Laser-induced resonant excitation of ethylene molecules in C_2H_4/C_2H_2/O_2 reactions to enhance diamond deposition

摘要

Vibrational resonant excitation of ethylene (C_2H_4) molecules using a carbon dioxide laser was employed to promote reactions in precursors of ethylene, acetylene (C_2H_2), and oxygen to enhance diamond deposition. One of the vibrational modes (CH_2 wag mode, v_7) of the C_2H_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.