Investigations on Diamond Nanostructuring of Different
Morphologies by the Reactive-Ion Etching Process and Their Potential
Applications
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Abstract
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