It took almost 60 years of effort to develop the precision to grow gemstone quality diamonds. Because the processes are similar to natural growth, there are still variations in color and clarity of grown diamonds. In other words, not all lab grown diamonds are colorless and flawless.
Today, there are two methods of growing diamond gemstones:
- High Pressure-High Temperature(HPHT):
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.
- Chemical Vapor Deposition (CVD):
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.
In recent years, CVD research has gained popularity and now modified versions of CVD are being used. These processes differ in the means by which chemical reactions are initiated. Some of these variations include:
- Low-pressure CVD (LPCVD)
- Ultrahigh vacuum CVD (UHVCVD)
- Plasma-enhanced chemical vapor deposition (PECVD)
- Microwave Plasma Vapor Deposition (MPCVD