In Situ treatments of nano-objects in the transmission electron microscope: the example of multiwall carbon nanotubes ,2015.6.5
作者:Jean-Luc Maurice, 发布日期:2015-06-05

2015.6.5 下午230




In Situ treatments of nano-objects in the transmission electron microscope: the example of multiwall carbon   nanotubes 


Jean-Luc Maurice 

Laboratory of physics of interfaces & thin films (LPICM), CNRS-Ecole polytechnique, Palaiseau, France




The observation of nano-objects (carbon nanotubes, semiconductor nanowires) in the transmission electron microscope (TEM), brings invaluable information on their structure at the atomic scale, which in turn allows one to understand and predict the properties of the objects. Understanding the way a given atomic structure is obtained, however needs recording pictures at different stages of growth. Given that cooling and passage in air add unwanted supplemental effects, those pictures should ideally be taken in the TEM, while the growth is going on in situ.


However, this requires injecting gas or molecular beams in the TEM column, without disturbing the electrons used for imaging. For allowing this, a prototype TEM has been ordered by CNRS (French national research centre) from the FEI company, which is going to be installed in September at Ecole polytechnique (NanoMAX project). 


This talk is about studies carried out to prepare the NanoMAX experiments. It is centred on multiwall carbon nanotubes for field emission application. These objects are ideally made of concentric cylinders of graphene. However most of the time, the cylinders are actually cones and the nanotubes are actually fibres made of stacks of these cones. An electrical current going through a nanotube thus flows less easily, as the resistivity perpendicular to the planes in graphite is 4 orders of magnitude higher than parallel to them. A goal of research in the growth of vertical multiwall nanotubes for field emission is to decrease their resistance and thus increase the parallelism of the graphene walls.


Thanks to the observation of growth in situ we have been able to isolate two growth modes of the carbon walls: layer by layer, giving cones, and in parallel, giving cylinders. This then allowed us to understand the conditions favouring cylinders and to prepare real nanotubes with parallel walls. 


Conclusions are then drawn on interesting prospects for in situ growth experiments.


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