Raman characterisation of MoS₂ microtube

A MoS₂ microtube synthesized by chemical transport reaction was studied by Raman line scan mapping. The Raman spectrum of the MoS₂ microtube closely resembles that of a MoS₂ single crystal. In both, first order A_1g and E_2g Raman lines are observed with equal wave numbers, while line widths are slightly larger in the microtube spectrum, which can be attributed to defects. In the line scan along the tube axis the wave numbers of first order peaks are constant, while a slight up-shift of the Raman lines is observed in a line scan perpendicular to the tube. Possible mechanisms are discussed and the heating effect is proposed. Line scan approach over the edge of an object thus enables accurate determination of positions of first order peaks in highly absorbing materials.