Characterizing herring bone structures in carbon nanofibers using selected area electron diffraction and dark field transmission electron microscopy

The use of selected area electron diffraction and centered dark field imaging using a transmission electron microscope is demonstrated for studying the herringbone structure of carbon nanofibers (CNFs). The experimental method is described and illustrated with CNFs that were grown via a chemical vapor deposition method with a nickel catalyst. It is demonstrated that this method gives the angle of the herringbone with great accuracy and gives insight into the uniformity of graphitic elements in the herringbone structure. It was found that the Ni catalyst could be removed from the fiber-tips by treatment in HNO₃, without affecting the carbon structure. These electron microscopy results were confirmed by XRD. The parameters that can be determined by application of this characterization method are expected to be useful to study and optimize growth conditions for carbon nanofibers grown by chemical vapor deposition.