Comparative Study on the Effect of Additional Gas Outlet in Substrate Holder on Diamond Quality and Growth Rate in an Microwave Plasma Chemical Vapor Deposition Reactor

The behavior of precursor gases (H 2 and CH 4 ) in a microwave plasma chemical vapor deposition (MPCVD) system plays a critical role in growing diamond with good quality and at a higher growth rate. In this work, the effect of an additional gas flow outlet integrated into the substrate holder (modified gas flow configuration) on diamond quality and growth rate in a clamshell‐type MPCVD reactor is investigated through simulation and experiments. A simulation using 3D computational fluid dynamics incorporating the gas flow dynamics, thermal, and species transport phenomena is done to evaluate the velocity, temperature, and molar concentration profiles of H 2 and CH 4 over the substrate holder. The modified substrate holder is fabricated and tested experimentally alongside the existing substrate holder under identical deposition conditions: 4% CH 4 in an H 2 CH 4 gas mixture, 4.5 kW microwave power, and 100 Torr chamber pressure. The grown diamond samples are analyzed using Raman, photoluminescence, UV–visible, and Fourier‐transform infrared spectroscopic techniques. From the analysis, the diamond grown with the additional gas outlet shows higher crystallinity and transmittance with less crystal defects, and lower nitrogen concentration than the diamond crystal grown with the existing gas flow configuration. Notably, the growth rate remains unaffected by the modification.