Abstract
Ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS) and surface photovoltage spectroscopy (SPV) were used to determine the electronic structure near the bandgap of strontium bismuth tantalate (SBT) thin films. The UPS results for nearly stoichiometric SBT have been compared with tight-binding calculations. The spectra for bismuth-excess SBT indicate additional density of states (DOS) in the wide bandgap of the material. SPV studies indicate that the surface bandgap of bismuth-excess SBT is approximately 2 eV, which also confirms that there are additional surface states in the bandgap. These electronic structural data are used to explain the observed dependency of the electrical properties of the SBT/electrode junction on the bismuth concentration.
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