Graphite Shell Film Formation Induced by Eduction Phenomenon of Ga Implanted by Focused Ion Beam

In this study, we used a transmission electron microscope (TEM) to evaluate the structure of the gallium (Ga) sphere formed on the tip of a diamond-like carbon (DLC) pillar fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD). Until now, details of the phenomenon induced by Ga eduction were remained unclear. We found that a graphite shell was formed on the surface of the Ga sphere after annealing. In addition, we demonstrated that this graphite shell film could be separated from the Ga sphere by performing a second annealing treatment. In-situ observations of the formation of the graphite shell film were carried out using TEM to clarify the process by which it was separated from the Ga sphere. The thermal expansion of Ga led to the separation of the graphite shell film, and Ga was vaporized from within the Ga sphere. These results imply that Ga is able to catalyze for the graphitization of carbon. The development of carbon nanodevices can be expected by using this novel phenomenon induced by Ga.