Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Room temperature ferromagnetism has been reported in chemical vapor deposition-grown mixed-phase MoS2-MoOx thin films after Xe ion irradiation. Magnetic moment has significantly been enhanced after ion irradiation. Deterioration in crystallinity after ion irradiation has been shown by X-ray diffraction and Raman spectroscopy measurements. The variation in the surface morphology and/or formation of edge states can be observed by secondary electron microscopy images. The reduction in the oxygen vacancy concentration, probed by analysis of the O 1s core level X-ray photoelectron spectrum for the film with the maximum magnetic moment, rules out the possibility of ferromagnetism due to oxygen vacancy. Enhancement in the Mo content in 5+ and 6+ oxidation states due to the occupation of sulfur vacancy sites by oxygen after ion irradiation, calculated from X-ray photoelectron spectroscopy core level of Mo 3d and S 2p and valence band spectra, has been observed. Density functional theory (DFT) calculations also show the one-to-one correspondence of saturation magnetic moment with Mo6+ content. So, the enhancement in the ferromagnetism in mixed-phase of MoS2-MoOx thin films is due to the increase of Mo in 6+ oxidation state and exchange interaction between the different oxidation states of Mo via p-orbital of anion and formation of edged states.