2 research outputs found
Electromechanical Coupling among Edge Dislocations, Domain Walls, and Nanodomains in BiFeO<sub>3</sub> Revealed by Unit-Cell-Wise Strain and Polarization Maps
The
performance of ferroelectric devices, for example, the ferroelectric
field effect transistor, is reduced by the presence of crystal defects
such as edge dislocations. For example, it is well-known that edge
dislocations play a crucial role in the formation of ferroelectric
dead-layers at interfaces and hence finite size effects in ferroelectric
thin films. The detailed lattice structure including the relevant
electromechanical coupling mechanisms in close vicinity of the edge
dislocations is, however, not well-understood, which hampers device
optimization. Here, we investigate edge dislocations in ferroelectric
BiFeO<sub>3</sub> by means of spherical aberration-corrected scanning
transmission electron microscopy, a dedicated model-based structure
analysis, and phase field simulations. Unit-cell-wise resolved strain
and polarization profiles around edge dislocation reveal a wealth
of material states including polymorph nanodomains and multiple domain
walls characteristically pinned to the dislocation. We locally determine
the piezoelectric tensor and identify piezoelectric coupling as the
driving force for the observed phenomena, explaining, for example,
the orientation of the domain wall with respect to the edge dislocation.
Furthermore, an atomic model for the dislocation core is derived
Atomically Resolved Electronic States and Correlated Magnetic Order at Termination Engineered Complex Oxide Heterointerfaces
We
map electronic states, band gaps, and interface-bound charges
at termination-engineered BiFeO<sub>3</sub>/La<sub>0.7</sub>Sr<sub>0.3</sub>MnO<sub>3</sub> interfaces using atomically resolved cross-sectional
scanning tunneling microscopy. We identify a delicate interplay of
different correlated physical effects and relate these to the ferroelectric
and magnetic interface properties tuned by engineering the atomic
layer stacking sequence at the interfaces. This study highlights the
importance of a direct atomically resolved access to electronic interface
states for understanding the intriguing interface properties in complex
oxides