Phase-Tunable Synthesis and Etching-Free Transfer of Two-Dimensional Magnetic FeTe

Abstract

Two-dimensional (2D) Fe-chalcogenides (e.g., FeS, FeSe, and FeTe, etc.) have sparked extensive interest due to their rich phase diagrams including superconductivity, magnetism, and topological state, as well as versatile applications in electronic devices and energy related fields. However, the phase-tunable synthesis and green transfer of such fascinating materials still remain challenging. Herein, we develop a temperature-mediated chemical vapor deposition (CVD) approach to grow ultrathin nonlayered hexagonal and layered tetragonal FeTe nanosheets on mica substrates, with their thicknesses down to ∼2.3 and ∼4.0 nm, respectively. Interestingly, we have observed exciting ferromagnetism with the Curie temperature approaching ∼300 K and high conductivity (∼1.96 × 105 S m–1) in 2D hexagonal FeTe. More significantly, we have designed a swift, high-efficiency, and etching-free method for the transfer of 2D FeTe nanosheets onto arbitrary substrates, and such a transfer strategy enables the cyclic utilization of growth substrates. These results should propel the further development of phase-tunable synthesis and green transfer of 2D Fe-chalcogenides, as well as their potential applications in spintronic devices.

Two-dimensional multiferroic material of metallic p-doped SnSe

“…Etching-free transfer and of 2D metallic p-doped SnSe nanosheets. The PVD-synthesized 2D metallic p-doped SnSe nanosheets were transferred by using the polystyrene assistant method 39 . The morphology, domain size, thickness, phase structure, optical property, and crystalline quality of 2D metallic p-doped SnSe nanosheets were characterized by OM (Olympus BX53M), AFM (Dimension Icon, Bruker), XPS (Thermo Scienti c K-Alpha+ system, and the binding energies were calibrated by C1s at ~284.8 eV), XRD (Rigaku Smartlab SE), Raman spectroscopy (Renishaw, with the excitation light of ~532 nm), and TEM (JEOL JEM-F200, with the acceleration voltage of ~200 kV).…”

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

“…The size of the prepared nanocrystal can be over 100 μm, which makes it easy to pattern electrodes on the sample and study electrical properties on the single nanocrystal level. Shi et al also reported the growth of 2D magnetic FeTe nanocrystals on mica substrate . The prepared sample can be as thin as 2.3 nm and as large as 120 μm.…”

“…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.…”

“…(h) The processes of transferring FeTe 2 nanoflakes from mica to SiO 2 /Si substrate. Reproduced with permission from ref . Copyright 2021 American Chemical Society.…”

Controllable Synthesis Quadratic-Dependent Unsaturated Magnetoresistance of Two-Dimensional Nonlayered Fe7S8 with Robust Environmental Stability

“…Finally, the PS/Fe 7 S 8 was soaked in toluene to dissolve PS and then blown dry by nitrogen gas. The etching-free method was also employed to transfer CVD-synthesized FeTe nanosheets …”