Main steps and principles for the preparation of large grains of high-quality diamonds by MPCVD meth

MPCVD (Microwave Plasma Chemical Vapour Deposition) is an effective method to prepare large grains of high quality diamond. The following are the main steps and principles of the MPCVD method for the preparation of high quality diamond with large particles:

Preparation of diamond substrate: Firstly, the diamond substrate is cleaned and placed into the MPCVD chamber and sealed for vacuum. This step ensures the purity of the diamond growth substrate and the cleanliness of the environment, which is conducive to the growth of diamond.

Gas injection and reaction: Reaction gases, such as methane, hydrogen and nitrogen, are passed into the chamber. Under the action of microwave, these gas molecules are cleaved into H, O and N atoms or groups such as CH2, CH3 and C2H2. These groups form a mixed gas-solid interface on the diamond surface, providing the necessary carbon source for diamond growth.

Microwave excitation and heating: Turn on the microwave source to form a plasma, increase the reaction gas flow and microwave power to heat to the process temperature. The microwave energy excites the gas molecules, generating a high concentration of plasma, which further promotes the deposition of carbon atoms and the growth of diamond crystals.

Pressure and temperature control: By adjusting the gas pressure and microwave power in the MPCVD chamber, a suitable environment is provided for the growth of diamond. Suitable pressure and temperature conditions contribute to the growth and quality of diamond crystals.

Crystal growth: Under suitable conditions, diamond crystals grow gradually to form large-grained diamond. By precisely controlling the growth parameters, such as growth time, air pressure, microwave power, etc., the precise regulation of the size and quality of diamond particles can be achieved.

Power density is an important growth parameter in the preparation of diamond by MPCVD. The quality and surface morphology of diamond grown at different power densities will be different. Therefore, it is necessary to adjust the equipment to a suitable power density to grow high-quality single crystal diamond.

In addition, the MPCVD method also accelerates the growth of diamond by optimising the growth parameters, such as increasing the air pressure in the chamber and the input microwave power during growth, to promote the decomposition and ionisation of the reaction gases, and to increase the concentration and activity of each reaction group. Meanwhile, the diamond growth efficiency can also be improved by improving the device to reduce the power loss.

Overall, the MPCVD method has successfully prepared high-quality large-grained diamond by precisely controlling the steps of gas injection, microwave excitation, heating and decomposition, pressure control, and crystal growth, combined with the optimisation of growth parameters and device improvement. This method has a wide application prospect in the field of diamond preparation.