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The application of standing surface acoustic wave (SSAW) tweezers based on backpropagation superposition to achieve precise behavior manipulation of microscale cells and even nanoscale bacteria has been widely studied and industrialized. However, the structure requires multiple transducer components or full channel resonance. It is very challenging to design a simple structure for nano-control by complex acoustic field. In this study, a reflector-interdigital transducer (R-IDT) acoustofluidic device based on unilateral coherence enhancement is proposed to achieve SSAW definition features of periodic particle capture positions. The SAW device based on a unilateral transducer can not only generate leaky-SAW in water-filled microchannel, but also have a contribution of spherical waves in the vibration area of the substrate-liquid interface due to the Huygens-Fresnel diffractive principle. Both of them form a robust time-averaged spatial periodicity in the pressure potential gradient, accurately predicting the lateral spacing of these positions through acoustic patterning methods. Furthermore, a reflector based on Bragg-reflection is used to suppress backward transmitted SAW and enhance forward conducted SAW beams. By using a finite element model, R-IDT structure's amplitude enhances 60.78% compared to single IDT structure. The particle manipulation range of the diffractive acoustic field greatly improves, verified by experimental polystyrene microspheres. Besides, biocompatibility is conformed through red blood cells and Bacillus subtilis. We investigate the overall shift of periodic pressure field that can still occur when the phase changes. This work provides a simpler and low-cost solution for the application of acoustic tweezer in biological cell culture and filtering. [ABSTRACT FROM AUTHOR]

The electrical properties and domain reversal in BiFeO 3 ferroelectric films were studied using sandwiched heterostructures and piezoresponse force microscopy. A robust polarization state was observed, combined with a switchable domain pattern and a remanent polarization of approximately 100 μC cm−2. In addition, domain reversal was explored using scanning probe microscopy. The results show that dipoles could be reversed along the direction of the electric field under a negative tip bias, leading to carrier gathering near the domain walls. The enhanced conductivity near the domain walls was owing to the discontinuous polarization boundary conditions. In addition, typical diode-like current transport properties are sensitive to various temperature conditions, which is attributed to the Schottky barriers at the contact interface. These findings extend the current understanding of domain texture reversal in ferroelectric films and shed light on their potential applications for future ferroelectric random-access memory operations over a wide temperature range. [ABSTRACT FROM AUTHOR]

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]

High-quality ferroelectric films of Mn-doped Pb(Zr 0.3 Ti 0.7)O 3 (PMZT) were prepared using the sol-gel method, and the temperature dependence of ferroelectric, dielectric, and leakage current properties (J – E) were explored in detail using the top electrode/ferroelectric films/bottom electrode capacitor heterostructure. The enhancement of polarization and dielectric properties by element doping is clearly observed by 3% Mn-doping. Such enhancement is beneficial for the application of these films in ferroelectric random-access memory. In addition, the analysis of leakage current reveals symmetric behavior with 3% Mn-doping and the leakage current density gradually increases with increasing temperature, which may be due to the movement of domain wall and oxygen vacancy. The dominant leakage current conduction mechanism is bulk-limited ohmic or interface-limited Schottky emission conduction within a wide temperature range. The results might be meaningful for further work on ferroelectric electrical devices with improved ferroelectric and dielectric properties. [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]

Nanomechanical properties are extremely critical to the applications of flexible electric devices and energy harvester; however, the direct mechanical measurement of composite nanofibers is challenging and rarely explored. In this work, we apply an effective method to obtain the elastic modulus distribution of lead zirconium titanate (PZT)-doped polyvinylidene fluoride (PVDF) nanofibers via bimodal amplitude modulated-frequency modulated scanning probe microscopy (AM-FM SPM). All the samples exhibit obvious piezoelectric properties, and the mechanical properties are clearly enhanced through doping of PZT. Compared with pure PVDF nanofibers, the composite nanofibers with PZT doping show higher elastic modulus which indicates superior stability under the same bending condition. The enhancement of mechanical properties in composite nanofibers via filler doping pave a way to the design of stable and flexible sustainable energy harvesters. [ABSTRACT FROM AUTHOR]

Lithium niobate on insulator (LNOI) is widely used in optical, acoustic, domain wall current (DWC)-based integrated circuits and other domain engineering devices, enabling higher material performance, higher domain integration density and more advanced applications. However, there are hidden dangers of thermal failure in these highly integrated domain engineering devices. Therefore, maintaining thermal stability of domain structures in ferroelectric single-crystal thin films is an important and challenging task. Here, thermally induced structure reconstruction of tailored metastable switched domains was research in a 500 nm thick congruent lithium niobate (CLN) thin film, and a method for enhancing the thermal stability of switched domains was proposed. Piezoresponse force microscopy (PFM) and a polyheater are used to accurately monitor the thermal evolution of switched domains in CLN thin film sample. The results indicate the switched domain structures determine the thermal stability, and the enhanced thermal stability of the switched domains increases from 55 to 85 °C–150 °C. In this contribution, the thermal failure in domain engineering devices can be avoided effectively. The investigation paves the way for the development of domain engineering devices based on lithium niobate (LN) thin films. [ABSTRACT FROM AUTHOR]

