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Ternary two-dimensional (2D) monoclinic Nb2SiTe4 has garnered significant attention for its potential applications in anisotropic photoelectronics. Yet, its intrinsic indirect bandgap nature and low hole mobility, attributed to the short Nb–Nb dimer configurations, hinder the efficient photogenerated carrier separation and transport. In this Letter, using density functional theory calculations, we demonstrate the interlayer intercalation of Si results in the formation of a metastable orthorhombic Nb2SiTe4 structure devoid of detrimental short Nb–Nb dimers. Notably, this Si intercalation leads to a remarkable reduction of hole effective masses of orthorhombic Nb2SiX4 (X = S, Se, and Te), a crucial factor for achieving high carrier mobility. Taking the orthorhombic Nb2SiTe4 monolayer as an example, the calculated hole mobility (>100 cm2 V−1 s−1) is comparable in magnitude to the respectable hole mobility observed in multiple layers of the monoclinic Nb2SiTe4. To simultaneously enhance electron and hole mobility, we establish a van der Waals junction between the monoclinic and orthorhombic Nb2SiTe4 structures, achieving high and comparable carrier mobilities. The Nb2SiTe4 junction exhibits a nearly direct bandgap of 0.35 eV, rendering it suitable for infrared light harvesting. Furthermore, carriers within the Nb2SiTe4 junction become spatially separated across different layers, resulting in an intrinsic built-in electric field, which is superior for efficient photo-generated charge separation and decreases the potential nonradiative carrier recombination. Our findings highlight the impact of cation coordination engineering on the electronic and optical properties of 2D Nb2SiTe4 and provide a feasible solution to achieve better carrier transport in low-dimensional photovoltaic functionalities. [ABSTRACT FROM AUTHOR]

Flexoelectricity of semiconductors usually exhibits large flexoelectric coefficients due to their significantly enhanced surface piezoelectricity caused by surface symmetry breaking. In this Letter, we reported a general paradigm to tune the semiconductor flexoelectricity through interface engineering. We selected Nb-SrTiO3 (Nb-STO) single crystals as the targets and tuned their surface piezoelectricity through depositing TiO2-terminated and SrO-terminated ultra-thin BaTiO3 (BTO) films. The results suggested that the deposition of TiO2-terminated and SrO-terminated ultra-thin BaTiO3 films to Nb-STO can induce a downward and upward out-of-plane surface polarization, respectively, thereby significantly increasing/decreasing the apparent flexoelectric coefficients of Nb-STO single crystals. Our work proves the feasibility of interface engineering in the application of flexoelectricity and also provides a possible route to achieve the large apparent flexoelectricity of semiconductor materials. [ABSTRACT FROM AUTHOR]

This Letter reports a wearable mechano-acoustic sensor for continuous cardiorespiratory monitoring. The sensing mechanism is based on reversible iodide/triiodide ( I − / I 3 − ) electrochemical redox reaction on microfabricated platinum electrodes, enabling an ultra-high sensitivity on the detection of mechano-acoustic signals of the cardiorespiratory system. Ecoflex, a flexible silicone rubber, is adopted as the material of the sensor body due to its excellent stretchability, robustness, and skin-compatibility. The developed sensor exhibited a noise floor of 4.5 μg/ H z at 10 Hz. Detection of heart sounds, lung sounds, and respiration rates was demonstrated. [ABSTRACT FROM AUTHOR]

Coupling between polarization and the strain gradient, namely, flexoelectricity, is a universal phenomenon that widely exists in all solid dielectrics and polymers. At a low level of the applied strain gradient, this electromechanical coupling is strictly a linear effect. In this Letter, a strong nonlinearity between the polarization and the strain gradient was experimentally found in polyvinylidene fluoride when the strain gradient was higher than a material-dependent threshold value. Such nonlinear behavior was in good accordance with an ion chain theory and could be fitted by a nonlinear equation. The observed flexoelectric nonlinearity in this work will help in the understanding of the discrepancy between the previous findings about the bulk materials and their nanoscale counterparts. [ABSTRACT FROM AUTHOR]

Flexoelectricity yields electric polarization through graded strains and exists in various kinds of solid dielectrics but usually with a weak coupling response. In this letter, several Bi-doped Pb(Mg2/3Nb1/3)O3-xPbTiO3 (PMN-xPT) ferroelectric ceramics were prepared and the interplay of their piezoelectricity and flexoelectricity was systematically investigated. The largest flexoelectric response (∼300 μC/m) was 30 times larger than that of pure PMN-PT and was observed in the Bi-doped PMN-32PT, where the after poling piezoelectric coefficients were also the largest (990 pC/N) among all the compositions. This suggests that the apparent flexoelectricity in ferroelectrics is highly related to the bulk piezoelectricity. Therefore, introducing a local structural heterogeneity is considered as a feasible approach to achieve an ultrahigh piezoelectric response while also providing an ultrahigh flexoelectricity. [ABSTRACT FROM AUTHOR]

