Metal to semiconductor transition of two-dimensional NbSe2 through hydrogen adsorption: A first-principles study

Based on first-principles calculations, we predict that the recently synthesized two-dimensional (2D) NbSe2 can be changed from the metallic to the semiconducting phase upon the adsorption of H with an indirect bandgap of 2.99 eV. The bandgap opening of the 2D NbSe2 only occurs when the hydrogen coverage is high, and it is sensitive to mechanical strain. The hydrogenated 2D NbSe2 is dynamically stable under a tensile strain of up to 9%, whereas a compressive strain leads to instability of the system. The optical spectra obtained from the GW-Bethe–Salpeter equation calculations suggest that 2D NbSe2 is highly isotropic, and it will not affect the polarization of light along the x- or y-direction. The optical bandgap, describing the transition energy of the exciton, is sensitive to the mechanical strain with the calculated exciton binding energy of ∼0.42 eV. These intriguing properties suggest that H functionalized 2D NbSe2, grown on a substrate with a larger lattice parameter, can be used to modulate the bandgap of NbSe2. This is beneficial in developing a nanoscale field effect and optoelectronic devices.