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The seeking of resonator with high Q and low insertion loss is attractive for critical sensing scenes based on the surface acoustic wave (SAW). In this work, 128° YX LiNbO3-based SAW resonators were utilized to optimize the output performance through IDT structure parameters. Once the pairs of IDTs, the acoustic aperture, the reflecting grid logarithm, and the gap between IDT and reflector are changed, a better resonance frequency of 224.85 MHz and a high Q of 1364.5 were obtained. All the results demonstrate the structure parameters design is helpful for the performance enhancement with regard to SAW resonators, especially for designing and fabricating high-Q devices. [ABSTRACT FROM AUTHOR]

Traditional accelerometers rely on batteries to provide energy, and the massive use of batteries caused great pressure on the natural environment. In this paper, a self‐powered acceleration sensor is designed. To more easily harvest weak vibration signals and effectively improve the sensitivity, this sensor is built on a magnetic levitation type double helix structure and ZnO‐doped triboelectric film. Experiments indicated that the open‐circuit voltage and short circuit current of the triboelectric nanogenerator (TENG) doped with ZnO are increased by 2.51 times and 2.07 times, respectively. Under shaking table test for simulating machine vibration environment, the sensor's sensitivity reaches 16.31 V (m s−2)−1 and its linearity is 0.993. The sensor power generation is 110 μW and its test range is ≈1–7 m s−2. Also, the sensor can be applied for monitoring human's movement state by installing in a sole. This design provides a new idea for the development of TENG‐based sensors. [ABSTRACT FROM AUTHOR]

Domain wall current (DWC) plays a key role in storage devices, logic devices and sensors due to its high on-off ratio and nano structure size in the era of nanoelectronics technology. In this work, the DWC of single crystal LiNbO3 thin film was studied by piezoresponse force microscope (PFM) and conducting atomic force microscope (c-AFM). We mainly focus on voltage and temperature dependence of DWC which increases with the voltage and temperatures. Based on this research, the packaged DWC temperature sensor is fabricated and applied in wide temperature range. The existence of domain walls makes the current on-off ratio as high as 103 at the voltage of 15 V. Our study shows that DWC has a negative temperature coefficient (NTC) from 140 K to 500 K. The current increases from 3 pA to $57 ~\mu \text{A}$ , which is attributed to the conductivity of switched domain. This work proposes a new type temperature sensor with wide temperature range and high compatibility and sensitivity. In addition, it provides support for harsh environment applications of ferroelectric domain engineering devices. [ABSTRACT FROM AUTHOR]

Domain engineering plays a pivotal role in the development of ferroelectric non-volatile memory devices. In this work, we mainly focus on the domain kinetic in ion-sliced single crystal LiNbO3 thin films under tip-induced electric fields using piezoresponse force microscope (PFM). Polarization reversal takes place when the electric fields are above threshold value (coercive voltage Vc) of films. Besides, the dependence of domain dynamic on pulse duration and amplitude were investigated in detail, and specific local domain reversal (5 μm) was completed by the optimized poling condition. All the results reveal that tip-induced polarization reversal could be an effective way to domain engineering, which gives much more promising prospects regarding to the high density non-volatile ferroelectric memory devices. [ABSTRACT FROM AUTHOR]

We demonstrated a BiFeO3single-crystalline thin film, which was deposited on a (100) SrTiO3single-crystal substrate by using a pulse laser deposition technology. The as-grown domain structure was investigated by piezoresponse force microscopy, which possesses two preferential downward <111> orientations in an angle of 71°. We have found that the abnormal out of plane stripe domain patterns match with the in-plane domains. According to schematic diagrams and quantitative equations, we explained that the coupling between the out of plane and in-plane domains arise from the buckling effect, which can open a new way to reconstruct the real polarization vectors. [ABSTRACT FROM AUTHOR]

