Executive Summary : | Ferroelectric materials offer promising prospects for next-generation devices, including non-volatile memories, field-effect transistors, and sensors. However, conventional ferroelectric materials face challenges in maintaining their ferroelectric properties when scaled down to the nanometer range due to the depolarization field, hindering the miniaturization of ferroelectric devices. Nevertheless, a recent breakthrough has emerged with the discovery of stable ferroelectricity in a two-dimensional (2D) material known as In2Se3, even at ultrathin scales. In2Se3 exhibits strong in-plane covalent bonds and weak out-of-plane van der Waal interaction, allowing for its exfoliation into single layers while retaining ferroelectric properties at elevated temperatures. Furthermore, In2Se3 is a III-VI compound semiconductor with a direct bandgap, positioning it as a prime candidate for low-power electronics. Despite these advancements, there remains a lack of comprehensive understanding regarding the structures and mechanisms underlying ferroelectric switching in 2D In2Se3. Additionally, there is a need for comprehensive studies exploring different types of ferroelectric devices, such as ferroelectric channel transistors, ferroelectric field-effect transistors, and ferroelectric memristors. Moreover, the coupled in-plane and out-of-plane polarization in In2Se3 suggests the potential for realizing low-energy flat bands at large twist angles, making it an ideal candidate for moire materials that exhibit a range of phenomena like exotic superconductivity and correlated insulating phases. However, the realization of moire superlattices in In2Se3 at large twist angles presents challenges due to limited reported cases achieved with small twist angles and low yields. Additionally, correlated states in moire materials strongly depend on the twist angle. Therefore, achieving moire effects in In2Se3 at large twist angles would be a significant leap forward in the study of moire materials, combining additional functionality with ferroelectricity. This proposal aims to demonstrate the existence of flat bands at large twist angles in twisted In2Se3 moire systems and unravel the origin of in-plane and out-of-plane ferroelectricity in few-layer In2Se3. The findings will not only contribute to the understanding of ferroelectric and moire systems but also advance the development of moire materials, ferroelectric memories, and meet the demands of integrated circuit miniaturization. |