Tuning Epitaxial Growth of Atomically Thin MnTe Films on Fe(001) for Creating van der Waals 2D Magnets

Layered two-dimensional (2D) van der Waals magnetic crystals have predominantly been synthesized using 3 d transition metals and chalcogenides via chemical vapor transport. However, for device applications, it remains critical to establish growth conditions that enable epitaxial, layer-by-layer film formation under vacuum, particularly on atomically flat solid substrates. In this study, we investigate manganese (Mn) and tellurium (Te) as a model system, due to the layered Mn–Te compound’s intriguing topological and magnetic properties. A clean body-centered-cubic Fe(001) substrate was used because it supports the epitaxial, layer-by-layer growth of atomically flat body-centered tetragonal Mn(001) films. Our findings using scanning tunneling microscopy and spectroscopy (STM/STS) combined with density functional theory calculation reveal that the direct growth of layered Mn/Te films on the ferromagnetic Fe(001) substrate is challenging, even at 300 K. The resulting surface comprises a mixture of Te, Te/Mn, Mn/Te, and MnTe alloy regions. However, post-annealing up to ∼650 K induces a transformation from these metastable states into a thermodynamically stable MnTe alloy phase, forming an atomically flat 2D surface. This study further highlights how combining machine learning with STM/STS enables precise chemical classification and accurate identification of multiple local density of states types, even within structurally complex or mixed-phase systems.