Department of Materials Science and Engineering, Izmir Institute of Technology, 35430, Izmir, Turkey.
Phys Chem Chem Phys. 2018 Jun 27;20(25):17380-17386. doi: 10.1039/c8cp02802h.
Motivated by the recent successful synthesis of Janus type single layers of transition metal dichalcogenides, we investigate the stability, vibrational and electronic properties of the Janus single layer structure of WSSe and its bilayers by means of density functional theory. The structural and vibrational analysis show that the Janus single layer of WSSe forms a dynamically stable structure in the 2H phase. Owing to its non-centrosymmetric structure, the Janus WSSe single layer has two in-plane (E) and two out-of-plane (A) Raman active phonon modes. The eigen-frequencies of the prominent Raman active modes are calculated to be 277 (A) and 322 (E) cm-1. Similar to single layer WS2 and WSe2, Janus WSSe is a direct band gap semiconductor that has two electronically different faces. In addition, the possible bilayer stacking orders of the Janus WSSe single layers are investigated. It is found that there are 3 stacking types of bilayer Janus WSSe and each stacking type has distinctive Raman characteristics in its vibrational spectrum. Our results show that thanks to the vibrational characteristics, which stem from the distinctive interlayer interactions at different sides, the stability and stacking types of the bilayer of WSSe Janus structure can be monitored.
受最近成功合成 Janus 型单层过渡金属二卤化物的启发，我们采用密度泛函理论研究了 WSSe 的 Janus 单层及其双层的稳定性、振动和电子性质。结构和振动分析表明，WSSe 的 Janus 单层在 2H 相中形成了一个动力学稳定的结构。由于其非中心对称结构，Janus WSSe 单层有两个面内（E）和两个面外（A）拉曼活性声子模式。突出的拉曼活性模式的本征频率计算为 277（A）和 322（E）cm-1。与单层 WS2 和 WSe2 类似，Janus WSSe 是一种直接带隙半导体，它有两个电子不同的面。此外，还研究了 Janus WSSe 单层的可能双层堆叠顺序。结果发现，双层 Janus WSSe 有 3 种堆叠类型，每种堆叠类型在其振动光谱中都有独特的拉曼特征。我们的结果表明，由于振动特性源于不同侧的独特层间相互作用，因此可以监测 WSSe Janus 结构的双层的稳定性和堆叠类型。