High-output triboelectric nanogenerators (TENGs) are promising complements of chemical batteries in wearable systems. However, the charge dissipation on tribomaterials in moisture environments remains a challenge impacting the stable energy supply. Herein, asymmetric permittivity manipulation is proposed as a novel strategy to simultaneously improve the output performances and humidity resistance of TENGs. An electrospinning bilayer polycaprolactone (PCL) nanofiber (BPF) composed of outer PCL and inner PCL/CNTs nanofibers which differ widely in permittivity is served as the efficient positive tribomaterial. Benefitting from the increased friction area and dual interfacial polarization in the bilayer dielectric, the transferred charge of the BPF-TENG increases by 740% compared to the PCL gel film-based device, reaching 210 nC at 1 Hz. Significantly, a high-speed camera system verifies that the porous hydrophobic PCL nanofiber with a water contact angle of 125 degrees can effectively reduce the accumulation of water droplet on the material surface, contributing to stable output from 20% to 80% relative humidity. The optimized BPF-TENG generates a high peak-to-peak voltage of 2.24 kV and a power density of 54 W/m2 in 80% humidity. Besides, by harvesting biomechanical energy, a 1000 µF capacitor can be charged to 3 V and continuously drive electronics to work in wet weather. This strategy can be extended to various commercialized tribo-negative polymers and enables large-scale industrial manufacturing of high-output and humidity-resistant TENGs. [Display omitted] • A highly tribopositive, hydrophobic, and asymmetric permittivity enhanced bilayer PCL nanofiber (BPF) is fabricated. • The enhanced specific surface area and interfacial polarization promote a 740% improvement of transferred charge. • A high-speed camera verifies that the PCL fiber can effectively reduce the accumulation of water droplet in high humidity. • The BPF-TENG generates a high peak-to-peak voltage and power density of 2.24 kV and 54 W/m2 by palm flapping in 80% RH. [ABSTRACT FROM AUTHOR]

[Display omitted] • Si-based LiNbO 3 films with the thickness 6.294 μm and roughness 585 pm are obtained by chemical mechanical polishing; • Oxygen plasma treatment reduced the water contact angle of the metal surface and improved the bonding strength; • Chemical mechanical polishing releases the compressive stresses that remain inside the wafer during the bonding; • Large-area ferroelectric domain with a period of 40 μm were reversed at the electric field of 320 kV/cm. In the post Moore era, as the size miniaturization approaches limit of the devices, silicon-based sensors cannot meet the requirements of micro/nano sensing with small size and high precision. The piezoelectric sensor based on lithium niobate (LN) single crystal thin film has excellent electromechanical property, photoelectric property, piezoelectric property, which can realize high precision sensing at small size. In our work, 4-inch silicon-based LN single crystal thin film was prepared based on low-temperature bonding technology and chemical mechanical polishing (CMP) method. The oxygen plasma treatment was adopted for increasing the surface hydrophilia to enhance the bonding strength. Grinding parameters under different film thickness were determined by experiments. The parameters of the film was characterized by scanning electron microscope (SEM) with a thickness of 6.294 μm and by atomic force microscope (AFM) obtained the surface roughness is 585 pm. The x-ray diffraction (XRD) test showed that the CMP process could release the compressive stress caused by the bonding, thus obtaining high quality LN single crystal films. The prepared films are polarized and the domain walls can be clearly observed by piezoresponse force microscopy (PFM). It provides a more comprehensive way to prepare ferroelectric domain devices. [ABSTRACT FROM AUTHOR]

It is a great challenge to detect in-situ high-frequency vibration signals for extreme environment applications. A highly sensitive and robust vibration sensor is desired. Among the many piezoelectric materials, single-crystal lithium niobate (LiNbO3) could be a good candidate to meet the demand. In this work, a novel type of micro-electro-mechanical system (MEMS) vibration sensor based on a single crystalline LiNbO3 thin film is demonstrated. Firstly, the four-cantilever-beam MEMS vibration sensor was designed and optimized with the parametric method. The structural dependence on the intrinsic frequency and maximum stress was obtained. Then, the vibration sensor was fabricated using standard MEMS processes. The practical intrinsic frequency of the as-presented vibration sensor was 5.175 kHz, which was close to the calculated and simulated frequency. The dynamic performance of the vibration sensor was tested on a vibration platform after the packaging of the printed circuit board. The effect of acceleration was investigated, and it was observed that the output charge was proportional to the amplitude of the acceleration. As the loading acceleration amplitude is 10 g and the frequency is in the range of 20 to 2400 Hz, the output charge amplitude basically remains stable for the frequency range from 100 Hz to 1400 Hz, but there is a dramatic decrease around 1400 to 2200 Hz, and then it increases significantly. This should be attributed to the significant variation of the damping coefficient near 1800 Hz. Meanwhile, the effect of the temperature on the output was studied. The results show the nearly linear dependence of the output charge on the temperature. The presented MEMS vibration sensors were endowed with a high output performance, linear dependence and stable sensitivity, and could find potential applications for the detection of wide-band high-frequency vibration. [ABSTRACT FROM AUTHOR]

