Laser-assisted synthesis of diamond crystals in open air through vibrational excitation of precursor molecules

Fast growth of diamond crystals in open air was achieved by laser-assisted combustion synthesis through vibrational excitation of precursor molecules. A wavelength-tunable CO(2) laser (spectrum range from 9.2 to 10.9 mu m) was used for the vibrational excitation in synthesis of diamond crystals. A pre-mixed C(2)H(4)/C(2)H(2)/O(2) gas mixture was used as precursors. Through resonant excitation of the CH(2)-wagging mode of ethylene (C(2)H(4)) molecules using the CO(2) laser tuned at 10.532 mu m, high-quality diamond crystals were grown on silicon substrates with a high growth rate of similar to 139 mu m/hr. Diamond crystals with a length up to 5 mm and a diameter of 1 mm were grown in 36 hours. Sharp Raman peaks at 1332 cm(-1) with full width at half maximum (FWHM) values around 4.5 cm(-1) and distinct X-ray diffraction spectra demonstrated the high quality of the diamond crystals. The effects of the resonant excitation of precursor molecules by the CO(2) laser were investigated using optical emission spectroscopy.