Donor doping can increase the dielectric constant of a material by several orders of magnitude due to induced space charge causing interfacial polarization. Giant dielectric properties and interface polarization are also both expected to greatly enhance the flexoelectric behavior of a material. In this work, a typical flexoelectric ceramic material, BaTiO3, was selected and donor doped using elemental Nb. Compared with the nominal BaTiO3 ceramic, the dielectric constant and flexoelectric coefficient of the Nb-doped BaTiO3 ceramics were significantly improved. The transverse flexoelectric coefficient of 0.3 mol. % Nb-BaTiO3 was found to increase to nearly 40 times the nominal value, reaching 387 μC/m. The results indicate that the giant dielectric response, and therefore the giant flexoelectric response, is the result of the combined effects of internal barrier-layer capacitance and surface barrier-layer capacitance. This study not only deepens the understanding of the semiconductor macro-dielectric effect and the flexoelectric mechanism caused by doping, but it also provides a feasible strategy for the design of giant dielectric/flexoelectric response materials and related devices with high dielectric constants and flexoelectric coefficients. [ABSTRACT FROM AUTHOR]

For nanostructured particles, the faceting planes and their terminating chemical species are two critical factors that govern their chemical behavior. The surface atomistic structure and termination of Ti2O3 crystals were analyzed using atomic-scale aberration-corrected scanning transmission electron microscopy (STEM) combined with density functional theory (DFT) calculations. STEM imaging reveals that the Ti2O3 crystals are most often faceted along (001), (012), (-114), and (1–20) planes. The DFT calculation indicates that the (012) surface with TiO-termination has the lowest cleavage energy and correspondingly the lowest surface energy, indicating that (012) will be the most stable and prevalent surfaces in Ti2O3 nanocrystals. These observations provide insights for exploring the interfacial process involving Ti2O3 nanoparticles. [ABSTRACT FROM AUTHOR]

AgNbO3 is a typical antiferroelectric ceramic with weak ferroelectricity at room temperature. Due to this feature, AgNbO3 has received a lot of attention in electromechanical applications, but most of these studies have focused on the doping of other elements in AgNbO3. In this study, curved AgNbO3 ceramics were fabricated using a gravity-driven annealing process, and the field-induced strains were investigated. The curved ceramic exhibited a significantly higher field-induced nominal strain compared to a flat ceramic. Experimental results revealed that the curved AgNbO3 sample exhibited a maximum nominal strain of 1.22%, significantly surpassing the theoretical value of 0.13%. Analysis of various characterizations confirmed the presence of flexoelectricity, and flexoelectricity played an important role in the ultrahigh electromechanical response of curved AgNbO3 ceramics. Additionally, we demonstrated that curved AgNbO3 ceramics can enhance the flexoelectric coefficient. These findings suggest that curved antiferroelectric ceramics can enhance their displacement output, meeting the requirements for applications in large-strain actuators. [ABSTRACT FROM AUTHOR]

Using density functional theory, it is shown that titanium doped heterofullerene has superior property of hydrogen storage. The single titanium atom lies at a double bond position of C60 and bonds to four carbons by Dewar interaction. Each titanium atom binds up to six hydrogen molecules. The first and second hydrogen molecules are dissociated to form carbon hydrides with binding energy of -0.43 eV/H. The other four adsorptions are molecular with binding energy of -0.14 eV/H2. For substitutionally dope C60 with six titanium atoms, the gravimetric density of hydrogen reaches the 7.7 wt % limit necessary for applications in the mobile industry. [ABSTRACT FROM AUTHOR]

Characterizing the photoactivation performance of highlighter fluorescence proteins (FPs) is crucial for screening better highlighter FPs and optimizing the photoactivation efficiency of a certain highlighter FP. Currently, photoactivation contrast and half-time values of photoactivation and photobleaching processes are used for such purpose. However, the relations among these parameters are not clear, and little guidance for practical experiments could be obtained from the half-time values. Here, we show that light dose dependent fluorescence curve, which is calculated from activation-intensity-dependent photoactivation and photobleaching rates, is capable of quantifying the photoactivation performance straightforwardly. Moreover, the photoactivation contrast is easily obtained from the curve. [ABSTRACT FROM AUTHOR]

