Device Applications Research Articles

Atomic Infusion Induced Reconstruction Enhances Multifunctional Thermally Conductive Films for Robust Low‐Frequency Electromagnetic Absorption

AbstractDeterministic fabrication of highly thermally conductive composite film with satisfying low‐frequency electromagnetic (EM) absorption performance exhibits great potential in advancing the application of 5G smart electric devices but persists challenge. Herein, a multifunctional flexible film combined with hetero‐structured Fe6W6C‐FeWO4@C (FWC−O@C) as the absorber and aramid nanofibers (ANFs) as the matrix was prepared. Driven by an atomic gradient infusion reduction strategy, the carbon atoms of absorbers can be precisely relocated from carbon shell to core oxometallate lattice, triggering in situ carbothermic reduction for customization of unique oxometallate‐carbide heterojunctions and surface geometrical structure. Such an atoms reconstruction process effectively regulates interface electronic structure and magnetic configuration, resulting in enhanced polarization loss from abundant heterointerfaces and crystal defects and magnetic loss from hierarchical structure endowed magnetic coupling interaction, which jointly contributes to the efficient low‐frequency EM absorption performance. Eventually, optimized FWC−O@C microplate exhibits a broad absorption bandwidth surpassed the entire C band, and the assembled FWC−O@C/ANFs composite film also performs a high thermal conductivity over 2500 % higher than that of the pure ANFs. These findings provide a new insight into the atomic reconstruction affected EM properties and a generalized methodological guidance for preparing multifunctional thermally conductive composite films.

Impact of the Lead‐Free Crystal Matrix 0.94NBaTiO3‐0.06SrTiO3 on the Photoluminescence Properties of Eu+3

The investigation reveals that the crystal field environment induces photoluminescence in Eu3+. These synthesized materials hold promise for a wide array of commercial applications, particularly in the light emitting diode industry, representing a significant advancement for the current generation of technology. The lead‐free electroceramics 0.94NB1−xEuxTiO3‐0.06SrTiO3 (x = 0 and x = 0.1) are fabricated using the conventional solid‐state reaction technique. Within these ceramics, both rhombohedral (R3c) and tetragonal (P4mm) structural phases coexist. The structural conformation and fluctuations in average grain size indicate the successful substitution of Eu3+ in 0.94NB1−xTiO3‐0.06SrTiO3 (x = 0). The incorporation of Eu3+ ions into the host matrix induces a long‐range ferroelectric state, marked by a rhombohedral (R3c) distortion, alongside enhanced tetragonal (P4mm) features. This structural modification results from the interaction between the Eu3+ ions and the host lattice, which fosters the emergence of a ferroelectric polarization. The coexistence of rhombohedral and tetragonal symmetries suggests a complex interplay of phases that collectively enhance the material's ferroelectric properties, potentially offering new avenues for applications in electronic and optical devices. Notably, compared to 0.94NB1−xEuxTiO3‐0.06SrTiO3 with (x = 0), the coercive field (Ec) significantly improves, while remanent polarization decreases in the presence of Eu3+. The domain orientation, particularly in Stage‐C, demonstrates a pronounced scaling behavior, which can be attributed to the crystal field surrounding the Eu3+ ions. This interaction influences the material's domain dynamics, enhancing its electromechanical properties. As a result, both of these lead‐free ceramics exhibit considerable potential for future electroceramic applications, offering a promising alternative in environmentally sustainable technologies.

Mid-infrared characterization of NbTiN superconducting nanowire single-photon detectors on silicon-on-insulator

Superconducting nanowire single-photon detectors are widely used for detecting individual photons across various wavelengths from ultraviolet to near-infrared range. Recently, there has been increasing interest in enhancing their sensitivity to single photons in the mid-infrared spectrum, driven by applications in quantum communication, spectroscopy, and astrophysics. Here, we present our efforts to expand the spectral detection capabilities of U-shaped NbTiN-based superconducting nanowire single-photon detectors, fabricated in a 2-wire configuration on a silicon-on-insulator substrate, into the mid-infrared range. We demonstrate saturated internal detection efficiency extending up to a wavelength of 3.5 μm for a 5 nm thick and 50 nm wide NbTiN nanowire with a dark count rate less than 10 counts per second at 0.9 K and a rapid recovery time of 4.3 ns. The detectors are engineered for integration on waveguides in a silicon-on-insulator platform for compact, multi-channel device applications.

