Nanoscale Ferroelectric Behavior from in situ Transmission Electron Microscopy

Speaker: 
Dr. Christopher T. Nelson
Event Date and Time: 
Fri, 2016-03-11 11:00 - 12:30
Location: 
Hennings 318
Local Contact: 
Leanne Ebbs / Andrea Damascelli
The defining characteristic of ferroelectricity is an electrically polar ground state which reorients under an applied electric field. This often results in many of their physical properties being strongly coupled to applied electrical fields with a corresponding hysteresis. This can be harnessed for obvious applications like nonvolatile memory elements (i.e. a replacement for flash) but in general the integration of such ferroelectric layers into nanocomposite systems is a straight forward route for designing extrinsic electrically tunable properties and studying the interfacial coupling thereof. The practical challenge for studying these systems is their low-dimensional geometry, necessitating very high spatial resolution characterization methods. Principle among these is transmission electron microscopy (TEM) which can resolve physical, chemical, and electrical structure down to atomic scales. In this talk I use TEM to explore both the steady-state and dynamic behavior of low-dimensional ferroelectric systems: epitaxial thin films of the prototypical oxide-ferroelectric materials PbZrxTi1-xO3 (PZT) and BiFeO3 (BFO). With TEM I show the dominant role of defects, particularly the ferroelectric interfaces, in dictating the ferroelectric layer properties including the switching behavior under in situ electrical excitation. In the end I show how tuning the ferroelectric layer confinement and the interface properties can generate a regular array of polar vortices, verifying theoretical predictions.
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