Multiple control of few-layer Janus MoSSe systems

In this computational work based on density functional theory, we study the electronic and electron transport properties of asymmetric multilayer MoSSe junctions, known as Janus junctions. Focusing on four-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 four-layer MoSSe can rectify out-of-plane electric current. The rectifying ratio reaches 34.1 in a model junction Zr/four-layer MoSSe/Zr and can be further enhanced by increasing the number of MoSSe layers. In addition, we show a drastic sudden vertical compression of four-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 $n=1,\phantom{\rule{0.16em}{0ex}}2,\phantom{\rule{0.16em}{0ex}}3,\ensuremath{\cdots},10$ is observed. These findings reveal the richness of physics in this asymmetric system, and they strongly suggest that the properties of four-layer MoSSe are highly tunable, thus providing a guide to future experiments relating to materials research and nanoelectronics.