Mechanical behavior of individual WS₂ nanotubes

The Young's modulus of WS₂ nanotubes is an important property for various applications. Measurements of the mechanical properties of individual nanotubes are challenged by their small size. In the current work, atomic force microscopy was used to determine the Young's modulus of an individual multiwall WS₂ nanotube, which was mounted on a silicon cantilever. The buckling force was measured by pushing the nanotube against a mica surface. The average Young's modulus of an individual WS₂ nanotube, which was calculated by using Euler's equation, was found to be 171 GPa. First-principle calculations of the Young's modulus of MoS₂ single-wall nanotubes using density-functional–based tight-binding method resulted in a value (230 GPa) that is close to that of the bulk material. Furthermore, the diameter dependence of the Young's modulus in both zigzag and armchair configuration was studied and was found to approach the bulk value for nanotubes with few-nanometer diameters. Similar behavior is expected for WS₂ nanotubes. The mechanical behavior of the WS₂ nanotubes as atomic force microscope imaging tips gave further support for the measured Young's modulus.