Spectroscopic Determination of Rotational Temperature in C₂H₄ /C₂H₂/O₂ Flames for Diamond Growth with and Without Tunable CO₂ Laser Excitation


Mait, Joseph N.


Optical emission spectroscopy (OES) and spectroscopic temperature determination were carried out to study C₂H₄/C₂H₂/O₂ flames used for diamond deposition with and without an excitation by a wavelength-tunable CO₂ laser. Strong emissions from C₂ and CH radicals were observed in the visible range in all the acquired OES spectra. When the flames were irradiated by using a continuous-wave (CW) CO₂ laser at a wavelength of 10.591-µm , the emission intensities of the C₂ and CH radicals in the flames increased owing to the laser excitation. The CO₂ laser was also tuned to a wavelength of 10.532-µm to precisely match the resonant frequency of the CH₂ -wagging vibrational mode of the C₂H₄ molecules. OES spectroscopy of the C₂ and CH radicals were performed at different laser powers. The rotational temperatures of CH radicals in the flames were determined by analyzing the spectra of the R branch of the A²Δ → X²II (0,0) electronic transition near 430-‰nm . The deposited diamond thin-films were characterized by scanning electron microscopy, stylus profilometry, and Raman spectroscopy. The deposition mechanism with and without the CO₂ laser excitation was discussed based on the OES spectral results.


Mechanical and Aerospace Engineering

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Article - Journal

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© 2010 Optical Society of America, All rights reserved.

Publication Date

01 Jan 2010