Abstract In this study, we investigated the impact of electrodes on the structural, crystal orientation, and electrical characteristics of lead zirconate titanate [Pb(Zr 0.52 Ti 0.48)O 3 , PZT] thin films, that were deposited on Pt, Au, and LaNiO 3 (LNO) electrodes through sol-gel processes. The peak voltage, that is, the voltage corresponding to the maximum switching current point, was developed to depict the novel peak-drift electric characteristics in ferroelectric thin films. It increases in the positive ferroelectric peak voltage, and decreases in the negative peak voltage with an increase in the driving voltage amplitude. Based on space-charge-limited bulk conduction, we evaluated the peak-drift phenomenon, Schottky contact and their influences on the switching current. When polarization orientation is reversed, the Schottky contact disappears at one side of the PZT/electrode, and forms at the other side synchronously. Our results indicate that the formation of a Schottky contact affects the shape of the switching curves, and its disappearance influences the magnitude of the current characteristics. [ABSTRACT FROM AUTHOR]

Obtaining highly purified intact living cells from complex environments has been a challenge, such as the isolation of circulating tumor cells (CTCs) from blood. In this work, we demonstrated an acoustic-based ultra-compact device for cell sorting, with a chip size of less than 2 × 1.5 cm2. This single actuator device allows non-invasive and label-free isolation of living cells, offering greater flexibility and applicability. The device performance was optimized with different-sized polystyrene (PS) particles and blood cells spiked with cancer cells. Using the narrow-path travelling surface acoustic wave (np-TSAW), precise isolation of 10 μm particles from a complex mixture of particles (5, 10, 20 μm) and separation of 8 μm and 10 μm particles was achieved. The purified collection of 10 μm particles with high separation efficiency (98.75%) and high purity (98.1%) was achieved by optimizing the input voltage. Further, we investigated the isolation and purification of CTCs (MCF-7, human breast cancer cells) from blood cells with isolation efficiency exceeding 98% and purity reaching 93%. Viabilities of the CTCs harvested from target-outlet were all higher than 97% after culturing for 24, 48, and 72 h, showing good proliferation ability. This novel ultra-miniaturized microfluidic chip demonstrates the ability to sorting cells with high-purity and label-free, providing an attractive miniaturized system alternative to traditional sorting methods. [Display omitted] • A novel acoustic-based ultra-compact device for cell sorting in complex scenarios is demonstrated. • A highly tunable narrow-path travelling surface acoustic wave with high energy density generated by a single actuator is proposed. • Non-invasive and label-free isolation of higher purity living cells. • A miniaturized system alternative to traditional sorting methods is proposed, which can be further integrated with other on-chip units. [ABSTRACT FROM AUTHOR]

SrRuO/BiFeO/SrRuO thin-film capacitors were fabricated to investigate the role of mobile oxygen vacancies in a switchable photovoltaic (PV) effect that depends on ferroelectric domain orientations. Normally, the flowing direction of the stabilized photocurrent is opposite to ferroelectric polarization orientation. However, an abnormal overshoot of initial positive transient photocurrent parallel to the ferroelectric polarization could be observed under light illumination for a poled BiFeO thin film with the polarization pointing to the bottom electrode. Moreover, the photocurrent has a strong response with respect to voltage poling time and relaxation time after poling, which seems to be correlated with time-dependent migration of oxygen vacancies and concurrent charge trapping effect. Our results not only reveal the scenario how oxygen-vacancy migration and charge trapping effect affect the switchable PV effect, besides ferroelectric polarization, but also are helpful for the understanding and designing of new switchable photoelectric devices. [ABSTRACT FROM AUTHOR]

The 0.95K0.42Na0.58Nb0.96Sb0.04O3–0.02BaZrO3–0.03Bi0.5K0.5HfO3 ceramic was fabricated via a conventional solid-state reaction. This ceramic exhibits the diffuse polymorphic phase boundary (PPB) near room temperature. The dielectric, ferroelectric, electromechanical, electrocaloric, and dielectric energy storage properties were studied systemically. The normalized large signal d33* values are approximately 400–600 pm/V at measured temperatures and electric fields, which are larger than or comparable with the values reported in other lead-free compositions. The electrocaloric strength is enhanced at the broad region of PPB provided by the indirect and direct measurements. At low field of 30 kV/cm, the dielectric energy storage is ∼0.12–018 J/cm3 at relative broad temperature range due to the diffuse nature of polymorphic phase boundary. Theoretical simulations reveal that multi-element dopants, such as Sb5+, Hf4+, Zr4+, and Bi3+ ions, could induce the breaking of local structure symmetry in the orthorhombic phase to form the PPB. In addition, the charge distribution may also break the long-range ferroelectric order through the analysis of Bader charge. Our study suggests that the K0.5Na0.5NbO3-based ceramic exhibits improved performance and good thermal stability in piezoelectric, electrocaloric, and dielectric energy storage characteristics in terms of the design of multi-element dopants to form the PPB and it will benefit the promising applications in electronic devices. [ABSTRACT FROM AUTHOR]

