Nitrogen-vacancy (NV) center magnetometers are advancing toward miniaturization, enabling large-scale and batch production. In recent research, standard microelectromechanical system (MEMS) fabrication processes were utilized to develop an integrated structure comprising a silicon microcap, a diamond antenna, and a siliconbased reflector. The resulting chip-scale integrated scalar NV magnetometer had a compact probe size of approximately 12 mm & times; 6 mm & times; 2 mm. A microwave power transfer transmission line with a dual-Omega configuration was directly fabricated on the diamond surface, while the microwave signal transmission port and fluorescence signal transmission port were bonded to the terminals of the silicon microcap using thermocompression bonding (TCB). The diamond was then inserted into the recess of the silicon-based reflector and combined with a photodetector and a bandpass filter to form a magnetic component, which was encapsulated in a ceramic tube. Here, we demonstrate that this chip-level integrated NV magnetometer has a test bandwidth of 0.1-60 Hz, a measured sensitivity of approximately 846pT/Hz1/2, and an estimated shot-noise-limited sensitivity of 121pT/Hz1/2, based on theoretical calculations. Compared with that of bare diamonds, the fluorescence collection efficiency is enhanced by more than 1.72 times. This design not only maintains a high sensitivity but also significantly improves integration and portability, making it highly suitable for practical applications.

Nitrogen-vacancy-center (NVC) vector magnetometers have emerged as one of the most promising quantum magnetic-sensing technologies owing to their high sensitivity and wide dynamic range. However, most reported integrated or portable NVC magnetometers are scalar systems, whereas vector implementations often remain optical-table-based and suffer from resonance-frequency drift on open-loop operation. This article presents a portable closed-loop NVC vector magnetometer using four-channel proportional–integral (PI) frequency tracking. The system consists of a miniaturized sensing probe (163 × 55 × 62 mm³) and a control-electronics unit (440 × 274 × 177 mm³). Four independent frequency-locking loops track the optically detected magnetic resonance (ODMR) frequencies of four NVC axes, allowing real-time three-dimensional magnetic-field vector reconstruction. Experimental results show that the closed-loop linear dynamic range reaches approximately ±200 μT for all three Cartesian axes. The measured magnetic-field sensitivities, evaluated at 10 Hz, are 0.897, 0.783, and 0.809 nT/Hz1/2 for the X, Y, and Z axes, respectively. Furthermore, stable three-dimensional vector reconstruction is achieved through four-channel closed-loop frequency tracking, and the closed-loop architecture enables robust resonance-frequency tracking over a wide range of magnetic-field conditions. These results confirm that the proposed portable closed-loop NVC vector magnetometer can achieve stable vector-field reconstruction and has potential for applications in magnetic-field monitoring and geomagnetic-anomaly detection.

Ultrasensitive magnetometers based on spin resonances have led to remarkable achievements. However, the field responsivities of these spin resonances are inherently constrained by these particles' gyromagnetic ratios, such as the electron, with a constant gyromagnetic ratio of γ_{e}=2π×28  GHz/T. Here, we demonstrate an ultrasensitive magnetometer based on the cusp point (CP) of photon-magnon synchronization modes (PMSMs). The PMSM's field responsivity at the CP is enhanced to 37γ_{e} and further amplified to 236γ_{e} by utilizing the sixth-order oscillating mode of the PMSM. Moreover, the emission linewidth of the PMSM can be reduced to 0.06 Hz, resulting in excellent sensitivity to weak magnetic fields. These outstanding properties position our magnetometer to potentially achieve superior sensitivity to conventional magnetometers. Our Letter introduces a cost-effective prototype for the next generation of magnetometry and may advance scientific research and technologies that rely on ultrasensitive magnetic field detection.

The delicate interfacial conditions and behaviors play critical roles in determining the valuable physical properties of two-dimensional materials and their heterostructures on substrates. However, directly probing these complex interfacial conditions remains challenging. Here, we reveal the coupled in-plane strain and out-of-plane bonding conditions in strain-engineered WS2 flakes by combining dual-harmonic electrostatic force microscopy (DH-EFM) and scanning microwave impedance microscopy (sMIM). A striking contradiction is observed between the compressive-strain-induced larger bandgap (lower electrical conductivity) detected by DH-EFM, and the enhanced conductivity probed by sMIM. Comparative measurements under different sMIM modes demonstrate that this contradiction originates from a tip-loading-force-induced dynamic puckering effect, which is governed by the interfacial bonding strength. Furthermore, the progressive accumulation and subsequent release of conductivity during forward/backward sMIM-contact scans further confirm this dynamic puckering behavior, revealing pronounced differences in interfacial conditions between the open-and closed-ring regions of WS2. This work establishes the correlation between electrical properties and interfacial conditions, and provides fundamental insights for interface-engineered devices.

