Electrostatic drift effects on near-surface defect distribution in TiO2

The present work employs a combination of isotopic self-diffusion measurements and diffusion-drift modeling to identify a unique mechanism for defect accumulation in surface space-charge layers of TiO2. During oxygen gas-exchange experiments at elevated temperatures, rutile ( 110) surfaces inject charged oxygen interstitials into the underlying bulk. Yet near-surface electric fields attract the injected defects back toward the surface, retarding their diffusional migration and leading to longer residence times within the space-charge layers. The extended residence time enhances kick-in reactions, resulting in measureable pile-up of the isotope. Related effects probably generalize to other related semiconductors. (C) 2013 AIP Publishing LLC.