CVD synthesis of diamond

The method of gas-phase synthesis of diamond is not so new. The first studies of this method were carried out at the Institute of Physical Chemistry and Electrochemistry. A.M. Frumkin, USSR Academy of Sciences in the mid-50s of the twentieth century. However, for a long time, the deposition rate of diamond did not exceed 0.1 μm / h and were far from the values ​​of practical interest. Only by the beginning of the 80s was it possible to achieve a growth rate of more than 10 μm / h. Currently, the CVD method allows one to obtain sufficiently pure polycrystalline diamond films and wafers with a diameter of more than 100 mm and a thickness from a few micrometers to 1-3 mm.
The CVD process is based on the decomposition of hydrocarbons (usually methane) in a mixture with hydrogen and the subsequent deposition of diamond on a heated substrate. The working mixture dissociates in a vacuum chamber under the influence of an electric discharge, microwave plasma or laser radiation. Dissociation on a hot filament or in a flame of a gas burner is also possible (in this case, an acetylene-oxygen mixture is used). Decomposition products (hydrocarbon radicals and atomic hydrogen) diffuse to a substrate heated to a temperature of 700–1000 ° С, on which diamond is deposited.