Growth of (111)-Orientated GdTe and TmTe Thin Films by van der Waals Molecular Beam Epitaxy

Thin films of GdTe and TmTe are prepared by van der Waals (vdW)-type molecular beam epitaxy on a graphene/SiC(0001) substrate following a similar growth mode. The (111)-orientated films consist of alternating layers of Gd3+ (Tm3+) and Te2– ions with both surfaces terminated by Te. Such a (111) polar surface is stabilized by the charge transfer of 5d electrons from the Gd site to the surface Te atoms as well as the surface reconstruction. The reconstructed surfaces show either 3×3 or 3×3 superstructures depending on the film thickness. The high-quality films promote the study of magnetic properties of rare earth monochalcogenides at the two-dimensional limit.