Dr. Shelly Conroy is a Royal Society University Research Fellow Principal Investigator and Associate Prof in Functional Thin Films and Microscopy, specializing in in-situ TEM, electron energy loss spectroscopy, and thin-film growth of dielectric materials. She worked at Pacific Northwest National Laboratory as a permanent staff scientist before joining the University of Limerick as a Science Foundation Ireland Analog Devices Research Fellow (PI). Dr. Conroy holds a Ph.D. Eng in polar AlN thin film growth and in-situ TEM from Tyndall National Institute and University College Cork Ireland.

Dr. Conroy’s Royal Society grant ‘Improper Ferroelectric Domain Wall Engineering for Dynamic Electronics’ is focused on thin-film growth of the ferroelectric/ferroelastic boracites and in-situ 4DSTEM strain analysis. The project is in collaboration with the National Center for Electron Microscopy at Lawrence Berkeley National Laboratory and SuperSTEM the EPSRC National Research Facility for Advanced Electron Microscopy.

Dynamic ferroelectric domain wall topologies overturn the classical idea that our nanoelectronics need to consist of fixed components of hardware. To harness the true potential of domain wall-based electronics, we must take a step back from the device design level, and instead re-look at the subatomic internal properties. With recent advances in experimental characterization and theoretical calculation approaches, in the last 5 years reports of non-classic internal structures and functionalities within domain walls have become a common occurrence. As the region of interest is at the nanoscale and dynamic, it is essential for the physical characterization to be at this scale spatially and time resolved.

This presentation focuses on using the applied electric field of aberration corrected scanning transmission electron microscopy (STEM) probes to move domain walls, and thus investigate their dynamics while imaging at the subatomic scale. As the STEM probe can be controlled in terms of dose, probe size, direction and speed, a diverse set of experiments is possible without complicated sample preparation. Using a segmented STEM detector (or 4DSTEM CoM experimental set-up) any changes in deflection and thus the changes in polarisation for each domain, can also be investigated with controlled variants in applied field conditions. By controlling the incoming STEM probe direction, parallel domain walls could be moved around to form stable vertex junctions, thus switching from a neutral to charged state. Then in each frame by quantifying the atomic displacement per unit cell using our open-source python based TopoTEM software package, the local polarisation at these charged topologies can also be monitored. Finally, we will show how changes in band structure can be monitored via ultrahigh energy resolution electron energy loss spectroscopy (EELS) as the domain walls switch from neutral to charge states. By combining the local atomic resolution structure, strain, charge density and band structure measurements we can resolve all the measurable parameters of interest within domain walls and thus start unravelling the fundamental physics governing their formation, dynamics and resulting functionality.