Structure of single-molecular-layer MoS2.

An analysis of x-ray diffraction line shape and Raman-scattering results shows that single-molecular-layer ${\mathrm{MoS}}_{2}$, prepared by exfoliation of lithium-intercalated ${\mathrm{MoS}}_{2}$ powder in water, has a structure in which the Mo atoms are octahedrally coordinated, in contrast to the trigonal prismatic coordination of Mo in bulk ${\mathrm{MoS}}_{2}$. The octahedral coordination of single-layer ${\mathrm{MoS}}_{2}$ is strongly distorted, with a 2${\mathit{a}}_{0}$ superlattice. For a restacked film, the octahedral coordination of ${\mathrm{MoS}}_{2}$ appears to be a metastable structure. On heating or aging, it transforms back to the trigonal prismatic coordination.