On a development possibility of a tunable microwave passband filter based on dielectric resonator with high TC film

Measurements of temperature dependence of "YBa₂Cu₃O_7-x thin film on SrTiO₃ substrate" structure effective impedance have been performed in 8-mm wave band by means of quasioptical dielectric resonator with whyspering gallery modes. This dependence appeared to be a series of quasiperiodical oscillation peaks of high steepness. Experiments on investigation of external electric field impact on parameters of the resonator loaded by the structure were carried out. It was found that electric field up to 3 kV/cm leads to a shift of the effective impedance temperature dependence to lower temperature and doesn't impact on the form of the dependence. Herewith the field of 2.5 kV/cm causes a shift of the resonator frequency by 108 MHz with negligible reduction of the loaded quality factor Q_L (less than in 1.5 times). Operating frequency was 35 GHz and loaded quality was about 10³. A proposal about possibility of tunable passband filter design and ways of retuning bandwidth enhancment are discussed.     

Phase Inversion: A Universal Method to Create High‐Performance Porous Electrodes for Nanoparticle‐Based Energy Storage Devices

The intrinsic properties of nanoscale active materials are always excellent for energy storage devices. However, the accompanying problems of ion/electron transport limitation and active materials shedding of the whole electrodes, especially for high‐loaded electrode composed of nanoparticles with high specific surface area, bring down their comprehensive performance for practical applications. Here, this problem is solved with the as proposed “phase inversion” method, which allows fabrication of tricontinuous structured electrodes via a simple, convenient, low cost, and scalable process. During this process, the binder networks, electron paths, and ion channels can be separately interconnected, which simultaneously achieves excellent binding strength and ion/electron conductivity. This is verified by constructing electrodes with sulfur/carbon (S/C) and Li₃V₂(PO4)₃/C (LVP/C) nanoparticles, separately delivering 869 mA h g^?1 at 1 C in Li–S batteries and 100 mA h g^?1 at 30 C in Li–LVP batteries, increasing by 26% and 66% compared with the traditional directly drying ones. Electrodes with 7 mg cm^?2 sulfur and 11 mg cm^?2 LVP can also be easily coated on aluminum foil, with excellent cycling stability. Phase inversion, as a universal method to achieve high‐performance energy storage devices, might open a new area in the development of nanoparticle‐based active materials.     

基于高Q值Si3N4片上光学微腔的孤子光频梳

高Q值片上微腔已被证明是一种性能优异的克尔孤子光学频率梳产生平台。由片上多模波导构成的Si₃N₄微腔可以同时实现产生暗孤子所必须的高品质因子和反常色散。为了进一步降低产生单孤子光频梳的阈值功率,文章设计了一种具有欧拉弯曲的新型跑道型Si₃N₄微腔,与传统的圆形弯曲波导相比,跑道型微腔直波导连接处弯曲半径的突然变化被显著抑制,这抑制了高阶模式耦合并降低了传播损耗,从而获得了超过5×10⁶的品质因子。基于该新型微腔,使用辅助激光加热方法仅用47mW泵浦激光器(估计片上泵浦功率为33mW)就产生了重复频率在Ka波段且带宽超过20nm(对应于129fs的脉冲持续时间)的单孤子微腔光频梳。     

Electrical and thermoelectric properties of ZnO under atmospheric and hydrostatic pressure

Temperature (for T = 77–400 K) and pressure (for P ≤ 8 GPa) dependences of conductivity σ(T,P). Hall coefficient R _H(T, P), and Seebeck coefficient Q(T) were studied in single-crystal n-ZnO samples with the impurity concentration N _i = 10¹⁷ ? 10¹⁸ cm^?3 and free-electron concentration n = 10¹³?10¹⁷ cm^?3. Single crystals were grown by the hydrothermal method. Dependence of the ionization energy of a shallow donor level on the impurity concentration E _d1(N _d) is determined, along with the pressure coefficients for the ionization energy ?E _d1/?P and static dielectric constant ?x/?P. A deep defect level with the energy E _d2 = 0.3 eV below the bottom of the conduction band is found. The electron effective mass is calculated from the obtained data on the kinetic coefficients R _H(T) and Q(T).     

