The dynamic observation of the field emission site of electrons on a carbon nanotube tip

A carbon nanotube (CNT) tip in an electric field was dynamically observed at an atomic scale. The field emission site of electrons was investigated by using a field ion microscope (FIM) and a field emission microscope (FEM). In-situ transmission electron microscope observations demonstrated that the CNT tip was deformed by bending the outer layers during field emission. The deformation process resulted in the formation of a nanoscale protrusion as an emission site at the CNT tip. The deformation mechanism can be explained by the reconstruction of carbon atoms. The high electric field that was concentrated in the vicinity of the pentagonal carbon rings on the CNT tip and the electrical attraction caused by applying the bias voltage between electrodes may have contributed to the formation of the protrusion. The atomic structural observations by FIM and FEM indicated that electrons were emitted from the nanoscale protrusion on the carbon network, rather than from the pentagonal carbon ring. The formation of the emission site contributed to the excellent field emission characteristics of the CNT. However, the structural change can be considered as damage caused to the CNT by the high electric field.