Oral: Room Temperature Persistent Photoconductivity of KTaO₃ single crystals.

Persistent photoconductivity is a phenomenon in which the conductivity of a material increases upon light exposure and remains without the source of exciting illumination. Potassium tantalate, KTaO₃ (KTO), is a cubic perovskite semiconductor with a wide bandgap of 3.6 eV. This novel material is a subject of interest due to its possible applications in electronic and storage devices.

In this work, KTO crystals were annealed in a silica ampoule filled with hydrogen gas and a piece of tantalum wire, creating an oxygen-poor environment and thus oxygen vacancies. IR spectroscopy showed a transmission threshold at 340 nm, free carrier absorption, and a reduction of the hydrogen peaks post-anneal treatment. After exposing the crystals to a 340 nm light-emitting diode (LED), evidence of persistent photoconductivity (PPC) was observed. Hall effect measurements indicate an increase in n-type conductivity of three orders of magnitude that lasts for several weeks. The PPC effect can be reversed by an open-air anneal and re-induced by repeating the irradiation.