Chong-Yun Park

Growth and emission characteristics of vertically well-aligned carbon nanotubes grown on glass substrate by hot filament plasma-enhanced chemical vapor deposition

Vertically well-aligned multiwall carbon nanotubes (MWNTs) were grown on nickel-coated glass substrates by plasma-enhanced chemical vapor deposition at low temperatures, below 600 °C, with and without hot filament. Acetylene and ammonia gas were used as the carbon source and a catalyst. Effects of growth parameters, such as plasma intensity, filament current, and substrate temperature, on the growth characteristics of MWNTs were investigated. Plasma intensity was found to be the most critical parameter controlling the growth of MWNTs. Field emission from the MWNTs was obtained using a phosphor anode with an onset electric field of 1.5 V/μm.

Growth characteristics of carbon nanotubes by plasma enhanced hot filament chemical vapor deposition

We successfully obtained vertically aligned multiwalled carbon nanotubes on different nickel-coated substrates by plasma enhanced hot filament chemical vapor deposition at low temperatures below 650°C. Acetylene and ammonia gas were used as the carbon source and a catalyst. The surface roughness of the nickel layer increased as NH3 etching time increased. The diameters of the nanotubes decreased and the density of nanotubes increased as NH3 etching time increased. The diameter of the nanotubes was 30–70 nm. A nickel cap was observed on the top of the grown nanotube and a very thin amorphous-carbon-like layer was found on the nickel cap. The morphology and microstructure of carbon nanotubes were measured using scanning electron microscopy and transmission electron microscopy.

Field emission properties of Ag-Cu-alloy coated CNT-emitters

The field emission properties of CNT-emitters coated with Ag-Cu alloy have been investigated. The vertical aligned multi-walled CNTs were synthesized by dc-plasma enhanced chemical vapor deposition (dc-PECVD) and the Ag-Cu alloy was coated by using dc-magnetron sputter. The morphology of alloy-coated and un-coated CNT-emitters was observed by using SEM and their field emission properties were also measured. Annealing the AgCu-coated CNTs at temperature more than , the Ag-Cu alloy was diffused to and aggregated on the top of the CNT as a Q-tip. A significant progress on the field emission was not observed with coating Ag-Cu alloy on the CNTs, but a certain improvement in a resistance against oxygen gas was made confirmation. It seems to be due to inertness of Ag-Cu alloy on the CNTs.

Synthesis of High-Quality Single-Walled Carbon Nanotube Fibers by Vertical CVD

Many routes have been developed for the synthesis of signle-walled carbon nanotubes (SWCNTs). We spun fibers of SWCNTs directly from vertical furnace using a liquid source of carbon and an iron-contained molecule. The solution was prepared by ethanol as a carbon source, in which ferrocene as a catalyst, thiophene were dissolved. It was then injected from the top of the furnace into hot zone with hydrogen as a carrier gas. We successfully synthesized high-quality SWCNTs by adjusting the various experimental conditions, such as concentration of ferrocene, solution injection rate, concentration of thiophene, and hydrogen flow rate. Measurement of Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy were carried out to find the optimized conditions. The synthesized SWCNTs (1.16~1.64 nm) appeared a bundle structure and well-aligned parallel to the direction of furnace. These results also provide an simple way for high-quality SWCNTs mass production and fabricating direct spining SWCNTs fiber. It will allow one-step production of SWCNTs fiber with potentially excellent properties and wide-range applications.

Synthesis of Vertically Aligned Single-Walled Carbon Nanotubes by Thermal Chemical Vapor Deposition

Carbon nanotubes have emerged as a promising material for multifaceted applications, such as composited nanofiber, field effect transistors, field emitters, gas sensors due to their extraordinary electrical and physical properties. In particular, synthesis of vertically aligned carbon nanotubes with a high aspect ratio has recently attracted attention for many applications. However, mass production of high-quality single-walled carbon nanotubes is still remain elusive. In this study, an effect of chemical vapor deposition conditions, including catalyst thickness, feedstock flow rate, and growth temperature, on synthesis of carbon nanotube was systematically investigated.

Selective Separation of Semiconducting Single-Walled Carbon Nanotubes via Microwave Irradiation

In this study, single-walled carbon nanotubes (SWCNTs) were synthesized on a Fe//Si layer by thermal chemical vapor deposition. Metallic SWCNTs were selectively removed by microwave irradiation. Electrical and structural characterizations of the SWCNTs clearly revealed that the metallic SWCNTs were almost removed by microwave irradiation for 120 sec. The remained semiconducting SWCNTs with a high crystalline structure were obtained over 95%. This method would provide useful information for applications to SWCNTs-based field effect transistors and multifaceted nanoelectronics.