O Plasma Treatment Enhanced Room Temperature Ferromagnetism in MoS2

MoS2 is a typical two-dimensional material with promising optical and electrical properties. The realization of ferromagnetism in MoS2 is important for its applications in semiconductor spintronics. A facile technique should be developed to induce the ferromagnetism in MoS2, and the possible extrinsic contribution should be avoided. In this paper, flower-like MoS2 nanostructures were fabricated by the hydrothermal method. X-ray diffraction spectra show the 1 T/2H mixed phases of as-prepared MoS2 nanostructures, which changes to pure 2H structure after the O plasma treatment. Raman spectra confirm the existence of Mo–O bonding, which is further confirmed by the X-ray photoelectron spectra after the O plasma treatment. Magnetization measurements at 300 K show the weak ferromagnetism in the as-prepared MoS2, with saturated ferromagnetic magnetization of 0.0012 emu/g. After the O plasma treatment, the weak ferromagnetism is strongly enhanced with saturated ferromagnetic magnetization of 0.0343 emu/g. First principle calculation has been performed to disclose the possible origin of ferromagnetism. Significant overlapping between the density of states of O and Mo, or O and S has been observed. The magnetic contribution from Mo and S is negligible, while O takes the main role for the enhanced ferromagnetism.