Enhanced chemical vapor deposition of diamond by wavelength-matched vibrational excitations of ethylene molecules using tunable CO_2 laser irradiation

摘要

Wavelength-matched vibrational excitations of ethylene (C_2H_4) molecules using a tunable carbon dioxide (CO_2) laser were employed to significantly enhance the chemical vapor deposition (CVD) of diamond in open air using a precursor gas mixture of C_2H_4, acetylene (C_2H_2), and oxygen (O2). The CH_2-wag vibration mode (v_7) of the C_2H_4 molecules was selected to achieve the resonant excitation in the CVD process. Both laser wavelengths of 10.591 and 10.532 μm were applied to the CVD processes to compare the C_2H_4 excitations and diamond depositions. Compared with 10.591 μm produced by common CO_2 lasers, the laser wavelength of 10.532 μm is much more effective to excite the C_2H_4 molecules through the CH_2-wag mode. Under the laser irradiation with a power of 800 W and a wavelength of 10.532 μm, the grain size in the deposited diamond films was increased by 400% and the film thickness was increased by 300%. The quality of the diamond crystals was also significantly enhanced.