Zongmin Ma

Optimization and Experimentation of Dual-Mass MEMS Gyroscope Quadrature Error Correction Methods.

This paper focuses on an optimal quadrature error correction method for the dual-mass MEMS gyroscope, in order to reduce the long term bias drift. It is known that the coupling stiffness and demodulation error are important elements causing bias drift. The coupling stiffness in dual-mass structures is analyzed. The experiment proves that the left and right masses’ quadrature errors are different, and the quadrature correction system should be arranged independently. The process leading to quadrature error is proposed, and the Charge Injecting Correction (CIC), Quadrature Force Correction (QFC) and Coupling Stiffness Correction (CSC) methods are introduced. The correction objects of these three methods are the quadrature error signal, force and the coupling stiffness, respectively. The three methods are investigated through control theory analysis, model simulation and circuit experiments, and the results support the theoretical analysis. The bias stability results based on CIC, QFC and CSC are 48 °/h, 9.9 °/h and 3.7 °/h, respectively, and this value is 38 °/h before quadrature error correction. The CSC method is proved to be the better method for quadrature correction, and it improves the Angle Random Walking (ARW) value, increasing it from 0.66 °/√h to 0.21 °/√h. The CSC system general test results show that it works well across the full temperature range, and the bias stabilities of the six groups’ output data are 3.8 °/h, 3.6 °/h, 3.4 °/h, 3.1 °/h, 3.0 °/h and 4.2 °/h, respectively, which proves the system has excellent repeatability.

Plasmon-enhanced sensitivity of spin-based sensors based on a diamond ensemble of nitrogen vacancy color centers

A method for enhancement of the sensitivity of a spin sensor based on an ensemble of nitrogen vacancy (NV) color centers was demonstrated. Gold nanoparticles (NPs) were deposited on the bulk diamond, which had NV centers distributed on its surface. The experimental results demonstrate that, when using this simple method, plasmon enhancement of the deposited gold NPs produces an improvement of ∼10 times in the quantum efficiency and has also improved the signal-to-noise ratio by approximately ∼2.5 times. It was also shown that more electrons participated in the spin sensing process, leading to an improvement in the sensitivity of approximately seven times; this has been proved by Rabi oscillation and optical detection of magnetic resonance (ODMR) measurements. The proposed method has proved to be a more efficient way to design an ensemble of NV centers-based sensors; because the result increases in the number of NV centers, the quantum efficiency and the contrast ratio could greatly increase the devices sensitivity.

Ensemble spin fabrication and manipulation of NV centres for magnetic sensing in diamond

Purpose This study aims to fabricate and manipulate ensemble spin of negative nitrogen-vacancy (NV−) centres optimally for future solid atomic magnetometers/gyroscope. Parameters for sample preparation most related to magnetometers/gyroscope are, in particular, the concentration and homogeneity of the NV− centres, the parameters’ microwave antenna of resonance frequency and the strength of the microwave on NV− centres. Besides, the abundance of other impurities such as neutral NV centres (NV0) and substitutional nitrogen in the lattice also plays a critical role in magnetic sensing. Design/methodology/approach The authors succeeded in fabricating the assembly of NV centres in diamond and they determined its concentration of (2-3) × 1016 cm−3 with irradiation followed by annealing under a high temperature condition. They explored a novel magnetic resonance approach to detect the weak magnetic fields that takes advantage of the solid-state electron ensemble spin of NV− centres in diamond. In particular, the authors set up a magnetic sensor on the basis of the assembly of NV centres. They succeeded in fabricating the assembly of NV centres in diamond and determined its concentration. They also clarified the magnetic field intensity measured at different positions along the antenna with different lengths, and they found the optimal position where the signal of the magnetic field reaches the maximum. Findings The authors mainly reported preparation, initialization, manipulation and measurement of the ensemble spin of the NV centres in diamond using optical excitation and microwave radiation methods with variation of the external magnetic field. They determined the optimal parameters of irradiation and annealing to generate the ensemble NV centres, and a concentration of NV− centres as high as 1016 cm−3 in diamond was obtained. In addition, they found that sensitivity of the magnetometer using this method can reach as low as 5.22 µT/Hz currently. Practical implications This research can shed light on the development of an atomic magnetometer and a gyroscope on the basis of the ensemble spin of NV centres in diamond. Social implications High concentration spin of NV− in diamond is one of the advantages compared with that of the atomic vapor cells, because it can obtain a higher concentration. When increasing the spin concentration, the spin signal is easy to detect, and macro-atomic spin magnetometer become possible. This research is the first step for solid atomic magnetometers with high spin density and high sensitivity potentially with further optimization. It has a wide range of applications from fundamental physics tests, sensor applications and navigation to detection of NMR signals. Originality/value As has been pointed out, in this research, the authors mainly worked on fabricating NV− centres with high concentration (1015-1016 cm−3) in diamond by using optimal irradiation and annealing processes, and they quantitatively defined the NV− concentration, which is important for the design of higher concentration processes in the magnetometer and gyroscope. Until now, few groups can directly define the NV− concentration. Besides, the authors optimized the microwave antenna parameters experimentally and explored the dependence between the splitting of the magnetic resonance and the magnetic fields, which dictated the minimum detectable magnetic field.

