A study of single-layer and restacked MoS₂by X-ray diffraction and X-ray absorption spectroscopy

Structural studies of single layers of MoS2 in aqueous suspension using X-ray diffraction and EXAFS show that single layers differ from bulk single-crystal MoS2 by having two nearest Mo-Mo distances at 2.8 and 3.8 AA substantially distorted from the bulk value of 3.16AA while the nearest Mo-S distance is essentially unchanged from the bulk value. As an aqueous suspension of single-layer MoS2 dries, a phase is obtained in which two monolayers of water are present between parallel but rotationally disordered MoS2 layers, and the bulk Mo-Mo distance starts to reappear. In dry restacked MoS2 only the bulk Mo-Mo distance is recovered, the same spacing between Mo layers as in single-crystal MoS2, is observed and the layers exhibit partial rotational order.