Electro-ultrasonic spectroscopy of polymer-based thick film layers

We have studied the properties of polymer-based thick film layers by electro-ultrasonic spectroscopy. Electro-ultrasonic spectroscopy method is based on the interaction between ultrasonic vibrations and electrical conductivity of solids. The ultrasonic vibrations of frequency f_U change the contact area between conducting grains in the thick film structure and then the resistance is modulated by the frequency of ultrasonic excitation. An intermodulation voltage is created on this structure. It depends on the value of AC current varying with frequency f_E and on the ultrasonic excited resistance change ΔR varying with frequency f_U. We have measured the intermodulation voltage U_m for a set of polymer-based thick film resistors made by different resistive pastes. It was found that for given sample the intermodulation component of frequency f_m = f_E − f_U increases linearly with electric excitation for the constant ultrasonic excitation. We have normalized the intermodulation voltage U_m by the electric current I_E and this quantity is proportional to the ultrasonic excited resistance change ΔR. The relative resistance change ΔR/R_X is of the order of 10⁻⁷–10⁻⁴. From the comparison of the results measured for the samples made by the same resistive pastes it follows, that relative resistance change ΔR/R_X can be used as an indicator of sample quality.     

Electrical properties of Pb1−xCdxS epitaxial films

We have measured the resistivity ρ and Hall coefficient R_H at 300, 77, and 4.2 K of p-type Pb_1−XCd_XS epitaxial films as a function of substrate temperature T_s, film thickness d, and composition x. The films were vapor deposited on cleaved (111) BaF₂ (111) SrF₂ , and (001) NaCl and polished (001) BaF₂ substrates. The Hall mobility μ_H at 77 K of p-type PbS films increased approximately linearly from 1 × 10⁴ to 2 × 10⁴ cm² V⁻¹ sec⁻¹ as T_s was varied from 400 to 500°C, respectively. Both μ_H and R_H increased with d due to the presence of a strong p-type surface layer on the exposed surface. The x of the films was controlled by the x of the source material and T_s. The mole fraction of CdS could be varied between 0.002 < x < 0.06 by varying T between 513 and 410°C, respectively, and using source material with x = 0.06. The electrical properties of samples grown on freshly cleaved (111) BaF₂ and (111) SrF₂ were essentially identical even though the lattice constant of SrF₂ is a better match to Pb_1−XCd_XS than BaF₂. The R_H and μ_H at 77 K were independent of thickness for low substrate temperatures and were observed to increase with increasing thickness for high substrate temperatures. The μ_H increased with decreasing temperature and became temperature independent below about 30 K, which is similar to the behavior observed in other lead salt compounds. However, the magnitude of μ_H was considerable lower throughout the 300 to 4.2 K temperature range than for PbS films. The R_H showed little temperature variation, which is typical lead salt behavior. Supported by Naval Surface Weapons Center Independent Research Funds.     

Small two-dimensional arrays of mid-wavelength infrared HgCdTe diodes fabricated by reactive ion etching-induced p-to-n-type conversion

The reactive ion etching (RIE) technique has been shown to produce high-performance n-on-p junctions by localized-type conversion of p-type mid-wavelength infrared (MWIR) HgCdTe material. This paper presents variable area analysis of n-on-p HgCdTe test diodes and data on two-dimensional (2-D) arrays fabricated by RIE. All devices were fabricated on x = 0.30 to 0.31 liquid-phase epitaxy (LPE) grown p-type (p = ∼1 × 10¹⁶ cm⁻³) HgCdTe wafers obtained from Fermionics Corp. The diameter of the circular test diodes varied from 50 μm to 600 μm. The 8 × 8 arrays comprised of 50 μm × 50 μm devices on a 100-μm pitch, and all devices were passivated with 5000 ? of thermally deposited CdTe. At temperatures >145 K, all devices are diffusion limited; at lower temperatures, generation-recombination (G-R) current dominates. At the lowest measurement temperature (77 K), the onset of tunneling can be observed. At 77 K, the value of 1/R₀A for large devices shows quadratic dependence on the junction perimeter/area ratio (P/A), indicating the effect of surface leakage current at the junction perimeter, and gives an extracted bulk value for R₀A of 2.8 × 10⁷ Ω cm². The 1/R₀A versus P/A at 195 K exhibits the well-known linear dependence that extrapolates to a bulk value for R₀A of 17.5 Ω cm². Measurements at 77 K on the small 8 × 8 test arrays were found to demonstrate very good uniformity with an average R₀A = 1.9 × 10⁶ Ω cm² with 0° field of view and D* = 2.7 × 10¹¹cm Hz^1/2/W with 60° field of view looking at 300 K background.     