Codoping of p-type GaN nanowires with Mg and oxygen was investigated using first-principles calculations. The Mg becomes a deep acceptor in GaN nanowires with high ionization energy due to the quantum confinement. The ionization energy of Mg doped GaN nanowires containing passivated Mg–O complex decreases with increasing the diameter, and reduces to 300 meV as the diameter of the GaN nanowire is larger than 2.01 nm, which indicates that Mg–O codoping is suitable for achieving p-type GaN nanowires with larger diameters. The codoping method to reduce the ionization energy can be effectively used in other semiconductor nanostructures. [ABSTRACT FROM AUTHOR]

We consider the stochastic electromagnetic Gaussian Schell-model (EGSM) beam and show that the polarization of stochastic electromagnetic EGSM beams in the source plane affect spectral switches of diffracted stochastic electromagnetic EGSM beams in the far field. For two cases of fully coherent and partially coherent δxx=δyy the behavior of spectral switches are same in different degrees of polarization of the source. [ABSTRACT FROM AUTHOR]

The evolution of an exploding titanium wire embedded in 10 kPa air was studied with Mach–Zehnder interferometry. The exploding wire is characterized by a central dense core as well as the surrounding plasma and a rapidly expanding gas shell. Based on the fringe shifts, the electron density of the plasma and the increased density in the gas shell were calculated to be about 1.94×1018/cm3 and 4.78×10-4 g/cm3, respectively. The expanding speed of the gas shell is about 2.28 km/s. A thermal expansion lag of the dense vapor core and two-phase vaporization of the wire were observed. Due to the wire exploding in “under heat” mode, the first phase of the vaporization is by the Joule heating and the second one by the plasma heating. [ABSTRACT FROM AUTHOR]

The microstructural evolution and resistive switching of glassy Ag30Ge17Se53 electrolyte films clipped by Ag active electrode, at which a positive bias was applied, and Pt inert electrode, were investigated by transmission electron microscopy observations and I-V measurements as functions of the period of electrical field treatment. It is revealed that an electrical field induced precipitation reaction forming conductive particles with orthorhombic Ag2Se structure and followed growth and networking of these particles, leading to an electrical percolation, are responsible for the transition from high resistive to high conductive state of the system. The kinetics of the precipitation reaction was also analyzed. [ABSTRACT FROM AUTHOR]

Electronic band structures of single-walled silicon carbide nanotubes are studied under uniaxial strain using first principles calculations. The band structure can be tuned by mechanical strain in a wide energy range. The band gap decreases with uniaxial tensile strain, but initially increases with uniaxial compressive strain and then decreases with further increases in compressive strain. These results may provide a way to tune the electronic structures of silicon carbide nanotubes, which may have promising applications in building nanodevices. [ABSTRACT FROM AUTHOR]

Complex impedance spectroscopy has been employed to investigate the conduction behavior of (Ba,Sr)(Zr,Ti)O3 thin films in the low- and high-resistance states for resistive switching applications. The domination of the grain bulk effect on the resistive switching is demonstrated. The analyses of activation energies for the conduction in the low- and high-resistance states have been executed comparatively. It is proposed that the first and the second ionization of oxygen vacancies are responsible for the conduction in the low- and high-resistance states, respectively. The transition of conduction mechanism is also discussed. [ABSTRACT FROM AUTHOR]

The thermal conductivity of GaN nanowires has been determined computationally by applying nonequilibrium atomistic simulation methods using the Stillinger-Weber [Phys. Rev. B 31, 5262 (1985)] potentials. The simulation results show that the thermal conductivity of the GaN nanowires is smaller than that of a bulk crystal and increases with increasing diameter. Surface scattering of phonons and the high surface to volume ratios of the nanowires are primarily responsible for the reduced thermal conductivity and its size dependence behavior. The thermal conductivity is also found to decrease with increasing temperature and exhibits a dependence on axial orientation of the nanowires. [ABSTRACT FROM AUTHOR]

Molecular dynamics methods with a Stillinger-Weber [Phys. Rev. B 31, 5262 (1985)] potential have been used to investigate the mechanical properties of wurtzite-type single-crystalline GaN nanotubes under applied tensile strains. At low temperatures, the nanotubes show brittle properties, whereas at high temperatures, they behave as ductile materials. The brittle to ductile transition (BDT) is systematically investigated and the corresponding transition temperatures have been determined in GaN nanotubes. The BDT temperature generally increases with increasing thickness of nanotubes and strain rate. [ABSTRACT FROM AUTHOR]