Polarization fatigue in (Pb 0.97 La 0.02 )(Zr 0.95 Ti 0.05 )O 3 (PLZT) antiferroelectric thin films deposited onto silicon wafers is studied by investigating the effect of the peak/average/root-mean-square cycling voltage through varying the waveform of the electrical excitation. Interestingly, it is found that the fatigue behavior of the film is determined by the root-mean-square voltage of the external driving excitation rather than by the peak or average voltages. Our results can be well explained in the framework of the local phase decomposition model and indicate that the root-mean-square voltage should be considered as the effective driving voltage determining the polarization fatigue in PLZT antiferroelectric films. [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]

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]

• Negative electrocaloric effect (ECE) could be obtained in PLZ thin films within wide temperature range (213–493 K). • Giant negative ECE (Δ T ≈ −13.2 K) and entropy change (Δ S ≈ −11.5 J K−1 kg−1) could be obtained in PLZ thin films. • The combination between negative and positive ECE promotes cooling efficiency during electrical bias processing. Antiferroelectric thin films have exhibited outstanding negative electrocaloric effect (ECE), which are potential candidate regarding to the solid-state refrigeration technology. In this work, Pb 0.97 La 0.02 ZrO 3 (PLZ) antiferroelectric thin films were prepared on LaNiO 3 (LNO)/Pt electrode and LNO electrode by sol-gel method. Giant negative electrocaloric effect (Δ T ~ −13.2 K) can observed in wide temperature range (213–493 K) that deposited on composite electrode, which can be attributed to better electric conductivity of LNO/Pt composite electrode than LNO electrode. In addition to outstanding negative ECE, positive ECE also can be obtained near curie temperature, which is caused by phase transition from ferroelectric (FE) to paraelectric (PE) state. The optimized ECE property contributed to the phase transition and introduction of composite electrode, which pave the giant prospect considering high-efficiency solid-state refrigeration devices through combination of positive and negative ECE. [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]

In this study, a novel approach for enhancing the rapid spreading of free liquid film on lithium niobate (LiNbO3) substrate under megahertz (MHz) surface acoustic wave (SAW) excitation is presented by treating it with surfactants. Through the design of a specific interdigital transducer structure, it was discovered that exciting the SAW at a frequency of 32.3 MHz can achieve optimal spreading performance for water droplets on the surface of surfactant-treated LiNbO3 substrate. The maximum average velocity reaches 1.76 mm/s at position P2 = 1250 μm in the water film front, and the stable film spreading speed shows a 204.9% increase compared to the existing research. Simultaneously, through the investigation of the spreading experiment phenomenon of silicone oil and de-ionized water droplets at varying frequencies, we have discovered the dynamic mechanism of "reverse phase" propagation in liquid film for the first time. This entails that the advancing edge of the wetting film demonstrates a spreading motion law that is opposite to the traditional spreading phenomena, with the spreading velocity in the central exceeding that on both sides. Our research demonstrates that this microfluidic device developed by SAWs enhances the spreading efficiency of the free films, enabling rapid expansion of the target liquid to form a high-surface area film layer. This advancement holds promise for overcoming the limitations of low sensitivity and short response time in the field of rapid pathological diagnosis in contemporary medicine. [ABSTRACT FROM AUTHOR]

• The flexible film was prepared by combining the controlled spalling technique with dry etching method. • The original substrate can be recycled, which conducive to saving resources. • The recoverable energy storage of flexible film increased by 21% at 500 kV/cm compared to that of the original substrate. • The energy storage characteristics of the flexible film were tested under wide temperature environment (−70 °C −200 °C). Flexible energy-storage capacitor has attracted great attention due to deformable and lightweight, which could be applied to wearable electronics, bendable smartphones. It is urgent to manufacture a capacitor combining excellent electrical properties with mechanical bending capacity. Here, flexible Pb 0.97 La 0.02 Zr 0.95 Ti 0.05 O 3 (PLZT 2/95/5) films are prepared by controlled spalling technology (CST) and exhibit outstanding electrical properties with polarization about 86.3 µC/cm2 at various tensile or compressive bending radii, which indicates excellent mechanical stability of films. It is worth mentioning that recoverable energy-storage density (W re) of films has increased by 21% at 500 kV/cm compared to the original substrate, which is caused by change in stress. Meanwhile, flexible films were measured under wide temperature range from −70–200 °C with W re fluctuating from 9.2 J/cm3 to 17.1 J/cm3, which is related to free energy barrier of phase transition. These studies provide reference for preparation of flexible capacitors which have great potential applications for future flexible micro-devices. [ABSTRACT FROM AUTHOR]

