MoS2/MX2 heterobilayers: bandgap engineering via tensile strain or external electrical field

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作者：

N Lu，H Guo，L Li，J Dai，L Wang，WN Mei，X Wu，XC Zeng

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摘要：

We have performed a comprehensive first-principles study of the electronic and magnetic properties of two-dimensional (2D) transition-metal dichalcogenide (TMD) heterobilayers MX2/MoS2(M = Mo, Cr, W, Fe, V; X = S, Se). For M = Mo, Cr, W; X = S, Se, all heterobilayers show semiconducting characteristics with an indirect bandgap with the exception of the WSe2/MoS2heterobilayer which retains the direct-bandgap character of the constituent monolayer. For M = Fe, V; X = S, Se, the MX2/MoS2heterobilayers exhibit metallic characters. Particular attention of this study has been focused on engineering the bandgap of the TMD heterobilayer materialsviaapplication of either a tensile strain or an external electric field. We find that with increasing either the biaxial or uniaxial tensile strain, the MX2/MoS2(M = Mo, Cr, W; X = S, Se) heterobilayers can undergo a semiconductor-to-metal transition. For the WSe2/MoS2heterobilayer, a direct-to-indirect bandgap transition may occur beyond a critical biaxial or uniaxial strain. For M (=Fe, V) and X (=S, Se), the magnetic moments of both metal and chalcogen atoms are enhanced when the MX2/MoS2heterobilayers are under a biaxial tensile strain. Moreover, the bandgap of MX2/MoS2(M = Mo, Cr, W; X = S, Se) heterobilayers can be reduced by the vertical electric field. For two heterobilayers MSe2/MoS2(M = Mo, Cr), PBE calculations suggest that the indirect-to-direct bandgap transition may occur under an external electric field. The transition is attributed to the enhanced spontaneous polarization. The tunable bandgaps in general and possible indirect–direct bandgap transitions due to tensile strain or external electric field make the TMD heterobilayer materials a viable candidate for optoelectronic applications.

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关键词：

Theoretical or Mathematical/ ab initio calculations chromium compounds deformation energy gap interface magnetism iron compounds magnetic moments magnetic semiconductors metal-insulator transition molybdenum compounds monolayers tungsten compounds/ bandgap engineering external electrical field first-principles calculations electronic properties 2D transition-metal dichalcogenide heterobilayers semiconducting properties monolayer metallic characters biaxial tensile strain semiconductor-to-metal transition direct-to-indirect bandgap transition magnetic moments chalcogen atoms vertical electric field PBE calculations spontaneous polarization magnetic properties uniaxial tensile strain MoS 2-MoS 2 MoS 2-MoSe 2 MoS 2-CrS 2 MoS 2-CrSe 2 MoS 2-WS 2 MoS 2-WSe 2 MoS 2-FeS 2 MoS 2-FeSe 2/ A7320A Surface states, surface band structure, surface electron density of states A6220F Deformation and plasticity A8140L Deformation, plasticity and creep A7115A Ab initio calculations (condensed