Hematite at its thinnest limit

Abstract

Motivated by the recent synthesis of two-dimensional α-Fe2O3 [Balan et al. Nat. Nanotech. 13, 602 (2018)], we analyze the structural, vibrational, electronic and magnetic properties of singleand few-layer α-Fe2O3 compared to bulk, by ab-initio and Monte-Carlo simulations. We reveal how monolayer α-Fe2O3 (hematene) can be distinguished from the few-layer structures, and how they all differ from bulk through observable Raman spectra. The optical spectra exhibit gradual shift of the prominent peak to higher energy, as well as additional features at lower energy when α-Fe2O3 is thinned down to a monolayer. Both optical and electronic properties have strong spin asymmetry, meaning that lower-energy optical and electronic activities are allowed for the single-spin state. Finally, our considerations of magnetic properties reveal that 2D hematite has anti-ferromagnetic ground state for all thicknesses, but the critical temperature for Morin transition increases with decreasing sample thickness. On all accounts, the link to available experimental data is made, and further measurements are prompted.

Tailoring the Electronic and Magnetic Properties of Hematene by Surface Passivation: Insights from First-Principles Calculations

“…The in-plane lattice parameters are found to be a = b = 5.17 Å in the most stable AFM configuration, which is slightly larger (2.5%) than that of the experimental lattice parameters of 5.04 Å 4 and in a very good agreement with the recent DFT report . The thickness of the relaxed sheet, which we refer to as a monolayer, is found to be 3.02 Å, matching very well with the previous report…”

“…In contrast to the Gaussian smearing method employed in ref. , we have used a more accurate tetrahedron method to calculate the occupancies of the states around the Fermi level, which does not depend on the smearing parameter …”

Surface functionalization of the honeycomb structure of zinc antimonide (ZnSb) monolayer: A first-Principles study

“…Recently, the effort on the synthesis of 2D structures of non-layered bulk materials has increased exponentially. With this regard, the 2D forms of Cr 2 S 3 [24], hematite [25,26], gallenene [27], and very recently ZnSb [28] have been demonstrated using different experimental techniques. Among the non-layered bulk materials, ZnSb has been extensively studied due to it promising thermoelectric properties.…”

Regulating Magnetic Behavior of Fe in Hematene by Defects to Improve Oxygen Evolution Reaction

“…22 The 2D hematene can be easily modulated and exhibits unique properties in comparison to its bulk counterpart. 23,24 Hematene has a narrower band gap compared to hematite, and it is an antiferromagnetic ground-state semiconductor. 25−27 Previous study revealed that the curie temperature increases monotonically with the compressive strains in hematene, which broadens its applications for spintronic, memory-based devices and valleytronics.…”

“…25 The optical and electronic properties of single-and multilayer hematene have been investigated by theoretical simulations; the prominent peak of the optical spectra shifts to higher energy, and the Morin transition temperature increases when it is reduced to a monolayer. 23 Additionally, Shang et al 24 claimed that Lidecorated hematene has a net out-of-plane magnetization on surface Fe atoms induced by the ferroelectric and ferromagnetic polarization. The hematene energetically prefers to be passivated with OH groups on the surface under oxygen-rich conditions, and its electronic structure could be tuned by mechanical deformation.…”