Synthesis and Characterization of Ultrathin FeTe₂ Nanocrystals

Abstract

Ultrathin crystals including monolayers have been reported for various transition-metal dichalcogenides (TMDCs) with van der Waals bonds in the crystal structure. Herein, we report a detailed synthesis procedure and characterization of ultrathin iron ditelluride crystals. This material crystallizes in an orthorhombic marcasite Pnnm crystal structure whose bonding is dominantly covalent and without loosely connected van der Waals (vdW) bonds, making monolayer FeTe 2 synthesis less straightforward than other TMDC monolayer syntheses. The chemical vapor deposition synthesis process described is simple, effective, and results in a range of crystal thicknesses from approximately 400 nm down to the FeTe 2 monolayer.

Phase Engineering of Two‐Dimensional Transition Metal Dichalcogenides

“…temperature. [127,129] CoTe 2 [132] and FeTe 2 [133] are found as the orthorhombic marcasite-like mineral, as well as in the 1T-like layered structure. However, a strong interlayer Te-Te interaction causes a relatively small layer separation and a small c/a lattice ratio, significantly increasing the cleavage energies.…”

“…Indeed, Larchev et al observed the marcasite phase of PdSe 2 at the environment of 7.5 GPa and 900 °C, whereas the pyrite‐phase was preferred above this temperature. [ 127,129 ] CoTe 2 [ 132 ] and FeTe 2 [ 133 ] are found as the orthorhombic marcasite‐like mineral, as well as in the 1T‐like layered structure. However, a strong interlayer Te–Te interaction causes a relatively small layer separation and a small c/a lattice ratio, significantly increasing the cleavage energies.…”

van der Waals 2D transition metal dichalcogenide/organic hybridized heterostructures: recent breakthroughs and emerging prospects of the device

“…Kafle et al also addressed the thickness dependence of the TMD layer with phthalocyanine molecules, using MoS 2 /ZnPc interfaces. 53 It is worth to mention that up until now, remarkable progress has been achieved with the study on 2D magnetic TMDs such as CrSe 2 , CrTe 2 , FeSe 2 , FeTe 2 and VeTe 2 , [239][240][241][242] and novel magnetic properties at the hybrid TMDO interface in the 2D limit remain virtually unexplored for diverse optoelectronic applications. Magnetic molecules, for example, TbPc 2 with 2D TMD could give novel properties in the future with diverse applications.…”

Recent Developments in Chemical Vapor Deposition of 2D Magnetic Transition Metal Chalcogenides

“…There are a variety of unique stoichiometric ratios, such as FeSe, FeSe 2 , Fe 3 Se 4 , Fe 7 Se 8 , FeTe, and FeTe 2 . − Even in the same composition, multiple phases could exist, for example, hexagonal and tetragonal FeTe. ,, The complicated structures in the iron chalcogenides form the basis of rich magnetic properties, where the exchange function between the iron ions can be altered in different structures. So far, only Fe 7 Se 8 , FeSe 2 , FeTe, and FeTe 2 have been prepared by the current solid-precursor-based CVD method. ,,− Hexagonal FeSe 2 and FeTe 2 are layered materials, where each Fe atom plane is sandwiched by two Se or Te atom planes (Figure a–d). , Besides, tetragonal FeTe also adopts layered structures, which comply with a P 4 g wallpaper group symmetry, as shown in the atomic model and zoom-in STEM image in Figure e–i. The rest, including Fe 7 Se 8 and hexagonal FeTe, are all intrinsically nonlayered materials (Figure j–n). , The CVD method enables the preparation of ultrathin nonlayered nanomaterials, making it possible to study the thickness-dependence of magnetic properties in these materials.…”