Engineering Optical and Electronic Properties of WS₂ by Varying the Number of Layers

Abstract

The optical constants, bandgaps, and band alignments of mono-, bi-, and trilayer WS₂ were experimentally measured, and an extraordinarily high dependency on the number of layers was revealed. The refractive indices and extinction coefficients were extracted from the optical-contrast oscillation for various thicknesses of SiO₂ on a Si substrate. The bandgaps of the few-layer WS₂ were both optically and electrically measured, indicating high exciton-binding energies. The Schottky-barrier heights (SBHs) with Au/Cr contact were also extracted, depending on the number of layers (1–28). From an engineering viewpoint, the bandgap can be modulated from 3.49 to 2.71 eV with additional layers. The SBH can also be reduced from 0.37 eV for a monolayer to 0.17 eV for 28 layers. The technique of engineering materials’ properties by modulating the number of layers opens pathways uniquely adaptable to transition-metal dichalcogenides