AVS 49th International Symposium
    Plasma Science Wednesday Sessions
       Session PS+TF-WeP

Paper PS+TF-WeP7
In situ Measurement of C@sub 2@ Radical Density in Microwave-Enhanced Methane/Hydrogen Plasma Used for Nanocrystalline Diamond Film Growth

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Plasma Etching & Deposition
Presenter: M. Hiramatsu, Meijo University, Japan
Authors: M. Hiramatsu, Meijo University, Japan
K. Kato, Meijo University, Japan
K. Ito, Meijo University, Japan
C.H. Lau, University of Oxford, UK
J.S. Foord, University of Oxford, UK
Correspondent: Click to Email
Conventional plasma-enhanced chemical vapor deposition (CVD) methods for diamond fabrication normally employ high-pressure (@>=@10 Torr), and methyl (CH@sub 3@) radicals are generally known to be important species for diamond formation. On the other hand, nanocrystalline diamond films were grown using fullerenes in a microwave argon plasma without addition of hydrogen. It was suggested that carbon dimer (C@sub 2@) radicals also might play an active role in conventional hydrogen-activated CVD. In the present work, C@sub 2@ radical density at the lowest excited state was measured in an ASTeX style conventional microwave plasma reactor with a CH@sub 4@/H@sub 2@ mixture using absorption spectroscopy. The Xe lamp emitting a continuous spectrum was used as a light source, and transmittance spectra through the plasma ball were obtained around 516.5 nm of (v' =0, v'' =0) bandhead of C@sub 2@ Swan system. Measurement was carried out under the conditions where nanocrystalline diamond films can be formed. At the typical growth conditions for the microwave plasma-enhanced CVD reactor used for nanocrystalline diamond film formation, the C@sub 2@ radical density in the plasma ball was of the order of 10@super 12@ cm@super -3@. The emission intensity of (0, 0) bandhead of C@sub 2@ Swan system was also measured. It was found that the emission intensity correlated linearly with C@sub 2@ radical density. C@sub 2@ radical density in the plasma ball under the condition where predominantly diamond can be formed was estimated to be 10@super 10@ - 2 x 10@super 11@ cm@super -3@.