The role of nanographitic phase on enhancing the electron field emission properties of hybrid granular structured diamond films: the electron energy loss spectroscopic studies

摘要

The electron field emission (EFE) properties of the hybrid granular structured diamond (HiD) films were markedly improved by N-ion implantation and annealing processes. The evolution of microstructure/bonding structure of the films due to these processes was investigated using the transmission electron microscopy (TEM) and the electron energy loss spectroscopy (EELS), respectively. The N-ion implanted/annealed HiD films showed a low turn-on field of (E_0)_(HiD) = 7.4Vμm~(-1) with large current density of (J_e)HiD = 600 μAcm~(-2), at 17.8Vμm~(-1), compared with pristine HiD films ((E_0) = 10.3Vμm~(-1), (J_e) = 95μAcm~(-2) at the same applied field). While the TEM studies revealed only the microstructural evolution due to N-ion implantation/annealing processes, the EELS elucidated the change in bonding structure, namely the transformation between the sp~3-bonded carbons and the sp~2-bonded ones. Therefore, the combined TEM/EELS analyses provided more insight into understand the mechanism by which the N-ion implantation/annealing processes enhanced the EFE properties of HiD films. These studies clearly demonstrated that the N-ion implantation/annealing processes induced the formation of nanographitic clusters. These nanographitic phases form an interconnected path throughout the film surface facilitating the easy transport of electrons and thereby markedly enhancing the EFE properties for the N implanted/annealed HiD films.