Ultraviolet light-sensitive organic optical sensor based on photovoltaic diode was demonstrated by using a phosphorescent Cu complex and a diamine derivative as electroacceptor and electrodonor, respectively. The Cu complex is Cu(DPEphos)((Bphen))BF4, in which DPEphos and Bphen denote 6,7-dicyanodipyrido [2,2-d:2′,3′-f] quinoxaline and bathophenanthroline. And the diamine derivative, m-MTDATA, is 4, 4′,4″-tris-(2-methylphenyl phenylamino) triphenylamine. The sensor is highly sensitive to UV light band from 300 to 420 nm while it has almost no response to the visible light, and under illumination of 365 nm light with power of 1.7 mW/cm2, the sensor exhibits an open circuit voltage of 1.86 V, a short circuit current of 105.3 μA/cm2, a fill factor of 0.246, and a power conversion efficiency of 2.83%. The dependences of ultraviolet responsive sensitivity on illumination intensity and working temperature were also discussed. [ABSTRACT FROM AUTHOR]

We present a method for generating atmospheric pressure plasma using a dielectric barrier discharge reactor with two liquid electrodes. Four distinct kinds of discharge, including stochastic filaments, regular square pattern, glow-like discharge, and Turing stripe pattern, are observed in argon with a flow rate of 9 slm. The electrical and optical characteristics of the device are investigated. Results show that high-power-density atmospheric pressure plasma with high duty ratio in space and time can be obtained. The influence of wall charges on discharge power and duty ratio has been discussed. [ABSTRACT FROM AUTHOR]

High-speed optical communication systems are built for real-time, massive, and remote information exchange; however, it is strongly reliant on the applied power. Herein, we developed a self-driven optical communication system based on a high-performance graphene/n-Si (Gr/n-Si) hybrid photodetector. Under zero bias, the Gr/n-Si device presents good performance at a wavelength of 520 nm, including the photoresponsivity of 0.27 A W−1, specific detectivity of 9.39 × 1011 Jones, and on/off ratio of 104 with a rise and fall time of 128 and 131 ns, respectively. This hybrid device also exhibits 3 dB bandwidth of 2.18 MHz as well as a small noise equivalent power of 1.68 × 10−17 W Hz−1/2. Furthermore, an optical communication system was constructed based on this hybrid photodetector, through which the audio and text signals were steadily and accurately transmitted under zero bias. Our work lays a solid foundation to demonstrate a promising application of Gr/n-Si hybrid devices toward self-driven optical communications. [ABSTRACT FROM AUTHOR]

Examines the overshoot in the capture transient of the DX center in n-aluminum gallium arsenide semiconductors. Measurement of deep level transient spectroscopy signal height of DX levels; Transport properties of n-type AlGaAs; Agreement between simulated and experimental capture transients.

Utilizes the deep level transient spectroscopy signal height as a function of applied stress data and the statistics of the occupancy of the DX center in aluminum gallium arsenide quantum well to obtain the stress dependence of the thermal binding energy of the neutral DX center, E[sub DX]. Localization of the DX center; Explanation of the different stress directions.

The identification of the liquid–liquid phase transition (LLPT) in liquids under shock compression is a long-standing challenge. In this Letter, by designing shock-release experiments in shock-driven molten Ce, we observe a first-order LLPT along the release path. The volume change associated with the transition is less than 6%, much smaller than the one (14%) obtained in static compression experiments, indicating that the LLPT in molten Ce is strongly rate dependent. The identified timescale for the LLPT is on the order of 200 ns. Our results, therefore, provide kinetic information of the LLPT in an unprecedented manner, which is extremely valuable for the construction of a non-equilibrium phase diagram. [ABSTRACT FROM AUTHOR]

Flexoelectricity couples strain gradient to polarization and usually exhibits a large coefficient in the paraelectric phase of the ferroelectric perovskites. In this study, we employed the relaxor 0.3Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PIN-PMN-PT) single crystals to study the relationship between flexoelectric coefficients and the crystal structure. The flexoelectric coefficients in PIN-PMN-PT single crystal are found to vary from 57 μC/m at orthorhombic/monoclinic phase to 135 μC/m at tetragonal phase, and decreases to less than 27 μC/m in the temperature above Tm. This result discloses that ferroelectricity can significantly enhance the flexoelectricity in this kind of perovskite. [ABSTRACT FROM AUTHOR]