The characterization of microwave fields holds significant engineering importance in high-frequency chip design and performance optimization. In this study, we propose a noninvasive wide-field imaging method based on the spectral hole-burning effect in optically detected magnetic resonance (ODMR). This wide-field imaging method enables imaging of microwave fields at different frequencies under near-field radiator operating conditions. Its feasibility is confirmed by characterizing near-field radiator-generated microwave fields across multiple frequency and power settings. Furthermore, the effectiveness of the method is validated through a comparative analysis of simulation results and experimental measurements. Under the current experimental conditions, the results show that the approach achieves a frequency resolution of 100 kHz over the range of the resonance region, a microwave detection sensitivity of 0.78 nT/Hz (1/2 ), a spatial imaging resolution of 1.55 mu m, and the minimum detectable power is 1 mW. The above methods indicate great potential for application in the fields of integrated circuit fault diagnosis, electromagnetic compatibility testing, and radio equipment parameter calibration.

Suspended two-dimensional (2D) materials in high-performance devices exhibit unique properties that are critically important for nanoscale mechanical and electromechanical applications, while their frictional laws remain poorly understood. Here, we investigate the nanoscale frictional behavior of suspended WS2 flakes under varying applied loads and scanning rates using atomic force microscopy (AFM), and successfully employ the Bowden-Tabor theory and the thermally activated Prandtl-Tomlinson (PTT) model to analyze the load- and scanning-rate-dependent friction characteristics of suspended 2D systems. The results show that suspended WS2 exhibits higher friction than supported WS2, whereas its friction increases more slowly with applied load, which can be well described by the Bowden-Tabor theory. Moreover, the friction exhibits a logarithmic dependence on scanning rate for both suspended and supported WS2. Quantitative analysis within the framework of the PTT model demonstrates that this model can be successfully extended to describe the rate-dependent friction of suspended WS2, providing a unified framework for both supported interfaces and suspended 2D systems. This work provides valuable guidance for understanding frictional dissipation mechanisms relevant to the design and optimization of WS2-based devices.

Importance of using nitrogen-vacancy (NV) center as quantum sensors in diamonds is of great significance in their high sensitivity and stability, which are widely applied in microwave detection area. Especially, the heterodyne technique can beyond the limitation of quantum coherence time and stands out with the advantage of high frequency resolution. However, the realization of high frequency resolution relies on long-time measurements, so how to reduce the noise and maintain the stability of the system during the long-time measurements has become an urgent problem. Here, we propose a novel method for NV sensors that combines common-mode rejection (CMR) and proportional and integral (PI) control techniques with the heterodyne technique. This method achieves a 5 dB increase in signal-to-noise ratio (SNR) and measurement stability over long periods of time with 2.4 times improvement in the minimum Allan variance averaging time. Where, the CMR and PI technologies achieve high SNR and longtime stability by matching the differential inputs to reduce the common mode noise and by decreasing steady-state error through an integral controller, respectively. A frequency resolution of 9.5 mHz and the minimum detectable magnetic field of 4.85pT over an average time of approximate to 2400 s have been achieved by using the hybrid heterodyne technique. Finally, we demonstrate the capability of audio recognition with this hybrid heterodyne technique, as well as having potential application in fields such as magnetic resonance imaging (MRI) and unknown signal exploration.

The efficient detection of digital signals plays a vital role in optimizing the reliability and stability of communication systems. This paper demonstrates a method to optically measure digital signals based on solid‐state quantum spin. The digital signals are non‐intrusively characterized by taking advantage of the optical readability of the spin states of the nitrogen‐vacancy (NV) centers array. Meanwhile, the resonance frequencies of optically detected magnetic resonance (ODMR) spectra are spatially encoded by means of an external magnetic field gradient, thereby realizing the simultaneous acquisition of three‐channel digital signals. Over a continuous detection bandwidth of 258 MHz, digital signals can be detected with a time resolution of 3 ms and a minimum signal strength of 0 dBm. Afterward, the ability of this system to capture digital signals is further substantiated by measuring signals in other channels. This proposal is competent for the simultaneous analysis of multi‐channel signals in real‐time and provides a valuable reference for radio spectrum monitoring, and signal intelligence reconnaissance.

