Dynamic Bending Stress Sensing Using NV Centers in a Single-Crystal Diamond MEMS Cantilever

In this study, a single-crystal diamond (SCD) MEMS cantilever was fabricated using a buried graphite sacrificial-layer process. A region containing nitrogen-vacancy (NV) centers formed near the ion-implantation-induced defective layer was directly utilized as the stress-sensing region of the released cantilever, enabling dynamic stress sensing without the use of externally attached nanodiamonds. We investigated the relationship between the stress induced by the cantilever vibration and the peak shift of the fluorescence intensity of the optically detected magnetic resonance (ODMR) spectrum. By approximately aligning the static magnetic field with one of the four NV-center crystallographic axes, we were able to evaluate the dependence of the peak shift on stress. Our findings revealed that the peak shift can effectively detect uniaxial stress due to normal vibration. In addition, as the vibration amplitude increased, the magnitude of the ODMR peak shift also increased, showing a trend consistent with previously reported NV-center stress responses. Furthermore, the ODMR shift exhibited periodic modulation corresponding to the cantilever’s vibration phase. These results indicate that NV centers in micromachined SCD cantilevers can be used to detect vibration-induced dynamic bending stress.