Organic Gas Sensing Performance of the Borophene van der Waals Heterostructure

Borophene is a novel kind of 2D nanomaterial that has received widespread attention recently. Using semiconducting 2H-MoS2 as the substrate, here we theoretically constructed a 2D van der Waals borophene/MoS2 heterostructure and explored the transport properties and the sensing performance for organic molecules CH4, C2H4, C2H2, CH3OH, and HCHO. On the basis of density functional theory, we first investigated the adsorption behaviors of the organic molecules on borophene in the heterostructure. The obtained results show that the interactions between CH4, C2H4, or CH3OH and borophene are very weak; the three organic molecules adopt physisorption. On the contrary, C2H2 and HCHO adopt chemisorption, and in the two organic molecules, the chemical bonds of the C atoms change to sp3 hybridization, owing to the strong chemical interactions with borophene. For the cases of chemisorption, utilizing nonequilibrium Green's function method, we studied the sensing performance of the heterostructure. We found that the sensing performance of the heterostructure is strongly anisotropic and that under very low bias voltages the heterostructure is very sensitive to C2H2 and HCHO. As a result, borophene/MoS2 heterostructure can be used as an excellent 2D gas sensor for organic molecules such as C2H2 and HCHO.