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modeling of sheath ion-molecule reactions in plasma enhanced chemical vapor deposition of carbon nanotubesIn many plasma simulations, ion-molecule reactions are modeled using ion energy independent reaction rate coefficients that are taken from low temperature selected-ion flow tube experiments. Only exothermic or nearly thermoneutral reactions are considered. This is appropriate for plasma applications such as high-density plasma sources in which sheaths are collisionless and ion temperatures 111 the bulk p!asma do not deviate significantly from the gas temperature. However, for applications at high pressure and large sheath voltages, this assumption does not hold as the sheaths are collisional and ions gain significant energy in the sheaths from Joule heating. Ion temperatures and thus reaction rates vary significantly across the discharge, and endothermic reactions become important in the sheaths. One such application is plasma enhanced chemical vapor deposition of carbon nanotubes in which dc discharges are struck at pressures between 1-20 Torr with applied voltages in the range of 500-700 V. The present work investigates The importance of the inclusion of ion energy dependent ion-molecule reaction rates and the role of collision induced dissociation in generating radicals from the feedstock used in carbon nanotube growth.
Document ID
20040086919
Document Type
Conference Paper
Authors
Hash, David B.
(NASA Ames Research Center Moffett Field, CA, United States)
Govindan, T. R.
(NASA Ames Research Center Moffett Field, CA, United States)
Meyyappan, M.
(NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
August 21, 2013
Publication Date
June 10, 2004
Subject Category
Plasma Physics
Meeting Information
57th Gaseous Electronics Conference(Bunratty)
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.