Plausible Colloidal Methods to Synthesize Semiconductor Nanowires: Deep Study From ZnSe Nanorods

AbstractWhen the diameter of semiconductor nanowires is below the Bohr radius, confined excitons in the radial direction can freely move along the elongated axis direction, highlighting their potential for applications in quantum information and optoelectronic devices. Controlled anisotropic growth and oriented attachment are viable strategies for producing ultra‐long semiconductor nanowires with precisely controlled lengths and diameters. Anisotropic ZnSe nanorods are used as the initial seeds for the controlled anisotropic growth and oriented attachment methods. ZnSe nanorods/nanowires with limiting lengths of tens to hundreds of nanometers are produced. The advantages and limitations of semiconductor nanowires via controlled anisotropic growth and oriented attachment are summarized. The perspective for the promotion of controlled anisotropic growth and oriented attachment is discussed, which allows to promotion of the precise synthesis of semiconductor ultra‐long nanowires to develop the fundamental research and applications of ultra‐long semiconductor nanowires.

On the Nature of the Out-Of-Plane Distortions in Subporphyrins.

The field of subporphyrins has garnered great interest in recent years owing to its unique structure and associated properties. They exhibit spectroscopic features similar to porphyrins and find applications in various optoelectronic devices, photodynamic therapy etc. Most of the synthesized subporphyrins have boron coordination with an axial ligand and exhibits a bowl-shaped geometry. The first isolation of a stable free-base subporphyrin is achieved recently with mesityl groups at two of the meso positions and anthracene at the other. X-ray studies reveal a markedly non-planar structure different from the bowl shape and is attributed to the steric hindrance of the inner N-H bonds. Herein, we report a systematic quantum chemical investigation assisted by symmetry principles on molecular models to characterize the out-of-plane (OOP) distortions observed so far in subporphyrins and unveil the electronic reasons. Correlation of the frontier molecular orbital (FMO) landscape between the D4h porphyrin and D3h subporphyrin gives insight into their electronic structure relative to one another and the nature of OOP distortions. Further the effect of a π-donor cum σ-acceptor substituent at the meso/beta positions of the subporphyrin ring as well as the impact of boron incorporation in the central cavity on the OOP distortions are also discussed.

Investigation of the effect of crystal size on the piezoelectric features of lead-free barium titanate ceramic using molecular dynamics simulation.

This study investigated the piezoelectric properties of BaTiO3 ceramics with different sizes through molecular dynamics simulations. The results show that all samples reached thermal equilibrium at 300K and equilibrium in potential energy within 10ns, confirming effective equilibration. As the size of the ceramics increased, the mean square displacement and diffusion coefficients decreased from 0.217 and 0.0034 to 0.1934 Å2 and 0.003 Å2/ns, attributed to a more uniform microstructure with fewer defects, resulting in reduced ion mobility. Furthermore, saturation polarization, residual polarization, and coercive field values increased from 0.35, 0.1, and 0.175 to 0.42 C/m2, 0.16 C/m2, and 0.282 MV/m, respectively, with increasing sample size, highlighting enhanced polarization responses due to a greater volume of ferroelectric material. Larger barium titanate (BaTiO3) crystals can have better polarization due to more domains aligning, but they may not deform as much (lower strain) because the walls among those domains can't move freely. While improved domain alignment contributed to higher polarization, the increased stress can restrict the mobility of the domain walls. These findings provided valuable insights into the size-dependent behavior of BaTiO3 ceramics, essential for optimizing their applications in electronic devices and sensors. The study underscored the importance of understanding microstructural effects on material properties for future advancements in ferroelectric technology.

Study of physical properties of zinc oxide thin films using the hydrothermal method

Zinc oxide (ZnO) is a versatile semiconductor material with unique physical, chemical, and optical properties. It has garnered significant attention in recent years due to its wide applications in electronics, photonics, sensors, and environmental devices. This paper provides a comprehensive review of the fundamental properties of ZnO, its synthesis methods, and the wide range of applications it enables. The focus is on the material’s electronic properties, optical characteristics, and how these features are being leveraged in innovative technologies such as transparent conductors, UV detectors, and gas sensors.

