Abstract
It is now well-established that boundaries separating tetragonal-like (T) and rhombohedral-like (R) phases in BiFeO3
thin films can show enhanced electrical conductivity. However, the
origin of this conductivity remains elusive. Here, we study mixed-phase
BiFeO3 thin films, where local populations of T
and R can be readily altered using stress and electric fields. We
observe that phase boundary electrical conductivity in regions which
have undergone stress-writing is significantly greater than in the
virgin microstructure. We use high-end electron microscopy techniques to
identify key differences between the R–T boundaries present in
stress-written and as-grown microstructures, to gain a better
understanding of the mechanism responsible for electrical conduction. We
find that point defects (and associated mixed valence states) are
present in both electrically conducting and non-conducting regions;
crucially, in both cases, the spatial distribution of defects is
relatively homogeneous: there is no evidence of phase boundary defect
aggregation. Atomic resolution imaging reveals that the only significant
difference between non-conducting and conducting boundaries is the
elastic distortion evident – detailed analysis of localised
crystallography shows that the strain accommodation across the R–T
boundaries is much more extensive in stress-written than in as-grown
microstructures; this has a substantial effect on the straightening of
local bonds within regions seen to electrically conduct. This work
therefore offers distinct evidence that the elastic distortion is more
important than point defect accumulation in determining the phase
boundary conduction properties in mixed-phase BiFeO3.
Original language | English |
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Pages (from-to) | 27954-27960 |
Number of pages | 7 |
Journal | RSC Advances |
Volume | 10 |
Issue number | 47 |
Early online date | 27 Jul 2020 |
DOIs | |
Publication status | E-pub ahead of print - 27 Jul 2020 |