Large-area van der Waals epitaxy and magnetic characterization of Fe₃GeTe₂ films on graphene

Abstract

Scalable fabrication of magnetic 2D materials and heterostructures constitutes a crucial step for scaling down current spintronic devices and the development of novel spintronic applications. Here, we report on van der Waals (vdW) epitaxy of the layered magnetic metal Fe3GeTe2 (FGT)—a 2D crystal with highly tunable properties and a high prospect for room temperature ferromagnetism (FM)—directly on graphene by employing molecular beam epitaxy. Morphological and structural characterization confirmed the realization of large-area, continuous FGT/graphene heterostructure films with stable interfaces and good crystalline quality. Furthermore, magneto-transport and x-ray magnetic circular dichroism investigations confirmed a robust out-of-plane FM in the layers, comparable to state-of-the-art exfoliated flakes from bulk crystals. These results are highly relevant for further research on wafer-scale growth of vdW heterostructures combining FGT with other layered crystals such as transition metal dichalcogenides for the realization of multifunctional, atomically thin devices.

Two-dimensional materials prospects for non-volatile spintronic memories

“…Indeed, considering that the first 2D magnets were reported in 2017 85,86 already observing 2D magnets with a Curie temperatures near room temperature is impressive and efforts are undergoing to achieve this objective, relying on new material sets, improved control and sample quality, and doping approaches. [152][153][154][155][156][157] Hence, despite the results being not yet competitive for nowadays room temperature standards, the tremendous effort made by the community and the fast pace of progress made in the recent years (from tunnel barriers to 2D magnets) to target functional large-scale spin-based technologies allow to envision the possibility of functional large-scale spin-based technologies operating at room temperature in the not so distant future.…”

Significant enhancement of ferromagnetism above room temperature in epitaxial 2D van der Waals ferromagnet Fe5−δGeTe2/Bi2Te3 heterostructures

“…6 While the material has been mostly grown in bulk form at equilibrium 7–9 and studied using exfoliated thin flakes, 3,10,11 a number of wafer scale epitaxial thin films have been reported, mostly by molecular beam epitaxy (MBE). 12–14 Fe 3 GeTe 2 /Bi 2 Te 3 heterostructures made by MBE exhibit T c above RT up to 400 K in thin (∼4 nm) films. 15…”

Two-dimensional single crystal monoclinic gallium telluride on silicon substrate via transformation of epitaxial hexagonal phase

“…For an ideal 2D heteroepitaxy we expect that the first layer will adopt its unstrained lattice constant, as reported for the vdW epitaxy of graphene/hBN 32 , NbSe 2 /MoS 2 19 , TMDs/graphene 33 , group-IV monochalcogenides/graphene 34 , and 2D magnetic materials/graphene 35 . Figure 1b shows the almost rapid lattice relaxation ( ~1 monolayer, ML) from 3.9 Å of the substrate to 4.1 Å of the epitaxial layers due to the successful vdW epitaxy (we note that a slow increase of the lattice constant to 4.12 Å is detected for the 11 ML GaTe after 80 min growth).…”