Modeling optimization and experimental verification of inch-scale heteroepitaxial single-crystal diamond nucleation with 915 MHz MPCVD

Inch-scale heteroepitaxial nucleation of single-crystal diamond remains a major bottleneck for large-area diamond fabrication, owing to the strong coupling among plasma–surface interactions, energy deposition, and bias-enhanced nucleation kinetics. Compared with conventional 2.45 GHz reactors, 915 MHz MPCVD systems provide deeper microwave penetration and improved potential for large-volume plasmas, yet their reactor design and multi-parameter coupling mechanisms during heteroepitaxial nucleation are not fully established. Here, we systematically investigate how reactor geometry and key process parameters jointly govern plasma characteristics and nucleation outcomes during inch-scale diamond nucleation. A three-dimensional numerical model of a 915 MHz MPCVD reactor was developed to optimize structural parameters and to quantify the coupled influences of microwave power, chamber pressure, and DC bias voltage on plasma distribution. Based on simulation-guided refinement, the reactor geometry was directionally redesigned and critical process windows were identified for achieving enhanced plasma uniformity and stable energy coupling. Inch-scale heteroepitaxial nucleation experiments were subsequently conducted, validating the simulation predictions and demonstrating improved nucleation density and crystalline quality. This work provides essential simulation and experimental evidence for large-scale single-crystal diamond preparation in 915 MHz MPCVD systems.