Nanofabrication

Large-area van der Waals epitaxy of ferromagnetic Fe3GeTe2 films on graphene

Magnetic two-dimensional (2D) materials are promising building blocks for realizing ultra-compact spintronic devices with enhanced performance. Their study is also expected to open new perspectives on a more versatile modulation of magnetic properties, beyond what can be achieved in traditional three-dimensional (3D) magnetic thin films and superlattices. In particular, combining magnetic 2D materials with other 2D crystals such as graphene and transition metal dichalcogenides (TMDCs) to create van der Waals (vdW) heterostructures offers great potential to tailor magnetism via proximity-induced phenomena. To date, experimental research on 2D magnets and related vdW heterostructures has mainly concentrated on micrometer-sized flakes exfoliated from bulk crystals, which are not scalable and incompatible with standard device fabrication. Hence, exploiting large-scale synthesis of such material systems is greatly demanded for the development of atomically thin magnetic vdW materials to be implemented into future applications.

Figure 1. Reflection high energy electron diffraction patterns taken along the [11-20] direction before (a) and after (b) the growth of a 10-nm-thick Fe3GeTe2 film on graphene/SiC(0001). The narrow streaks appearing in (b) indicate epitaxial growth of a 2D film with smooth surface and good structural quality. (c) Transverse resistance RXY of a 1 cm2 Fe3GeTe2/graphene van der Pauw structure during downward and upward magnetic field sweeps at different temperatures. The anomalous Hall effect is detected as a square-shape hysteresis loop, which reflects the ferromagnetic order in the Fe3GeTe2 film with a strong perpendicular magnetic anisotropy.

Here, we report on the vdW epitaxy of the ferromagnetic metal Fe3GeTe2—a 2D crystal with tunable properties and great potential for room temperature ferromagnetism—via molecular beam epitaxy on a graphene/SiC(0001) template. Morphological and structural characterization confirmed the realization of large-area, continuous Fe3GeTe2/graphene heterostructure films with high structural and interface quality. Additionally, magneto-transport and X-ray magnetic circular dichroism investigations revealed a robust out-of-plane ferromagnetism in the films with a Curie temperature around 220 K, which is comparable to flakes exfoliated from state-of-the-art bulk single crystals. These results are highly relevant for further research on wafer-scale growth of vdW systems containing magnetic 2D crystals for the realization of multifunctional, atomically thin devices. By combining Fe3GeTe2 with other selected 2D crystals including TMDCs and h-BN, which can also be grown by precise methods such as MBE, we envision the realization of spintronic devices with dimensions and performance not achievable with conventional bulk materials.

1 Autor J. M. J. Lopes , D. Czubak , E. Zallo , A.I. Figueroa , C. Guillemard , M. Valvidares , J.R. Zuazo , J. López-Sanchéz , S.O. Valenzuela , M. Hanke , M. Ramsteiner
Titel

Large-area van der Waals epitaxy and magnetic characterization of Fe 3 GeTe 2 films on graphene

Source 2D Mater. , 8 , 041001 ( 2021 )
DOI : 10.1088/2053-1583/ac171d | arxiv: arXiv:2104.09184 | 3248 Cite : Bibtex RIS
J. M. J. Lopes, D. Czubak, E. Zallo, A.I. Figueroa, C. Guillemard, M. Valvidares, J.R. Zuazo, J. López-Sanchéz, S.O. Valenzuela, M. Hanke, and M. Ramsteiner