Pb(Zr 0.3 Ti 0.7)O 3 - x mol% Mn (PZTM) (x = 0, 1, 2, and 3) thin films with high density and good crystallinity were obtained using a sol-gel method. Improved crystallization, domain, and ferroelectricity through controlling the lead/oxygen vacancies in Mn-doped lead zirconate titanate (PZT) thin films were investigated. Enhanced ferroelectricity and piezoelectricity were obtained in the 1 mol% Mn-doped PZT thin films. According to the Bragg equation, a small amount of Mn replaces the A-site (Pb2+) to achieve donor doping, which is conducive to the movement of domains and enhances the ferroelectric performance and piezoelectric coefficient. The pinning effect leads to reduced ferroelectric performance, which is caused by oxygen vacancies generated by Mn2+ replacing the B-site (Zr4+/Ti4+) during acceptor doping. The research results show that Mn doping is an effective method for improving the ferroelectric performance of PZT thin films. • The Mn contant dependence of the ferroelectricity and domain switching behavior is thoroughly investigated by PFM. • The Mn first replaces the A-site when the Mn content is small, and replaces the B-site as the Mn content increases. • Enhanced ferroelectricity and piezoelectricity are obtained in the 1mol% Mn-doped PZT thin films. [ABSTRACT FROM AUTHOR]

The enrichment domain state and its stability consist an imperative part regarding to the high density non-volatile ferroelectric random access memory (FRAM) devices. In this work, epitaxial BiFeO 3 (BFO) thin films were prepared by pulsed-leaser deposition (PLD) technology, and the morphology, local polarization state and piezoelectric response were characterized by scanning probe microscopy (SPM) and piezoresponse force microscopy (PFM). The robust in-plane domain dynamic process is observed under the external electric fields. Furthermore, good retention and repeatability are observed especially under high temperature. The new-developed domain patterns are nearly stable, which is quite different from the existed research. The formation of these domains is probably induced by the combination of built-in electric fields and distribution of tip fields, both of which affect the polarization dynamic process. All the obtained results pave a great way for application corresponding to the FRAM devices especially under high temperature circumstance. • Epitaxial BiFeO 3 (BFO) thin films were prepared by Pulsed-Leaser Deposition (PLD) technology. • The abundant domain dynamic were investigated by scanning probe microscopy (SPM) and piezoresponse force microscopy (PFM). • Interesting domain dynamics with good retention and repeatability are observed under the external electric fields. [ABSTRACT FROM AUTHOR]

A novel piezoelectric hydrophone sensor was analyzed, designed and fabricated with PZT-on-Si process platform, which can be used for acquiring or recording underwater sound signals. • A novel passive piezoelectric MEMS vector hydrophone was designed and fabricated based on PZT films. • The hydrophone has excellent low-frequency response and high sensitivity (up to up to -189.3dB in the frequency of 920Hz). • The piezoelectric MEMS vector hydrophone shows good "8" directivity. Hydrophone, serving as a part of sonar, has a significant effect on the performance of acoustic sensors such as frequency characteristics and sensitivity, however, some limitation such as high cost and complexity in SOI manufacturing technique hinder the industrial application of hydrophones. Therefore, a novel Micro-Electro-Mechanical Systems (MEMS) piezoelectric vector hydrophone based on PZT (lead zirconate titanate) film has been adopted in obtaining vector information of underwater sound field. The piezoelectric hydrophone sensor was analyzed, designed and fabricated with PZT-on-Si substrate, and the structure consists of a four-cantilevers and an acoustics columnar cilium fixed on the center micro mass. According to the simulation results, the piezoelectric films are optimally distributed at the tip of the four beams, where the maximum strain locates. Finally, the piezoelectric vector hydrophone was characterized by comparative calibration experiments in a standing wave bucket. This passive MEMS piezoelectric hydrophone has the characteristics of receiving sensitivity with −189.3 dB at 920 Hz (0dB = 1 V/μPa) and a typical directional pattern of "8" shape, low noise output and high dynamic test range, which is suitable for high precision passive underwater detection. [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 this study, a critical parameter termed as “effective electric strength” is developed to depict polarization fatigue in antiferroelectric thin films. Specifically, the effect of pulse width, frequency, and magnitude of driving voltage (or field) on polarization fatigue of antiferroelectric (Pb,La)(Zr,Ti)O 3 (PLZT) thin films was investigated in detail. By transforming all the waveforms with different pulse-widths/voltages/frequencies into their effective electric strength, a strong correlation between the effective strength and the degree of polarization fatigue in the PLZT films is revealed. For instance, it was found that appreciable fatigue usually occurs when the effective strength is larger than or equal to the voltage of phase transition from antiferroelectric phase to ferroelectric phase. In addition, it is shown that the films are more prone to fatigue for a lower frequency of the same effective strength. Our findings could be well explained in the framework of the local phase decomposition arising from switching induced charge injection. [ABSTRACT FROM AUTHOR]

