Tuning the conducting types of VSi2N4 by van der Waals engineering

Abstract

VSi₂N₄, as a notable member of the MA₂Z₄ material family, has consistently attracted great interest in the field of spintronics due to its distinct electronic properties. However, the nonexistence of states around the Fermi level makes it hardly directly applicable in many situations. This work presents an exhaustive exploration of the modulation of the electronic characteristics, and particularly, the conducting types, of VSi₂N₄ by integrating VSi₂N₄ with MoS₂, graphene, and NbS₂, each noted as a representative of semiconductor, semimetal and metal, respectively, to form van der Waals (vdW) heterostructures. First-principles calculations disclose an absence of charge transfer at the VSi₂N₄/MoS2interface, thereby highlighting its ineffectiveness in electronic modulation of VSi2N4. In contrast, graphene was found to effectively induce charge transfer to VSi₂N₄ in both spin-up and spin-down channels. Importantly, NbS₂, characterized by its large work function, emerges as a potent mediator of VSi₂N₄’s electronic states, inducing an efficient transition from a half-semiconducting to a half-metallic phase. Interestingly, due to such a transition, fully spin polarized transport and giant tunnel magnetoresistance (with tunnel magnetoresistance ratio ∼ 1.15 × 10₄%) are achieved in the magnetic tunnel junction constructed with the VSi₂N₄/NbS₂ vdW heterostructure. The findings provide a promising foundation for extending the application potential of VSi₂N₄ in the construction of nanoelectronic and spintronic devices.