The synthesis of diamond nano-tips for enhancing the plasma illumination characteristics of the capacitive type plasma devices

The enhancement on the plasma illumination characteristics of a capacity-type plasma devices (CP-devices) utilizing the diamond coated Si-nanotips as cathodes was systematically investigated. The improvement on these characteristics was closely correlated with the electron field emission (EFE) properties of diamond films coated. The microcrystalline diamond films grown a ultrananocrystalline diamond nucleation layer ((MCD/UNCD), which possessed lowest turn-on field for inducing the EFE process (E
₀
=4.67 V/μm) with largest EFE current density (J
_e
=0.31 mA/cm
²
), resulted in the best plasma illumination performance for the CP-devices, as compared with those made of the MCD/Si films grown without the nucleation layer. The plasma can be triggered at the lowest threshold field of E
_th
=0.24 V/μm. Transmission electron microscopic studies revealed that the secondary microwave plasma enhanced CVD process altered the microstructure of the UNCD nuclear layer, instead of growing a layer of large-grain diamond films on top of the UNCD nuclear layer. The MCD/UNCD films that contained large diamond aggregates evenly distributed among the ultra-small grain matrix, with the induction of a-few-layer graphite, surrounding the large aggregates exhibit superior EFE and plasma illumination characteristics for the MCD/UNCD films/devices, as compared with those of the MCD/Si ones. The presence of graphene-like phase is presumed to be the prime factor resulting in superior EFE properties for the MCD
_I
films and the better plasma illumination characteristics for the CP-devices.