Ta Doping Enhanced Room‐Temperature Ferromagnetism in 2D Semiconducting MoTe₂ Nanosheets

Abstract

Room temperature ferromagnetic semiconductors remain one of the most puzzling issues to be solved in tens of years. Nowadays, 2D ferromagnetic transition metal dichalcogenides (TMDCs) nanosheets attract continuous interest due to their exceptional electronic structure and properties. Here, it is identified that semiconducting 2H‐phase MoTe2 few/mono‐layer mixed nanosheets present a room temperature ferromagnetic property with Curie temperature above 400 K, although the MoTe2 bulk counterpart shows diamagnetic properties. The origin of such observed room temperature ferromagnetism is attributed to the combination of their structural defects including Te vacancies, disorders, and amorphous imperfections and edge‐states caused by reduced dimensionality. Moreover, a distinct enhancement of ferromagnetic properties at room temperature is revealed by a non‐magnetic Ta doping strategy. Such structural defects and edge‐states modulated ferromagnetism offers a feasible strategy to search for more robust room temperature ferromagnetic TMDCs nanosheets, which is essential to explore novel electronic and spintronic devices where both carrier charge and spin freedom can be controlled.

Tunable and Robust Near-Room-Temperature Intrinsic Ferromagnetism of a van der Waals Layered Cr-Doped 2H-MoTe2 Semiconductor with an Out-of-Plane Anisotropy

“…Figure b shows the typical XRD results of our grown pristine and Cr-doped 2H-MoTe 2 single crystals. Clearly, all of the four samples were verified to exhibit only four prominent peaks (00L) in the range of 10–55°, which are well consistent with the standard hexagonal 2H-MoTe 2 (PDF# 73-1650), thus implying their good crystalline quality . As a comparison, the (002) peak gradually shifted to a lower diffraction angle with the increase of Cr dopants for Cr-doped 2H-MoTe 2 and the peak width did not change significantly (see the right panel of Figure b), indicating the larger lattice spacing after Cr doping.…”

“…However, most ferromagnetic semiconductors are blocked by the low Curie temperature ( T c ) or serious incompatibility with existing semiconductor integration technologies. − More recently, a series of two-dimensional (2D) van der Waals (vdW) layered materials have gradually emerged, which are appealing for spintronics. − The intrinsic ferromagnetism has been found in bulk and exfoliated Cr 2 Ge 2 Te 6 and CrI 3 semiconductors, while their Curie temperatures are quite low (CrI 3 : bulk 61 K, monolayer 45 K; Cr 2 Ge 2 Te 6 : bulk 68 K, bilayer 30 K), which are far below room temperature of 300 K. On the other hand, 2D vdW layered transition-metal dichalcogenides (TMDCs) such as MoS 2 , MoSe 2 , MoTe 2 , and WS 2 have displayed potential in spintronics owing to their strong SOC and tunable band gaps within the 1–2 eV range. ,− Among the TMDCs, MoTe 2 shows several outstanding properties including variable polymorphism, small band gap, and strong SOC, − while the intrinsically nonmagnetic feature limits its further applications in spin-related devices . However, experimentally, only defect-induced, nonintrinsic poor ferromagnetism with weak and negligible magnetic moment has been found in MoTe 2 so far. − …”

Two‐dimensional magnetic transition metal chalcogenides

“…Doping 2D nonmagnetic materials with magnetic atoms is an alternative route to induce magnetism in the material. It has been theoretically and experimentally demonstrated that robust ferromagnetic ordering can be achieved in 2D TMC systems (e.g., MoS 2 , MoTe 2 , WS 2 , WSe 2 , and SnS 2 ) through the substituted doping of transition metal atoms (e.g., V, Cr, Mn, Fe, Co, Ti, Ta, and Ni) 37,38,90–97 . In particular, room‐temperature ferromagnetism has been observed in ML V‐doped MoTe 2 , 93 Co‐doped MoS 2 , 95 V‐doped WSe 2 37,38 and V‐doped WS 2 , 97 resulting in dilute magnetic semiconductors.…”

Two‐Dimensional Metal Telluride Atomic Crystals: Preparation, Physical Properties, and Applications

“…For the nonmagnetic‐doping induced magnetic ordering, our group [ 191 ] reported that Ta doped few/mono‐layer 2H MoTe 2 nanoplates exhibit a room‐temperature ferromagnetic property ( T C > 400 K). The fundamental reasons for such room‐temperature ferromagnetism are the combination of structural defects, including amorphous imperfections, disorders, and Te vacancies, as well as the edge‐states resulted from the reduced dimensionality.…”