Optical emission spectroscopy study of resonant vibrational excitation of precursor molecules in the CO2 laser-assisted flame deposition of diamond

Abstract

Diamond thin films were deposited using 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 powers. The overall intensity of C2 and CH species were calculated from these spectra. The Boltzmann equation was used to obtain rotational 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 flame temperature. For each condition, the intensity ratios and temperatures obtained using OES were correlated with the diamond films deposited on cemented tungsten carbide (WC-Co) substrates.Diamond thin films were deposited using 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 powers. The overall intensity of C2 and CH species were calculated from these spectra. The Boltzmann equation was used to obtain rotational 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 o...