Hydrogen : a metastable donor in TiO₂ single crystals

Abstract

The properties of TiO₂ (110) single crystals are greatly changed after hydrogen is doped into them through electrochemical hydrogen charging, in which the crystals have been placed in 0.01M NaOH solution to deposit hydrogen on their electrodes through the electrolysis of water. The changes in properties, including great increases in leakage current, strong dielectric dispersions over 10²-10[sup 6] Hz, and a strong aging phenomenon suggest that hydrogen is a donor in TiO₂ while ionized hydrogen is not bound to an oxygen site by a strong O-H bond. This behavior of hydrogen, which can be characterized as a metastable donor, is different from the usual donor behavior of hydrogen in oxides and should be interesting for a better understanding of the behavior of hydrogen in oxides.