Chemical vapour deposition, CVD, is an extremely versatile process for creating thin solid films and is a generic term for a group of chemical processes that involve depositing a solid material from a gas or mixture of gases onto a substrate. As well as its application in diamond synthesis, CVD processes are widely used in the fabrication of semiconductor devices and in the manufacture of coatings for wear parts and machine tool components, for example.

CVD processes for diamond synthesis can be used for the growth of both single crystal and polycrystalline forms of the material. The actual conditions required for making each type of diamond are very similar; it is the choice of substrate that determines which will grow. For single crystal CVD diamond, the substrate needs to be single crystal diamond and the new diamond film grows epitaxially, with the deposited film taking on the lattice structure and orientation identical to those of the substrate. For polycrystalline diamond, a non-diamond substrate is used. A variety of materials can be used in this context; primarily silicon, silicon carbide and a range of carbide forming metals including molybdenum and tungsten.