Schottky-Ohmic transition and tunable ferromagnetism in van der Waals monolayer Cr2Ge2Te6 heterostructure

The recent discovery of two-dimensional (2D) long-range magnets provides a wide platform to develop nonvolatile spintronic devices at the limit of miniaturization, and the contacts between 2D magnets and metals are crucial as the spintronic device performances are currently plagued by the Fermi-level pinning (FLP) effect, magnetic phase transition temperature, and tunneling resistance. Hence, a detailed atomic-scale understanding of the van der Waals (vdWs) ferromagnetic contacts to the 2D metals is a necessity. Herein, we propose a series of 2D metals vdWs contacts to 2D ferromagnetic monolayer Cr2Ge2Te6 (CGT) as the example to investigate the characteristics. The calculations reveal that strong FLP effects are observed in the Ohmic metal contacts to TaS2, VSe2, NbS2, VS2, and MoS2, while the Schottky metal contacts to TaSe2 and NbSe2 are weak. Further investigations uncover that the origin of strong FLP is the interfacial potential step Delta V. The magnetic phase transition based on Monte Carlo (MC) simulations demonstrates that interfacete charge injection and lattice mismatch jointly determine the Curie temperature (T-c) of herostructures, and the discovered supreme T-c approximately 97 K of CGT/TaSe2 reach three times the T-c approximately 34 K of free-standing CGT. Furthermore, interfacial transports and magnetic anisotropy energy (MAE) were calculated and screened. Our studies can provide potential guidance for designing multifunctional 2D spintronic devices with selective contacts in the future.