Under 980 nm excitation, high multi-photon upconversion (UC) emission from the 2H11/2/4S3/2 (green) and 4F9/2 (red) levels of Er3+ ions were observed from Er3+ singly doped BiOCl microcrystals. These high-energy excited states were populated by a three to ten photon UC process conditionally, which depended on the pump power density and the Er3+ ion doping concentration, characterizing as a hetero-looping enhanced energy transfer avalanche UC process. UC emission lifetime and Raman analysis suggest that the unusual UC phenomena are initiated by the new and intense phonon vibration modes of BiOCl lattices due to Er3+ ions doping. [ABSTRACT FROM AUTHOR]

Complex oxide thin films and superlattices with the perovskite ABO3 structure have been found to possess multifunctional properties. Here, we present our discovery of antisite defects, La ions in Fe(Mn) sites (denoted as LaB), in a La0.7Sr0.3MnO3/La0.7Sr0.3FeO3 superlattice. The antisite defect was directly characterized by atomic resolution Z-contrast imaging and the composition and electronic structure were analyzed by electron energy loss spectroscopy in an aberration-corrected scanning transmission electron microscope. Density functional theory was used to calculate the formation energy, showing that the formation of the detected antisite defects is a consequence of the slightly reducing conditions during sample growth. [ABSTRACT FROM AUTHOR]

We reported an enhanced flexoelectricity in Al2O3-doped Ba(Ti0.85Sn0.15)O3 (BTS) ceramics. The transverse flexoelectric coefficient of the 0.5wt. % Al2O3-doped BTS ceramic was measured to be 40.5 µC/m at 23 °C, which is almost 2 times larger than that of pure BTS. Above Curie temperature, the temperature dependence of the flexoelectric coefficients in the 0.5wt. % Al2O3-doped ceramic was found much more sensitive compared with that of the pure BTS ceramic. It is concluded that the enhanced flexoelectricity is possibly related to inner microstrains or the non-crystalline polar phases. [ABSTRACT FROM AUTHOR]

We reported an enhanced flexoelectricity in Al2O3-doped Ba(Ti0.85Sn0.15)O3 (BTS) ceramics. The transverse flexoelectric coefficient of the 0.5 wt. % Al2O3-doped BTS ceramic was measured to be 40.5 µC/m at 23 °C, which is almost 2 times larger than that of pure BTS. Above Curie temperature, the temperature dependence of the flexoelectric coefficients in the 0.5 wt. % Al2O3- doped ceramic was found much more sensitive compared with that of the pure BTS ceramic. It is concluded that the enhanced flexoelectricity is possibly related to inner microstrains or the noncrystalline polar phases. [ABSTRACT FROM AUTHOR]

A photoluminescence (PL) method to characterize phase transition processes of Li+/Er3+:BaTiO3 (BLET) ferroelectric ceramics by infrared fluorescence intensities has been proposed. The fluorescence intensities are applied to detect the phase transition of BLET ceramics in multiple phase transition regions. It proves that the change in fluorescence intensities at the phase transition is due to a variation in the radiative transition probability of the 4I13/2 level. A physical mechanism is elucidated considering the relationship between fluorescence properties and the phase structure. Our research benefits an in-depth understanding of the relationship between the PL characteristics and the phase structure of ferroelectric materials and further develops the application potential of PL methods in ferroelectric phase transition detection. [ABSTRACT FROM AUTHOR]

An asymmetric (ASY) multiple quantum wells (MQWs) structure consisting of emission and detection regions with different In components and thicknesses is presented for suppressing the Stokes shift in monolithically integrated photonic chips. Compared with conventional MQWs, the total luminescence intensity of ASY MQWs is improved due to the action of the potential field for transferring more holes to the quantum well near the n-GaN side. Meanwhile, resulted from about 25–30 nm redshift in response spectra, a 4.5-fold increase in the overlap of luminescence-detection spectra is realized. A photodetector exhibits a photo-to-dark current ratio of up to 107 at 0 V bias. Furthermore, the reported ASY MQWs diode shows a maximum bandwidth (−3 dB) of 173 MHz, suggesting that a monolithically integrated chip has tremendous potential on the application of the on-chip visible light communication. [ABSTRACT FROM AUTHOR]

