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Title: Deposition of vertically oriented carbon nanofibers in atmospheric pressure radio frequency discharge

Abstract

Deposition of vertically oriented carbon nanofibers (CNFs) has been studied in an atmospheric pressure radio frequency discharge without dielectric barrier covering the metallic electrodes. When the frequency is sufficiently high so that ions reside in the gap for more than one rf cycle ('trapped ions'), the operating voltage decreases remarkably and the transition from a uniform glow discharge to an arc discharge is suppressed even without dielectric barriers. More importantly, the trapped ions are able to build up a cathodic ion sheath. A large potential drop is created in the sheath between the bulk plasma and the electrode, which is essential for aligning growing CNFs. At the same time, the damage to CNFs due to ion bombardment can be minimized at atmospheric pressure. The primary interest of the present work is in identifying the cathodic ion sheath and investigating how it influences the alignment of growing CNFs in atmospheric pressure plasma-enhanced chemical-vapor deposition. Spectral emission profiles of He (706 nm), H{alpha} (656 nm), and CH (432 nm) clearly showed that a dark space is formed between the cathode layer and the heated bottom electrode. However, increasing the rf power induced the transition to a nonuniform {gamma}-mode discharge which creates intensemore » plasma spots in the dark space. Aligned CNFs can be grown at moderate input power during the initial stage of the deposition process. Catalyst particles were heavily contaminated by precipitated carbon in less than 5 min. Alignment deteriorates as CNFs grow and deposition was virtually terminated by the deactivation of catalyst particles.« less

Authors:
; ; ; ; ; ;  [1];  [2]
  1. Department of Mechanical and Control Engineering, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro Tokyo 1528552 (Japan)
  2. (United States)
Publication Date:
OSTI Identifier:
20787801
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 99; Journal Issue: 2; Other Information: DOI: 10.1063/1.2163997; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ATMOSPHERIC PRESSURE; CARBON; CARBON FIBERS; CATALYSTS; CATHODES; CHEMICAL VAPOR DEPOSITION; DEACTIVATION; DIELECTRIC MATERIALS; ELECTRIC ARCS; GLOW DISCHARGES; ION BEAMS; IONS; LAYERS; NANOSTRUCTURES; PLASMA; PLASMA SHEATH; PRECIPITATION; RADIOWAVE RADIATION; TRAPPING

Citation Formats

Nozaki, Tomohiro, Goto, Tomoya, Okazaki, Ken, Ohnishi, Kuma, Mangolini, Lorenzo, Heberlein, Joachim, Kortshagen, Uwe, and Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455. Deposition of vertically oriented carbon nanofibers in atmospheric pressure radio frequency discharge. United States: N. p., 2006. Web. doi:10.1063/1.2163997.
Nozaki, Tomohiro, Goto, Tomoya, Okazaki, Ken, Ohnishi, Kuma, Mangolini, Lorenzo, Heberlein, Joachim, Kortshagen, Uwe, & Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455. Deposition of vertically oriented carbon nanofibers in atmospheric pressure radio frequency discharge. United States. doi:10.1063/1.2163997.
Nozaki, Tomohiro, Goto, Tomoya, Okazaki, Ken, Ohnishi, Kuma, Mangolini, Lorenzo, Heberlein, Joachim, Kortshagen, Uwe, and Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455. Sun . "Deposition of vertically oriented carbon nanofibers in atmospheric pressure radio frequency discharge". United States. doi:10.1063/1.2163997.
@article{osti_20787801,
title = {Deposition of vertically oriented carbon nanofibers in atmospheric pressure radio frequency discharge},
author = {Nozaki, Tomohiro and Goto, Tomoya and Okazaki, Ken and Ohnishi, Kuma and Mangolini, Lorenzo and Heberlein, Joachim and Kortshagen, Uwe and Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455},
abstractNote = {Deposition of vertically oriented carbon nanofibers (CNFs) has been studied in an atmospheric pressure radio frequency discharge without dielectric barrier covering the metallic electrodes. When the frequency is sufficiently high so that ions reside in the gap for more than one rf cycle ('trapped ions'), the operating voltage decreases remarkably and the transition from a uniform glow discharge to an arc discharge is suppressed even without dielectric barriers. More importantly, the trapped ions are able to build up a cathodic ion sheath. A large potential drop is created in the sheath between the bulk plasma and the electrode, which is essential for aligning growing CNFs. At the same time, the damage to CNFs due to ion bombardment can be minimized at atmospheric pressure. The primary interest of the present work is in identifying the cathodic ion sheath and investigating how it influences the alignment of growing CNFs in atmospheric pressure plasma-enhanced chemical-vapor deposition. Spectral emission profiles of He (706 nm), H{alpha} (656 nm), and CH (432 nm) clearly showed that a dark space is formed between the cathode layer and the heated bottom electrode. However, increasing the rf power induced the transition to a nonuniform {gamma}-mode discharge which creates intense plasma spots in the dark space. Aligned CNFs can be grown at moderate input power during the initial stage of the deposition process. Catalyst particles were heavily contaminated by precipitated carbon in less than 5 min. Alignment deteriorates as CNFs grow and deposition was virtually terminated by the deactivation of catalyst particles.},
doi = {10.1063/1.2163997},
journal = {Journal of Applied Physics},
number = 2,
volume = 99,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2006},
month = {Sun Jan 15 00:00:00 EST 2006}
}