Abstract
In this computational work based on density functional theory we study the electronic and electron transport properties of asymmetric multi-layer MoSSe junctions, known as Janus junctions. Focusing on 4-layer systems, we investigate the influence of electric field, electrostatic doping, strain, and interlayer stacking on the electronic structure. We discover that a metal to semiconductor transition can be induced by an out-of-plane electric field. The critical electric field for such a transition can be reduced by in-plane biaxial compressive strain. Due to an intrinsic electric field, a 4-layer MoSSe can rectify out-of-plane electric current. The rectifying ratio reaches 34.1 in a model junction Zr/4-layer MoSSe/Zr. This ratio can be further enhanced by increasing the number of MoSSe layers. In addition, we show a drastic sudden vertical compression of 4-layer MoSSe due to in-plane biaxial tensile strain, indicating a second phase transition. Furthermore, an odd-even effect on electron transmission at the Fermi energy for Zr/$n$-layer MoSSe/Zr junctions with $n=1, \, 2,\, 3, \,\dots,\, 10$ is observed. These findings reveal the richness of physics in this asymmetric system and strongly suggest that the properties of 4-layer MoSSe are highly tunable, thus providing a guide to future experiments relating materials research and nanoelectronics.
Highlights
Two-dimensional (2D) transition-metal dichalcogenides (TMDs) have potential applications in electronics/ optoelectronics [1,2] due to the presence of a direct band gap and sufficiently high mobility
III B, we show a metal-to-semiconductor transition in four-layer MoSSe induced by an out-of-plane external electric field
We examine how the critical electric field for the metal-to-semiconductor transition is affected by in-plane biaxial strain in Sec
Summary
Two-dimensional (2D) transition-metal dichalcogenides (TMDs) have potential applications in electronics/ optoelectronics [1,2] due to the presence of a direct band gap and sufficiently high mobility. Since it is the intrinsic electric field that causes the band gap closing in four-layer MoSSe, we wondered whether the band gap can reopen upon application of a compensating external electric field It is not a surprise, as we will show in the Results section (Sec. III), that a metal-to-semiconductor transition in four-layer MoSSe can be induced by an external out-of-plane electric field. Strain engineering of the electronic structure of heterogeneous bilayers MoSSe/WX2 (X = S, Se) [20] and MoSSe/WSSe [21] has been reported These discoveries motivate us to investigate the influence of in-plane biaxial strain on the critical electric field for the metal-to-semiconductor transition.
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