Simulation, development, and optical emission spectroscopy of microwave plasma chemical vapor deposition reactor for synthesis of large-area single crystal diamond

The work presents the geometrical advancement in the clamshell microwave plasma chemical vapor deposition reactor (2.45 GHz, 6 kW) to overcome the growth limitations of single crystal diamonds. Using electromagnetic and simplified fluid models, the geometrical parameters of a 2D axisymmetric cavity were optimized and developed to obtain a uniform plasma density over a diameter of ∼60 mm at chamber pressures of 120–130 Torr in hydrogen plasma. The maximum field strength above the substrate was found to be 4 × 10 5 V.m −1 for cavity mode TM 01 at 6 kW microwave input power. The estimated electron temperature from optical spectroscopy is ∼1.9 eV at chamber pressure 110 Torr and microwave power 6.0 kW, which is in the agreement with the simulated value. A batch growth of homo-epitaxial large-area (∼ 15 mm × 15 mm) single crystal diamonds was conducted on (100) oriented diamond seeds placed in a 3 × 3 matrix, with a uniform growth rate of ∼11 µm/h. X-ray photoelectron spectroscopy confirms the presence of diamond ( sp 3 ) carbon ∼94.5 % and oxygen ∼5.5 % with no other contaminants detected on the surface. The grown diamond samples attain < 100 > orientation as validated by X-ray Diffraction. The Raman characteristic peak ∼1332 cm −1 with uniform full width at half maximum (∼3 cm −1 ) of all the samples confirms the phase purity of the grown diamond. Moreover, Fourier transform infrared spectroscopy demonstrates that the nitrogen impurities in the samples are less than 10 ppm. The simulation results demonstrate the validation and advancement in the clamshell reactor geometry for the synthesis of high-quality and large-area single crystal diamonds for gem, semiconductor, and quantum applications.