Ferromagnetic ordering in a THAB exfoliated WS₂ nanosheet

Abstract

Because of the important role of two-dimensional (2D) magnetic semiconductors in low-dimensional spintronic devices, the generation of ferromagnetism within an ultrathin semiconducting sheet of a transition metal dichalcogenide is highly desirable. A pristine WS2 sheet is a diamagnetic semiconducting transition metal dichalcogenide with superior electronic properties. In this study, we synthesised a free-standing WS2 sheet by a chemical route followed by electrochemical exfoliation by a giant molecule. During exfoliation of the WS2 crystal, atomic vacancies were created in the sheet with a lower number of layers. To understand the mechanism of exfoliation, we carried out x-ray diffraction, transmission electron microscopy, atomic force microscopy and Raman measurements. The types of atomic vacancies were realised by energy-dispersive x-ray spectroscopy, high-resolution transmission electron microscopy (fast Fourier transform), and x-ray photoelectron spectroscopy studies. We also observed a ferromagnetic ordering within the exfoliated WS2 sheet, which is explained on the basis of the generation of an atomic vacancy induced spin-moment. The transport study of the exfoliated WS2 sheet suggests that the electro-transport behaviour still remains as a semiconductor even after exfoliation. This ferromagnetic semiconducting system will be applicable in spintronic devices and this technique will enrich the literature, particularly for the preparation of a 2D semiconducting ferromagnet in a facile fashion.

Identifying the effects of oxygen on the magnetism of WS2 nanosheets

“…As reported, defects contained in the structure of the samples can be identified from the lattice patterns of IFFT. 34 One can find that there are some defects in the exfoliated WS 2 nanosheets. To quantitatively analyze the layer number of the WS 2 nanosheets, the atomic force microscopy (AFM) images were obtained.…”

“…As reported, the 1T phase and vacancies formed during exfoliation would introduce magnetic moments. 24,26,28,34,35,41 In addition, the spin polarized edge states of the zigzag edge in the WS 2 nanosheets also can contribute to the magnetism. 15 Thus, the 1T phase, vacancies and spin polarized edge states contained in the structure of the exfoliated WS 2 nanosheets would contribute to the paramagnetism.…”

“…WS 2 nanosheets are usually obtained via mechanical exfoliation, wet chemical approaches, sulfurization of ultrathin WO 3 films and so on, 30–32 which generally contain 1T and 2H phases, defects, and also some oxygen. 28,33,34 The detected ferromagnetism in the WS 2 nanosheets was generally attributed to defects, spin-polarized edge states and the 2H to 1T phase transition generated during the production process. 26–29,34,35 The oxygen usually contained in the prepared WS 2 nanosheets may also give effect to the magnetism.…”

“…28,33,34 The detected ferromagnetism in the WS 2 nanosheets was generally attributed to defects, spin-polarized edge states and the 2H to 1T phase transition generated during the production process. 26–29,34,35 The oxygen usually contained in the prepared WS 2 nanosheets may also give effect to the magnetism. It is important to identify the effects of oxygen on the magnetism of WS 2 nanosheets for their application in spintronics.…”

Interfacial negative magnetization in Ni encapsulated layer-tunable nested MoS2 nanostructure with robust memory applications

“…During the past few years, intensive studies have been carried out on two-dimensional (2D) transition-metal (TM)-based nanostructures grown on graphene and MoS 2 surfaces. 1–3 Although many intriguing results on TM-based 2D surfaces have been demonstrated, the appearance of a negative magnetization state while inducing magnetism in diamagnetic MoS 2 has not yet been discussed.…”