Synergetic effect of edge states and point defects to tune ferromagnetism in CVD-grown vertical nanostructured MoS2: A correlation between electronic structure and theoretical study

Abstract

Room-temperature ferromagnetism (RTFM) exhibited by nanostructured two-dimensional semiconductors for spintronics applications is a fascinating area of research. The present work reports on the correlation between the electronic structure and magnetic properties of defect-engineered nanostructured MoS₂ thin films. Low-energy light and heavy-mass ion irradiation have been performed to create defects and tune the magnetic properties of MoS₂. Vertical nanosheets with edge termination in the pristine sample have been examined by field emission scanning electron microscopy (FESEM). Deterioration of vertical nanosheets is observed in low-energy Ar⁺ and Xe⁺ irradiated samples. High-resolution transmission electron microscopy (HR-TEM) analysis confirmed the sample’s crystallinity and the (002) plane formation. An appreciably high magnetization value of 1.7 emu/g was observed for edge-oriented nanostructured pristine MoS₂ thin films, and it decreased after ion irradiation. From X-ray photoelectron spectroscopy (XPS) data, it is evident that, due to oxygen incorporation in the sulfur vacancy sites, Mo 5+ and 6+ states increase after ion irradiation. The density functional theory (DFT) calculations suggest that the edge-oriented spins of the prismatic edges of the vertical nanosheets are primarily responsible for the high magnetic moment in the pristine film, and the edge degradation and reduction in sulfur vacancies by the incorporation of oxygen upon irradiation result in a decrease in the magnetic moment.