Chemical Vapor Deposition (CVD)
(Image Courtesy of GIA)
In the Chemical Vapor Deposition (CVD) diamond growth method, the process starts with a small carbon seed. This small piece of carbon is then placed inside a low pressure vacuum chamber. Then, a combination of carbon containing gases like methane are introduced, further enhancing the environment that promotes diamond crystal growth. A source of energy, like a high power microwave beam then ignites this plasma ball, breaking down the atomic bonds of the hydrogen gas molecules. This separates the carbon atoms from the hydrogen atoms, resulting in freed carbon atoms, which rain downward onto the flat diamond seed plates. Diamond growth occurs vertically, atom by atom, similar to the way snow collects on a table. The diamond growth occurs in thin layers, and its final thickness depends on the amount of time allowed for growth. Crystallization occurs over a period of several weeks to create a number of crystals. The exact number depends on the size of the chamber and the number of seed plates. This results in flat, tabular crystals with a rough exterior edge coated in black graphite crystals. This is a natural process of crystal growth beyond human control once the process starts. The results are similar kinds of imperfections, otherwise known as “inclusions” that occur in mined diamonds.