Ferroelectric materials have been widely explored for photostrictive action, but their high performance being limited to ultra violet light demands to look for efficient visible light photostrictive materials. Transition metal vanadates, exhibiting the Kagome structural features besides being active in visible light, are the interesting materials for the photostriction study. Here, we investigate the photostriction of the non-magnetic member zinc ortho-vanadate Zn3(VO4)2 or Zn3V2O8. Corresponding to the photostriction response of ∼10−3 under a 405 nm laser (response time, τ = 5.7 s) and ∼10−4 (τ = 5.8 s) under a 665 nm laser, it exhibits a large photostriction efficiency of ∼10−11 and ∼10−12 m3/W, respectively. Thermal expansion investigation indicates that the non-thermal strain dominants the photostriction of Zn3V2O8 ceramics. The peak shift in x-ray diffraction (XRD) pattern as well as in Raman spectra under external laser irradiance revealing, increased anisotropic distortions with increasing stretching and vibrations in the bonds of ZnO6 octahedrons and VO4 tetrahedrons, is proposed as the underlying mechanism of the photostriction response in Zn3V2O8. The good visible light photostriction, rapid response time, and stability functionalities make it a potential candidate for future generation optoelectronics, such as light driven micro-actuators, robots, relays, and other optomechanical devices. [ABSTRACT FROM AUTHOR]

We first investigate the phase control of the switch between bright and dark states in the transmitted probe, four-wave mixing (FWM) and fluorescence signals in a four-level 85Rb atomic system. With the relative phase modulated from 0 to -π, pure dark state in the FWM and fluorescence channels can be switched to pure bright state, corresponding to the switch from electromagnetically induced transparency to electromagnetically induced absorption. Meanwhile, the results could be obtained in solid crystals. Such phase controlled switch could have potential applications in optical communication and quantum information processing. [ABSTRACT FROM AUTHOR]

A low-cost, small molecular monomer, 5′-bis(9–(4-vinylbenzyl)-2-carbazol)-2,2′-bithiophene, termed VB-CB, is designed, synthesized, and polymerized to form a uniform film as the hole-transporting material for the fabrication of inverted planar perovskite solar cells with high performance. The presence of a suitable energy level in the polymerized VB-CB layer can effectively promote the transport of holes and block electrons from the perovskite layer, thus decreasing photon energy loss due to charge recombination. Designing perovskite solar cells with polymerized VB-CB as the hole-transporting material helps us to obtain a high power conversion efficiency of 17.58% with small hysteresis effect, which is higher than that with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the hole-transporting material. Additionally, as compared to PEDOT:PSS, the devices with polymerized VB-CB exhibit better stability under one sun illumination at maximum power point tracking, such that the T80 of the champion devices could exceed 1000 h. The results suggest that the polymerized VB-CB is a suitable hole-transporting material for commercial applications in planar perovskite solar cells, given its low-cost, high efficiency, and good stability. [ABSTRACT FROM AUTHOR]

We present a method and results for measurement of electron density in atmospheric-pressure dielectric barrier discharge. The electron density of microdischarge in atmospheric pressure argon is measured by using the spectral line profile method. The asymmetrical deconvolution is used to obtain Stark broadening. The results show that the electron density in single filamentary microdischarge at atmospheric pressure argon is 3.05×1015 cm-3 if the electron temperature is 10 000 K. The result is in good agreement with the simulation. The electron density in dielectric barrier discharge increases with the increase of applied voltage. [ABSTRACT FROM AUTHOR]

Ferroelectrics with a perovskite structure, exhibiting strong coupling between photons, carriers, and phonons, have been demonstrated to show a strong photostrictive response. Limited by the optical bandgap, most of the reported ferroelectric perovskites respond only to UV light or weakly respond to visible light below 550 nm. Herein, the photostrictive performance of CaCu3Ti4O12 (CCTO) ceramics, with a low bandgap of ∼1.5 eV (ideal for solar spectrum absorption), is comprehensively investigated. Although the compound presents no ferroelectricity, in general, a giant photostriction of ∼10−3 with a large photostrictive efficiency of ∼10−11 m3/W in CCTO ceramics is observed by applying purple (405 nm), green (520 nm), and red (655 nm) laser illumination. Evidenced by the XRD peak shifts under external laser illumination and the phonon mode shifts via the power-dependent Raman spectrum, the light-induced non-thermal deformation in CCTO is attributed to the enhanced stretching of O–Ti–O chains and the distortions of TiO6 octahedrons. The excellent and uniform photostrictive performance of CCTO ceramics in the visible-light region makes them potential candidates for practical applications in next-generation photo-driven electromechanical devices. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) ferromagnets with tunable magnetic anisotropies have great potential in developing spintronic devices. However, until now, there are a few feasible means to control the magnetic anisotropies in 2D ferromagnets. Here, we propose that magnetic easy axes can be switched by ferroelastic strain in 2D ferromagnets: CrSX (X = Cl, Br, I) monolayers. Our ab initio studies reveal that CrSX (X = Cl, Br, I) monolayers are 2D multiferroic materials, which exhibit both ferromagnetism and ferroelasticity. CrSX monolayers also show strongly in-plane magnetic anisotropic character due to their anisotropic structures. By such coexistence, we demonstrate that the in-plane magnetic anisotropy in CrSX monolayers can be manipulated by the reversible ferroelastic strain. Our findings provide a promising platform to control the spintronic properties by incorporating ferroelastic phase transition. [ABSTRACT FROM AUTHOR]

