Boosting the gas sensing performances of 2H–MoSe2 bilayer upon alkali metal intercalation: Insights from DFT calculations

Abstract

Realizing the multilayer or bulk MoSe2 cross from indirect bandgap to direct bandgap has drawn increasing attention due to the more practically useable and novel optoelectronic properties. In this work, the feasibility to realize indirect-to-direct band gap transition by intercalating alkali metals into 2H–MoSe2 bilayer was explored and its effect on the gas adsorption performance was evaluated utilizing first-principles calculation. The calculated results show that only Li and Na can be stably intercalated into the interlayer of 2H–MoSe2 bilayer. And the intercalated alkali metals as n-type dopant can realize the band gap transition from indirect to direct of 2H–MoSe2 bilayer, which is mainly ascribed to the decoupled interlayer interaction and built-in electric field in 2H–MoSe2 bilayer. Additionally, the adsorption performance of reducing gases is basically unchanged, while that of oxidizing gases (NO, NO2 and O2) is gradually enhanced with the intercalation concentrations of alkali metals increasing. The enhancement in adsorption performance for oxidizing gases is mainly ascribed to an indirect-to-direct bandgap transition along with the built-in electric field along the z-axis of 2H–MoSe2 bilayer. Through alkali metal intercalation, this research can provide a new method for the design and synthesis of transition metal dichalcogenides with enhanced gas-sensing performances.