The role of permanent and induced electrostatic dipole moments for Schottky barriers in Janus MXY/graphene heterostructures: a first-principles study

Abstract

The Schottky barrier height (E_SBH) is a crucial factor in determining the transport properties of semiconductor materials and it directly regulates the carrier mobility in opto-electronics devices. In principle, van der Waals (vdW) Janus heterostructures offer an appealing avenue for controlling the E_SBH. However, the underlying atomistic mechanisms are far from understood conclusively, which prompts further research in the topic. To this end, here we carry out an extensive first-principles study of the electronic properties and E_SHB of several vdW Janus MXY/graphene (M = Mo, W; X, Y = S, Se, Te) heterostructures. The results of the simulations show that by changing the composition and geometry of the heterostructure's interface, it is possible to control its electrical contact, and thence electron transport properties, from ohmic to Schottky with up to a factor seven variation in the E_SBH. Detailed analysis of the simulations enables rationalization of this highly attractive property on the basis of the interplay between the permanent dipole moment of the Janus MXY sheet and the induced one due to interfacial charge redistribution at the MXY/Gr interface. Such an interplay is shown to be highly effective in altering the electrostatic potential difference across the vdW Janus heterostructure, determining its E_SBH, and thence Schottky (ohmic) contact type. These computational findings contribute guidelines to control the electrical contacts in Janus heterostructures towards the rational design of electrical contacts in nanoscale devices.