Stabilization of the rhombohedral polytype in MoS2 and WS2 microtubes:: TEM and AFM study

MoS2 and WS2 micro- and nanotubes prepared by chemical transport reaction grow by spiral rolling of the molecular layers up to few millimetres in length and up to several micrometers in diameter. Each rolling molecular layer has to satisfy the stacking order and orientation relationship regarding the previous layer. Therefore, the strain appears in the tube walls, which relaxes in the nanotubes by formation of edge dislocations, whereas in the microtubes, it stabilizes a rhombohedraI polytype. Transmission electron diffraction evidence of rhombohedral stacking in the microtubes is reported. Surface structure of the microtubes is shown by atomic resolution using the atomic force microscopy. Different superstructures observed on the microtubes' surface are discused in the context of stacking order domains. (C) 1999 Elsevier Science B.V. All rights reserved.