Keywords: in situ TEM, mechanical properties, field emission, zinc oxide nanobelts, carbon nanotubes, one-dimensional nanostructures, nanotechnology, nanowires, transmission electron microscopy, nanomaterials
In situ TEM probing properties of individual one-dimensional nanostructures
One-dimensional nanomaterials are a fundamental component of nanoscience and nanotechnology. Property measurements of individual one-dimensional nanostructures, including nanowires and nanotubes, are challenging due to their small size, which constrains the applications of the well-established testing and measurement techniques. We have developed an alternative novel approach that allows the direct measurements of the mechanical and physical properties of individual nanostructures inside high-resolution transmission electron microscopy (TEM), by which microstructures of the nanomaterials can be characterised in situ. Thus the properties of nanostructures can be directly correlated with their well-defined structures by this technique. This paper will review our progress in using in situ TEM method to measure the mechanical and field emission properties of individual nanowires and nanotubes. Mechanical resonance of zinc oxide (ZnO) nanobelt, as a new important class of nanowire, was induced by an alternating electric field. Due to the rectangular cross-section of the nanobelt, two fundamental resonance modes have been observed, corresponding to the two orthogonal transverse vibration directions, showing the versatile applications of nanobelts as nanocantilevers and nanoresonators. The elastic modulus of the ZnO nanobelts was measured to be ∼52 GPa and the damping time constant of the resonance in vacuum of 10-8 Torr was ∼1.2 ms. Field emission properties of individual carbon nanotubes have been systematically studied. The field emission behaviours have been directly linked with in situ nanotube tip morphology and their real work function. The dynamic field emission of a nanotube at mechanical resonance was also studied by in situ TEM method.