来源：ACS Publications
The growth of high-entropy alloy (HEA) thin films using the molecular beam epitaxy (MBE) technique widens our horizons in materials design. This technique offers precise control of key parameters (deposition rate, substrate orientation, interfacial, or lattice strain), and it becomes possible to study the interplay existing between the elemental choice, their respective stoichiometry, and the associated physical and chemical properties. Such fine-tuning of HEA with an immense compositional space will bring additional advanced materials with exotic properties. Here, we report the epitaxial growth of a rare-earth (RE) HEA thin film on a buffer layer of Nb by MBE. The structure and chemistry of the DyGdHoLuTb thin film have been investigated in the bulk and at the surface under ultra-high vacuum (UHV) conditions, confirming a random chemical distribution on an ordered hexagonal closed-packed structure. We demonstrate how such a heterostructure exhibits magnetic properties that slightly depart from the magnetic phase diagram reported for polycrystalline materials of a similar system.
The current work shows that it is possible to grow (near-)equiatomic epitaxial Dy–Gd–Ho–Lu–Tb thin films by the molecular beam epitaxy technique, giving both an outlook to extend the previously performed studies on RE HEA physical properties and to enrich our knowledge of RE HEAs by performing surface studies. Through a thorough analysis of the bulk structure and chemistry, a homogeneous elemental distribution on a well-defined hcp lattice was confirmed for our sample. Furthermore, we have demonstrated the possibility of using such a single crystal as a model system by studying the structure and composition of the DyGdHoLuTb(0001) surface. Differences between the magnetic properties of this thin film and of polycrystalline materials of the same nature will also be discussed. All in all, the availability of MBE-synthesized thin films that can be considered as thin RE HEA single crystals is expected to bring exciting opportunities: (i) to play with dimensionality (thin to ultrathin films, slowly approaching a 2d material), (ii) to supply samples on demand, (iii) to study the surface properties of the materials, and (iv) to determine the impact of grain boundaries on the system intrinsic properties when compared to polygrain samples, as already discussed in previous studies.