Frequent meteorological disasters pose more and more extensive threats to human life and property. However, the traditional meteorological sensors based on external power supply, for natural disaster monitoring and early warning, are severely limited in remote and unattended areas. Herein, a self‐powered multi‐parameter meteorological sensor (SMPM‐sensor) for various weather monitoring is proposed, which can monitor the weather through the feedback of electrical energy output while collecting natural energy. The designed 360° omnidirectional array structure facilitates efficient collection of all‐weather solar energy and rain energy in different directions and monitoring the light intensity without the influence of solar azimuth. Based on the four‐segmented disc‐shaped structure and the introduced Ecoflex transition layer, the frequency and amplitude of the wind electrical output can be effectively improved. Owing to structure and material optimizations, a good linearity of 0.9746 between the current and the solar illuminance is exhibited, a wide monitoring range of rainfall intensity changes from 0.1 to 11.9 mm min−1, and the linearity between wind speed and voltage frequency can be as high as 0.9986. Therefore, based on excellent sensing performances, good stability, and real‐time characteristic, the fabricated SMPM sensor provides a potential technological strategy for the field of meteorological disaster monitoring. [ABSTRACT FROM AUTHOR]

The substrate impurities scattering will lead to unstable temperature-sensitive behavior and poor linearity in graphene temperature sensors. And this can be weakened by suspending the graphene structure. Herein, we report a graphene temperature sensing structure, with suspended graphene membranes fabricated on the cavity and non-cavity SiO2/Si substrate, using monolayer, few-layer, and multilayer graphene. The results show that the sensor provides direct electrical readout from temperature to resistance transduction by the nano piezoresistive effect in graphene. And the cavity structure can weaken the substrate impurity scattering and thermal resistance effect, which results in better sensitivity and wide-range temperature sensing. In addition, monolayer graphene is almost no temperature sensitivity. And the few-layer graphene temperature sensitivity, lower than that of the multilayer graphene cavity structure (3.50%/°C), is 1.07%/°C. This work demonstrates that piezoresistive in suspended graphene membranes can effectively enhance the sensitivity and widen the temperature sensor range in NEMS temperature sensors. [ABSTRACT FROM AUTHOR]

Ubiquitous environmental energy has become an important energy source for ensuring long‐lasting operation of unattended monitoring systems. However, several technical bottlenecks remain for achieving improved collection performance of environmental energy. Herein, a transparent composite film comprising micro‐pyramid arrays (mp‐arrays) and a conductive ionic liquid (IL) based on polydimethylsiloxane (PDMS) is innovatively generated as a difunctional layer that acts as an antireflective coating for solar cells and an enhanced triboelectric layer for the raindrop‐harvesting triboelectric nanogenerator (RH‐TENG). The regular mp‐arrays fabricated using the template transfer technology according to the matched refractive index between IL and PDMS effectively inhibit the surface reflection and improve the light trapping ability of solar cells. Owing to a significant increase in transmittance, the power conversion efficiency of the solar cell is enhanced by 10.92% owing to the IL@PDMS coating with mp‐arrays (mp‐IL@PDMS). Further, the conductive IL significantly improves the dielectricity of PDMS film. Due to the improved dielectric constant, increased aspect ratio, and excellent hydrophobicity, the output voltage and current of the RH‐TENG with mp‐IL@PDMS are enhanced by ≈24‐ and 44‐fold, respectively. Overall, this study, which is based on the incorporation of transparent conductive IL, provides a new technical path for efficient multiclimate energy harvesting. [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]

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]

Graphene nanostructures are widely perceived as a promising material for fundamental components; their high-performance electronic properties offer the potential for the construction of graphene nanoelectronics. Numerous researchers have paid attention to the fabrication of graphene nanostructures, based on both top-down and bottom-up approaches. However, there are still some unavoidable challenges, such as smooth edges, uniform films without folds, and accurate dimension and location control. In this work, a direct writing method was reported for the in-situ preparation of a high-resolution graphene nanostructure of controllable size (the minimum feature size is about 15 nm), which combines the advantages of e-beam lithography and copper-catalyzed growth. By using the Fourier infrared absorption test, we found that the hydrogen and oxygen elements were disappearing due to knock-on displacement and the radiolysis effect. The graphene crystal is also formed via diffusion and the local heating effect between the e-beam and copper substrate, based on the Raman spectra test. This simple process for the in-situ synthesis of graphene nanostructures has many promising potential applications, including offering a way to make nanoelectrodes, NEMS cantilever resonant structures, nanophotonic devices and so on. [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]