Improvement of the morphological and electrical characteristics of Al3+, Fe3+ and Bi3+-doped TiO2 compact thin films and their incorporation into hybrid solar cells

Compact titanium dioxide (TiO₂) hole-blocking layers are commonly employed in organic-inorganic solar cells, however, their importance in terms of morphology and electrical conductivity is frequently overlooked in this novel type of solar energy converters. In this work, single TiO₂ thin films were prepared by a sol-gel method, observing large pinhole densities and low electrical conductivities. As a means to solve the morphological issue, the deposition of a second TiO₂ film was explored, which effectively reduced the surface irregularities obtained in single oxide films. The limited electrical conductivity of single and double layers was successfully increased by doping with the trivalent cations of aluminum, iron (III) and bismuth (III), observing an increase from 2.48 × 10⁻⁸ S/cm for an undoped TiO₂ double layer to 51.41 × 10⁻⁸ S/cm for a Fe³⁺-doped TiO₂ double layer. The incorporation of these hole blocking layers in hybrid solar cells led to further insights in the important role of trivalent doping cations in the transference and transport of electrons on the surface and in the bulk of the prepared TiO₂ compact films.     

Transport phenomena in the anisotropic layered compounds MeBi4Te7 (Me = Ge, Pb, Sn)

The transport coefficients (the Nernst-Ettingshausen coefficient Q ₁₂₃, electrical conductivity ??₁₁, thermal conductivity ?? _ii , the Seebeck coefficients S ₁₁ and S ₃₃, and the Hall coefficient R ₂₁₃) in samples of layered compounds of the homologous series A^IVB^VI-A ₂ ^V B ₃ ^VI (A^IV = Ge, Sn, Pb; A^V = Bi, Sb; B^VI = Te), specifically, SnBi₄Te₇ and PbBi₄Te₇ (of n-type conductivity), have been experimentally studied in the temperature range of 77?C400 K. The crystals were grown by the Czochralski method. Analysis showed that the obtained data on the transport phenomena in SnBi₄Te₇ and PbBi₄Te₇ can be considered in the one-band energy spectrum model. Comparison of the parameters found for the stoichiometric samples demonstrated that the electron density of states and the fraction of electrons scattered at impurity ions increase when passing from GeBi₄Te₇ to SnBi₄Te₇ and PbBi₄Te₇. It is found that additional doping of PbBi₄Te₇ with cadmium and silver significantly affects its electronic and phonon systems, just as doping with copper affects the electric and thermal properties of GeBi₄Te₇.     

Microstructure coarsening during static annealing of 60Sn40Pb solder joints: III intermetallic compound growth kientics

The growth of the total (Cu₃Sn+Cu₆Sn) intermetallic compound layer in Cu-60Sn40Pb solder joints during static annealing at 50°C to 150°C was described by the equation hi=h_o+A_o exp(−Q_a/RT)t^p with h_o=0–0.3 μm, p=0.38–0.70, A_o=1.9×10⁻⁴–3.4×10⁻⁴ m/s^p, and Q_a=25.5–30.9 kJ/mole. These constants are within the range of those obtained by others and give values of D_o and Q which are in reasonable accord with those for the diffusion coefficients in Cu₃Sn and Cu₆Sn₅ determined in diffusion couples. The deviation of the values of the time exponent p from the ideal of 0.5 for diffusion growth may be due to inaccuracies or errors pertaining to the measured thickness (especially h_o) and the complex nature of the diffusion process.     

