Shi Wenwu, Wang Zhiguo
School of Electronics Science and Engineering, Center for Public Security Technology, University of Electronic Science and Technology of China, Chengdu 610054, People's Republic of China.
J Phys Condens Matter. 2018 May 31;30(21):215301. doi: 10.1088/1361-648X/aabd59. Epub 2018 Apr 11.
The mechanical and electronic properties of Janus monolayer transition metal dichalcogenides MXY (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W; X/Y = S, Se, Te) were investigated using density functional theory. Results show that breaking the out-of-plane structural symmetry can be used to tune the electronic and mechanical behavior of monolayer transition metal dichalcogenides. The band gaps of monolayer WXY and MoXY are in the ranges of 0.16-1.91 and 0.94-1.69 eV, respectively. A semiconductor to metallic phase transition occurred in Janus monolayer MXY (M = Ti, Zr and Hf). The monolayers MXY (M = V, Nb, Ta and Cr) show metallic characteristics, which show no dependence on the structural symmetry breaking. The mechanical properties of MXY depended on the composition. Monolayer MXY (M = Mo, Ti, Zr, Hf and W) showed brittle characteristic, whereas monolayer CrXY and VXY are with ductile characteristic. The in-plane stiffness of pristine and Janus monolayer MXY are in the range between 22 and 158 N m. The tunable electronic and mechanical properties of these 2D materials would advance the development of ultra-sensitive detectors, nanogenerators, low-power electronics, and energy harvesting and electromechanical systems.
利用密度泛函理论研究了Janus单层过渡金属二硫属化物MXY（M = Ti、Zr、Hf、V、Nb、Ta、Cr、Mo、W；X/Y = S、Se、Te）的力学和电学性质。结果表明，打破面外结构对称性可用于调节单层过渡金属二硫属化物的电学和力学行为。单层WXY和MoXY的带隙分别在0.16 - 1.91 eV和0.94 - 1.69 eV范围内。Janus单层MXY（M = Ti、Zr和Hf）发生了从半导体到金属的相变。单层MXY（M = V、Nb、Ta和Cr）表现出金属特性，且不依赖于结构对称性的破坏。MXY的力学性质取决于其组成。单层MXY（M = Mo、Ti、Zr、Hf和W）表现出脆性特征，而单层CrXY和VXY具有韧性特征。原始和Janus单层MXY的面内刚度在22至158 N/m之间。这些二维材料的可调电学和力学性质将推动超灵敏探测器、纳米发电机、低功耗电子器件以及能量收集和机电系统的发展。
