Epitaxial Monolayers of the Magnetic 2D Semiconductor FeBr₂ Grown on Au(111)

Intrinsically Patterned Two-Dimensional Transition Metal Halides

“…Furthermore, the superstructure unit cell is commensurate to the Au lattice with as proven by LEED, Figure b–d. We observe a ±13.9° rotation of the superstructure toward the high symmetry axes of the Au lattice, as well as a ±5.21 and ±26.99° rotation of the FeBr 2 and CoBr 2 lattice, respectively, toward the Au lattice (Figures S14 and S15), consistent with ref . There are four distinct domains with , see Table S2 and Figure S16.…”

“…In conclusion, we find that the growth of the periodic vacancy lattice is facilitated by strain engineering at the TMH–gold interface in combination with the low energy costs for Br vacancy formation. We note that for the second layer, no periodic vacancy lattice was observed, which confirms that it is stabilized by the TMH–gold interface, see Figure S21 …”

“…TMHs have gained significant interest since the recent discovery of intrinsic ferromagnetism in these 2D vdW materials. , Consequently, the electronic and magnetic properties of first-row 2D transition metal trihalides such as CrI 3 came into the focus of first-principles calculations and experimental studies . For 2D transition metal dihalides, in contrast, only a limited number of experimental surface science studies have been presented so far that provide atomic-scale insights into the structure, growth, and defects. − This might be related to challenges in their preparation: on the one hand, some materials decompose during the growth by molecular beam epitaxy in ultrahigh vacuum (UHV) . On the other hand, some ex situ prepared and exfoliated layers suffer from limited environmental stability in ambient conditions. , Analogous to the structure of TMDCs, TMH monolayers can adopt both trigonal prismatic (1H) or octahedral coordination (1T) of the metal cation, see Figure S1. , However, 1T stacking is the energetically most favorable structure for most TMHs.…”

Ferromagnetic Order in 2D Layers of Transition Metal Dichlorides

“…Small values for the orbital magnetic moment were also found in other similar systems. [8,30] In the case of the spin magnetic moment, while the value obtained for NiCl 2 accurately approaches the theoretical estimation, FeCl 2 differs substantially from its predicted value. We speculate that the survival of the theoretical Ni 2 + spin moment over the metallic substrates is probably favored by its orbital configuration, which is more energetically stable than the configuration of Fe 2 + .…”

“…The surviving magnetic order detected for monolayers of FeCl 2 and NiCl 2 is particularly intriguing because these lie directly on top of a metallic substrate. Contrary to related divalent bromide salts, [ 8,30 ] the TMCl 2 layers are structurally unperturbed on the metal, lying in a very weak adsorption state as found by STM. We thus speculate that the Cl ions at the interface with the metal prevent the interaction of the transition metal atoms with the gold substrate, preserving the collective magnetization order in the layers.…”