Modulating the contact properties of XY2/Sc2CCl2 (X = Nb, Ni, Ti, V, Mn, Ta; Y = S, Se) heterostructures via layer number, electric field, and vertical strain

Abstract

High contact resistance induced by low quantum tunneling probability (TP) limits the performance of 2D electronic devices, making the modulation of Schottky barrier height (SBH) and contact types crucial. van der Waals heterostructures (vdWHs) composed of 2D transition metal carbides (MXenes) and metallic transition metal dichalcogenides (TMDs) serve as an ideal platform for exploring the interface contact physics in high-performance 2D devices. Via first-principles calculations, this study systematically investigates the geometric structures, stability, and electronic properties of nine XY₂/Sc₂CCl₂ (X = Nb, Ni, Ti, V, Mn, Ta; Y = S, Se) vdWHs. The contact characteristics of these vdWHs were explored using three modulation strategies: semiconductor layer number, vertical electric field, and vertical strain. All vdWHs exhibit good thermodynamic, dynamic, and thermal stability. Except for TiS₂/Sc₂CCl₂, which forms a p-type Schottky contact, the other eight vdWHs form n-type Schottky contacts, with their SBH dominated by the metal work function. In the intrinsic state, all vdWHs show low TP (2.67–4.87%), indicating high contact resistance. The three modulation strategies are effective: increasing the number of Sc₂CCl₂ layers raises SBH and reduces TP; a vertical external electric field induces reversible Schottky–Ohmic transitions (the critical field is related to the metal work function); vertical strain modulates barrier width/height via interlayer coupling, and compressive strain boosts the TP to nearly 100%. This work elucidates the modulation mechanisms of 2D metal–semiconductor interfaces, providing a theoretical basis and design strategies for low-contact-resistance, high-performance 2D electronic devices.