Layered structure of MoS2 investigated using electron energy loss spectroscopy

Transition metal dichalcogenide MoS2 has attracted significant interest for its unique electronic, optical and catalytic properties. Layered crystalline MoS2 can be mechanically exfoliated into single monolayers. With the advancement of microscopic and analytical techniques, significant insight knowledge has been obtained on the structure and properties of two-dimensional (2D) materials. In this paper, the authors have carried out high resolution transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) to investigate MoS2 layers transferred on silicon substrate. Due to the weak nature of van der Waal forces between the S-S layers, stability of layers poses a challenge at high electron acceleration voltages. Dark field STEM (DF-STEM) and EELS, used on 11 layers of MoS2, reveal an interlayer spacing of ~6.25 Å, which is consistent with the reported crystal structure of MoS2.