Exploring the Interplay between Charge, Strain and Polarization in Ferroelectric Nanostructures

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NON-TECHNICAL DESCRIPTION: Ferroelectric materials are characterized by a spontaneous electric polarization, which can be reoriented with an applied electric field. The ability to form and manipulate nanoscale regions of uniform polarization (domains) makes ferroelectrics a promising candidate for future low-power electronic devices, particularly computer memories. When ferroelectrics is integrated with other materials, new and unique properties can emerge from interfaces where the two materials join. To understand these emergent properties, it is critical to characterize the atomic structure, chemical bonding, electric field, charge distribution at interfaces. Modern electron microscopy is capable of directly imaging the atomic structure, but the other properties must generally be inferred from these images. This project aims to develop new imaging methods that enable to determine all of these properties simultaneously. This will give a full picture of how and why unique properties can emerge at the interface and will inform the design and fabrication of future electronic devices. Although the research focuses on ferroelectrics, the microscopy techniques developed during and scientific knowledge gained from this project are broadly applicable to many different types of materials. The research is integrated with education and outreach activities to attract diverse junior scientists, including women and underrepresented minority groups, and will help train future leaders to address critical societal challenges.TECHNICAL DETAILS: This project leverages unique electron microscopy facilities at the Irvine Materials Research Institute where the PI serves as the director. This project aims to develop a novel four-dimensional scanning transmission electron microscopy (4D STEM) method that enables the measurement of atomic scale structure, local electric field, charge density, valence states, and polarization configuration in nanostructures and interfaces under different boundary conditions with atomic resolution. 4D STEM will also be combined with electron energy-loss spectroscopy and scanning probe microscopy in a unique multimodal approach to probe the atomic scale structure and properties of interfaces and to gain a fundamental understanding of the interaction between ferroelectric polarization, bound charge, epitaxial strain, charge screening, and structure reconstruction in ferroelectric interfaces under different conditions or surrounding topological defects in doped ferroelectric thin films. The detailed characterization of ferroelectric interfaces is required to gain deep insights into the atomic mechanisms of emergent phenomena at interfaces and provide guidance for engineering ferroelectric nanostructures with novel functionalities. The integration of this research with the education and training of students allows the results from this project to be disseminated to the diverse student populations on campus through coursework and independent studies for undergraduate students, as well as to high school students from diverse backgrounds through summer school programs, which promotes their interest in scientific research and education.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.