Persistent photoconductivity in barium titanate

Barium titanate is an oxide perovskite that is known for its ferro- and piezoelectric properties. Single crystal BaTiO₃ was annealed under a flowing atmosphere of humid hydrogen and systematically exposed to a series of visible-region LEDs while simultaneously taking IR spectra. Persistent photoconductivity was observed at room temperature with a factor of two change in electrical resistance and a dramatic increase in absorbance in the mid-IR. Some optical and electrical recovery was observed in the two days following exposure to the final LED. The onset of the phenomenon was observed to be approximately 2.9 eV, which is consistent with previous experiments using strontium titanate. The observation of room temperature persistent photoconductivity in a second material suggests the phenomenon is general, not restricted uniquely to strontium titanate. Furthermore, the combination of ferroelectricity, piezoelectricity, and persistent photoconductivity could lead to the creation of novel devices.