2 research outputs found
Investigations on Diamond Nanostructuring of Different Morphologies by the Reactive-Ion Etching Process and Their Potential Applications
We report the systematic studies
on the fabrication of aligned, uniform, and highly dense diamond nanostructures
from diamond films of various granular structures. Self-assembled
Au nanodots are used as a mask in the self-biased reactive-ion etching
(RIE) process, using an O<sub>2</sub>/CF<sub>4</sub> process plasma.
The morphology of diamond nanostructures is a close function of the
initial phase composition of diamond. Cone-shaped and tip-shaped diamond
nanostructures result for microcrystalline diamond (MCD) and nanocrystalline
diamond (NCD) films, whereas pillarlike and grasslike diamond nanostructures
are obtained for Ar-plasma-based and N<sub>2</sub>-plasma-based ultrananocrystalline
diamond (UNCD) films, respectively. While the nitrogen-incorporated
UNCD (N-UNCD) nanograss shows the most-superior electron-field-emission
properties, the NCD nanotips exhibit the best photoluminescence properties,
viz, different applications need different morphology of diamond nanostructures
to optimize the respective characteristics. The optimum diamond nanostructure
can be achieved by proper choice of granular structure of the initial
diamond film. The etching mechanism is explained by in situ observation
of optical emission spectrum of RIE plasma. The preferential etching
of sp<sup>2</sup>-bonded carbon contained in the diamond films is
the prime factor, which forms the unique diamond nanostructures from
each type of diamond films. However, the excited oxygen atoms (O*)
are the main etching species of diamond film
Role of Carbon Nanotube Interlayer in Enhancing the Electron Field Emission Behavior of Ultrananocrystalline Diamond Coated Si-Tip Arrays
We
improved the electron field emission properties of ultrananocrystalline
diamond (UNCD) films grown on Si-tip arrays by using the carbon nanotubes
(CNTs) as interlayer and post-treating the films in CH<sub>4</sub>/Ar/H<sub>2</sub> plasma. The use of CNTs interlayer effectively
suppresses the presence of amorphous carbon in the diamond-to-Si interface
that enhances the transport of electrons from Si, across the interface,
to diamond. The post-treatment process results in hybrid-granular-structured
diamond (HiD) films via the induction of the coalescence of the ultrasmall
grains in these films that enhanced the conductivity of the films.
All these factors contribute toward the enhancement of the electron
field emission (EFE) process for the HiD<sub>CNT/Si‑tip</sub> emitters,
with low turn-on field of <i>E</i><sub>0</sub> = 2.98 V/μm
and a large current density of 1.68 mA/cm<sup>2</sup> at an applied
field of 5.0 V/μm. The EFE lifetime stability under an operation
current of 6.5 μA was improved substantially to τ<sub>HiD/CNT/Si‑tip</sub> = 365 min. Interestingly, these HiD<sub>CNT/Si‑tip</sub> materials also show enhanced plasma illumination behavior, as well
as improved robustness against plasma ion bombardment when they are
used as the cathode for microplasma devices. The study concludes that
the use of CNT interlayers not only increase the potential of these
materials as good EFE emitters, but also prove themselves to be good
microplasma devices with improved performance