CO_2 LASER RESONANT EXCITATION OF PROPYLENE MOLECULES IN DIAMOND DEPOSITION USING COMBUSTION-FLAME METHOD

摘要

CO_2 laser resonant excitation of propylene molecules was investigated in propylene/oxygen (C_3H_6/O_2) combustion diamond deposition in open air. The wavelength of the CO_2 laser is 10.591μm, while the central wavelength for the C-H vibration mode in propylene molecules is 10.684μm. The absorption peak of this mode is broadened by the high ambient pressure and the flame temperature, and thus covers the CO_2 laser wavelength to enable the resonant absorption. The inner cone of the C_3H_6/O_2 flame became shorter and brighter with the CO_2 laser irradiation with a laser power of 800 W. The scanning electron microscopy (SEM) images showed that better crystal grains in the diamond films were deposited with the CO_2 laser excitation. The film thickness also had an obvious increase within the same deposition time, indicating a higher growth rate of diamond films. The effect of different positions where the laser irradiated the flames was also studied. It was found that the enhancement of the diamond growth was due to the balance of the generation and the dispersion of the beneficial radicals.