Irradiation damage determined field emission of ion irradiated carbon nanotubes

Figuring out the underlying relationship between the field emission (FE) properties and the ion irradiation induced structural change of carbon nanotubes (CNTs) is of great importance in developing high-performance field emitters. We report here the FE properties of Si and C ion irradiated CNTs with different irradiation doses. It is found that the FE performance of the ion irradiated CNTs ameliorates before and deteriorates after an irradiation-ion-species related dose. The improved FE properties are ascribed to the increased amount of defects, while the degraded FE performance is attributed to the great shape change of CNTs. These two structural changes are further characterized by a structural damage related parameter: dpa (displacement per atom), and the FE performance of the ion irradiated CNTs is surprisingly found to be mainly dependent on the dpa. The optimal dpa for FE of the ion irradiated CNTs is ∼0.60. We ascribe this to the low irradiation doses and the low substrate temperature that make the ion irradiation play a more important role in producing defects rather than element doping. Furthermore, the ion irradiated CNTs exhibit excellent FE stability, showing promising prospects in practical applications.