Ma Suping, Li Guanghao, Li Zhuo, Zhang Yawen, Lu Haolin, Gao Zhansheng, Wu Jinxiong, Long Guankui, Huang Yi
National Institute for Advanced Materials, Tianjin Key Laboratory of Metal and Molecule Based Material Chemistry, Key Laboratory of Functional Polymer Materials, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Materials Science and Engineering, Nankai University, Tianjin300350, People's Republic of China.
School of Materials Science and Engineering, National Institute for Advanced Materials, Renewable Energy Conversion and Storage Center (RECAST), Nankai University, Tianjin300350, People's Republic of China.
ACS Nano. 2022 Nov 22;16(11):19439-19450. doi: 10.1021/acsnano.2c09143. Epub 2022 Oct 26.
A 2D van der Waals (vdW) magnet can get rid of the constraints of lattice matching and compatibility and then create a variety of vdW heterostructures, which provides a opportunity for spintronic devices. However, the ability to reliably exfoliate large, high-quality vdW ferromagnetic FeGeTe (FGT) nanoflakes in scaled-up production is severely limited. Herein, an efficient and stable three-stage sonication-assisted liquid-phase exfoliation was developed for mass preparation of high-structural-integrity few- and single-layer FGT nanoflakes with a greatly enhanced intrinsic exchange bias. The three stages include slicing crystals, weakening interlayer vdW forces, and using ultrasonic cavitation. The highest yield of FGT nanoflakes is 22.3 wt % with single layers accounting for 6%. The size is controllable, and several micrometers, tens of micrometers, and a maximum of 103 μm are available. The 200 mg level output has overcome the limitations of mechanical exfoliation and molecular beam epitaxy in economically amplificated production. An intrinsic exchange bias is observed in the restacked nanoflakes due to the magnetic proximity on the interface of the FGT/natural surface oxide layer. The material reaches 578 Oe (2 K) and 2300 Oe after further oxidation, at least 250% higher than other precisely tailored vdW magnetic heterostructures. In addition, the unusual semiconductivity of the liquid-phase exfoliated FGT nanoflakes is reported. This work skillfully utilizes oxidation to enhance the potential of FGT for large-scale spintronics, optoelectronics, efficient data storage, and various extended applications, and it is beneficial for exfoliating other promising magnetic vdW materials.
二维范德华（vdW）磁体可以摆脱晶格匹配和兼容性的限制，进而创建各种vdW异质结构，这为自旋电子器件提供了契机。然而，在规模化生产中可靠地剥离出大尺寸、高质量的vdW铁磁体FeGeTe（FGT）纳米片的能力受到严重限制。在此，开发了一种高效且稳定的三阶段超声辅助液相剥离法，用于大规模制备具有极大增强的固有交换偏置的高结构完整性的少层和单层FGT纳米片。这三个阶段包括切割晶体、削弱层间vdW力以及利用超声空化。FGT纳米片的最高产率为22.3 wt%，其中单层占6%。尺寸可控，有几微米、几十微米，最大可达103μm。200mg级别的产量克服了机械剥离和分子束外延在经济放大生产方面的局限性。由于FGT/天然表面氧化层界面上的磁近邻效应，在重新堆叠的纳米片中观察到了固有交换偏置。该材料在进一步氧化后达到578 Oe（2 K）和2300 Oe，比其他精确定制的vdW磁性异质结构至少高250%。此外，还报道了液相剥离的FGT纳米片具有异常的半导体特性。这项工作巧妙地利用氧化来增强FGT在大规模自旋电子学、光电子学、高效数据存储及各种扩展应用方面的潜力，并且有利于剥离其他有前景的磁性vdW材料。
