurements it is concluded that the top of the valence band emission is due to an oxygen surface state. This interpretation is supported by band structure calculations for thin films of BaTiO3 of Marathe et al. A band gap state at 0.9 eV (BaTiO3) and 1.2 eV (SrTiO3) below the bottom of the conduction band can be detected on oxygen deficient surfaces and is interpreted as arising from Ti3+ species. In UHV annealed surfaces are 1 × 1 ordered. They show a 2 × 2 or two mutually perpendicular 2 × 1 LEED patterns in case of a higher concentration of Ti3+—O‐vacancy defects due to defect ordering.
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