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In Situ Infrared Spectroscopy of the Gaseous Species Present in a Diamond Chemical Vapor Deposition SystemWe interfaced a Hot-Filament Chemical Vapor Deposition (HFCVD) system to the emission port of an FT-IR spectrometer, in order to study the gas phase species present during the deposition of diamond thin films. The implementation of the infrared (IR) emission technique in situ allowed the study of various carbon-containing species believed to be crucial in diamond film growth. The two IR-active vibrational fundamentals of methane, v(3)(f2) and v(4)(f2), were observed at three different filament temperatures: 1000, 1500 and 2000 C. However, the net signal of v(3) was emission, while that of v(4) was absorption. These results indicate that the v(4) fundamental is excited beyond equilibrium, while the v(3) fundamental remains mostly in the ground state. This is due to the small concentration of methane, the low energy of v(4) compared to v(3) or to the Hz vibrational mode, and symmetry considerations that forbid interaction among the four fundamentals of methane. Thus, the excitation of v(3) is more likely than its decay under HFCVD conditions, producing a non-equilibrium population. At a filament temperature of 2000 C, the v(3) (sigma(+)(3)) fundamental of acetylene and a band at 1328 cm-l also ascribed to acetylene (v5 (pi(U)) + v4) appear in net absorption. This correlates well with the onset of molecular hydrogen breaking by the filament, which occurs at temperatures around 2000 C and above. The hydrogen atoms produced in this heterogeneous reaction give rise to a chain of reactions that lead to acetylene, among other carbonaceous species.
Document ID
20000032316
Acquisition Source
Headquarters
Document Type
Conference Paper
Authors
Morell, G.
(Puerto Rico Univ. San Juan, Puerto Rico)
Weiner, B. R.
(Puerto Rico Univ. San Juan, Puerto Rico)
Date Acquired
August 19, 2013
Publication Date
February 22, 1998
Publication Information
Publication: NASA University Research Centers Technical Advances in Aeronautics, Space Sciences and Technology, Earth Systems Sciences, Global Hydrology, and Education
Volume: 2 and 3
Subject Category
Inorganic, Organic And Physical Chemistry
Report/Patent Number
98URC154
Funding Number(s)
CONTRACT_GRANT: NCCW-56
CONTRACT_GRANT: DE-FG02-94ER-75764
CONTRACT_GRANT: NAGW-4059
CONTRACT_GRANT: FIPI-8-80-032
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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