Donor and acceptor-like self-doping by mechanically induced dislocations in bulk TiO2

Abstract

Dislocations have been recently introduced as a novel tool to tailor the conductivity of functional ceramics. However, tuning strategies suffer from poor insight into the structural complexity of dislocations and their networks. Here, we demonstrate that dislocations can be used to both enhance and reduce the overall conductivity in the same ceramic material. Accurate control of the arrangement of dislocations within the dislocation network enables tailoring TiO2 bulk samples to behave like being chemically modified either with an acceptor or donor dopant. Our approach combines ultra-high voltage electron microscopy, oxygen partial pressure, and temperature dependent electrical conductivity measurements combined with time-of-flight secondary ion mass spectrometry. This allows us to focus on mechanically tailored interaction of next neighbor dislocations and to differentiate between percolating conductive pathways and separated charge carrier zones. This seemingly simple approach purposefully tailors the conductivity of TiO2, opening new avenues to engineer functional ceramics beyond common chemical doping strategies.