Excitations of Precursor Molecules by Different Laser Powers in Laser-Assisted Growth of Diamond Films

Abstract

Excitations of precursor molecules by different laser powers in laser-assisted growth of diamond films using a wavelength-tunable CO2 laser were studied. The wavelength of the CO2 laser was tuned to 10.532 μm to match a vibration mode of a precursor molecule, ethylene. The density of the incident laser power was adjusted to modify diamond crystal orientation, optimize diamond quality, and achieve high-efficiency laser energy coupling. It was observed that at incident laser power densities between 5.0 × 103 and 1.0 × 104 W/cm2, (100)-faceted diamond crystals were grown uniformly in the center areas of the diamond films. Higher incident laser powers, although further promoted growth rate, suppressed the uniformity of the diamond (100) facets. Best diamond quality was obtained within a laser power density range of 5.0 × 103 to 6.7 × 103 W/cm2, whereas the highest energy efficiency was achieved within a laser power density range of 3.3 × 103 to 6.7 × 103 W/cm2. The effects of the resonant laser energy coupling were investigated using optical emission spectroscopy.