Nondestructive Characterization of Subsurface Metal Microstructure Using Quantum Wide-Field Microscope

To meet the need for high-resolution, nondestructive inspection of subsurface metal microstructure, we propose a method for characterizing subsurface metal microstructure with high-resolution via quantum wide-field microscopy based on nitrogen-vacancy (NV) centers. In a view of $1050\times 1050~\mu $ m2, the feasibility of the method is verified by reconstructing the induced microwave field generated by far-field free-space microwaves in the metal microstructure using quantum microscopy. In addition, the induced microwave fields are explored scrupulously at varying distances between quantum microscopy and metal microstructure. The results show that the method can detect subsurface metal microstructure at a distance of $1700~\mu $ m between the quantum microscopy and metal microstructure, with a vertical resolution of $10~\mu $ m, and optimal NV detection sensitivity is 0.75 nT/ ${\mathrm {Hz}}^{\text {1/2}}$ . A width detection sensitivity of 3.2 kHz/ $\mu $ m for metal microstructure can be achieved using this method. This work is critical for advancing the performance evaluation of engineered structures and the development of quantum testing techniques.