• A novel thermal management technology has been proposed using a surface-modified silicon chip and TSV for packaging 3D ICs. • Transient thermal property measurement system is originally designed using Raman spectroscopy to assess cooling performance. • Cooling performance for each specific surface-modified silicon chip is extracted by characterized time constant value τ. A novel surface-modified silicon-based thermal management technology has been proposed for 3D IC architecture in this study. 2 × 2 cm2 double sides polished silicon chips' surface with micro-fin (MF) and micro-pin fin (MPF) structures have been achieved by applying silicon microfabrication technology of deep reactive ion etching, which is applicable to the interlayer of 3D IC packaging technology. By integrating a mini wind tunnel with Raman spectrometer, the transient thermal property measurement system is originally designed to evaluate the cooling capability of the surface-modified silicon interlayer. Finite Element Analysis was involved to confirm this view by taking fluid dynamics and heat transfer into account. The sample with 100 × 100 µm2 MPF structure expresses the appropriate exponential decay time constant τ (with unit of 1), which is 4.71 and 8.53 under cooling and heating measurement conditions, respectively. This also proved that the combination of Raman thermometry with forced gas flow could be a relevant measurement tool for transient thermal property. [ABSTRACT FROM AUTHOR]

Collecting energy from body movements to supply power for equipment is an important method to rapidly develop wearable intelligent equipment. This method places high requirements, such as being lightweight and stable, on a nanogenerator. Herein, a bioinspired helical triboelectric nanogenerator (BH‐TENG) that realizes energy acquisition through the intensity and frequency of body movement is designed based on the helical structure of DNA. The helical structure facilitates more contact areas and provides increased stability to complete the power generation process than the simple structure with planar electrodes and functional layers in the same volume. It is found that when the frequency is 4 Hz and the impact load is 50 N, the output current reaches 17 µA and the voltage reaches 300 V with a charge transfer capacity of 371 nC. When the BH‐TENG is fitted in the sole of a shoe, it can light 120 LEDs when a subject is walking. After simple rectification output and capacitance matching, the BH‐TENG is verified to work independently and stably for 20 min to provide power for small digital thermometer. The above experiments show the advantages of the BH‐TENG in acquiring body motion energy. [ABSTRACT FROM AUTHOR]

The Single Event Transient (SET) phenomenon, which occurs in combinational circuits, has emerged as the primary source of soft errors in Integrated Circuits (IC) in advanced deep-submicron technologies. Therefore, it is imperative to investigate the underlying mechanisms of SET effects in order to gain valuable insights for mitigating SET in combinational circuits. In advanced technologies, specifically those at the 28-nm and below, tap cells are commonly utilized as the well and substrate contact to achieve higher device density. This article presents a comprehensive study on the impact of tap cells on SET sensitivity for the first time. Furthermore, a comparison is made between the SET sensitivity of conventional and tap cell-based well and substrate contact. [ABSTRACT FROM AUTHOR]

Owing to their high remanent polarization, fast switching behavior, and controllable preparation process, Pb(Zr 0·3 Ti 0.7)O 3 (PZT) thin films are considered to be one of the most promising materials for non-volatile ferroelectric random access memory (FRAM). In this work, high-quality PZT thin films with a preferred (111) orientation and smooth surface are obtained by the sol–gel method. The temperature dependence of the ferroelectricity and domain switching behavior is thoroughly investigated by piezoresponse force microscopy (PFM). The domain structure undergoes distinct 180° switching and reconstruction under an external DC voltage. Polarization hysteresis loop analysis of PZT reveals that the spontaneous polarization (P s), remanent polarization (P r), and coercive voltage (V c) decrease as the temperature increases from 20 to 70 °C, in agreement with the Landau classical theory of phase transition. In addition, the PFM results show that the PZT films consistently exhibit good switching behavior as the temperature increases from 23.7 to 70 °C. An increase in the piezoelectric constant (D max) with increasing temperature is ascribed to more rapid domain wall movement and easier domain reorientation, as predicted by thermodynamic theory. This investigation suggests that the temperature strongly affects the ferroelectricity and switching behavior of PZT thin films and offers guidance for the design of FRAM. [ABSTRACT FROM AUTHOR]

Abstract As a functional ferroelectric material, PbZr 0.53 Ti 0.47 O 3 (PZT) film is widely used in many electronic devices. However, with the rapid development of intelligent terminal, traditional PZT device cannot meet the demand for flexible wearable devices. In this work, a high-quality flexible PZT film is fabricated by the controlled spalling technology (CST) for the first time, which is novel, simple and cost-efficient. LaNiO 3 (LNO) film by sol-gel process is used as the buffer layer for the PZT film growth due to good lattice match and low cost. The PZT film on silicon substrate is successfully transferred onto a flexible one by electroplating Ni stressor layer. LNO buffer layer thickness has an important influence on the spalled silicon depth and Ni stressor layer thickness during the spalling process. The exfoliated PZT film based on sandwich capacitor structure Au/PZT/Au with an area of 1 cm2 exhibits good ferroelectric properties under different mechanical deformation. Moreover, the ferroelectric response of flexible PZT film does not show obvious deterioration after repeated operation cycles. Therefore, the flexible PZT thin film has a good application prospect on wearable ferroelectric microelectronics. [ABSTRACT FROM AUTHOR]