The ferroelectric materials own the natural anti-irradiation property, paving great potentials and applications regarding the aerospace fields. Benefiting from this property, LiNbO 3 -based surface acoustic wave (SAW) devices can be used for high accuracy sensing signal test under extreme circumstances. In this work, the 128° YX cut LiNbO 3 substrate was adopted for SAW resonator temperature sensor application, and the response frequency varied from 180.44 MHz to 177.628 MHz with temperature from 21.9 ℃ to 199.9 ℃. Subsequently, the device irradiated by 100 Krad Gamma ray was tested with vector network analyzer (VNA). A maximum frequency shift of ~ 0.38% was found under γ-ray irradiation with a dose of 100 Krad on account of slight irradiation effect. The results verify the radiation resistance ability of SAW for development of highly reliable temperature sensor in the irradiation environment. A novel SAW temperature sensor was analyzed, designed and fabricated with 128°YX LiNbO3 process platform, which can be used for testing temperature under irradiation experiment. [Display omitted] • A SAW temperature sensor was fabricated by 128° YX cut LiNbO3 which could work under the irradiation experiment. • The sensor has good anti-irradiation property, that a maximum frequency shift of 0.38% was found under γ-ray irradiation. • The SAW temperature sensor was standardized and tested, and the device showed good stability. [ABSTRACT FROM AUTHOR]

(Pb,La)(Zr,Ti)O antiferroelectric 1.4 μm-thick films have been prepared on Pt (111)/Ti/SiO/Si(100) substrates by sol-gel process. The structures and dielectric properties of the antiferroelectric thick films were investigated. The films displayed pure perovskite structure with (100)-preferred orientation. The surface of the films was smooth, compact and uniform. The antiferroelectric (AFE) characterization have been demonstrated by P (polarization)-E (electric field) and C(capacitance)-V (DC bias) curves. The AFE-ferroelectric (FE) and FE-to-paraelectric (PE) phase transition were also investigated as coupling functions of temperature and direct current electric field. With the applied field increased, the temperature of AFE-to-FE phase transition decreased and the FE-to-PE phase shifted to high temperature. The AFE-to-FE phase transition was adjustable by direct current electric field. (Pb,La) (Zr,Ti) O antiferroelectric films have broad application prospects in microelectromechanical systems because of the phase transition. [ABSTRACT FROM AUTHOR]

An integration technology for wafer-level LiNbO3 single-crystal thin film on Si has been achieved. The optimized spin-coating speed of PI (polyimide) adhesive is 3500 rad/min. According to Fourier infrared analysis of the chemical state of the film baked under different conditions, a high-quality PI film that can be used for wafer-level bonding is obtained. A high bonding strength of 11.38 MPa is obtained by a tensile machine. The bonding interface is uniform, completed and non-porous. After the PI adhesive bonding process, the LiNbO3 single-crystal was lapped by chemical mechanical polishing. The thickness of the 100 mm diameter LiNbO3 can be decreased from 500 to 10 μm without generating serious cracks. A defect-free and tight bonding interface was confirmed by scanning electron microscopy. X-ray diffraction results show that the prepared LiNbO3 single-crystal thin film has a highly crystalline quality. Heterogeneous integration of LiNbO3 single-crystal thin film on Si is of great significance to the fabrication of MEMS devices for in-situ measurement of space-sensing signals. [ABSTRACT FROM AUTHOR]

