Product Code: ICAL08_M202

Optical Emission Spectroscopy Study of Resonant Vibrational Excitation of Precursor Molecules in the CO2 Laser-Assisted Flame Deposition of Diamond
Authors:
H. Ling, University of Nebraska-Lincoln; Lincoln NE USA
T. Gebre, University of Nebraska-Lincoln; Lincolnq NE USA
Y.X. Han, University of Nebraska-Lincoln; Lincoln NE USA
Z.Q. Xie, University of Nebraska-Lincoln; Lincoln NE USA
X.K. Shen, University of Nebraska-Lincoln; Lincoln NE USA
Y.F. Lu, University of Nebraska-Lincoln; Lincoln NE USA
Presented at ICALEO 2008

Diamond thin films were deposited using C2H2/O2, C2H4/C2H2/O2, and C3H6/O2 combustion flames. At points where the diamond films were being deposited, Optical Emission Spectroscopy (OES) measurements showed that excited C2 and CH species appear abundantly. The relative emission intensity of these species depended on the precursors used to generate the combustion flames; in addition, the irradiation of C2H4/C2H2/O2 and C3H6/O2 flames by a continuous-wave CO2 laser beam (10.591 μm) resulted in increased optical emission intensity from the excited species due to resonant absorption of laser energy. OES was used to obtain molecular spectra of the excited C2 and CH species in the flames for different gas combinations and laser fluences. The ratio of the intensity of C2 species to CH species were calculated from these spectra. The Boltzmann equation and simulated molecular spectra were used to obtain rotational and vibrational temperatures from the spectra of the excited species. The results were used to understand the mechanism of the vibrational excitation and to study the effect of laser irradiation on temperature. For each condition, the intensity ratios and temperatures obtained using OES were correlated with the quality, grain size, and growth rate of diamond films on cemented tungsten carbide (WC-Co) substrates. The results were summarized to find which overall intensities, temperatures, and C2 to CH intensity ratios are optimums for diamond deposition using these combustion flames.