Stress management of large size (001) and (111) diamond wafers for quantum-optical applications

Large size (001) and (111) diamond wafers are essential for various applications in quantum sensing and quantum computing. Notably, (111) diamond wafers offer the advantage of self-organized single alignment of nitrogen-vacancy (NV) centers, which are crucial for these applications. In this work, we demonstrate the near-single alignment of NV centers across the entire area of 2 inch (111) diamond wafers. However, several challenges arise during the growth process by chemical vapor deposition. When attempting to grow wafers, stress induces a curvature of the wafer. The curvature can lead to crack formation. Here, we propose solutions to prevent cracking such as cyclic growth with growth and etch steps, columnar growth, and epitaxial lateral overgrowth in two layers. We discuss hypothesis that explain why and under what circumstances these solutions are successful, providing evidence through methods such as photoluminescence mapping, Raman spectroscopy, SEM analysis, and x-ray diffraction. Interestingly, all the different growth methods reveal the same systematic characteristics of growth type, related stresses, and radii of curvature. Furthermore, measures are implemented to reduce the defect density. Optically detected magnetic resonance analysis of NV centers in our monocrystalline diamond wafers yield T2 coherence times of 26 µs.