First principles-based study of monolayer WSSe and metal interface.

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MTech (Res); 2023; Electronic systems engineering

The semiconductor-metal interface is universal for any electron device. Two-dimensional semiconductors have the advantages of free dangling bonds and atomically flat surfaces, making them promising materials to substitute bulk-Silicon in next-generation transistors. However, two-dimensional material like transition metal dichalcogenides (TMD) makes highly resistive contact with metallic electrodes in electronic devices. A material with intrinsic dipole can optimize this effect. 2D Janus TMD MoSSe has structural symmetry like MoS2 and contains intrinsic dipoles that strongly modify the metal contact properties. A study of MoSSe with potential electrode materials has already seen where both the S and Se sides of MoSSe tend to have ohmic behavior. Along with MoSSe, WSSe is also available commercially for experimental efforts. The study of Janus WSSe material shows that it is an excellent photocatalyst for water splitting, and doped WSSe nanosheet is an efficient nanosensor. However, the electronic nature of this material’s interface with metals is not investigated yet. In this work, we have examined the interfacial properties of monolayer WSSe with bulk metal electrodes. Using density functional theory-based electronic structure calculation, we evaluated the structural and electronic properties of top contacts of WSSe with six metals Ag, Au, Ru, Pd, Pt, and Ti, considering both the S and Se sides. For the side contacts, we have selected three metals Ag, Au, and Ti, and investigated the electronic properties using ab-initio quantum transport simulation. Band structures of the Janus material contacted with Ru, Pd, Pt, and Ti are highly hybridized, leading to no Schottky barrier height in the vertical direction. However, with Au and Ag, Schottky contacts are formed in both lateral and vertical directions. The contacts' nature and barrier heights differ for Au and Ag. This investigation gives insight into the interfacial properties of Janus materials to use in future nanoelectronics devices.