Electronic, mechanical and contact properties of Mo_4/3B₂T₂ (T=F, O, OH) monolayer: A first principles study

Single-layer 2D molybdenum boride sheets, Mo4/3B2T2 (T = F, O and OH), have been realized in recent experiment. Here, the electronic structure and mechanical flexibility of its most stable configurations are investigated by using first principles calculations. Mo4/3B2F2 and Mo4/3B2(OH)2 perform as 2D metal, while Mo4/ 3B2O2 is a semiconductor with indirect band gap -0.36 eV. These three monolayers can individually sustain the maximum stress and the strain limits at least -15 Gpa and 15 %, such mechanic flexibility is comparable to borophene and MoS2. When forming heterojunction with MoS2, p-type and n-type Schottky contact with barrier height -0.16 eV and 0.23 eV occur in Mo4/3B2F2 and Mo4/3B2(OH)2, respectively. Fortunately, the contact barrier can be eliminated by external field. In addition, a type-II heterojunction with a large conduction band offset is found in Mo4/3B2O2/MoS2, which may be a potential candidate for optoelectronics.