CVD diamond growth occurs within vacuum plasma reactors. Thin diamond plates are placed in a growth cell, and then hydrocarbon gas is injected on top of the diamond plates. High power microwaves break the bonds of the hydrocarbon gas, separating the carbon atoms from the hydrogen atoms.
The resulting free carbon within the reactor ‘precipitates’ onto the diamond plates, similar to the way that snowflakes collects on a table, vertically growing the diamond atom by atom.
The resulting CVD diamonds are then subjected to extreme pressure to ‘compress’ the CVD diamond, like a footprint compresses snow. This additional step improves the quality of the diamond crystal, giving the diamond better color and light performance.
HPHT diamond growth occurs within massive pressure cookers. Small diamond seeds are placed into a growth cell, and then graphite is inserted on top of the diamond seeds. The pressure cooker is heated to 1500 degrees C and pressurized to approximately 70,000 times the pressure at sea level.
At this extreme temperature and pressure, the graphite in the growth cell is melted into liquid carbon and then carefully cooled into the strongest form of carbon, a diamond crystal.