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 1050x1050 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/Hz1/2. 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.

Electron‐hole activation, transforming closed‐ to open‐shell reactive oxygen species on photocatalytic TiO 2 surfaces, is essential for designing effective photocatalysts capable of providing specific functionalities and enhanced performance. However, at atomic level, the activation mechanism of the oxygen species remains murky. To shed light, we used a combination of atomic force microscopy, Kelvin probe force spectroscopy under ultrahigh vacuum conditions with density functional theory simulations to understand the atomic‐scale mechanism of electron and hole injection into the chemisorbed oxygen species supported on the rutile TiO 2 (110) surface. Specifically, the closed‐shell oxygen species, such as the peroxo () molecule​, can be manipulated by applied local electric field to induce its hopping between different adsorption sites or molecular rotation, while the open‐shell oxygen species, such as the superoxo () molecule, can be synthesized by injecting holes into their corresponding closed‐shell form. Combining applied local electric field with hole injection we have been able to activate a tip‐induced Langmuir–Hinshelwood reaction leading to ozone (O 3 ) molecule formation and, for the first time, visualize its synthesis at atomic resolution. The formation of long‐lived superoxo and ozone molecules directly demonstrates their strong oxidative properties, which persist on the timescale of seconds highlighting their prominent role in photocatalysis.

Au/CeO2(111), as an important catalyst system, has demonstrated excellent catalytic performance in a variety of fields such as the catalytic oxidation and the water-gas shift reactions. In order to deeply reVeal Au/CeO2(111) catalytic mechanism, especially to understand the interaction of the active components on the atomic scale. In this paper, the adsorption properties on the Au/CeO2(111) surface are investigated by calculating the adsorption energy, differential charge density, Bader charge, and the density of states using density functional theory (DFT+U). First, five adsorption sites of Au/CeO2(111) were identified in the planar region of CeO2(111), and the most stable adsorption configuration was found to be located at the bridging position between surface oxygen atoms (the oxygen-oxygen bridging site). It suggests that Au interacts more closely with the oxygen-oxygen bridging sites. Further, the differential charge density and Bader charge reVeal the charge transfer mechanism during the adsorption process: the Au atoms are oxidized to Au+, while the Ce4+ ions in the second nearest neighbor of Au are reduced to Ce3+, and the adsorption process is accompanied by a charge transfer phenomenon. Au also exhibits a unique adsorption behavior in the CeO2(111) step-edge region, where a highly under-allocated environment is formed due to the decrease in the coordination number of atoms in the step edge, which enhances the adsorption of Au in a highly under-allocated environment. The adsorption of Au at the step edge is enhanced by the lower coordinated environment due to the reduced coordination number of the atoms at the step edge. By comparing four different types of step structures (Type I, Type II, Type II*, and Type III), we find that the higher adsorption energies of Au at the Type II* and Type III sites are mainly attributed to the lower coordinated state of Ce atoms at these sites. Charge transfer is also particularly pronounced at the Type III sites. It is also accompanied by electron transfer from Au to Ce4+ ions, making Type III the preferred adsorption site for Au atoms. By constructing a more comprehensive Au/CeO₂ model, this study breaks through the preVious limitation of focusing only on planar adsorption and reVeals the adsorption mechanism of Au/CeO₂ at the edge of the step, which provides a new perspective for us to deeply understand the catalytic mechanism of Au/CeO₂(111).

With the state-of-the-art quantum measurement devices,such as atomic clocks,atomic gyroscopes,and atomic magnetometers,as their central components,the spatiotemporal evolution of atomic spin polarization in the atomic vapor cell has a major effect on both increasing the bandwidth of magnetometer and improving the accuracy of magnetic gradient measurements.However,the major factor impeding the further improvement of the performance of quantum measurement instrument is the inherent static nature of the traditional intra-vapor cell segmentation imaging technique,which makes it challenging to achieve the real-time capture of the dynamic evolution of atomic spin states.In this work,we suggest a dynamic spin imaging method for alkali metal atomic vapor cells with real-time modification of atomic spin polarization states in order to overcome this technological difficulty.In particular,to ensure that the laser can precisely act on the alkali metal atoms in various regions in the vapor cell,we employ a complex beam array management system to modify the on/off state of the laser beams at various positions in the spatial dimension in real time.In the meantime,we generate laser fields with particular spatial distribution and frequency characteristics by using frequency modulation techniques in the time series to accurately regulate the on-off frequency of each laser beam in the beam array.These laser beams cause dynamic changes in the atomic spin polarization state by interacting with alkali metal atoms at various points in the vapor cell.Through precise adjustment of the laser properties,we can see and study the dynamic evolution of the atomic spin-polarization state in real time.According to the experimental data,the technology outperforms the traditional static spin imaging techniques by achieving an excellent temporal resolution of 355 frames per second and a spatial resolution of 95.9 micrometers.The effective use of this method enables us to monitor and evaluate the dynamic aspects of magnetic field distribution with unprecedented precision,also greatly enhance our understanding of the dynamic characteristics of atomic spin polarization.

