Superior spin-polarized electronic structure in MoS₂/MnO₂ heterostructures with an efficient hole injection

Two-dimensional (2D) materials with intrinsic magnetism and low hole injection barriers to transition metal dichalcogenides are crucial to develop dopant-free all-2D p-type spin field effect transistors for CMOS logic and spintronic applications. Here, the electronic structures of 2D MoS₂/MnO₂ heterostructures are investigated by first-principles calculations, where the monolayered MnO₂ has two polymorphs including magnetic metal h-MnO₂ and magnetic semiconductor t-MnO₂. Both the MoS₂/h-MnO₂ and MoS₂/t-MnO₂ heterostructures show p-type doping for MoS₂. In the MoS₂/h-MnO₂ model with a semiconductor/metal contact, the charge transfer can affect the occupation of Mn 3d and O 2p orbitals, which results in a half-metallic characteristic of the heterostructure with a Schottky barrier height of only 0.15 eV. However, the MoS₂/t-MnO₂ model with a semiconductor/semiconductor contact shows a spin-gapless electronic structure. Moreover, the type-II band alignment of the MoS₂/t-MnO₂ heterostructure can facilitate the effective separation of electrons and holes, which can enhance the lifetime of interlayer excitons. The long interlayer exciton lifetime makes it a good candidate for electron-hole separators and related optoelectronic devices. By applying vertical compression, the spin channel of the half-metallic MoS₂/h-MnO₂ heterostructure can be reversed and the spin-gapless band structure of the MoS₂/t-MnO₂ heterostructure becomes half-metallic. Furthermore, by applying a gate voltage, the Schottky barrier height and the spin-gapless gap can be tailored. The tunable spin polarization, spin-polarized direction and exciton recombination rate provide a feasible way toward spintronics and optoelectronics.