Domain pattern formation is one of
the most common phenomena in nature and is a topic of immense interest in many
fields including materials science, physics, chemistry, and biology. The main
objective of this research program is to explore the basic sciences concerning
the thermodynamic stability of mesoscale polarization domain patterns and their
temporal evolution mechanisms during formation and subsequent switching in
ferroelectric nanostructures and heterostructures. This research employs the
phase-field method in combination of microelasticity and electrostatic
theories. An important aspect of the work involves the validation of
computational predictions through closely working together with experimental
collaborators performing microscopic analysis and observations of high-quality
ferroelectric films and nanostructures synthesized with atomic scale control.
The proposed research is motivated by the recent discoveries that new
thermodynamically stable mesoscale polar states might emerge from ferroelectric
heterostructures at the nanoscale. Specifically, the project will be focused on
the basic understanding of (1) the spatial length scales, temperature ranges,
and electromechanical conditions leading to the emergence of both transient and
stable novel polarization states containing vortex lattices in ferroelectric
superlattices; and (2) the switching and relaxation mechanisms of these
polarization vortex lattices under electrical and mechanical excitations and
the impact of polarization vortex formation and switching on other forms of
domain states such as magnetic spin configurations. The proposed research ideas
are conceived through recent discussions and close collaborations between the
PI’s group and a number of world-class experimental groups who use High
Resolution Transmission Electron Microscopy (HRTEM), in situ TEM with Scanning
Probe Microscopy (SPM), or Piezoresponse Force Microscopy (PFM) to characterize
the atomic/mesoscale domain states and dynamics in high-quality ferroelectric
thin films. Fundamental understandings of these exotic polarization domain
states will not only significantly advance the basic science on the stability
of mesoscale polar states and pattern evolution but also improve our ability to
control and engineer ferroelectric thin films and heterostructures for
potential applications in nanoscale electronic devices.