In conventional electrides, excess electrons are localized in crystal voids to serve as anions. Most of these electrides are metallic and the metal cations are primarily from the s-block, d-block, or rare-earth elements. Here, we report a class of p-block metal-based electrides found in bilayer SnO and PbO, which are semiconducting and feature electride states in both the valence band (VB) and conduction band (CB), as referred to 2D “bipolar” electrides. These bilayers are hybrid electrides where excess electrons are localized in the interlayer region and hybridize with the orbitals of Sn atoms in the VB, exhibiting strong covalent-like interactions with neighboring metal atoms. Compared to previously studied hybrid electrides, the higher electronegativity of Sn and Pb enhances these covalent-like interactions, leading to largely enhanced semiconducting bandgap of up to 2.5 eV. Moreover, the CBM primarily arises from the overlap between metal states and interstitial charges, denoting a potential electride and forming a free-electron-like (FEL) state with small effective mass. This state offers high carrier mobilities for both electron and hole in bilayer SnO, suggesting its potential as a promising p-type semiconductor material.
近日，中国人民大学物理学院王聪副研究员、季威教授等与北京大学物理学院陈剑豪教授、北京大学谢心澄院士、刘阳研究员、叶堉研究员、山西大学韩拯教授等组成研究团队，采用第一性原理计算结合高精密电容测量的研究方法，在双层石墨烯与二维磁性材料CrOCl组成的异质结体系中观测到非易失态的磁电协同控制行为。相关研究成果以“Magnetic-Electrical Synergetic Control of Non-Volatile States in Bilayer Graphene-CrOCl Heterostructures”为题发表于《先进材料》（Advanced Materials）。
该工作通过高精密电容测量，结合第一性原理计算，揭示了BLG-CrOCl异质结构中磁电协同的调控机制，为表界面新物态的探索与利用提供了新的材料平台，有望实现具有非易失性存储功能的新型电子器件。相关研究成果于11月28日以“Magnetic-Electrical Synergetic Control of Non-Volatile States in Bilayer Graphene-CrOCl Heterostructures”为题在线发表在《先进材料》（Advanced Materials）上，物理学院副研究员王聪和北京大学物理学院量子材料科学中心博士后曹世民、博士研究生郑润杰为论文的共同第一作者。物理学院季威教授和北京大学陈剑豪教授、北京大学叶堉研究员、山西大学韩拯教授为论文的共同通讯作者。该工作的理论计算部分由人民大学完成，实验部分由合作单位完成。该工作得到了国家重点研发计划、国家自然科学基金、教育部、中国科学院和中国人民大学的资助。
Miniaturizing van der Waals (vdW) ferroelectric materials to atomic scales is essential for modern devices like nonvolatile memory and sensors. To unlock their full potential, their growth mechanisms, interface effects, and stabilization are preferably investigated, particularly for ultrathin 2D nanosheets with single-unit cell thickness. This study focuses on Bi2TeO5 (BTO) and utilizes precise control over growth kinetics at the nucleation temperature to create specific interfacial reconfiguration layers. Ultrathin BTO nanosheets with planar ferroelectricity at a single-unit cell thickness are successfully grown. Atomic-scale characterization reveals a disordered distribution of elements in the interfacial layer, which buffers strain from lattice mismatch. The theoretical calculations support these observations. Furthermore, this strategy also can be extended to the growth of a variety of 2D ternary oxide nanosheets. This work contributes to a better understanding of growth and stability mechanisms in 2D ultrathin nanosheets.
The structure and dynamics of ferroelectric domain walls are essential for polarization switching in ferroelectrics, which remains relatively unexplored in two-dimensional ferroelectric α-In2Se3. Interlayer interactions engineering via selecting the stacking order in two-dimensional materials allows modulation of ferroelectric properties. Here, we report stacking-dependent ferroelectric domain walls in 2H and 3R stacked α-In2Se3, elucidating the resistance switching mechanism in ferroelectric semiconductor-metal junction devices. In 3R α-In2Se3, the in-plane movement of out-of-plane ferroelectric domain walls yield a large hysteresis window. Conversely, 2H α-In2Se3 devices favor in-plane domain walls and out-of-plane domain wall motion, producing a small hysteresis window. High electric fields induce a ferro-paraelectric phase transition of In2Se3, where 3R In2Se3 reaches the transition through intralayer atomic gliding, while 2H In2Se3 undergoes a complex process comprising intralayer bond dissociation and interlayer bond reconstruction. Our findings demonstrate tunable ferroelectric properties via stacking configurations, offering an expanded dimension for material engineering in ferroelectric devices.
