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Ferroelectricity in two-dimensional (2D) van der Waals (vdW) layers has revolutionized our understanding of the vdW layered coupling, and has been introduced in the domains of moiré superlattice patterns generated by interlayer twisting or sliding. In the smallest limit of thickness, untwisted and epitaxial vdW stacking layers exhibiting ferroelectricity would clearly serve as building blocks for realizing 2D devices with nonvolatile and reconfigurable functionalities. In this study, we grew ferroelectric hexagonal boron nitride (h-BN) films on single-crystal graphene synthesized on a SiC (0001) substrate using nitrogen plasma-assisted molecular beam epitaxy (PA-MBE). Systematic angle-resolved photoemission spectroscopy (ARPES) studies and first-principles calculations revealed that the epitaxial mono-, bi-, and tri-layer h-BN films exhibit layer-number-dependent µ-band dispersions due to an AB stacking sequence on a Bernal-stacked graphene substrate. Furthermore, our piezoelectric force microscopy (PFM) confirmed the coexistence of robust moiré and sliding ferroelectricity at the well-aligned h-BN/graphene heterojunction and in multilayered h-BN films, respectively. In principle, as-developed epitaxially ferroelectric h-BN is limited only by the size of the crystalline graphene substrate, thereby providing a versatile and scalable 2D ferroelectric platform with promising exotic physics and vdW device applications down to a few atomic layers.

Multiferroics-materials that exhibit coupled ferroic orders-are considered to be one of the most promising candidate material systems for next-generation spintronics, memory, low-power nanoelectronics and so on. To advance potential applications, approaches that lead to persistent and extremely fast functional property changes are in demand. Herein, it is revealed that the phase transition and the correlated ferroic orders in multiferroic BiFeO

Control of nonlinear dielectrics can be realized by mechanical bending., Strain-sensitive BaxSr1−xTiO3 perovskite systems are widely used because of their superior nonlinear dielectric behaviors. In this research, new heterostructures including paraelectric Ba0.5Sr0.5TiO3 (BSTO) and ferroelectric BaTiO3 (BTO) materials were epitaxially fabricated on flexible muscovite substrate. Through simple bending, the application of mechanical force can regulate the dielectric constant of BSTO from −77 to 36% and the channel current of BTO-based ferroelectric field effect transistor by two orders. The detailed mechanism was studied through the exploration of phase transition and determination of band structure. In addition, the phase-field simulations were implemented to provide theoretical support. This research opens a new avenue for mechanically controllable components based on high-quality oxide heteroepitaxy.

With the rise of Internet of Things, the presence of flexible devices has attracted significant attention owing to design flexibility. A ferroelectric field-effect transistor (FeFET), showing the advantages of high speed, nondestructive readout, and low-power consumption, plays a key role in next-generation technology. However, the performance of these devices is restricted since conventional flexible substrates show poor thermal stability to integrate traditional ferroelectric materials, limiting the compatibility of wearable devices. In this study, we adopt flexible muscovite mica as a substrate due to its good thermal properties and epitaxial integration ability. A flexible FeFET composed of oxide heteroepitaxy on muscovite is realized by combining an aluminum-doped zinc oxide film as the semiconductor channel layer and a Pb(Zr

Control of inhomogeneity in materials in order to avoid unexpected effects to the system remains a challenge. In this study, we seek to engineer inhomogeneity in materials and anticipate new properties. Through precise control of composition at the atomic scale, an electrical polarization is induced in the composition-graded LaAlO3–SrTiO3 solid solution epitaxially deposited on NdGaO3 substrates. By tailoring the direction of compositional gradient, the relationship between structure and electrical polarization is simulated via phase-field modeling and revealed by a combination of scanning transmission electron microscopy and scanning probe microscopy. The analysis of the results indicates that the induced polarization is due to the flexoelectric effect in the compositional gradient system. The results of this study provide a new pathway for obtaining a new material genome. Moreover, by a suitable design of the new genome, that is, by using different combinations of compositional gradient geometries, local conduction can be obtained and manipulated, providing a new approach to obtain the desired properties. Controlling the crystal quality of oxide thin films offers a way to engineer unexpected and novel material properties. Altering the distance between atoms in a crystalline film, by growing it on a different substrate for example, induces a physical strain and alters its properties. The characteristics of the film can also be altered by varying its composition. Researchers led by Chun-Gang Duan from the East China Normal University, Shanghai, China, and Ying-Hao Chu from National Chiao Tung University, Hsinchu, Taiwan, combined these two approaches by controlling the atomic strain in a combination of strontium titanate and lanthanum aluminate. The team’s computer model indicated that this allowed the creation of a material with so-called flexoelectric properties, where the electric and elastic properties are interlinked. This was verified using electron and piezoresponse force microscopy. In this work we report the electrical polarization can be induced by composition-graded LaAlO3-SrTiO3 solid solution. The analysis indicates that the induced polarization is attributed to the flexoelectric effect in the compositional gradient system. By a suitable combination of compositional gradient in geometry, a local conduction can be created and manipulated, delivering a new approach to obtain unveiled properties. delivering a new pathway to acquire material genome based on material inhomogeneity.