Enhanced room temperature ferromagnetism in MoS2 by N plasma treatment

Abstract

The introduction of ferromagnetism in MoS2 is important for its applications in semiconductor spintronics. MoS2 powders were synthesized by hydrothermal method, followed by the N plasma treatment at room temperature. Weak ferromagnetism with saturated ferromagnetic magnetization of 0.64 memu/g has been observed in the as-synthesized MoS2 at room temperature, which is significant enhanced to 3.67 memu/g after the N plasma treatment for the proper duration. X-ray photoelectron spectroscopy demonstrates the adsorption of N, and higher valence state of Mo than +4 due to the bonding with N after the N plasma treatment. First principle calculation has been performed to disclose the possible origin of ferromagnetism. One chemical adsorbed N ion on S ion may form conjugated π bonds with adjacent two Mo ions to have a total magnetic moment of 0.75 μB, contributing to the enhanced ferromagnetism.

O Plasma Treatment Enhanced Room Temperature Ferromagnetism in MoS2

“…After the O plasma treatment, all these three peaks shift to higher energy (Mo 3d 3/2 at 232.85 eV, Mo 3d 5/2 at 229.65 eV, and S 2 s at 227.05 eV). This is similar to previous results for MoS 2 treated by N plasma, which is due to the high electronegativity of O and more electrons are transferred from S and Mo to O [12]. This indicates that the O ions are chemically adsorbed on MoS 2 , the Mo-O and S-O bondings are formed.…”

“…2. As can be seen, the as-prepared MoS 2 particles show the nanosphere structure composed of nanosheets with wellexposed edge sites, similar to the previous results, which is the general shape of MoS 2 particles prepared by the hydrothermal method [12,20]. Such structure may provide more surface area, which is beneficial for exposing to O plasma.…”

“…Such structure may provide more surface area, which is beneficial for exposing to O plasma. After the O plasma treatment, the morphology of O 40 -MoS 2 keeps almost unchanged, indicating that O plasma treatment will not cause the structural collapse [12].…”

“…The MoS 2 nanostructures were prepared by the hydrothermal method [12]. 1.7655 g ammonium molybdate tetrahydrate (H 24 Mo 7 N 6 O 24 ⋅4H 2 O) and 1.5225 g thiourea (CH 4 N 2 S) as precursors were added to the 60 mL deionized water.…”

“…M. Chen doped the monolayer MoS 2 with N via a conventional chemical vapor deposition method; ferromagnetism has been observed which persisted up to room temperature [11]. In our previous work, N plasma was applied to treat the MoS 2 nanostructures; robust room temperature ferromagnetism was achieved by the appropriate duration [12]. O 2 is abundant in the atmosphere, which is chemical active.…”