Van der Waals epitaxial growth of air-stable CrSe2 nanosheets with thickness-tunable magnetic order

Van der Waals epitaxial growth of air-stable CrSe2 nanosheets with thickness-tunable magnetic order

by | Mar 1, 2021 | 2021, Highlighted, 本组论文

Nature Materials 20, 818–825 (2021)

Bo Li#, Zhong Wan#, Cong Wang#, Peng Chen#, Bevin Huang, Xing Cheng, Qi Qian, Jia Li, Zhengwei Zhang, Guangzhuang Sun, Bei Zhao, Huifang Ma, Ruixia Wu, Zhongming Wei, Yuan Liu, Lei Liao, Yu Ye, Yu Huang, Xiaodong Xu, Xidong Duan*, Wei Ji* & Xiangfeng Duan*

Abstract

The discovery of intrinsic ferromagnetism in ultrathin two-dimensional van der Waals crystals opens up exciting prospects for exploring magnetism in the ultimate two-dimensional limit. Here, we show that environmentally stable CrSe2 nanosheets can be readily grown on a dangling-bond-free WSe2 substrate with systematically tunable thickness down to the monolayer limit. These CrSe2/WSe2 heterostructures display high-quality van der Waals interfaces with well-resolved moiré superlattices and ferromagnetic behaviour. We find no apparent change in surface roughness or magnetic properties after months of exposure in air. Our calculations suggest that charge transfer from the WSe2 substrate and interlayer coupling within CrSe2 play a critical role in the magnetic order in few-layer CrSe2 nanosheets. The highly controllable growth of environmentally stable CrSe2 nanosheets with tunable thickness defines a robust two-dimensional magnet for fundamental studies and potential applications in magnetoelectronic and spintronic devices.

A Gd@C82 single-molecule electret

A Gd@C82 single-molecule electret

by | Oct 12, 2020 | 2016-2020, Highlighted, 本组论文

Nat. Nanotechnol. 15, 1019–1024 (2020)

Kangkang Zhang, Cong Wang, Minhao Zhang, Zhanbin Bai, Fang-Fang Xie, Yuan-Zhi Tan, Yilv Guo, Kuo-Juei Hu, Lu Cao, Shuai Zhang, Xuecou Tu, Danfeng Pan, Lin Kang, Jian Chen, Peiheng Wu, Xuefeng Wang, Jinlan Wang, Junming Liu, You Song, Guanghou Wang, Fengqi Song, Wei Ji, Su-Yuan Xie, Su-Fei Shi, Mark A Reed & Baigeng Wang

Abstract

Electrets are dielectric materials that have a quasi-permanent dipole polarization. A single-molecule electret is a long-sought-after nanoscale component because it can lead to miniaturized non-volatile memory storage devices. The signature of a single-molecule electret is the switching between two electric dipole states by an external electric field. The existence of these electrets has remained controversial because of the poor electric dipole stability in single molecules. Here we report the observation of a gate-controlled switching between two electronic states in Gd@C82. The encapsulated Gd atom forms a charged centre that sets up two single-electron transport channels. A gate voltage of ±11 V (corresponding to a coercive field of ~50 mV Å–1) switches the system between the two transport channels with a ferroelectricity-like hysteresis loop. Using density functional theory, we assign the two states to two different permanent electrical dipole orientations generated from the Gd atom being trapped at two different sites inside the C82 cage. The two dipole states are separated by a transition energy barrier of 11 meV. The conductance switching is then attributed to the electric-field-driven reorientation of the individual dipole, as the coercive field provides the necessary energy to overcome the transition barrier.