Highlights • A stretchable piezoelectric elastic composite is demonstrated in this paper. • The output voltage and current of our composite can reach 8 V and 0.4 μA, respectively. • The proposed composite can be conformally attached on human body for energy harvesting and posture monitoring. Abstract In this work, a stretchable piezoelectric elastic composite has been developed by incorporating PbZr 0.52 Ti 0.48 O 3 (PZT) particles into polymer matrix. The output voltage and current can reach 8 V and 0.4 μA, respectively. Likewise, the steady piezoelectric signal can respond to different strain rates. The measurement on human body shows that the piezoelectric composite can be used to capture kinetic energy and monitor limb motion for body sensor network application. This work is significant for the conformal assembly of piezoelectric devices used in artificial intelligence system. [ABSTRACT FROM AUTHOR]

Porous nanosheets assembled Mn-based oxides (Mn 2 O 3 , MnCo 2 O 4 and CoMn 2 O 4 ) microspheres of diameters about 3–6 μm and pore size distribution mainly around 10 nm have been synthesized by the same facile solvothermal route without any surfactant followed by a calcination process. In virtue of the porous nanosheets constructed microspheres, the Mn-based oxides microspheres Mn 2 O 3 present specific capacities of 650 mAh/g after 100 charge and discharge cycles. Additionally among the three Mn-based oxides the representative specific capacities present an increasing trend as with the increasing percentage of Co element, the plateau of charge and discharge present a lower trend as with the increasing percentage of Mn element which is more suitable as anode materials in high output full batteries. Then the oxides with different components could be applied in different conditions such as the need for high specific capacity or high output lithium-ion batteries. Consequently the easy fabrication of microspheres and excellent electrochemical performances demonstrate Mn-based oxides’ great potential in lithium-ion batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • The average output power of the energy harvester can reach 2 W. • The energy conversion efficiency of the energy harvester can reach 65.2%. • The intersection beam structure can magnify the compression distance of 3.4 times. • The intersecting beam structure converts the vertical compression force to the horizontal direction. • The intersection beam structure changes the direction of the compression force. The sustainability of power supply for mobile electronic devices is a problem that needs to be solved urgently. The energy from human motion is an optimal solution for this problem. As for the traditional energy harvesters based on electromagnetic, triboelectric, and piezoelectric induction, energy management is the largest challenge because of the low conversion efficiency and output power. In this paper, a high-efficiency and high-power energy harvester (EPEH) is presented based on the intersecting beam array structure. It can effectively harvest the pressure energy of humans under the soles at the states of walking, running, and weight-bearing walking. The EPEH does not impair the flexibility of humans compared with joint energy harvesters. The intersecting beam array structure is key component, which can magnify the compression distance in the vertical direction of 3.4 times in the horizontal direction, facilitating maximum energy harvesting within a limited height. On the other hand, the design of rolling friction structure can effectively reduce energy loss and improve energy conversion efficiency. The result shows that the maximum average output power can reach 2 W at 7 k m / h. Because of the high output power, the energy management circuits and voltage regulator circuits can be derived and stable work, the energy harvested by the EPEH can be stored in the lithium battery (3.7 V , 50 m A h). Furthermore, the generated energy could supply mobile phones, smart watches, light bulbs, flashlights, children's anti-lost devices, and so on. Through the energy management circuit and voltage regulator circuit (1.5 V and 5 V), the energy conversion efficiency of the device can reach 65.2 % at a compression velocity of 2500 m m / m i n and a frequency of 1.25 H z. It is of great significance for the practical application of wearable energy harvesting technology and has multiple application prospects. [ABSTRACT FROM AUTHOR]

A scheme to perform ultra-narrow filter bandwidth and high frequency selectivity microwave photonic filter (MPF) with wide tuning range is proposed and experimentally demonstrated. The ultra-narrow bandwidth of the MPF is implemented by a Brillouin laser resonator, which is composed of a cascaded ring Fabry–Pérot (CR-FP) resonator formed by a main cavity with a cavity length of 100 m and a secondary cavity with a cavity length of 10 m. A Brillouin laser resonator is formed by the main cavity to obtain an extremely narrow comb-shaped Brillouin gain spectrum. The Vernier effect of the double ring cavity can effectively suppress the side modes, thereby realizing the narrow linewidth Brillouin laser filtering. Besides, two identical tunable lasers provide the stimulated Brillouin scattering (SBS) pump light and optical carrier signal for this device respectively. After the interaction between the Brillouin gain spectrum and the optical modulation signal, the filter passband can be stably tuned by simply changing the wavelength of SBS pump light. The experimental results show that the microwave photonic filter can be stably tuned in the frequency range of 0–20 GHz, the out-of-band rejection ratio is about 20 dB, and the minimum 3 dB bandwidth is about 114 Hz. • A MPF with ultra-narrow passband and wide tuning range is proposed. • Brillouin laser resonator with the Vernier effect can greatly compress the passband width. • The narrowest passband width is about 114 Hz and stably tuned range is more than 0–20 GHz. • The MFP has great potential in ultra-narrow band and high flexibility microwave signal processing applications. [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]