Minuscule pressure/stress detection with high sensitivity can recognize and deal with potential hazards timely, which is crucial for guaranteeing the security of human and stability of social functioning. Lithium niobate (LiNbO 3) single crystal possessing excellent piezoelectric and ferroelectric properties is suitable for fabricating piezoelectric pressure sensors. Therefore, in this paper, the pressure sensors based on LiNbO 3 single crystals with parallel connected structure were researched. Sensors with parallel connected structure can improve the sensitivity from 4.86 V/N of single sheet structure to 8.71 V/N under the stress between 0.01 N and 0.2 N at 30 °C. Both types of the sensors can detect the minuscule stress low to 0.01 N and minuscule pressure generated by balloon pump, blowing largely or slowly. The influence of temperature on sensors was also researched, and the results exhibited that sensors performed well from 30 °C to 60 °C and still sustained high sensitivity of 5.26 V/N of parallel connected structure and 3.71 V/N of single sheet structure at 60 °C. Besides, the response time of sensors to the pressure of balloon pump is 60 ms under different temperature. These excellent properties indicate the great potential applications of fabricated sensors in practical minuscule pressure/stress detection. [ABSTRACT FROM AUTHOR]

In situ measurements of sensing signals in space platforms requires that the micro-electro-mechanical system (MEMS) sensors be located directly at the point to be measured and in contact with the subject to be measured. Traditional radiation-tolerant silicon-based MEMS sensors cannot acquire spatial signals directly. Compared to silicon-based structures, LiNbO3 single crystalline has wide application prospects in the aerospace field owing to its excellent corrosion resistance, low-temperature resistance and radiation resistance. In our work, 4-inch LiNbO3 and LiNbO3/Cr/Au wafers are fabricated to silicon substrate by means of a polyimide bonding method, respectively. The low-temperature bonding process (≤ 100 °C) is also useful for heterostructure to avoid wafer fragmentation results from a coefficient of thermal expansion (CTE) mismatch. The hydrophilic polyimide surfaces result from the increasing of -OH groups were acquired based on contact angle and X-ray photoelectron spectroscopy characterizations. A tight and defect-free bonding interface was confirmed by scanning electron microscopy. More importantly, benefiting from low-temperature tolerance and radiation-hardened properties of polyimide material, the bonding strength of the heterostructure based on oxygen plasma activation achieved 6.582 MPa and 3.339 MPa corresponding to room temperature and ultra-low temperature (≈ −263.15 °C), which meets the bonding strength requirements of aerospace applications. [ABSTRACT FROM AUTHOR]

The microcantilevers based on the antiferroelectric (AFE) (Pb0.97La0.02)(Zr0.95Ti0.05)O3 (PLZT) thick films were fabricated by bulk silicon micromachining process. The conspicuous electrostrictive strain properties with phase transition of the AFE PLZT films induced by electric field were investigated. The resonant vibration velocity and tip deflection on a 650-\mum-long cantilever were up to 6767 mm/s and 45.7 \mum, under the square wave excitation with the voltage of 40 V, matched to the AFE-ferroelectric phase transition electric field of 210 kV/cm. The ratio of induced tip displacement and cantilever length per unit voltage [d(\delta)/L/dV] was proposed to show the mutation response ability. In addition, the new AFE PLZT microcantilevers exhibited superior value of 10.77/kV, further higher than the traditional ones. Extensive application requirements for microdevices would be met in various fields of microelectromechanical systems. [ABSTRACT FROM PUBLISHER]

As a new energy harvesting strategy, triboelectric nanogenerators which have a broad application prospect in collecting environmental energy, human body mechanical energy, and supplying power for low‐power electronic devices, have attracted extensive attention. However, technology challenges still exist in the stretchability for the preparation of some high‐performance triboelectric materials. In this work, a new strategy for nonmetallic nylon‐modified triboelectric nanogenerators (NM‐TENGs) is reported. Nylon is introduced as a high performance friction material to enhance the output performance of the stretchable TENG. The uniform matrix reduces the difficulty of heterogeneous integration and enhances the structural strength. The open‐circuit voltage (VOC) and short‐circuit current (ISC) of NM‐TENG can reach up to 1.17 kV and 138 µA, respectively. The instantaneous power density reaches 11.2 W m−2 and the rectified output can directly light ≈480 LEDs. The transferred charge density is ≈100 µC m−2 in one cycle when charging the capacitor. In addition, a low‐power electronic clock can be driven directly by the rectified signal without additional circuits. NM‐TENG also has high enough strain rate and can be attached to the human body for energy harvesting effectively. This work provides a new idea for fabrication of stretchable TENGs and demonstrates their potential application. [ABSTRACT FROM AUTHOR]