Fluorescence abnormalities associated with the ferroelectric phase transition of Li+/Er3+:BaTiO3 (BLET) ceramics were studied based on photoluminescence (PL) spectra. Sharp changes were found in the integrated intensities, peak intensities, and fluorescence intensity ratios of both upconversion spectra (2H11/2/4S3/2−4I15/2) and downconversion infrared spectra (4I13/2−4I15/2) around the ferroelectric-paraelectric phase transition temperature in BLET ceramics under the excitation of a 980 nm laser. All changes happened within the temperature interval of 126 °C–130 °C. The relative changing rate (RCR) was adopted to quantitatively describe this structure-sensitive PL. For the system under study, the maximum RCR occurs for the PL peak intensity at 542.7 nm. [ABSTRACT FROM AUTHOR]

A nonvolatile memory structure with a high-k composite of ZnO-TiO2 as a charge-trapping dielectric was fabricated by using rf-sputtering and atomic layer deposition techniques, in which the potential of the conduction-band minimum of the composite was designed to be lower than that of Si by the use of the special energy-band offsets among Si, ZnO, and TiO2. Compared to the conduction-band minimum of Si, a relatively negative potential of the high-k composite leads to a continuous rise in the shift of the flat-band potential of the memory device except a drop at the beginning part of the time-dependent retention curve after a programming operation. The drop was attributed to the escape of trapped charges at the Si/Al2O3 interface. After extracting the contribution to the deterioration of the retention curve from the traps at the Si/Al2O3 interface, it was identified that the band alignment in a charge-trapping memory device dominated its retention behaviors. [ABSTRACT FROM AUTHOR]

In this letter, we report on significant flexoelectric fatigue in lead-free (K,Na,Li)(Nb,Sb)O3 (KNNLS) ceramics. In the ferroelectric phase of KNNLS, the observed effective transverse flexoelectric coefficient, which is initially as high as 1 μC/m, decreases nonlinearly with increasing cycles of strain gradient, and the fatigue regulation is well reproduced by a stretched exponential function. By comparing the time dependence of dielectric permittivity and ferroelectricity in KNNLS ceramics, we conclude that large flexoelectric and flexocoupling coefficients in the ferroelectric phase originate mainly from ferroelectricity and that the related flexoelectric fatigue is likely due to the pinning effect of ferroelectric domains. [ABSTRACT FROM AUTHOR]

The conduction behavior of metal-induced laterally crystallized (MILC) polycrystalline silicon (poly-Si) was studied and compared to that of the conventional solid-phase crystallized and low-pressure chemical vapor deposited poly-Si. MILC poly-Si was found to exhibit superior electrical properties, with significantly lower grain-boundary (GB) trap density, as well as much higher carrier mobility and conductivity. Furthermore, a unique anisotropic conduction behavior was discovered in MILC poly-Si, with the resistivity and its activation energy showing remarkable difference for conduction transverse or parallel to the MILC direction. These phenomena have been related to the fluctuation of the potential barrier associated with the longitudinal GBs separating the relatively ordered elongated grains in MILC poly-Si. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Oxide-based binary resistive switching memories using metal nitride as one of the electrodes usually have a limited ratio of the resistances of the high- and low-resistance states. Here, we propose a competing mechanism to enhance the switching ratio by modifying the high-resistance state with extra inherent interfacial oxygen diffusion against what happens at the oxide/nitride interface. This is implemented in Pt/ZrO2/Ta2O5/TaN bilayer structures, where a resistance ratio above 104, about one to two orders of magnitude greater than that in Pt/Ta2O5/TaN monolayer structures, is achieved. This competing mechanism is further corroborated by the failed enhancement in the switching ratio when using an altered stacking arrangement of the two oxide layers. [ABSTRACT FROM AUTHOR]