Room-temperature ferromagnetic MnGa nanoparticles in dilute magnetic semiconductor (Ga, Mn)As thin film: preparation and characterization

The GaAs based diluted magnetic semiconductor, (Ga, Mn)As, with the unique advantage of manipulating the spin and charge was widely investigated in the scientific community and considered as a potential material for the spintronic devices. However, its Curie temperature (Tc), which is limited to around 200 K, hinders the research progress of diluted magnetic semiconductors for potential device applications. Herein, we propose an approach to prepare the MnGa nanoparticles embedded in (Ga, Mn)As matrix using the magnetron sputtering deposition of Mn on GaAs surface, followed by the nano-second pulsed laser annealing (PLA), which gives aTcabove 400 K. We demonstrate that the MnGa nanoparticles are only formed in (Ga, Mn) As thin film during the nano-second PLA under a critical range of energy density (0.4-0.5 J cm-2). The highest achieved coercivity, saturation magnetization and remanent magnetization are 760 Oe, 11.3 emu cm-3and 9.6 emu cm-3, respectively. This method for preparing the hybrid system of ferromagnetic metal/dilute magnetic semiconductor builds a platform for exploring the interesting spin transport phenomenon and is promising for the application of spintronic devices.

Organic cation‐supported layered vanadate cathode for high‐performance aqueous zinc‐ion batteries

AbstractLayered vanadates are ideal energy storage materials due to their multielectron redox reactions and excellent cation storage capacity. However, their practical application still faces challenges, such as slow reaction kinetics and poor structural stability. In this study, we synthesized [Me2NH2]V3O7 (MNVO), a layered vanadate with expended layer spacing and enhanced pH resistance, using a one‐step simple hydrothermal gram‐scale method. Experimental analyses and density functional theory (DFT) calculations revealed supportive ionic and hydrogen bonding interactions between the thin‐layered [Me2NH2]+ cation and [V3O7]− anion layers, clarifying the energy storage mechanism of the H+/Zn2+ co‐insertion. The synergistic effect of these bonds and oxygen vacancies increased the electronic conductivity and significantly reduced the diffusion energy barrier of the insertion ions, thereby improving the rate capability of the material. In an acidic electrolyte, aqueous zinc‐ion batteries employing MNVO as the cathode exhibited a high specific capacity of 433 mAh g−1 at 0.1 A g−1. The prepared electrodes exhibited a maximum specific capacity of 237 mAh g−1 at 5 A g−1 and maintained a capacity retention of 83.5% after 10,000 cycles. This work introduces a novel approach for advancing layered cathodes, paving the way for their practical application in energy storage devices.

Investigation of optical and thermoelectric characteristics of novel zintl-phase alloys CaZn2X2 (X = P, As, Sb) for green energy applications

Abstract This study examines the photovoltaic and thermoelectric response of calcium-based novel Zintl-phase alloys CaZn2X2 (X = P, As, Sb). The structural, optoelectronics, and transport features of Zintl CaZn2X2 (X = P, As, Sb) compounds have been analyzed using the full potential linearized augmented plane wave (FPLAPW) technique. Investigations on formation energy and phonon dispersion have confirmed the formation and dynamical stabilities. These compounds exhibit a semiconductor behavior, as their predicted bandgap values: 1.76 eV for CaZn2P2, 1.14 eV for CaZn2As2, and 0.32 eV for CaZn2Sb2. By investigating the optical properties, we have discovered their potential applicability in optoelectronic and photovoltaic devices, as evidenced by the optical response of these phases. The traditional Boltzmann transport theory has assessed transport characteristics against temperature and chemical potential. Significantly higher values of the Seebeck coefficient are achieved at room and elevated temperatures. Moreover, the power factor demonstrates a linear relationship with rising temperature. The remarkable optoelectronic properties and exceptional power factor values suggest that these materials are suitable for deployment in photovoltaic and transport devices.

First-principles calculations of the effect of vacancy defects on the optoelectronic and mechanical properties of the double perovskite Cs2NaInCl6