This article demonstrates a simultaneous detection of multiple radio frequency (RF) information and visualization coding method based on nitrogen vacancy (NV) centers. By applying an external magnetic field gradient to spatially encode the resonance frequency of the optical detection magnetic resonance (ODMR) spectrum, the continuous detection bandwidth is extended to 250 MHz. By precisely controlling the excitation of different RF signals through timing and combining it with wide-field imaging techniques to capture consecutive frames of images and superimpose them, a wide range of complex RF information is encoded into a 2-D pattern. The barcodes as well as letter patterns generated in the experiment clearly show the characteristics of different RF signals. The experiments were conducted in the 3.50-3.75-GHz band with a dynamic range of 40 dBm and a detection sensitivity of 8.07 nT/Hz(1/2) . The program detects multiple RF signals synchronously in real time and presents their signal characteristics in a visual pattern, which provides a new technical approach for intuitively analyzing complex signals in areas, such as radar, navigation, and wireless communications.

As the central element of state-of-the-art quantum measurement devices like atomic clocks, atomic gyroscopes, and atomic magnetometers, the spatial and temporal evolution of atomic spin polarization inside the atomic vapor cell has a major effect on both increasing the magnetometers' bandwidth and improving the precision of magnetic gradient measurements. However, the major factor preventing the further advancement of quantum measurement instruments' performance is the inherent static nature of the conventional intra-vapor cell segmentation imaging technique, which makes it challenging to achieve the real-time capture of the dynamic evolution of atomic spin states. Our research team suggests a dynamic spin imaging method for alkali metal atomic vapor cells with real-time modification of atomic spin polarization states in order to overcome this technological difficulty. In particular, to guarantee that the laser can precisely act on the alkali metal atoms in various regions within the vapor cell, we employ a complex beam array management system to modify the on/off state of the laser beams at various positions in the spatial dimension in real time. In the meantime, we generate laser fields with particular spatial distribution and frequency characteristics by using frequency modulation techniques in the time series to accurately regulate the on-off frequency of each laser beam in the beam array. These laser beams cause dynamic changes in the atomic spin polarization state by interacting with alkali metal atoms at various points within the vapor cell. Through precise adjustment of the laser properties, we have been able to see and study the dynamic evolution of the atomic spin-polarization state in real time. According to the experimental data, the technology outperforms the conventional static spin imaging techniques by achieving an excellent temporal resolution of 355 frames per second and a spatial resolution of 95.9 micrometers. The effective use of this method allows us to monitor and evaluate the dynamic aspects of magnetic field distribution with previously unheard-of precision, in addition to significantly enhancing our understanding of the dynamic properties of atomic spin polarization.

The fabrication of nitrogen-vacancy (NV) center magnetometers utilizing micro-electro-mechanical systems (MEMSs) has gained popularity due to the low cost, good consistency, and easy of system integration. This article presents the fabrication of an NV magnetometer using MEMS process, which integrates a silicon-based resonator for microwave transmission, a diamond waveguide for fluorescence emission, and a silicon-based reflector for fluorescence collection. The magnetometer operates on the principle of continuous-wave optically detected magnetic resonance (CW-ODMR) for magnetic field detection. The inhomogeneity of the silicon-based resonator in the 1.9x1.9 mm area of hole is 7.7%. The combined effect of the silicon-based reflector and diamond waveguide achieves a 2.82-fold enhancement in fluorescence collection efficiency. The silicon-silicon interface between the resonator and reflector components is fabricated via thermal compression bonding to form a groove for subsequent diamond waveguide integration. The processed components are placed within a ceramic tube shell and subsequently encapsulated in glass. The integrated magnetometer, with dimensions of 14x14x12 mm, achieves a sensitivity of 901.96 pT/Hz (1/2 )within the 1-55 Hz, a photon shot noise limited sensitivity of 121 pT/Hz (1/2 ), and a magnetic field detection range of +/- 168.2 mu T.

