In-situ electron microscopy investigation of ferroelectric domain switching kinetics

Abstract

Due to their ultra-high piezoelectricity, pyroelectric properties, mechanical/electrical hysteresis properties and their possessing of non-volatile polarization states, ferroelectric materials have been used in various electronic devices, including various sensors, actuators, transducers, micromotors, and non-volatile memories. The mechanical, electrical, electromechanical, and thermoelectric properties are crucial factors for device applications of ferroelectric materials. These properties are particularly sensitive to the change of the embedded microscopic structures. Therefore, the mechanical and electrical characterisation of ferroelectric materials and the observation of their microstructural evolution under external stimuli are necessary for understanding their unique properties. However, this is not an easy task because of the difficulty of mechanical and electrical testing of nano/microscale materials. Various techniques have been used to investigate the mechanical and electrical behaviours of ferroelectric materials, among which the in-situ transmission electron microscopy is one of the most effective techniques. This thesis aims to combine state-of-the-art in-situ transmission electron microscopy techniques, the scanning transmission electron microscopy high-angle annular dark-field imaging technique, and phase-field modelling to investigate microstructural evolution in ferroelectric materials under different external stimuli. One of the ultimate goals of this research is to improve the performance of non-volatile ferroelectric memory devices.