A method of measuring micro-displacement based on spin magnetic resonance effect of diamond color center

As one of the excellent piezoelectric materials, piezoelectric ceramic has been widely used to develop a highly precise displacement measurement system, which is the key part of the scanning probe system of the high-precision measuring instrument. Based on the high-precision scanning probe system, the micro/nano structures can be easily and accurately detected by the instrument system. However, due to the limitations caused by the character of hysteresis and nonlinearity, it is difficult to further improve the precision of highly precise displacement measurement system. In this work, we present a novel method to develop the highly precise displacement measurement system based on the quantum spin effect. The nitrogen vacancy (NV) color center of single crystal diamond as a sensitive element senses the change of the micro-displacement. Based on the electron spin magnetic resonance effect of diamond nitrogen vacancy color center, the variation of the magnetic field generated from the magnetic steel can be detected with high precision by the electron spin. The relative relation between the displacement and the magnetic gradient field can be used to establish the correlation model between the displacement and the electron spin resonance peak. In the experiment, a corresponding micro-displacement measurement system is established based on the cylindrical permanent magnet, according to the correlation model between the electron spin resonance effect and micro-displacement. The linear region of magnetic field gradient is designed to detect the micro-displacement. Firstly, the intensity distribution of magnetic field gradient is measured by the gauss meter. As the measurement results show, the gradient value is 7.77 Gauss/mm along the core axis of cylindrical permanent magnet, and the intensity of magnetic field gradient distribution region is linear in the millimeter range. Meanwhile, the electron spin magnetic resonance peak of diamond nitrogen vacancy color center is achieved by the optically detected magnetic resonance technology. The electron spin magnetic resonance peak is approximately 2.79 MHz/Gauss in the magnetic field achieved by the fluorescence spectrum of diamond nitrogen vacancy color center, attributed to the relation model between Zeeman splitting effect and magnetic field. In the experiment, the electron spin magnetic resonance signal of diamond nitrogen vacancy color center is lockedin by the demodulation method to achieve the change of micro-displacement. As the results show, the sensitivity is about 16.67 V/mm at the corresponding demodulation frequency of 3000.56 MHz. By the calculation, the resolution of micro-displacement measurement system is about 60 nm based on our method. It proves out a high precision and well reliability method to detect the micro-displacement. By the further theoretical calculation, based on the electron spin effect, the detection resolution of our method can be enhanced up to sub-nanometer scale by reducing the distance between the NV color center and the magnet. It presents a new research direction and field for the micro-displacement detection system.