Diamond films and particles growth in hydrogen microwave plasma with graphite solid precursor: Optical emission spectroscopy study

We report on growth of diamond particles on graphite sheets and continuous films on Si substrates in a hydrogen microwave plasma using a graphite solid precursor. The special feature of the process is that no methane is added in the CVD reactor, instead, the diamond growth is realized by forming CHx radicals and other carbon species by the graphite etching with atomic hydrogen. The diamond particles deposited on the graphite substrates with very poor adhesion, can be easily collected, thus the approach allows a production of CVD diamond grit. The grit with similar to 10 mu m "diameter" was characterized with SEM, Raman spectroscopy and a dynamic laser scattering. Optical emission spectra (OES) of the plasma in the course of the graphite etching/diamond deposition single process were systematically studied, and a quantitative analogy with conventional growth in CH4H2 mixtures was derived. The graphite etch rate up to 150 mu m/h was measured, but found to monotonically decrease with the process time, as monitored for more than 10 h. A correlation of OES intensities of CH and C-2 lines with the measured graphite etch rate is established. The graphite/H-2 system for diamond growth is attractive as a high local flux of hydrocarbon species can be formed in proximity of the substrate.