Abstract Cs2NaInCl6 have become a hot research topic in perovskite optoelectronic materials. However, there is no research on the vacancy properties of Cs2NaInCl6 at present. Herein，using density functional theory-based first-principles calculations, the impact of Cs, Na, In, and Cl single vacancies on the microstructure, electronic, optical, and mechanical properties of the double perovskite Cs2NaInCl6 were investigated. The research shows that the presence of vacancy defects leads to distortion of the Cs2NaInCl6 double perovskite structure and an increase in the unit cell volume. Cs vacancy (VCs) and Na vacancy (VNa) cause an increased band gap for Cs2NaInCl6, by 2.92eV and 3.1eV respectively, without changing the characteristics of the initial direct band gap; VIn and VCl cause the intrinsic semiconductor Cs2NaInCl6 to transform into p-type and n-type semiconductors, respectively, altering the conductivity of Cs2NaInCl6. In terms of optical properties, different vacancy defect systems exhibit different absorption abilities in the visible and ultraviolet light ranges. The defect system overall improves light absorption in the low energy region, and as the incident photon energy increases, the material exhibits the best optical performance at around 15eV. In addition, it is found that VCs, VNa, and VIn caused blue shift in the absorption edge of Cs2NaInCl6, while VCl caused red shift in the absorption edge. In terms of mechanical properties, defects cause varying degrees of reduction in Young's modulus (E), shear modulus (G), and bulk modulus (B) of Cs2NaInCl6, which to some extent alters the mechanical properties of Cs2NaInCl6. These research results provide theoretical guidance for understanding the influence of vacancies on the properties of Cs2NaInCl6 double perovskite and optimizing the performance of perovskite optoelectronic devices, and they also enhance its applications in photovoltaic cells, optoelectronic sensors, and other optoelectronic coupling devices.

Adaptive Compression-Aware Split Learning and Inference for Enhanced Network Efficiency

The growing number of AI-driven applications in mobile devices has led to solutions that integrate deep learning models with the available edge-cloud resources. Due to multiple benefits such as reduction in on-device energy consumption, improved latency, improved network usage, and certain privacy improvements, split learning, where deep learning models are split away from the mobile device and computed in a distributed manner, has become an extensively explored topic. Incorporating compression-aware methods (where learning adapts to compression level of the communicated data) has made split learning even more advantageous. This method could even offer a viable alternative to traditional methods, such as federated learning techniques. In this work, we develop an adaptive compression-aware split learning method (“deprune”) to improve and train deep learning models so that they are much more network-efficient, which would make them ideal to deploy in weaker devices with the help of edge-cloud resources. This method is also extended (“prune”) to very quickly train deep learning models through a transfer learning approach, which tradesoff little accuracy for much more network-efficient inference abilities. We show that the “deprune” method can reduce network usage by 4× when compared with a split-learning approach (that does not use our method) without loss of accuracy, while also improving accuracy over compression-aware split-learning by up to 4 percent. Lastly, we show that the “prune” method can reduce the training time for certain models by up to 6× without affecting the accuracy when compared against a compression-aware split-learning approach.

Effect of carbon nanotubes and zinc oxide on electrical and mechanical properties of polyvinyl alcohol matrix composite by electrospinning method.

In this study, polymer composite nanofibers and thin membranes were synthesized using Carbon Nanotubes (CNTs) and Zinc Oxide (ZnO) as fillers in a Polyvinyl Alcohol (PVA) matrix, aiming to evaluate their electrical and mechanical properties. The composite nanofibers and thin membranes were prepared by incorporating different weight ratios of CNTs and ZnO into the PVA matrix using electrospinning and solution casting techniques, respectively. Solutions were prepared by mixing specific weight ratios of PVA, ZnO, and CNTs, followed by magnetic stirring and ultrasonication for homogenization. Electrospinning was performed at 20kV with a syringe-to-collector distance of 14.5cm at flow rate of 2.4ml/hr. The composites were characterized using FTIR spectroscopy and Scanning Electron Microscopy (SEM). The PVA/5%ZnO/0.5%CNT composite exhibited the highest dielectric constant of 10.3 at high frequencies, while PVA/5%CNT showed the highest capacitance of 31.1 pF at 2MHz. The maximum AC conductivity of 2.72 × 10- 7S/m was also observed for the PVA/5%ZnO/0.5%CNT composite. Mechanical testing revealed significant improvements in Young's modulus, stress yield, and load yield, with PVA/5%CNT achieving a Young's modulus of 387.12 MPa and a stress yield of 6.92 MPa. The addition of ZnO and CNT fillers resulted in enhanced electrical and mechanical properties, making these composites suitable for applications in microelectronic devices and packaging materials.

