Zi Yanbo, Li Chong, Niu Chunyao, Wang Fei, Cho Jun-Hyung, Jia Yu
International Laboratory for Quantum Functional Materials of Henan, School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001, People's Republic of China.
J Phys Condens Matter. 2019 Oct 30;31(43):435503. doi: 10.1088/1361-648X/ab330e. Epub 2019 Jul 17.
Alloying is a feasible and practical strategy to tune the electronic properties of 2D layered semiconductors. Here, based on first-principles calculations and analysis, we demonstrate band engineering through alloying W into a prototype MoS/MoSe heterostructure. Especially, when the W compositions x > 0.57 in Mo W S/MoSe, it exhibits remarkable and reversible direct- to indirect-gap transition. This is because for Mo W S/MoSe, the valence band maximum located at the K point originates from dominant MoSe, while the competing Γ state stems from the hybridization of both MoW S and MoSe, which is extremely sensitive to the interlayer coupling. Consequently, alloying in MoS layer induces direct- to indirect-gap transition and gap increase due to the weakened p-d coupling. We also observe that whether initial alloying in MoS or MoSe, the µMo-µW poor condition should always be used. Our findings are generally applicable and will significantly expand the band engineering to other alloying TMDs heterostructures.
合金化是一种调节二维层状半导体电子性质的可行且实用的策略。在此，基于第一性原理计算与分析，我们展示了通过将钨合金化到原型MoS/MoSe异质结构中来实现能带工程。特别地，当MoWS/MoSe中钨的成分x > 0.57时，它呈现出显著且可逆的直接带隙到间接带隙的转变。这是因为对于MoWS/MoSe，位于K点的价带最大值源于占主导的MoSe，而与之竞争的Γ态源于MoWS和MoSe两者的杂化，这对层间耦合极为敏感。因此，在MoS层中进行合金化会由于p-d耦合减弱而导致直接带隙到间接带隙的转变以及带隙增大。我们还观察到，无论最初是在MoS还是MoSe中进行合金化，都应始终采用µMo - µW较差的条件。我们的发现具有普遍适用性，将显著地把能带工程扩展到其他合金化的过渡金属二卤化物异质结构。
