Professor Jeong You

The objective of this research project is to investigate ferroelectric responses of particles and films with the presence of various defects (e.g., crystalline defects, surfaces, interfaces, grains, etc.) and external fields (e.g., electric, electromagnetic, displacement, etc.). The work is performed using atomic-based continuum modeling to obtain ferroelectric stability, dielectric constants, hysteresis characteristics, time-dependent polarization decay, electromagnetic interference, and capacitance as a function of ferroelectric particle sizes, film thickness, operating temperature, and external fields. The atomic-based continuum modeling is based on the first-principles effective Hamiltonian which brings the detailed atomic-level ferroelectric information to large-scale continuum modeling. The main advantage of using the first-principles effective Hamiltonian is its simplicity in adding/removing individual effects (e.g. defects and external fields) by adding/removing the corresponding energy terms and by applying proper boundary conditions. Also, combined with molecular dynamics (MD) simulations, it enables the researchers to investigate the time-dependent properties of ferroelectric particles and films. The goal of this work is to have a fundamental understanding and comprehensive modeling of ferroelectric particles and films to provide a practical design tool for EMI shielding ferroelectric particles and negative capacitance.