Tuning electronic phase of monolayer [formula omitted]-borophene via adsorbed gas molecules: Generation of van Hove singularity

Abstract

We consider manifolds of the tunable electronic density of states in single-layer β12-borophene, parameterized by a manifold electron hopping amplitude. We study the hybridization properties of orbitals in the presence of gas molecules (GM) with a tight-binding model and Green’s function approach. Independent of how we dope the layer by GM, van Hove singularities are significantly generated and associated with various broadness and flatness features of bands. We demonstrate that β12-borophene with GM-doped {a,e}, {a,c}, {b,d}, and {b,c} atoms is described by a semimetallic phase, where the metallic phase is washed out in the vicinity of Fermi level. We also find a gapless semiconducting phase at the Fermi energy for GM-doped c atoms; however, the most inherent character of the system remains unchanged once all atoms are simultaneously doped with GM. These findings can apply to tuning field-effect transistor-based gas sensors.