In diamond, nitrogen defects like the substitutional nitrogen defect $\left({\mathrm{N}}_{\mathrm{s}}\right)$ or the nitrogen-vacancy-hydrogen complex (NVH) outnumber the nitrogen-vacancy (NV) defect by at least one order of magnitude creating a dense spin bath. While neutral ${\mathrm{N}}_{\mathrm{s}}$ has an impact on the coherence of the NV spin state, the atomic structure of NVH reminds of a NV center decorated with a hydrogen atom. As a consequence, the formation of NVH centers could compete with that of NV centers possibly lowering the N-to-NV conversion efficiency in diamond grown with hydrogen-plasma-assisted chemical vapor deposition (CVD). Therefore, monitoring and controlling the spin bath is essential to produce and understand engineered diamond material with high NV concentrations for quantum applications. While the incorporation of ${\mathrm{N}}_{\mathrm{s}}$ in diamond has been investigated on the nano- and mesoscale for years, studies concerning the influence of CVD parameters and the crystal orientation on the NVH formation have been restricted to bulk N-doped diamond providing high-enough spin numbers for electron paramagnetic resonance and optical absorption spectroscopy techniques. Here, we investigate submicron-thick (100)-diamond layers with nitrogen contents of $(13.8\pm 1.6)\mathrm{ppm}$ and $(16.7\pm 3.6)\mathrm{ppm}$, and exploiting the NV centers in the layers as local nanosensors, we demonstrate the detection of ${}^{}{\mathrm{NVH}}^{-}$ centers using double electron-electron resonance (DEER). To determine the ${}^{}{\mathrm{NVH}}^{-}$ densities, we quantitatively fit the hyperfine structure of ${}^{}{\mathrm{NVH}}^{-}$ and confirm the results with the DEER method usually used for determining ${}^{}{{\mathrm{N}}_{\mathrm{s}}}^0$ densities. With our experiments, we access the spin bath composition on the nanoscale and enable a fast feedback loop in CVD recipe optimization with thin diamond layers instead of resource- and time-intensive bulk crystals. Furthermore, the quantification of ${}^{}{\mathrm{NVH}}^{-}$ plays a very important role for understanding the dynamics of vacancies and the incorporation of hydrogen into CVD diamond optimized for quantum technologies.

• Received 8 November 2023
• Accepted 30 January 2024

DOI:https://doi.org/10.1103/PhysRevMaterials.8.026203

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Published by the American Physical Society