Microstructural Underpinnings of Giant Intrinsic Exchange Bias in Epitaxial NiCo2O4 Thin Films

AbstractUnderstanding intrinsic exchange bias in nominally single‐component ferromagnetic or ferrimagnetic materials is crucial for simplifying related device architectures. However, the mechanisms behind this phenomenon and its tunability remain elusive, which hinders the efforts to achieve unidirectional magnetization for widespread applications. Inspired by the high tunability of ferrimagnetic inverse spinel NiCo2O4, the origin of intrinsic exchange bias in NiCo2O4 (111) films deposited on Al2O3 (0001) substrates are investigated. The comprehensive characterizations, including electron diffraction, X‐ray reflectometry and spectroscopy, and polarized neutron reflectometry, reveal that intrinsic exchange bias in NiCo2O4 (111)/Al2O3 (0001) arises from a reconstructed antiferromagnetic rock‐salt NixCo1‐xO layer at the interface between the film and the substrate due to a significant structural mismatch. Remarkably, by engineering the interfacial structure under optimal growth conditions, it can achieve exchange bias larger than coercivity, leading to unidirectional magnetization. Such giant intrinsic exchange bias can be utilized for realistic device applications. This work establishes a new material platform based on NiCo2O4, an emergent spintronics material, to study tunable interfacial magnetic and spintronic properties.

Multiple conformal-contact transfer of large-area crack-free transition metal dichalcogenide stacks

Abstract Atomically-thin two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as an ideal platform for both physics investigation and device applications. By stacking different layers into homo- or hetero-structures, an extra degree of freedom is involved in further tuning their properties, thereby boosting scenarios in twistronics, moiré photonics and optoelectronics. However, interfacial imperfections such as contaminations and cracks, frequently occur during the layer stacking sequence and accumulate layer by layer, greatly degenerating the interface quality. In this study, we developed a multiple conformal-contact transfer method to construct TMD stacks with crack-free intrinsic interfaces. The design of a deformable buffer layer is crucial to guarantee the conformal contact and intact transfer of each layer, contributing to the successful construction of centimetre-scale TMD stacks up to 8 layers. Precise control over spatial location and interlayer twist angle is also feasibly achieved, evidenced by the stacking-dependent interlayer exciton (IE) effects in WS2-WSe2 heterostructures. This work provides a facile and precise approach for architecting 2D stacks with perfect interfaces, which will further accelerate the customized design for their device functionalization.

Does the Traditional Band Picture Correctly Describe the Electronic Structure of n-Doped Conjugated Polymers? A TD-DFT and Natural Transition Orbital Study.

Doped conjugated polymers have a variety of potential applications in thermoelectric and other electronic devices, but the nature of their electronic structure is still not well understood. In this work, we use time-dependent density functional theory (TD-DFT) calculations along with natural transition orbital (NTO) analysis to understand electronic structures of both p-type (e.g., poly(3-hexylthiophene-2,5-diyl), P3HT) and n-type (e.g., poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)}, N2200) conjugated polymers that are both p-doped and n-doped. Of course, the electronic transitions of doped conjugated polymers are multiconfigurational in nature, but it is still useful to have a one-electron energy level diagram with which to interpret their spectroscopy and other electronic behaviors. Based on the NTOs associated with the TD-DFT transitions, we find that the "best" one-electron orbital-based energy level diagram for doped conjugated polymers such as P3HT is the so-called traditional band picture. We also find that the situation is more complicated for donor-acceptor-type polymers like N2200, where the use of different exchange-correlation functionals leads to different predicted optical transitions that have significantly less one-electron character. For some functionals, we still find that the "best" one-electron energy level diagram agrees with the traditional picture, but for others, there is no obvious route to reducing the multiconfigurational transitions to a one-electron energy level diagram. We also see that the presence of both electron-rich and electron-poor subunits on N2200 breaks the symmetry between n- and p-doping, because different types of polarons reside on different subunits leading to different degrees of charge delocalization. This effect is exaggerated by the presence of dopant counterions, which interact differently with n- and p-polarons. Despite these complications, we argue that the traditional band picture suffices if one wishes to employ a simple one-electron picture to explain the spectroscopy of n- and p-doped conjugated polymers.

Thread-Filler: A Standardized Combination Therapy

Advanced technology and increasing knowledge about aging faces have combined to create the illusion of thread lifting to replace surgical interventions. However, results that came far beyond expectations led to a heavy suspicion of these tools. However, combined treatments with fillers would have better outcomes with a synergetic effect. In this study, 52 patients were treated with a specific thread, whereas soft tissue support was added to supervene the lifting effect of the threads. With a mean age of 48 years, these patients were treated with 3 pairs of mid and lower facial areas, and one for eyebrows. With a median amount of 5 mL fillers were added simultaneously at the same treatment plan. The follow-up period was 32 months. Assessment with a Likert Scale questionnaire revealed most of the patients (n = 42) were delighted, whereas only one patient was unsatisfied. The only unsatisfied patient experienced the most frustrating complication, which was thread removal due to infection. The literature shows unauthorized, unspecialized applications of such medical devices cause failure and loss of reliability. Therefore, the most important point of this technique is the sterile setting. Other issues that are discussed in this paper also aim to direct the reader to achieve the most benefit of these 2 techniques.

