Chemical Vapor Deposition of Bismuth Ferrite-Based Multiferroics for Device Applications

Epitaxial bismuth ferrite and substituted bismuth ferrite films have attracted significant attention due to their potential application in energy-efficient memory and logic devices. However, bismuth ferrite suffers from processing and application issues that can be addressed by improving and optimizing synthetic techniques. Chemical vapor deposition (CVD) is one of the suitable techniques for the high-volume manufacturing of bismuth ferrite. CVD can quickly produce conformal coating over a large area and still produce a superior-quality epitaxial layer. However, development in the CVD of bismuth ferrite has been slow and fragmentary. Very limited works have grown good-quality epitaxial bismuth ferrite films with robust ferroelectric properties using CVD. In this dissertation, a systematic study has been carried out to understand the problems underlying the synthesis of bismuth ferrite by CVD. Moreover, the crucial role of stoichiometry and lattice misfit strain in controlling ferroelectric switching has been elucidated, and the effect of vapor flow dynamics in controlling ferroelectric domain orientation and, subsequently, ferroelectric switching properties has been explained.The importance of the miniaturization of devices and the need for high-density, high-speed, and energy-efficient material systems for memory and logic applications has been mounting. Hence, understanding the application of the finite-size effect in CVD-grown bismuth ferrite is critical. The finite-size effect in CVD-grown bismuth ferrite has been validated by confirming the application of the Kay-Dunn law in the thickness scaling of switching voltage in the material. The insufficiency of thickness scaling to lower the switching voltage of the material to the desired range prompted us to explore the efficacy of samarium substitution in lowering the switching voltage of bismuth ferrite. A 50% reduction in switching voltage has been achieved by samarium substitution at the bismuth site.