Magnetic two-dimensional (2D) van der Waals (vdWs) materials are receiving increased attention due to their exceptional properties and potential applications in spintronic devices. Because exchange bias and spin–orbit torque (SOT)-driven magnetization switching are basic ingredients for spintronic devices, it is of pivotal importance to demonstrate these effects in the 2D vdWs material-based magnetic heterostructures. In this work, we employ a vacuum exfoliation approach to fabricate Fe₃GeTe₂ (FGT)/Ir₂₂Mn₇₈ (IrMn) and FGT/Pt bilayers, which have high-quality interfaces. An out-of-plane exchange bias of up to 895 Oe is obtained in the former bilayer, which is larger than that of the previously studied bilayers. In the latter bilayer, the SOT switching of the perpendicularly magnetized FGT is realized, which exhibits higher SOT-driven switching performance compared to the previously studied FGT/Pt bilayer devices with interfacial oxidation. The minimum of SOT efficiency is
Electron-electron interactions play an important role in graphene and related systems and can induce exotic quantum states, especially in a stacked bilayer with a small twist angle. For bilayer graphene where the two layers are twisted by the ‘magic angle’, flat band and strong many-body effects lead to correlated insulating states and superconductivity. In contrast to monolayer graphene, the band structure of untwisted bilayer graphene can be further tuned by a displacement field, providing an extra degree of freedom to control the flat band that should appear when two bilayers are stacked on top of each other. Here, we report the discovery and characterization of displacement field-tunable electronic phases in twisted double bilayer graphene. We observe insulating states at a half-filled conduction band in an intermediate range of displacement fields. Furthermore, the resistance gap in the correlated insulator increases with respect to the inplane magnetic fields and we find that
Two-dimensional molybdenum disulfide (MoS₂) is an emergent semiconductor with great potential in next-generation scaled-up electronics, but the production of high-quality monolayer MoS₂ wafers still remains a challenge. Here, we report an epitaxy route toward 4 in. monolayer MoS₂ wafers with highly oriented and large domains on sapphire. Benefiting from a multisource design for our chemical vapor deposition setup and the optimization of the growth process, we successfully realized material uniformity across the entire 4 in. wafer and greater than 100 μm domain size on average. These monolayers exhibit the best electronic quality ever reported, as evidenced from our spectroscopic and transport characterizations. Our work moves a step closer to practical applications of monolayer MoS₂.
Atomically thin molybdenum disulfide (MoS₂) is a promising semiconductor material for integrated flexible electronics due to its excellent mechanical, optical and electronic properties. However, the fabrication of large-scale MoS₂-based flexible integrated circuits with high device density and performance remains a challenge. Here, we report the fabrication of transparent MoS₂-based transistors and logic circuits on flexible substrates using four-inch wafer-scale MoS₂ monolayers. Our approach uses a modified chemical vapour deposition process to grow wafer-scale monolayers with large grain sizes and gold/titanium/ gold electrodes to create a contact resistance as low as 2.9 kΩ μm−1. The field-effect transistors are fabricated with a high device density (1,518 transistors per cm2) and yield (97%), and exhibit high on/off ratios (1010), current densities (~35 μA μm−1), mobilities (~55 cm2 V−1 s−1) and flexibility. We also use the approach to create various flexible int
