Gamma-Ray Irradiation Induced Ultrahigh Room-Temperature Ferromagnetism in MoS₂ Sputtered Few-Layered Thin Films

Abstract

Defect engineering is of great interest to the two-dimensional (2D) materials community. If nonmagnetic transition-metal dichalcogenides can possess room-temperature ferromagnetism (RTFM) induced by defects, then they will be ideal for application as spintronic materials and also for studying the relation between electronic and magnetic properties of quantum-confined structures. Thus, in this work, we aimed to study gamma-ray irradiation effects on MoS2, which is diamagnetic in nature. We found that gamma-ray exposure up to 9 kGy on few-layered (3.5 nm) MoS2 films induces an ultrahigh saturation magnetization of around 610 emu/cm3 at RT, whereas no significant changes were observed in the structure and magnetism of bulk MoS2 (40 nm) films even after gamma-ray irradiation. The RTFM in a few-layered gamma-ray irradiated sample is most likely due to the bound magnetic polaron created by the spin interaction of Mo 4d ions with trapped electrons present at sulfur vacancies. In addition, density functional theory (DFT) calculations suggest that the defect containing one Mo and two S vacancies is the dominant defect inducing the RTFM in MoS2. These DFT results are consistent with Raman, X-ray photoelectron spectroscopy, and ESR spectroscopy results, and they confirm the breakage of Mo and S bonds and the existence of vacancies after gamma-ray irradiation. Overall, this study suggests that the occurrence of magnetism in gamma-ray irradiated MoS2 few-layered films could be attributed to the synergistic effects of magnetic moments arising from the existence of both Mo and S vacancies as well as lattice distortion of the MoS2 structure.

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“…Therefore, maximizing the number of active sites is crucial for catalytic applications. Strategies such as creating large quantities of small nanosheets or engineering defective surfaces are considered [45][46][47][48].…”

Recent Advances in the Preparation and Application of Two-Dimensional Nanomaterials

“…However, it also has some disadvantages, such as material selection limitations, the requirement for a high vacuum environment, and relatively slow growth rates [68]. Anbalagan et al [69] investigated the impact of gamma-ray irradiation on MoS 2 thin films by magnetron sputtering. They demonstrated in their experimental study that fewer-layered sputtered MoS 2 films exhibit long-range ferromagnetic (FM) behavior with a magnetization (M s ) of approximately 610 emu/cm 3 at room temperature following 9 kGy of gamma-ray irradiation, as shown in Figure 5a.…”

Recent Advances in Molybdenum Disulfide and Its Nanocomposites for Energy Applications: Challenges and Development

“…Chemical vapor deposition (CVD), liquid-chemical exfoliation, hydrothermal synthesis, solvothermal synthesis, and mechanical exfoliation are among the popular methods used for synthesis. The synthesis methodologies for MoS 2 and its related composites are varied and provide researchers with a range of options for producing high-quality materials for a wide range of applications [ 75 , 76 , 77 , 78 ].…”