Magnetometry for precision measurement using frequency-modulation microwave combined efficient photon-collection technique on an ensemble of nitrogen-vacancy centers in diamond

Sensitivity of magnetometers that use color centers is limited by poor photon-collection and detection efficiency. In this paper, we present the details of a newly developed all-optical collection combined frequency-modulated microwave method. The proposed method achieves a high sensitivity in static magnetic-field detection both theoretically and experimentally. First, we demonstrate that this collection technique enables both a fluorescence collection as high as 40% and an efficient pump absorption. Subsequently, we exploit the optically detected magnetic resonance (ODMR) signal and quantitative magnetic detection of an ensemble of nitrogen vacancy (NV) centers, by applying a frequency-modulated (FM) microwave method followed by a lock-in technique on the resonance frequency point. Based on the results obtained using all-optical collection combined FM microwaves, we verified that the sensitivity of the magnetometer can achieve approximately 14 nT/√Hz at 1 Hz, using a discrete Fourier transform detection method experimentally. This method provides a compact and portable precision-sensor platform for measuring magnetic fields, and is of interest for fundamental studies in spintronics.

Preparation of Well-Aligned TiO2 Nanotubes with High Length-Diameter Aspect Ratio by Anodic Oxidation Method

This paper focused on the influence of various oxidation parameters such as electrolyte composition, reaction time, calcination temperature and current change on the morphology and structure of TiO2 nanotube arrays. It was found that ammonium fluoride with a high viscosity reduced the diffusion rate of fluoride ions and significantly increased the length of TiO2 nanotubes, creating nanotubes with ordered arrays and uniform diameters. Meanwhile, the time of anodic oxidation determined the length of TiO2 nanotube arrays. Well-aligned nanotube arrays could be obtained after 0.5-2.5 h of oxidation. In addition, when the oxidation temperature was about 30 °C, the TiO2 nanotube arrays achieved the optimal uniformity and the maximum length-diameter aspect ratio. The morphology and quality of the TiO2 nanotubes fabricated were estimated through current as a function of reaction time. Consequently, formation mechanism of TiO2 nanotube arrays was investigated undergoing three major periods. The findings of this study can shed some light on the optimal conditions for preparing well-aligned TiO2 nanotube arrays with high length-diameter aspect ratio.

The Development of a Dual-Warhead Impact System for Dynamic Linearity Measurement of a High-g Micro-Electro-Mechanical-Systems (MEMS) Accelerometer

Despite its extreme significance, dynamic linearity measurement for high-g accelerometers has not been discussed experimentally in previous research. In this study, we developed a novel method using a dual-warhead Hopkinson bar to measure the dynamic linearity of a high-g acceleration sensor with a laser interference impact experiment. First, we theoretically determined that dynamic linearity is a performance indicator that can be used to assess the quality merits of high-g accelerometers and is the basis of the frequency response. We also found that the dynamic linearity of the dual-warhead Hopkinson bar without an accelerometer is 2.5% experimentally. Further, we verify that dynamic linearity of the accelerometer is 3.88% after calibrating the Hopkinson bar with the accelerometer. The results confirm the reliability and feasibility of measuring dynamic linearity for high-g accelerometers using this method.

The design of nano-film tunneling-effect micro gyroscope

The micro gyroscope based on the nano-film tunneling effect is designed and the mesoscopic piezoresistive effect theory of resonant tunneling film structure (RTS) is also researched in this paper. In the mean time, the structure and its material of the RTS are designed and manufactured. The RTS which can explain the resonant tunneling effect reduces the parasitic capacitance of the sensor, improves the negative resistance characteristics of the sensitive film and it can be used in micro gyroscope. Meanwhile, the structure and the parameters of the tunneling effect gyroscope based on the resonant tunneling effect are established. The principle and the simulation of the gyroscope are also made and the simulation results are consistent with the principle.