Universal Mechanism of Band-Gap Engineering in Transition-Metal Dichalcogenides

Abstract

Two-dimensional (2D) van-der-Waals semiconductors have emerged as a class of materials with promising device characteristics owing to the intrinsic bandgap. For realistic applications, the ideal is to modify the bandgap in a controlled manner by a mechanism that can be generally applied to this class of materials. Here, we report the observation of a universally tunable bandgap in the family of bulk 2H transition metal dichalcogenides (TMDs) by in situ surface doping of Rb atoms. A series of angle-resolved photoemission spectra unexceptionally shows that the bandgap of TMDs at the zone corners is modulated in the range of 0.8 ~ 2.0 eV, which covers a wide spectral range from visible to near infrared, with a tendency from indirect to direct bandgap. A key clue to understand the mechanism of this bandgap engineering is provided by the spectroscopic signature of symmetry breaking and resultant spin splitting, which can be explained by the formation of 2D electric dipole layers within the surface bilayer of TMDs. Our results establish the surface Stark effect as a universal mechanism of bandgap engineering based on the strong 2D nature of van-der-Waals semiconductors.

References in corpus (10)

• Atomically thin MoS2: A new direct-gap semiconductor
• Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides
• Bandgap Engineering of Strained Monolayer and Bilayer MoS2
• Direct observation of the transition from indirect to direct bandgap in atomically thin epitaxial MoSe2
• Observation of tunable bandgap and anisotropic Dirac semimetal state in black phosphorus
• Novel High-Mobility Field-Effect Transistors Based on Transition Metal Dichalcogenides
• Direct observation of spin-polarised bulk bands in an inversion-symmetric semiconductor
• Electric Field Effects on Armchair MoS2 Nanoribbons
• First-principles theory of field-effect doping in transition-metal dichalcogenides: Structural properties, electronic structure, Hall coefficient, and electrical conductivity
• Transition-metal dichalcogenide bilayers: switching materials for spin- and valleytronic applications

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