Highly tunable Raman scattering and transport in layered magnetic Cr ₂ S ₃ nanoplates grown by sulfurization

Abstract

The recent discovery of intrinsic two-dimensional (2D) ferromagnetism has sparked growing interests in the search for new 2D magnets with diverse and tunable properties for both fundamental scientific advances and novel spintronic applications. Here we report on the synthesis of layered chromium sulfide (Cr2S3) nanoplates via a facile sulfurization approach and the studies of their highly tunable Raman and (magneto-)transport properties. Depending on the specific growth conditions, we have achieved both epitaxial (and hence strained) and non-epitaxial nanoplates of Cr2S3 on the c-cut sapphire substrates. Via Raman scattering and density functional theory (DFT) calculations, we determined both types of nanoplates to be a rhombohedral R3 phase whose bulk counterpart exhibits weak ferromagnetism below a metal–insulator transition (MIT) temperature of ~120 K. Compressive strain from the lattice-mismatched substrate yields a red-shift of up to 8 cm−1 in Raman peaks in comparison to the strain-free nanoplates obtained from the non-epitaxial growth. The strain-free nanoplate shows a variable-range-hopping type of insulating behavior, while the strained nanoplates exhibit an enhanced MIT up to ~275 K in comparison to 120 K in bulk samples. The room temperature resistivity values of the two types of nanoplates differ by 2 to 3 orders of magnitude. The distinct transport properties can be understood qualitatively based on the electronic band structures calculated by DFT.

An Atomically Thin Air‐Stable Narrow‐Gap Semiconductor Cr2S3 for Broadband Photodetection with High Responsivity

“…The lattice parameters of the unitcell were calculated to be a = 5.92 Å, c = 16.74 Å on the basis of ferromagnetic order for Cr, which was validated to be the most stable one among different magnetic orders. [ 23 ] Due to its quasi‐layered structure, it is possible to implement epitaxial growth on substrates such as mica, which is atomic flat and dangling bond free where precursors have less moving resistance. [ 24 ] Herein, high‐quality ultrathin Cr 2 S 3 nanoflakes were synthesized on freshly cleaved mica substrate by atmospheric‐pressure chemical vapor deposition method.…”

Soft Chemical Synthesis of HxCrS2: An Antiferromagnetic Material with Alternating Amorphous and Crystalline Layers

“…However, these compounds have not yet been exfoliated and the method was not successful for synthesizing CrS 2 . Very recent studies in creating magnetic Cr chalcogenide-based nanosheets all aimed at synthesizing thin Cr 2 S 3 platelets. − These platelets were synthesized by chemical vapor deposition methods and maintained the three-dimensional non-van der Waals structure down to a few nanometers in thickness.…”

Near Degeneracy of Magnetic Phases in Two-Dimensional Chromium Telluride with Enhanced Perpendicular Magnetic Anisotropy

“…In parallel to the immense efforts on devices, there is great interest in discovering 2D magnetic compounds with high magnetic ordering temperatures and different magnetic phases. − Room-temperature ferromagnetism has been realized in molecular beam epitaxy (MBE) grown MnSe x monolayer films and mechanically exfoliated thin Fe 3 GeTe 2 flakes under ionic gating . Beyond vdW magnets, other layered non-vdW materials, such as hematene α-Fe 2 O 3 layers, have been successfully exfoliated from their bulk crystals, in which magnetic order at room temperature has been observed .…”