Mechanical energy with low frequency is a widely distributed energy in environment. Triboelectric nanogenerator (TENG) and electromagnetic energy harvester (EMG) are considered as promising methods to harvest low-frequency mechanical energy. In this study, a three-dimensional (3D) full-space triboelectric-electromagnetic hybrid nanogenerator (FSHG) based on a magnetic ball and Polystyrene (PS) spherical shells is presented. The external excitation can be transformed into the relative motion between different units. The mover composed of the PS spherical shell 3 and a magnet ball transforms 3D full-space mechanical energy into electrical energy through friction electrification and electromagnetic induction effect. The results of experiments show that the performance of TENG and EMGs can be influenced by the direction of external vibration and excitation frequency. The output performances of TENG and EMGs increase as the excitation frequency increases. The results show that the maximum output power of TENG is 18 μW at an external loading resistance of 200 MΩ, and the maximum output power of EMG is 640 μW at an external loading resistance of 1000 Ω. The FSHG demonstrates a quick charging ability for capacitor and the capability to power hundreds of LEDs. After storing energy in the capacitor, the DC signal can power a humidity/temperature sensor. • The device can harvest energy from all directions rather than a single direction. • A harvester combined with TENG and EMG can harvest energy at wider frequencies. • Energy capture can be improved by the moveable magnet ball and PS shell. [ABSTRACT FROM AUTHOR]

• Piezoelectric elastic composite based on BaTiO 3. • Sandwich structure with stable mechanical structure and electrical output. • Lead-free environmental friendly wearable piezoelectric sensor. So far, many kinds of piezoelectric composite have been developed to prepare flexible motion sensors. However, some lead-based materials are harmful to human body and cannot be used for motion posture detection, despite their excellent performances. In this work, a lead-free stretchable piezoelectric composite is developed by introduce BaTiO 3 (BTO) powder into silicone rubber matrix. The peak-to-peak values of the voltage and current can reach up to 38 V and 0.8 μA under the periodic stretching excitation. It can respond to different strain stimulations. When fixed on the body, it can effectively detect the angle and frequency of limb movement, suitable as human motion sensor. The flexible stretchable composite provides a good solution for wearable piezoelectric devices. [ABSTRACT FROM AUTHOR]

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]

Because of high temperature process, it has been a challenge to fabricate flexible piezoelectric or ferroelectric devices based on PbZr 0.53 Ti 0.47 O 3 (PZT). In this work, a high-quality flexible PZT film is successfully fabricated by the controlled spalling technology (CST). The PZT film deposited on sapphire substrate using sol-gel method is transferred onto a flexible polyimide (PI) substrate through electroplating Ni stressor layer, realizing the flexible heterogeneous integration of PZT film and PI substrate. The obtained PZT film exhibits a good crystalline perovskite structure and a smooth surface before and after spalling process. The ferroelectric response of the spalled PZT film based on Au/PZT/Au structure does not show obvious deterioration under different mechanical deformation, which indicates good ferroelectric property and stable mechanical performance. Further, the film on flexible Ni layer has the better piezoelectric property compared with that on conventional rigid Pt/Ti/SiO 2 /Si substrate. This work has the important significance for the development of flexible ferroelectric and piezoelectric devices like sensors, memorizers and nanogenerators. • High-quality PZT film on sapphire is successfully transferred onto flexible PI by CST. • Ferroelectric performance of spalled PZT film does not deteriorate after deformation. • The spalled PZT film on flexible Ni layer has a better piezoelectric property. [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]

Bismuth ferrite (BiFeO 3 , BFO) epitaxial thin films with the thickness of 100 nm have been grown on SrRuO 3 (SRO) coated SrTiO 3 (STO) (111) substrates, forming the structure of Pt/BFO (111)/SRO (111)/STO (111) stacking layers fabricated by pulsed laser deposition (PLD). From electrical measurements of current–voltage curves and polarization–voltage hysteresis loops, it is found that oxygen vacancies depending on different in situ annealing oxygen pressures can influence the electrical characteristics of BFO thin film significantly. High in situ annealing oxygen pressure can reduce the leakage current, brings a steeper current–voltage curve, which arises from the polarization reverse. Meanwhile, the sample under high annealing oxygen pressure has a better rectification, with the On/Off diode currents ratio of around 40:1, which is obviously larger than those under low annealing oxygen pressures. By different conduction mechanism fittings, it is observed that Schottky emission mainly dominates the conduction mechanism at On state, while space-charge limited current emission becomes dominating the leakage at Off state. [ABSTRACT FROM AUTHOR]