For HPHT, there are three primary machine designs, but they all create intense heat and pressure, and dissolved graphite slowly builds up on a diamond seed (1. BARS press. It is a Russian design from the 1980s capable of up to 2-3 carat polished sizes, and was one of the first methods to commercially grow jewelry-grade diamonds. It is much less efficient than modern presses though.
2. Cubic press. This is a much larger 3-axis press used primarily in China to spontaneously grow diamond grit and powder. Some of these have been converted and upgraded to run longer cycles needed for large single crystals. These can grow multiple diamonds at a time or fewer larger diamonds, and have been used to grow the largest diamonds currently available (5-10 carat), however success rates and control within the larger growth cell are still low. We are in the process of developing our own modern cubic press (rather than a refurbished grit press).
3. Single axis. This our own in-house design. It has similar growth capabilities as a BARS press, but is much more efficient with greater control and can grow multiple diamonds simultaneously. For qualified parties, we can sell these presses as well as license the IP and diamond growth "recipes".
CVD reactors are basically a vacuum chamber with plasma over a growth surface. That surface holds diamond plates, which are just thin slices of diamond, and usually come from larger CVD or HPHT single-crystal diamonds. Methane provides a carbon source, which is broken up into its elemental components by the plasma. The carbon "rains" down onto the diamond seed plates and basically grows straight up, so the finished dimensions are limited by the starting length and width of the seed plate. Some CVD reactors use microwaves to assist while others do not. There are a few companies that sell complete CVD reactor systems, but no one I am aware of that offers IP or "recipes", so those would have to be developed on your own.