We have fabricated GaN-based light-emitting diodes (LEDs) with different quantum well (QW) thicknesses to investigate the influence of the quantum confined Stark effect (QCSE) and carrier localization effect on the carrier recombination processes under both direct current (DC) and alternating current (AC) biases. At low current density, QCSE dominates the carrier recombination and decreases the radiative recombination rate. With increasing the current density, QCSE will be screened by injected carriers, and both optical power and modulation bandwidth can be increased. When the polarization field is completely compensated, the carrier localization effect starts to dominate. By reducing the influence of the QCSE and carrier localization effect, a high modulation bandwidth of ∼700MHz was achieved at a low current density of 425A/cm2 for the LED with 5 nm QW. Our findings will pave an alternative solution for co-optimization of the modulation bandwidth and efficiency for LEDs at a relatively low current density for visible light communications. [ABSTRACT FROM AUTHOR]

The reproducible and reliable resistive switching is observed in the ultrathin Bi2FeCrO6 (BFCO) epitaxial film on (001) SrTiO3 substrate with SrRuO3 as the bottom electrode. The as-grown BFCO film allows its ferroelectric polarization switching under external electric field. With a 100-nmradius tip contacting film surface, a stable bipolar resistive switching was observed through the conductive atomic force microscope. Furthermore, the resistive switching at negative bias was observed and its high/low current ratio is above 15 among a thousand of current versus voltage curves measured by the scanning tunneling microscope with a non-contacting nm-scale tip. It is argued that this transport mechanism is due to quantum tunneling, and the resistive switching in these junctions is because of ferroelectric switching. [ABSTRACT FROM AUTHOR]

The exploration of colossal dielectric permittivity (CP) materials with low dielectric loss in a wide range of frequencies/temperatures continues to attract considerable interest. In this paper, we report CP in (Al+Nb) co-doped rutile SnO2 ceramics with a low dielectric loss at room temperature. Al0.02Nb0.05Sn0.93O2 and Al0.03Nb0.05Sn0.92O2 ceramics exhibit high relative dielectric permittivities (above 10³) and low dielectric losses (0.015

We have conducted an in-situ upconversion (UC) mechanism study through fluorescence enhancement induced by electric field in the Er3+ doped 0.75Pb(Mg1/3Nb2/3)O3-0.25PbTiO3 transparent ceramic. Under the excitation of a 980 nm diode laser, the sample shows a strong green UC fluorescence, which increases with electric field. A maximum enhancement of 150% was achieved in fluorescence intensity by the applied electric field due the lowering of crystal symmetry by the electric field induced strains. Combined with an in-situ analysis of time-resolved spectra, we proved that the dominant UC mechanism in this system should be the energy transfer (ET) process. [ABSTRACT FROM AUTHOR]

Noncontact monitoring temperature is very important in modern medicine, science, and technologies. The fluorescence intensity ratio (FIR) technique based on the Boltzmann distribution law exhibits excellent application potential, but the observed FIR deviates from the Boltzmann distribution law in the low temperature range. We propose a fluorescence intensity ratio relation FIR*= ηFIR by introducing a quantity η representing thermal population degree, which can be obtained from measured fluorescencedecay curves of the upper emitting level. Using Eu3+ as an example, the method is confirmed that the deviated FIR is able to be corrected and return to follow the Boltzmann law. [ABSTRACT FROM AUTHOR]

The prototypical charge-trapping memory devices with the structure p-Si/Al2O3/(Ta2O5)x(Al2O3)1-x/Al2O3/Pt(x = 0.5, 0.3, and 0.1) were fabricated by using atomic layer deposition and RF magnetron sputtering techniques. A memory window of 7.39V with a charge storage density of 1.97 × 1013 cm-2 at a gate voltage of ±11V was obtained for the memory device with the composite charge trapping layer (Ta2O5)0.5(Al2O3)0.5. All memory devices show fast program/erase speed and excellent endurance and retention properties, although some differences in their memory performance exist, which was ascribed to the relative individual band alignments of the composite (Ta2O5)x(Al2O3)1-x with Si. [ABSTRACT FROM AUTHOR]

A self-pumped phase conjugate reflection induced by another mutually coherent incident beam has been observed and explained successfully for the first time in a photorefractive crystal BaTiO3. Other relevant phenomena, such as the destruction of the coupling channel when two incident beams are mutually coherent, have also been studied. Possible applications are pointed out. [ABSTRACT FROM AUTHOR]

An effective method to generate traps at the interface was developed to enhance the charge trapping capability of HfO2/Al2O3 multilayered memory devices. A high charge density was obtained in the inter-diffusion layer in which additional trap sites could be created by thermal-treatment induced inter-diffusion. By keeping the consistent thickness of the charge trapping layer and increasing the number of the inter-diffusion layers, more traps can be introduced in the charge trapping layer. So, creating more trap sites by enhancing the inter-diffusion at the interface of different high-k dielectrics could be a potential choice for future memory applications. [ABSTRACT FROM AUTHOR]