As a promising functional material, ferroelectric Pb(ZrxTi1−x)O3 (PZT) are widely used in many optical and electronic devices. Remarkably, as the film thickness decreases, the materials' properties deviate gradually from those of solid materials. In this work, multilayered PZT thin films with different thicknesses are fabricated by Sol-Gel technique. The thickness effect on its microstructure, ferroelectric, and optical properties has been studied. It is found that the surface quality and the crystalline structure vary with the film thickness. Moreover, the increasing film thickness results in a significant increase in remnant polarization, due to the interfacial layer effect. Meanwhile, the dielectric loss and tunability are strongly dependent on thickness. In terms of optical properties, the refractive index of PZT films increase with the increasing thickness, and the photorefractive effect are also influenced by the thickness, which could all be related to the film density and photovoltaic effect. Besides, the band gap decreases as the film thickness increases. This work is significant for the application of PZT thin film in optical and optoelectronic devices. [ABSTRACT FROM AUTHOR]

The highest classification average accuracy of 87.29% with outstanding decoding performance is obtained for the EEGNet with SimAM attention module, which could be attributed to the fact that the neural feature of finger flexion could be reflected by the different motor cognition. [Display omitted] • Optimized EEGNet for decoding motor imagery EEG singles of left and right hand of index and thumb with an average accuracy 72.91%. • The feature of event related desynchronization (ERD) and event related synchronization (ERS) of index and thumb were studied. • Optimized EEGNet provided an explanatory convolutional neural network for the neuroscience research based on EEG. As a cutting-edge technology of connecting biological brain and external devices, brain-computer interface (BCI) exhibits promising applications on extensive fields such as medical and military. As for the disable individuals with four limbs losing the motor functions, it is a potential treatment way to drive mechanical equipments by the means of non-invasive BCI, which is badly depended on the accuracy of the decoded electroencephalogram (EEG) singles. In this study, an explanatory convolutional neural network namely EEGNet based on SimAM attention module was proposed to enhance the accuracy of decoding the EEG singles of index and thumb fingers for both left and right hand using sensory motor rhythm (SMR). An average classification accuracy of 72.91% the data of eight healthy subjects was obtained, which were captured from the one second before finger movement to two seconds after action. Furthermore, the character of event-related desynchronization (ERD) and event related synchronization (ERS) of index and thumb fingers was also studied in this study. These findings have significant importance for controlling external devices or other rehabilitation equipment using BCI in a fine way. [ABSTRACT FROM AUTHOR]

• High-resolution graphitized arrays with 23.89 nm feature size and less than 5 nm roughness in-situ synthesized by e-beam irradiation process. • The obvious fluorescence spectrum with center wavelength at 600 nm were presented at periodic solid carbon-based nanostructures. • The photoluminescence intensity was enhanced by a factor of 17 times with the help of surface state doping of NH 3 ·H 2 O molecule. • Constructing the composite structure with zero-dimensional carbon dots and two-dimensional film for study of luminescence superposition. Photoluminescent carbon nanomaterials have been widely studied for their low biological toxicity, outstanding biocompatibility, unique physical–chemical properties and obvious PL properties. The reliable fabrication of high-resolution fluorescence arrays has important significance in further studies and applications. The organic resist can be in-situ transferred into specific carbon-based micro-nano structure with fluorescence properties under e-beam irradiation. In this work, polymethyl methacrylate (PMMA) thin film was adopted for preparing solid-carbon nanostructures with 23.89 nm feature size. In a dark field environment, the structure has presented broad luminescent spectrum with maximum at 600 nm. Considering the significant influence of the surface molecular state on solid-carbon arrays, ammonia solution was used to enhance the PL intensity of the sample. The results verified that PL intensity was enhanced by a factor of 17 before and after ammonia solution treatment. Then carbon-based nanostructures were also fabricated on the surface of MoS 2 film for studying PL properties between 2D materials and carbon-based dot arrays. The results show that superposition state was produced based on PL intensity and peak location of the solid-carbon dot array and MoS 2 film. The optical behavior study of high-resolution solid-carbon arrays will provide a powerful supplement for carbon-based photophysical study and high-performance sensing devices. [ABSTRACT FROM AUTHOR]