Thickness-dependent structural and growth evolution in relation to dielectric relaxation behavior and correlated barrier hopping conduction mechanism in Ni0.5Co0.5Fe2O4 ferrite thin films.

Ferrite thin films are explored due to their promising properties, which are essential in various advanced electronic devices. However, depositing a film with pure phase and uniform microstructure is challenging. The Ni0.5Co0.5Fe2O4 ferrite thin films are deposited using pulsed laser deposition (PLD) technique to explore the effect of thickness on structural properties, growth evolution, temperature-dependent dielectric behavior, and conduction mechanisms. Microstructural analysis revealed that the films are uniformly grown, exhibiting surface roughness ranging from  2 to 4 nm. The dielectric response, adhering to a modified Debye model, exhibited multiple relaxation processes, with notable changes in the dielectric constant and loss as film thickness increased. Impedance spectra exhibited both space charge and dipolar relaxation phenomena, corroborated by Cole-Cole and electrical modulus plots. The analysis of the imaginary electric modulus using the Kohlrausch-Williams-Watts (KWW) function revealed non-Debye-type relaxation in all deposited films, characterized by thermally activated broad peaks. Conductivity decreased up to a certain film thickness, and the frequency exponent derived from Jonscher's power law suggested a correlated barrier hopping model for AC conduction. Activation energies improved with film thickness up to 125 nm, consistent with a constant energy barrier for polarons during relaxation and conduction phases. The film with 125 nm thickness exhibited the optimal dielectric properties, with the maximum dielectric constant, minimum dielectric loss, and highest activation energy. These findings highlight the potential of dense, uniformly grown films with high dielectric constants and low dielectric losses for advanced electronic device applications.

Bioinspired Antireflective and Antifogging Surface for Highly Efficient and Stable Inverted Solar Cells.

Photovoltaic devices are essentially solar energy collectors that convert incident photons into charge carriers. However, light reflection losses and external factors (e.g., fog) can lead to an inefficient utilization of incident photons. Therefore, the development of antifogging surface materials that can efficiently reduce reflection is a critical issue in the upgradation of photovoltaic devices. Herein, inspired by the wing scale structures of butterfly Trogonoptera brookiana, an antireflective and antifogging surface (BRFS) was prepared by a method combining biotemplate and sol-gel. Remarkably, the BRFS possesses a relatively large surface roughness and exhibits superhydrophilic property (static water contact angle of 0°), which can quickly split fog droplet film within 6.6 s to realize the antifogging effect. In addition, the final transmittance of BRFS is as high as 90.25%. Furthermore, as an application demonstration, BRFS was applied to the surface of the reverse organic solar cells. Without compromising the inherent performance of the panels, the BRFS enhances the electrical performance of the inverted solar panels by 18%. This work provides a simple and effective strategy for designing surfaces with superior antifogging and antireflective properties and offers significant potential value for the practical application of photoelectric devices.

Negative piezoelectricity in quasi-two/one-dimensional ferroelectrics

Abstract In recent years, the investigation of low-dimensional ferroelectrics has attracted great attention for their promising applications in nano devices. Piezoelectricity is one of the most core properties of ferroelectric materials, which plays the essential role in micro-electromechanical systems. Very recently, the anomalous negative piezoelectricity has been predicted/discovered in many quasi-two-dimensional layered ferroelectric materials. In this Topical Review, we will briefly introduce on the negative piezoelectricity in quasi-two/one-dimensional ferroelectrics, including its fundamental concept, typical materials, theoretical predictions, as well as experimental phenomena. The underlying physical mechanisms for negative piezoelectricity are divergent and varying from case by case, which can be categorized into four types. First, the soft van der Waals layer is responsible for the volume shrinking upon pressure while the electric dipoles is from non van der Waals layer. Second, the noncollinearity of local dipoles creates a ferrielectricity, which leads to orthogonal ferroelectric and antiferroelectric axes. Third, the electric dipoles come from interlayer/interchain couplings, which can be enhanced during the volume shrinking. Fourth, the special buckling structure contributes to local dipoles, which can be enhanced upon pressure. In real materials, more than one mechanism may work together. Finally, the future directions of negative piezoelectricity and their potential applications are outlooked.