Yong Sook Shin

Effects of N2 on the Growth of Multiwalled Carbon Nanotubes Synthesized by Plasma-Enhanced Chemical Vapor Deposition

We have investigated the role of N2 in the synthesis of carbon nanotubes (CNTs) by dc hot-filament plasma-enhanced chemical vapor deposition. An NH3 and C2H2 gas mixture with a ratio of 4:1 was used as a precursor for the synthesis of CNTs on nickel-coated TiN/Si (100) substrates. N2 gas was introduced at a flow rate of 30–120 sccm with the precursor. The structure and composition of CNTs synthesized with/without N2 were investigated by scanning electron microscopy, transmission electron microscopy, X-ray photoemission spectroscopy (XPS), and Raman spectroscopy. The multiwalled carbon nanotubes (MWCNTs) synthesized with N2 were 2–5 times longer than those synthesized without N2, and the morphology of the MWCNTs was improved. An XPS core level spectrum shows that nitrogen is in the CNX and C–NH2 forms.

Field emission properties of ZnO nanorods coated with NiO film

The field emission (FE) properties of ZnO and NiO-coated ZnO (NiO∕ZnO) nanorods are investigated under vacuum of 7×10−7Torr and oxygen rich vacuum of 1×10−5Torr. The ZnO nanorods were synthesized on a Si(100) substrate by metal-organic chemical vapor deposition, and the NiO film with the thickness of ∼15nm was coated by using atomic layer deposition. The turn-on voltages of the NiO∕ZnO nanorod and the ZnO nanorod were ∼5.2 and ∼3.0V∕μm at 1μA∕cm2, respectively. The electron FE stability of the NiO∕ZnO nanorods to the ZnO nanorod was significantly improved in oxygen rich vacuum even.

Synthesis of Crystalline Carbon Nanotube Arrays on Anodic Aluminum Oxide Using Catalyst Reduction with Low Pressure Thermal Chemical Vapor Deposition

Well-aligned crystalline carbon nanotubes (CNTs) were synthesized on anodic aluminum oxide (AAO) template using low-pressure thermal chemical vapor deposition (TCVD). The AAO templates were fabricated using an anodization process, and Fe as a catalyst was electrochemically deposited inside the bottom of the pores on the AAO template. For promotion of catalytic reaction of Fe, pore widening and catalyst reduction were performed. The enhancement of the catalytic reaction between C2H2 and the Fe catalyst particles results in CNTs with good crystallinity and a high packing density without the deposition of amorphous carbon on the pore surface of the AAO templates. The diameter and density of the CNTs were approximately 50 nm and 7×109 CNTs/cm2 (70% of pore density), respectively. When the threshold voltage of the electron emission was measured with a gap of 300 µm, it showed a very low turn-on field of 0.87 V/µm and the field enhancement factor was greater than 5600.

Nitrogen-incorporated multiwalled carbon nanotubes grown by direct current plasma-enhanced chemical vapor deposition

The nitrogen-incorporated multiwalled carbon nanotubes (N-MWCNTs) were synthesized by dc plasma-enhanced chemical vapor deposition with a gas mixture of C2H2, NH3, and N2. Nitrogens in the N-MWCNTs were pyridinic nitrogen and graphitic nitrogen. With increase in the flow rate of N2 gas during the synthesis of MWCNTs, the pyridinic nitrogen increased much more than graphitic nitrogen. The near-edge x-ray absorption fine structure spectra revealed that the density of states such as π*, σ*, and π*+σ* bands of the N-MWCNTs decreased with increase of concentration of pyridinic nitrogen incorporated in the MWCNTs. The intensity ratio of the D band to the G band of Raman spectrum increased with the incorporation of nitrogen into MWCNTs.