Spectroscopic determination of carbon dimer densities in Ar-H{sub 2}-CH{sub 4} and Ar-H{sub 2}-C{sub 60} plasmas.
In contrast to conventional methods of diamond chemical vapor deposition (CVD), nanocrystalline diamond CVD takes place with only a small fraction of feed gas hydrogen. Minimal amounts of CH{sub 3}, believed critical in hydrogen-rich CVD, are expected to be produced in hydrogen-deficient systems and alternative mechanisms for diamond growth must be considered. The carbon dimer, C{sub 3}, is believed to be an important species in these growth environments. We have experimentally determined the density of gas phase C{sub 2} in Ar - H{sub 2} - CH{sub 4} and AR - H{sub 2} - C{sub 60} microwave plasmas used to deposit nanocrystalline diamond. The C{sub 2} density is monitored using high-sensitivity absorption spectroscopy of the d {sup 3}{Pi} {l_arrow} a {sup 3}{Pi} (0, 0) band as chamber pressure, microwave power, substrate temperature and feed gas mixtures are varied for these two chemical systems. The absolute density of C{sub 2} is most sensitive to the total chamber pressure and fraction of carbon in all molecular species in the feed gas in Ar - H{sub 2} - C{sub 60} discharges and to the total chamber pressure and substrate temperature in Ar - H{sub 2} - CH{sub 4} plasmas. We discuss possible C{sub 2} production channels in both chemical systems. The efficiency of C{sub 2} production from fullerene precursors is over an order of magnitude greater than that from hydrocarbon precursors.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- ER
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 938167
- Report Number(s):
- ANL/CHM/JA-27822
- Journal Information:
- J. Phys. D, Journal Name: J. Phys. D Journal Issue: 16 ; Aug. 21, 1998 Vol. 31; ISSN 0022-3727; ISSN JPAPBE
- Country of Publication:
- United States
- Language:
- ENGLISH
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