Browsing by Author "Sankaran, Kamatchi Jothiramalingam"

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Investigations on Diamond Nanostructuring of Different Morphologies by the Reactive-Ion Etching Process and Their Potential Applications
(2013-08-14)
Kunuku, Srinivasu
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Sankaran, Kamatchi Jothiramalingam
;
Tsai, Cheng-Yen
;
Chang, Wen-Hao
;
Tai, Nyan-Hwa
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-2/CF4 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-2-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(2)-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.
Structural and Electrical Properties of Conducting Diamond Nanowires
(2013-02-27)
Sankaran, Kamatchi Jothiramalingam
;
Lin, Yen-Fu
;
Jian, Wen-Bin
;
Chen, Huang-Chin
;
Panda, Kalpataru
Conducting diamond nanowires (DNWs) films have been synthesized by N-2-based microwave plasma enhanced chemical vapor deposition. The incorporation of nitrogen into DNWs films is examined by C Is X-ray photoemission spectroscopy and morphology of DNWs is discerned using field-emission scanning electron microscopy and transmission electron microscopy (TEM). The electron diffraction pattern, the visible-Raman spectroscopy, and the near-edge X-ray absorption fine structure spectroscopy display the coexistence of sp(3) diamond and sp(2) graphitic phases in DNWs films. In addition, the microstructure investigation, carried out by high-resolution TEM with Fourier transformed pattern, indicates diamond grains and graphitic grain boundaries on surface of DNWs. The same result is confirmed by scanning tunneling microscopy and scanning tunneling spectroscopy (STS). Furthermore, the STS spectra of current-voltage curves discover a high tunneling current at the position near the graphitic grain boundaries. These highly conducting regimes of grain boundaries form effective electron paths and its transport mechanism is explained by the three-dimensional (3D) Mott's variable range hopping in a wide temperature from 300 to 20 K. Interestingly, this specific feature of high conducting grain boundaries of DNWs demonstrates a high efficiency in field emission and pave a way to the next generation of high-definition flat panel displays or plasma devices.