Traditionally, electron microscopes are mainly used to characterize structures while electron beam damage to the sample should be avoided. The combination of electron microscopes and nanomanipulators provides an intuitionistic, real-time and in situ way to study nanomaterials, enabling us to relate directly the properties of nanomaterials to their structures. Although scanning electron microscope (SEM) does not provide atomic structure information like transmission electron microscope (TEM) does, its large specimen chamber can accommodate multi-nanomanipulators and enables various multi-terminal measurements, such as electrical and mechanical measurements.
Here, we demonstrate a set of novel methods for performing in situ measurements on individual thin carbon nanotubes (CNTs) using nanomanipulators inside a SEM. With the methods, the mechanical and electronic properties of individual thin CNTs were studied. In addition, the measured properties were correlated directly to the atomic structures of the CNTs.
The mechanical response of individual double-walled and triple-walled carbon nanotubes (CNTs) and CNT ropes consisting of only two double-walled CNTs (DWCNTs) under tensile load was measured using nanomanipulators in a SEM. The breaking strain and strength and Young’s modulus of individual CNTs were measured. Carbon nanotube ropes exhibited one-step or stepwise breaks depending on the relative breaking strains of the two CNTs.
The electronic properties of individual thin CNTs under a known axial tensile load were studied. A strain induced metallic-to-semiconducting transition of a DWCNT and a bandgap increase of a SWCNT were observed. The electromechanical properties of the SWCNT were also correlated to its chirality determined by electron diffraction.
The vibration properties of individual CNTs under axial tension were quantitatively determined experimentally. A gradual beam-to-string transition from multi-walled CNTs to SWCNTs was observed. The continuum beam theory was found to be applicable to even single-walled CNTs.
