A microwave plasma reactor for diamond growth that allows for highly controllable process conditions is presented. The position of the diamond substrate within the reactor can be accurately controlled. Thus, equilibration of plasma conditions can be carried out after changes in process parameters. With this approach, sharp layer transitions among doped, undoped, and isotopically controlled diamond films can be obtained. In addition to the sample transfer, the growth temperature is maintained through a substrate heater, and a clean reactor environment is realized by a load‐lock sample exchange system. The plasma conditions are constantly monitored by optical emission spectroscopy. Using this system, the growth of nanoscopic sandwich structures is demonstrated with controlled isotopic ratios down to ≈10 nm thickness and N(V) layers below 50 nm are obtained on (001)‐oriented diamond. Growth rates and doping efficiencies depending on the used methane concentration are presented. Characterization with continuous‐wave optically detected magnetic resonance yields an average contrast of 4.1% per nitrogen vacancy (NV) orientation in layers with a thickness below 100 nm. Depending on the used methane concentration, surface morphology and NV doping homogeneity are influenced as observed by photoluminescence and atomic force microscopy measurements.

A simple and effective method to extend the area of bias enhanced nucleation (BEN) for heteroepitaxial diamond growth is introduced. Two-inch substrates are placed on a flat and smooth surface of approximately 3-in. Mo substrate holder and then treated via BEN with or without metal-covered Si plates located right outside of the substrates. It is clarified that not only the plates themselves but also their thickness has a great impact on the BEN area, or in other words, the homogeneity of nucleation density on the substrates. As a result, the epitaxial diamond nucleation is successfully performed on nearly the whole area of a 2-in. Ir/YSZ/Si(001) substrate using the 1 mm thick half-ring plates. For a proof of this concept, finite element method simulations are also performed to investigate the influence of such plates on plasma (electron) density distributions above the substrates. Throughout this study, the significance of substrate holder configurations for the widely accessible wafer-scale diamond heteroepitaxy is revealed.

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