Abstract
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 MoS2/MoSe2 heterostructure. Especially, when the W compositions x > 0.57 in Mo1−xWxS2/MoSe2, it exhibits remarkable and reversible direct- to indirect-gap transition. This is because for Mo1−xWxS2/MoSe2, the valence band maximum located at the K point originates from dominant MoSe2, while the competing Γ state stems from the hybridization of both Mo1−xWxS2 and MoSe2, which is extremely sensitive to the interlayer coupling. Consequently, alloying in MoS2 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 MoS2 or MoSe2, 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.
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