In this paper, we present a real-time vector magnetic field tracking method based on nitrogen vacancy (NV) centers magnetic detection technique. By combining optical detection magnetic resonance (ODMR) spectroscopy with multi-channel microwave frequency modulation (FM) technology, magnetic field information for each NV axis is extracted from the fluorescence signals captured by a single photodetector (PD), followed by real-time demodulation. The real-time vector magnetic field tracking method is more than 28 times faster than the frequency hopping method. Subsequently, multi-channel feedback control is introduced to track the resonance frequency of each NV axis in real-time, enabling real-time vector tracking measurements. The experimental results show that the dynamic range of the AC magnetic field is ±148.8 µT for the X, ± 151.2 µT for the Y, and ±152.5 µT for the Z. The sensitivities are 0.93nT/Hz, 0.76nT/Hz, 0.54nT/Hz respectively, which further validated the feasibility of the method. The method has potential applications in space exploration, medical diagnosis, navigation and other fields.

The common ways to activate a chemical reaction are by heat, electric current, or light. However, mechanochemistry, where the chemical reaction is activated by applied mechanical force, is less common and only poorly understood at the atomic scale. Here we report a tip-induced activation of chemical reaction of carbon monoxide to dioxide on oxidized rutile TiO2 (110) surface. The activation is studied by atomic force microscopy, Kelvin probe force microscopy under ultrahigh-vacuum and liquid nitrogen temperature conditions, and density functional theory (DFT) modeling. The reaction is inferred from hysteretic behavior of frequency shift signal further supported by vector force mapping of vertical and lateral forces needed to trigger the chemical reaction with torque motion of carbon monoxide towards an oxygen adatom. The reaction is found to proceed stochastically at very small tip-sample distances. Furthermore, the local contact potential difference reveals the atomic-scale charge redistribution in the reactants required to unlock the reaction. Our results open up new insights into the mechanochemistry on metal oxide surfaces at the atomic scale.

The charge state of noble metal atoms on a semiconductor surface is an important factor in surface catalysis. In this study, Au atoms were deposited on the rutile TiO2(110) surface to characterize its charge properties using atomic force microscopy with Kelvin probe force microscopy at 78 K. Au single atoms, dimers, and trimers at different sites on the surface were investigated. Positively charged Au atoms were verified at oxygen sites, while negatively charged Au atoms were found near oxygen vacancy sites. Furthermore, the charge states of small Au nanoclusters were clarified. Understanding the charge states of Au atoms is significant for identifying their efficient catalytic effects in surface catalysis.

In this paper, we propose a method for simultaneously recovering multiple radio wave signals based on nitrogen-vacancy (NV) centers in diamond combining optically detected magnetic resonance (ODMR) spectrum. A controlled magnetic field gradient applied to the laser excitation area on the surface of diamond widens the detectable ODMR bandwidth to 200 MHz. Three different frequency-modulated (FM) signals with distinct carrier frequencies falling within the resonance frequency range are received and demodulated in real-time. Subsequently, the FM signal reception capability of this system is further investigated by measuring baseband signal frequencies ranging from 0.1 Hz to 200 Hz and adjusting the carrier power within a dynamic range from -10 dBm to 30 dBm. This proposal, which accomplishes multi-channel demodulation using a compact and single device, has potential applications in fields such as wireless communication, radar and navigation.

Nitrogen Vacancy (NV) centers in Diamond exhibits the advantages of high resolution, high sensitivity, and error-free sensing in the field of vector field detection, which bolstering the potential of NV centers magnetometers for practical applications. However, most of the NV centers magnetometers is still limited by the constraints imposed by bulky laboratory instruments, and the method of sweeping frequency points to detect resonance frequencies can also lead to slower detection of vector magnetic field (MF). To address these limitations, enhancing the portability of integrated vector magnetometers, we made an integrated vector magnetometer based on NV centers and proposed a microwave (MW) frequency-hopping method to realize vector MF triaxial real-time (400 ms) detection. The experimental results indicate that the magnetometer dynamic range is ± 130 μT along the x-axis, ± 110 μT along the y-axis, and ± 260 μT along the z-axis, with the minimum standard deviation of vector MF measurements across all three axes being 1.84 nT. The frequency-hopping method is more than 87 times faster than the sweeping method and the size of the integrated NV magnetometer fit in the palm of the hand to portable usage. This proposal, which accomplishes vector MF rapidly measure using a self-made NV centers magnetometer, has potential applications in fields such as medical diagnosis, new energy battery testing and geomagnetic detection.