Spectroscopic Characterization of the Atomic Hydrogen Energies and Densities and Carbon Species during Helium−Hydrogen−Methane Plasma CVD Synthesis of Diamond Films

Abstract

Polycrystalline diamond films were synthesized on silicon substrates for the first time without diamond seeding by a very low power (38 W) microwave plasma chemical vapor deposition reaction of a mixture of helium-hydrogen-methane (48.2/48.2/3.6%). The films were characterized by time-of-flight secondary ion mass spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and X-ray diffraction. It is proposed that He + served as a catalyst with atomic hydrogen to form an energetic plasma. CH, C 2 , and C 3 emissions were observed with significantly broadened H α, β, y, and δ lines. The average hydrogen atom temperature of a helium-hydrogen-methane plasma was measured to be 120-140 eV versus 3 eV for pure hydrogen. Bombardment of the carbon surface by highly energetic hydrogen formed by the catalysis reaction may play a role in the formation of diamond. Then, by this novel pathway, the relevance of the CO tie line is eliminated along with other stringent conditions and complicated and inefficient techniques which limit broad application of the versatility and superiority of diamond thin film technology.