Structure changes of an individual carbon nanocoil and its field-emission enhancement by laser treatment

Abstract

The electron field-emission properties of an individual carbon nanocoil (CNC) have been investigated. The electron diffraction patterns and Raman scattering spectra for the CNC before and after the field emission show that the sp2 grains in the amorphous sp3 network are increased both in size and amount and the graphitic sp2 grains turn to align to the same orientation in the CNC. Joule heating induced by the high field-emission current is considered to be the main reason for this result. Furthermore, morphology of a CNC is also modified by a laser irradiation. The modified CNC exhibits a lower turn-on voltage and a smaller slope of Fowler–Nordheim plot, indicating that the field-emission properties of the CNC are improved. It is found that the curvature radius of the modified CNC tip is smaller than that of the initial one, which is the main factor contributing to the enhancement of field-emission properties.