INTERACTIONS OF HYDROGEN AND METHYL RADICALS WITH DIAMOND C(111) STUDIED BY SUM-FREQUENCY VIBRATIONAL SPECTROSCOPY

Methyl-radical and atomic hydrogen adsorption on C(111) have-been stud ied by infrared-visible sum-frequency vibrational spectroscopy. Methyl iodide, di-tert-butyl-peroxide, and methane passing through a hot fil ament are used to produce methyl radicals (CH3). Low-energy CH3 from p yrolytic dissociation at similar to 800 degrees C adsorb intact on the surface, but with surface annealing above 350 degrees C, convert to t etrahedrally bonded CH. High-energy CH3 produced at similar to 1800 de grees C convert readily to CH upon adsorption. Go-dosing a high-temper ature (similar to 800 degrees C) C(111) substrate with hydrogen and me thane via a hot filament at similar to 1800 degrees C yields only the stable tetrahedrally-bonded CH-species on the surface. They appear to stabilize the diamond surface structure. The coverage is not full, lea ving sites open for CH3 to adsorb and convert to CH as is necessary fo r chemical vapor deposition diamond growth.