Eun Chang Choi

Synthesis of carbon nanotubes on diamond-like carbon by the hot filament plasma-enhanced chemical vapor deposition method

Carbon nanotubes (CNTs) have attracted considerable attention as possible routes to device miniaturization due to their excellent mechanical, thermal, and electronic properties. These properties show great potential for devices such as field emission displays, transistors, and sensors. The growth of CNTs can be explained by interaction between small carbon patches and the metal catalyst. The metals such as nickel, cobalt, gold, iron, platinum, and palladium are used as the catalysts for the CNT growth. In this study, diamond-like carbon (DLC) was used for CNT growth as a nonmetallic catalyst layer. DLC films were deposited by a radio frequency (RF) plasma-enhanced chemical vapor deposition (RF-PECVD) method with a mixture of methane and hydrogen gases. CNTs were synthesized by a hot filament plasma-enhanced chemical vapor deposition (HF-PECVD) method with ammonia (NH3) as a pretreatment gas and acetylene (C2H2) as a carbon source gas. The grown CNTs and the pretreated DLC films were observed using field emission scanning electron microscopy (FE-SEM) measurement, and the structure of the grown CNTs was analyzed by high resolution transmission scanning electron microscopy (HR-TEM). Also, using energy dispersive spectroscopy (EDS) measurement, we confirmed that only the carbon component remained on the substrate.

Synthesis of CNTs with Plasma Density and Tilt Degree of Substrate

We need to control the growth orientation of CNTs on a substrate for applications to various electric devices. Generally, the flow direction of feed gases and electric field between two electrode affect to growth orientations of CNTs. In this paper, we varied tilt degrees of substrates on a cathode and DC bias voltages (0, 500, 700 V) applied between two electrodes in order to change growth orientations of CNTs. We confirmed that tilt degrees of the substrate and variation of DC bias voltages affected to the shape and orientation of the grown CNTs on the substrate.

Etching Treatment of Vertically Aligned Carbon Nanotubes for the Application to Biosensor

The metal catalyst particles which there is as impurities on a tip part of carbon nanotube (CNT) are not good to apply it to a nano-electronic device. It was very important the opening of CNT-tip to fix a target bio material and a material to accept in CNT in a biosensor, so we performed wet etching to remove the metal catalyst particle which there was on a tip part of CNT grown up in the study and observed the opened CNT-tip with etching time. We synthesized the CNTs using a HF-PECVD method and choses the CNT length of 700 nm for the application of nano-electronic device such as a biosensor etc.. We observed the opened CNT-tip with wet etching times of (10, 30, 60 min). From the results, we observed that the CNT-tip was opened with the increase of wet etching time lively. In case of CNTs etched during 60 min, we confirmed that there was not the ratio of Ni included in CNTsI as catalyst. Conclusively, in the case of CNT etched for 60 minutes, it is completely good for application of a biosensor and, in addition, the metal-free CNTs will contribute to the application of other nanoelectronic devices.

Effect of Ni Catalyst Thickness on Carbon Nanotube Growth Synthesized by Hot-filament PECVD

본 연구에서는 탄소나노튜브의 성장특성을 결정짓는 여러 요소 중 한가지인 촉매층 두께의 변화에 따라서 형성되어지는 탄소나노튜브의 형태 변화를 관찰하였다. Ni 촉매층은 마그네트론 스퍼터링법을 이용하여 증착하였으며, Ni 촉매층의 두께는 20～80 ㎚의 범위에서 설정하였다. 두께에 따른 Ni 촉매층 기판을 hot-filament 플라즈마 화학기상 증착(HF-PECVD) 장치를 이용하여 탄소나노튜브를 합성하였으며, 성장되어진 탄소나노튜브의 성분분석은 에너지 분산형 X-선 측정기(EDS)를 통해 분석하였고, 고배율 투과전자현미경(HRTEM) 분석과 전계방사 주사전자현미경(FESEM) 분석을 통해 성장된 탄소나노튜브 성장 형태를 관찰하였다. 그 결과로써, 고배율 투과전자현미경(TEM) 분석을 통해서는 탄소나노튜브는 내부가 비어있으며, 다중벽으로 구성되어 있는 것을 관찰하였고, 탄소나노튜브 상부에 니켈 금속이 포함된 것을 확인하였다. 이것은 분산형 X-선 측정을 통해 탄소나노튜브의 구성성분이 접착층인 Ti, 촉매층인 Ni 그리고 탄소(C)로 이루어졌음을 다시한번 확인하였으며, 성장형태에서도 알 수 있듯이 탄소나노튜브 성장 전에 행해여지는 전처리는 촉매층의 입자를 변화시키고 변화된 촉매층의 표면은 다른 형태의 탄소나노튜브를 성장시킴을 알수 있었다. 결과적으로, 40 ㎚의 촉매층을 지니는 기판에서 가장 좋은 형태를 나타내는 탄소 탄소나노튜브가 성장되었음을 알 수 있다.

Synthesis and Surface Characterization of Carbon Nanotubes by Hot-Filament Plasma Enhanced Chemical Vapor Deposition

In this paper, the catalyst layer is deposited on silicon substrate using magnetron sputtering system and carbon nanotubes(CNTs) were grown in gas by hot-filament plasma enhanced chemical vapor deposition (HFPECVD) system. A growth temperature of carbon nanotubes was changed from . We observed the shape of CNTs by a field-emission scanning electron microscope(FE-SEM) measurement and analyzed the surface characteristic of CNTs layer by contact angle measurement. That is, the growth temperature of CNTs is the important factor leads to the variation of the properties.