Giant electrode effect on tunneling magnetoresistance and electroresistance in van der Waals intrinsic multiferroic tunnel junctions using VS2

Van der Waals multiferroic tunnel junctions (vdW-MFTJs) with multiple nonvolatile resistive states are highly suitable for new physics and next-generation storage electronics. However, currently reported vdW-MFTJs are based on two types of materials, i.e., vdW ferromagnetic and ferroelectric materials, forming a multiferroic system. This undoubtedly introduces additional interfaces, increasing the complexity of experimental preparation. Herein, we engineer vdW intrinsic MFTJs utilizing bilayer ${\mathrm{VS}}₂$. By employing the nonequilibrium Green's function combined with density functional theory, we systematically investigate the influence of three types of electrodes (including non-vdW pure metal Ag/Au, vdW metallic $1\mathrm{T}\text{\ensuremath{-}}{\mathrm{MoS}}₂/2\mathrm{H}\text{\ensuremath{-}}{\mathrm{PtTe}}₂$, and vdW ferromagnetic metallic ${\mathrm{Fe}}₃{\mathrm{GaTe}}₂/{\mathrm{Fe}}₃{\mathrm{GeTe}}₂$) on the electronic transport properties of ${\mathrm{VS}}₂$-based intrinsic MFTJs. We demonstrate that these MFTJs manifest a giant electrode-dependent electronic transport characteristic effect. Comprehensively comparing these electrode pairs, the ${\mathrm{Fe}}₃{\mathrm{GaTe}}₂/{\mathrm{Fe}}₃{\mathrm{GeTe}}₂$ electrode combination exhibits optimal transport properties, the maximum TMR (TER) can reach 10949% (69%) and the minimum resistance-area product (RA) is 0.45 $\mathrm{\ensuremath{\Omega}}$ $\textmu{}{\mathrm{m}}²$, as well as the perfect spin filtering and negative differential resistance effects. More intriguingly, TMR (TER) can be further enhanced to 34 000% (380%) by applying an external bias voltage, while RA can be reduced to 0.16 $\mathrm{\ensuremath{\Omega}}$ $\textmu{}{\mathrm{m}}²$ under the influence of biaxial stress. Additionally, considering the impact of surface dangling bonds of pure metal electrodes on the multiferroicity of ${\mathrm{VS}}₂$, we introduce a graphene interlayer between them. This strategy effectively preserves the intrinsic properties of ${\mathrm{VS}}₂$ and significantly amplifies the TMR (TER) of the MFTJ composed of Ag/Au electrode pairs by an order of magnitude. Our proposed concept of designing vdW-MFTJs using intrinsic multiferroic materials points towards new avenues in experimental exploration.