Resonant vibrational excitation of ethylene molecules in laser-assisted diamond deposition

The influence of resonant vibrational excitation of ethylene molecules in combustion chemical vapor deposition of diamond was investigated. Resonant vibrational excitation of the CH₂-wagging mode (a type c fundamental band, υ 7, at 949.3 cm^-1) in ethylene molecules was achieved by using a wavelength-tunable CO₂ laser with a matching wavelength at 10.532 m. By comparing to laser irradiation at off-resonance wavelengths, an on-resonance vibrational excitation is more efficient in energy coupling, increasing flame temperatures, accelerating the combustion reactions, and promoting diamond deposition. Anenhanced rate of 5.7 was achieved in terms of the diamond growth rate with an improved diamond quality index at a high flame temperature under a resonant excitation of the CH₂-wagging mode. This study demonstrates that a resonant vibrational excitation is an effectiveroute for coupling energy into the gas phase reactions and promoting the diamond synthesis process.