Manipulation of native point defect behavior in rutile TiO2 via surfaces and extended defects

Abstract

Semiconductor surfaces offer efficient pathways for exchanging native point defects with the underlying bulk. For rutile TiO₂(1 1 0), isotopic self-diffusion studies of oxygen have suggested that the surface may act as a source for O_i while simultaneously acting as a sink for titanium interstitials Ti_i. Through self-diffusion measurements with labeled Ti as well as O, the present work develops a more complete picture of the diffusion-reaction network involving O_i and Ti_i, complete with the surface acting as a source for whichever elements are available from the gas phase and a sink for elements that are not. The picture points to the importance of extended defects such as platelets and crystallographic shear planes as reservoirs of O_i and Ti_i, acting as net sources or sinks of these species depending upon specific conditions. The results exemplify the combined roles of surfaces and extended defects in regulating point defect behavior even in macroscopic metal oxide crystals, and point to specific strategies for manipulating that behavior intentionally.