Understanding the dynamic behaviour and evolution of electric domains in BTO under applied electric field using in situ TEM

• Main Author: Li, Patrick Wen Feng
• Other Authors: Lam Yeng Ming
• Format: Thesis-Master by Research
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Chemistry; Engineering; Physics; Transmission electron microscopy; In situ TEM; Focused ion beam; Scanning electron microscopy; FIB-SEM; Barium titanate; Ferroelectricity
• Online Access: https://hdl.handle.net/10356/180284
• Institution: Nanyang Technological University

Barium titanate, BiTaO3 (BTO), is a highly researched material due to being one of the oldest ferroelectric materials and also its remarkable properties. Its ferroelectric properties give rise to applications in devices such as ferroelectric random-access memories, capacitors and more. To understand more about the dynamics and interactions within BTO in order to improve its functionality, the ferroelectric domains in the material have to be studied. However, these domains are on the nanoscale and need a technique such as transmission electron microscopy (TEM) to image them. Inside the TEM, these domains can be imaged and influenced in situ using an applied external electric field. This requires special equipment and training. Furthermore, BTO has four main temperature dependent crystal structures, three of which are ferroelectric. Two of the ferroelectric phases exist below room temperature and therefore will require cooling to reach. In summary, the equipment required to fully explore the different ferroelectric domains associated with each phase of BTO will need the ability to apply an external electric bias whilst also cooling the sample down to below room temperature ranges. Nanyang Technological University (NTU) has one such TEM specimen holder capable for such experiments. Unfortunately, it is proprietary and lacks any sort of consistent workflow to produce the suitable specimen. In this work, not only is a consistent workflow for these experiments created but also a new and more efficient design for the micro electromechanical systems (MEMS) chips is devised from the experience of preparing the specimens for such experiments. Finally, the workflow is successfully carried on the aforementioned BTO material, showing the ability to cool, heat and apply and electrical bias. Thus, proving the success of the workflow and demonstrating the capabilities and potential of this technique.