Twist angle between adjacent layers of two-dimensional (2D) layered materials provides an exotic degree of freedom to enable various fascinating phenomena, which opens a research direction-twistronics. To realize the practical applications of twistronics, it is of the utmost importance to control the interlayer twist angle on large scales. In this work, we report the precise control of interlayer twist angle in centimeter-scale stacked multilayer MoS₂ homostructures via the combination of wafer-scale highly-oriented monolayer MoS₂ growth techniques and a water-assisted transfer method. We confirm that the twist angle can continuously change the indirect bandgap of centimeter-scale stacked multilayer MoS₂ homostructures, which is indicated by the photoluminescence peak shift. Furthermore, we demonstrate that the stack structure can affect the electrical properties of MoS₂ homostructures, where 30° twist angle yields higher electron mobility. Our work provides a firm basis for th
Van der Waals heterostructures of transition metal dichalcogenides with interlayer coupling offer an exotic platform to realize fascinating phenomena. Due to the type II band alignment of these heterostructures, electrons and holes are separated into different layers. The localized electrons induced doping in one layer, in principle, would lift the Fermi level to cross the spin-polarized upper conduction band and lead to strong manipulation of valley magnetic response. Here, we report the significantly enhanced valley Zeeman splitting and magnetic tuning of polarization for the direct optical transition of MoS₂ in MoS₂/WS₂ heterostructures. Such strong enhancement of valley magnetic response in MoS₂ stems from the change of the spin-valley degeneracy from 2 to 4 and strong many-body Coulomb interactions induced by ultrafast charge transfer. Moreover, the magnetic splitting can be tuned monotonically by laser power, providing an effective all-optical route towards engineering and
Monolayer MoS₂ is an emerging two-dimensional (2D) semiconductor with promise on novel electronics and optoelectronics. Standard micro-fabrication techniques such as lithography and etching are usually involved to pattern such materials for devices but usually face great challenges on yielding clean structures without edge, surface and interface contaminations induced during the fabrication process. Here a direct writing patterning approach for wafer-scale MoS₂ monolayers is reported. By controllable scratching by a tip, wafer-scale monolayer MoS₂ films on various substrates are patterned in an ultra-clean manner. MoS₂ field effect transistors fabricated from this scratching lithography show excellent performances, evidenced from a room-temperature on-off ratio exceeding 1010 and a high field-effect mobility of 50.7 cm2 V−1 s−1, due to the cleanness of as-fabricated devices. Such scratching approach can be also applied to other 2D materials, thus providing an alternate patte
二维材料是一种具有单个或几个原子层厚度的新型晶体材料，其二维层内的原子之间存在着牢固的共价键，而层与层之间通常通过较弱的范德华力堆叠在一起。
支持二维材料蓬勃发展的重要因素是材料本身及其维度，与界面相关的独特物理特性和广阔的应用前景。高质量的二维原子晶体材料在探索新的物理现象以及进一步扩展其在微电子和光电子领域的应用方面发挥着重要作用。
从最初的微/纳米电子器件和光电器件，到自旋电子器件和谷极化器件，再到后来的光/电催化剂，锂电池，太阳能电池等，预计二维材料将被广泛用于新一代电子信息和能源存储领域。
二维材料的出现，为探索各种功能材料体系打开了新的广阔空间，为突破传统半导体器件在性能上的各种限制提供了重要的新途径。在绝缘衬底上制备高质量、晶圆级大面积单层薄膜对实现二维材料在大规模集成半导体电子器件和光电器件领域的应用尤为关键。其中材料的均匀度与晶体取向的单一性对于半导体器件的性能优化至关重要，进而决定器件大规模应用实现。
此外，二维材料还可以用于构筑二维范德华异质结。在这种结构中，范德华力构筑的界面在设计和调控材料的物理特性，实现相关器件的应用中起着关键作用。二维范德华异质结结合了两种或多种二维材料的特点，极大地丰富了二维材料的特性，并且可以轻松生产出自然界中不存在但可以针对性能进行设计的人造材料。近年来，采用转角层间堆垛的方法，在二维材料中形成稳定的摩尔超晶格，成为了调控二维材料物性的崭新维度。
该方法成功地在转角石墨烯中实现了多种奇异物态，并成为当代凝聚态物理和材料科学发展的又一关键领域。大力推动对以转角石墨烯为代表的摩尔超晶格体系的研究，对推动我国微电子和信息技术的发展具有重要意义。
团队与捷克理工大学Tomas Polcar团队合作，针对大晶格失配范德华异质界面的超滑现象进行了系统地研究。该工作在实验上探究了一类大晶格失配范德华异质界面中的各向同性超滑现象，为设计和应用超滑界面提供了新思路。工作同时表明，在界面超滑体系中要尽量避免晶格边界、界面台阶及位错等结构缺陷，从而降低其对结构超滑的负作用。
恭喜团队博士后李娜成功入选2021年度博士后创新人才支持计划。“博士后创新人才支持计划”简称“博新计划”，是人力资源和社会保障部、全国博士后管委会新设立的一项青年拔尖人才支持
此奖项是为表彰献身科学事业、潜心钻研学术、长期从事纳米科学和纳米技术前沿领域研究并做出杰出贡献的优秀青年科学家，由《纳米研究》编辑部设立的年度纳米研究青年科学家奖(NR45 Young Innovators Award)。候选人由《纳米研究》编委会中一线科学家推荐、由奖项委员会严格评选，最终获奖人为有望实现重大科研突破、在该领域具有潜力做出巨大贡献、现已取得杰出成就的青年科学家。NR45奖每年按照科研领域授予最多45位年龄不超过45岁的优秀青年科研人员。
张广宇研究员于2020年12月接受科学新闻记者采访，采访中，张广宇研究员表示他已经在二维材料领域耕耘了整整12年，源于兴趣，才驱动了高质量创新研究。
二维材料团队
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