Functional groups and vertical strain regulate the electronic properties of Nb2NT2/MoTe2 heterojunction

Abstract

In the current effort, a novel attempt to construct heterojunctions using Nb2N two-dimensional MXene materials with fascinating property and MoTe2 transition metal disulfide compounds is proposed. The effect of vertical strain on the electronic structure and interfacial contact properties of the heterojunction is investigated by first principles calculations. The O, F, and OH functional groups prefer to be adsorbed on top of the N atoms of the Nb2N MXene material. The configuration III of heterojunction has the lowest energy and stable model, and the equilibrium layer spacing is within the range of 3.061 Å to 3.328 Å, indicating that they belong to typical vdW heterojunctions. The large work function difference between the two components induces the transfer and rearrangement of charge. 0.12 e per cell spontaneously transfer from MoTe2 to Nb2NO2 layer. In contrast, the Nb2NF2 and Nb2N(OH)2 layers transfer 0.01 e and 0.21 e to the MoTe2 layer, respectively. n-type Ohmic contacts are formed in O terminal system, while p-type and n-type Schottky contacts are formed in F and OH terminal systems, respectively. Additionally, for vertical strain, with the decrease of the layer spacing, the p-type Schottky barrier height (SBH) decreases from 0.270 eV to 0.095 eV in former system, meanwhile the n-type Schottky barrier height in the latter system also decreases from 0.260 eV to 0.156 eV. These regulations of interest lays a theoretical foundation for bandgap engineering and Schottky junction preparation and opens a window into MXene-based heterojunction electron device.