Effect of the gas mixture flow rate on the process of diamond synthesis from a high-velocity microwave plasma

A method of gas-phase deposition of diamond structures with the use of a high-velocity jets for transporting gases activated in a microwave plasma to the substrate is developed. The diamond structures are synthesized from a hydrogen-methane mixture with the methane concentration of 1%. The influence of the gas mixture flow rate on the synthesis of the diamond structures with an unchanged composition of the mixture, pressure in the deposition chamber, and substrate temperature is studied. It is found that an increase in the flow rate leads to an increase in the polycrystalline film density and in the size of the diamond crystals forming the film. The composition of the mixture at the discharge chamber exit is numerically analyzed for different flow rates of the gas mixture. A correlation of the mixture composition with the growth rate and quality of the diamond structures is demonstrated.