Hydrogen-free CVD diamond synthesis with graphite rod heating

The graphite rods were used as heaters and, at the same time, carbon sources. In argon (99.99%; 4N), high-purity argon (6N), helium (4N5) or nitrogen (4N) atmosphere, without hydrogen gas, diamond particles were synthesized with the graphite rod heating method for the first time in the world. One-micrometer-diameter particles in argon gas, 0.8 μm particles in high-purity argon, 0.6 μm particles in helium, and 0.4 μm particles in nitrogen, were all confirmed as diamond with the SEM photographs and Raman spectroscopy; results will be reported in this paper.