In situ transmission electron microscopy of individual carbon nanotetrahedron/nanoribbon structures in Joule heating

Abstract

Collapse of a carbon nanotube results in the formation of a nanoribbon, and a switching of the collapse direction yields a nanotetrahedron in the middle of a nanoribbon. Here, we report in-situ transmission electron microscopy observations of the behavior of carbon nanotetrahedron/nanoribbon structures during Joule heating to reveal their thermal stability. In addition, we propose that the observed process is related to the formation process of the structure. V C 2014 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4894003]Stability of nanomaterials such as nanotubes and nanowires under Joule heating is crucial when they are utilized for electronic devices and wiring; therefore, the behavior of nanomaterials under Joule heating has been investigated by means of transmission electron microscopy (TEM) by many research groups. [1][2][3][4] For example, we reported in-situ TEM observations of Joule heating of nanowires such as Si nanochains 5,6 and SiC nanowires. 7,8 These studies show that both Si nanochains and SiC nanowires are converted into carbon-nanotubes by Joule heating. In the conversion of Si nanochains to carbon nanotubes, the carbon source is the surface carbon contamination, and the empty core of the nanotube is formed by vaporization of the Si oxide of the chains. In the conversion of SiC nanowires to carbon nanotubes, the graphitization of SiC nanowires is induced by Si vaporization. One of the important points of the transformation by Joule heating lies in the possibility to convert a highly resistive nanostructure (Si nanochain) to an excellent conductor (carbon nanotube). The relative ease of Joule heating-a simple application of high current by microprobes-makes the nanostructures transformations a very important candidate for nanowiring applications. It is therefore clear that structural changes of nanomaterials by Joule heating are an important topic with yet undiscovered possibilities. In the final analysis, both the good durability and the structural change can be utilized if the behavior is understood well.We previously reported the formation of carbon nanoribbons by flattening of carbon nanotubes, and the formation of nanotetrahedra by switching of the flattening direction (see Fig. 1). 9 The structure consisting of nanotetrahedra inside a nanoribbon host is interesting since it may modulate the charge transport properties and could be useful for nanodevices. In addition, a junction of a nanotetrahedron and a nanoribbon could be utilized to change the direction of nanowiring. All these possible applications require knowledge of the durability of the nanostructures against Joule heating. In this study, we investigate the structural changes and durability of the nanotetrahedron/nanoribbon structure by means of in-situ TEM observation. We show that carbon nanotetrahedra have an excellent thermal durability and do not change their shape up to the temperature at which carbon nanoribbons are broken off near the electrode. In addition, we observed a process in which a carbon nanotetrahedron was ab...

In situ transmission electron microscopy of individual carbon nanotetrahedron/ribbon structures in bending

“…In order to examine whether our carbon nanotetrahedron/nanoribbon structures can be used for this purpose, we have examined their durability against Joule heating in a transmission electron microscope, and revealed that the nanotetrahedra were as stable as CNTs. 12 When using the carbon nanotetrahedron/nanoribbon structure in flexible devices, it is also important to understand its durability against mechanical strain. In this paper, we focus on the mechanical behavior of the carbon nanotetrahedron/nanoribbon structure under bending.…”