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

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