Laser-induced resonant excitation of ethylene molecules in C ₂H₄/C₂H₂/O₂ reactions to enhance diamond deposition

Vibrational resonant excitation of ethylene (C₂H₄) molecules using a carbon dioxide laser was employed to promote reactions in precursors of ethylene, acetylene (C₂H₂), and oxygen to enhance diamond deposition. One of the vibrational modes (CH₂ wag mode, v₇) of the C₂H₄ 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 C₂ 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.