Laser-induced resonant excitation of ethylene molecules in C2H4/C2H2/O2 reactions to enhance diamond deposition

Abstract

Vibrational resonant excitation of ethylene ͑C 2 H 4 ͒ molecules using a carbon dioxide laser was employed to promote reactions in precursors of ethylene, acetylene ͑C 2 H 2 ͒, and oxygen to enhance diamond deposition. One of the vibrational modes ͑CH 2 wag mode, v 7 ͒ of the C 2 H 4 molecules was selected to achieve the resonant excitation in the reactions. Optical emission spectroscopy was used to study the effects of laser resonant excitation on the reactions for diamond deposition. The optical emissions of CH and C 2 species were enhanced with the laser excitation, indicating that there are more active species generated in the reactions. Thicknesses and grain sizes of the deposited films were increased correspondingly. Temperature calculations from the line set in the R-branch of CH emission spectra indicated that a nonthermal process is involved in the enhanced diamond deposition.

Enhanced chemical vapor deposition of diamond by wavelength-matched vibrational excitations of ethylene molecules using tunable CO2 laser irradiation

“…In our previous study, the film thickness was increased by 50% with a laser excitation of 600 W at this wavelength using different gas ratio. 7 Figures 5͑e͒-5͑g͒ show the profiles of the films with perfect matching excitations at 10.532 m. The film thickness is about 14 m in Fig. 5͑f͒ with 400 W excitation and 16 m in Fig.…”

“…In our previous study, it was demonstrated that the vibrational excitation of the C 2 H 4 molecules in the flame is a nonthermal process during the diamond depositions. 7 Under current experimental conditions, it is still difficult to achieve a real bond-selective chemistry through the vibrational resonant excitation. However, the continuous vibrational excitation of the C 2 H 4 molecules in open-air reactions was beneficial to promote the diamond growth.…”

“…This is similar to the results obtained in our previous study. 7 Figure FIG. 1 2͑b͒ shows the optical images of the flame under laser irradiations with the wavelength of 10.532 m, which is a perfect match with the CH 2 -wag vibration mode of C 2 H 4 ͑ 7 ͒.…”

“…In our previous study, a common CO 2 laser at 10.591 m was used to achieve the vibrational resonant excitation of C 2 H 4 molecules through the broadening of the absorption band. 7 In this study, a tunable CO 2 laser with a high power output up to 1000 W was used to replace the common CO 2 laser. The CO 2 laser wavelength can be precisely tuned to match the CH 2 -wag mode ͑ 7 ͒ of C 2 H 4 molecules to achieve the optimal resonant excitation to significantly improve the diamond deposition in the chemical vapor deposition ͑CVD͒ processes using the C 2 H 4 / C 2 H 2 / O 2 gas mixture.…”

Short pulse laser micro/nano manufacturing: fundamentals and applications

“…The resonant excitation was utlised for selective bond breaking and reaction pathways control. It was demonstrated that both diamond growth rate and film quality can be improved by using resonant laser coupling (Ling et al, 2009a(Ling et al, , 2009b. Laser resonance absorption may be an important future way to improve the controllability, productivity and selectivity of micro/nano-fabrication.…”