Electrical properties of substitutionally doped cvd amorphous silicon

Electrical properties of phosphorus doped amorphous Si (a-Si) prepared by chemical vapor deposition (CVD) have been investigated. The gaseous impurity ratio R = Np_PH3/ N_SiH4, was varied from 2×10^-6 to 1.1×10^-2. When the ratio R exceeds R_C =4.2 ×10^-4, the room temperature conductivity is dominated by the conduction in the extended states and rapidly increases with R up to 10^-1 (Ω-cm)^-1 at the ratio R = 1.1×10^-1. It is found that phosphorus doping below R_C results in the compensation of native defects or dangling bonds and that an efficient shift of the Fermi level as well as a narrowing of the tailing width of the extended states take place by doping above R_C. The magnetoresistance is explained as a modification of the spin-flip relaxation time of localized electrons by external magnetic field.     

Analysis of the magnetic properties of (La<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>0.93</Subscript>MnO<Subscript>3</Subscript> manganites at high temperatures

For the first time, the Faraday method is used to measure the temperature dependence of paramagnetic susceptibility χ(T) of (La_{1 ? x} Sr _x )_0.93MnO₃ (x = 0.2, 0.25, or 0.3) manganites in the temperature interval 60–850°C. It is demonstrated that the dependences have two kinks and three linear sections. The kink of curve χ^?1(T) is related to polymorphic transformations (Q′ → Q* and Q* → R) that take place in the crystal lattices of the samples. The main magnetic characteristics of the samples are determined with the least-squares processing of curve χ^?1. Is is demonstrated that dependence χ^?1(T) obeys the Curie-Weiss law. The energy state of the magnetoactive manganese atom in the Q′-and Q*-phase samples is close to the energy state of a free Mn²⁺ ion. In the R phase, this state is close to the state of a free Mn³⁺ ion.     

Low power resistive switching memory using Cu metallic filament in Ge0.2Se0.8 solid-electrolyte

Bipolar resistive switching memory device using Cu metallic filament in Au/Cu/Ge_0.2Se_0.8/W memory device structure has been investigated. This resistive memory device has the suitable threshold voltage of V_th > 0.18 V, good resistance ratio (R_High/R_Low) of 2.6 × 10³, good endurance of >10⁴ cycles with a programming current of 0.3 mA/0.8 mA, and 5 h of retention time at low compliance current of 10 nA. The low resistance state (R_Low) of the memory device decreases with increasing the compliance current from 1 nA to 500 μA for different device sizes from 0.2 μm to 4 μm. The memory device can work at very low compliance current of 1 nA, which can be applicable for extremely low power-consuming memory devices.     

600-V shielded trench split-gate VDMOS improving the figure of merit

ABSTRACT

A shielded trench split-gate vertical double-diffused metal-oxide-semiconductor field-effect transistor (ST-SG-VDMOS) is proposed, and the analytical model for the main components of specific on-resistance (R _on,sp) is derived. The polysilicon vertical field plate (VFP) with the thick oxide layer in every trench modulates the electric field distribution to ensure no degradation of breakdown voltage (BV). Moreover, due to the strong assistant depletion effect caused by VFPs, R _on,sp is effectively reduced by increasing the doping concentration among trenches. Not only the gate is shielded from the drain bias by VFPs, but also the split-gate structure is adopted to reduce the specific gate-drain charge (Q _gd,sp). When compared to the conventional VDMOS (C-VDMOS) in 600 V class, the simulation results by the technology computer aided design (TCAD) show that the R _on,sp and Q _gd,sp in ST-SG-VDMOS decrease from 128.8 to 85.77 mΩ·cm² and from 88.3 to 14.1 nC/cm², respectively. Finally, the product of R _on,sp and Q _gd,sp called as figure of merit is reduced by 89.4% in the ST-SG-VDMOS. The performance of ST-SG-VDMOS has been significantly improved when compared with C-VDMOS.     

The photoassisted MOVPE growth of ZnSSe using tertiary-butylmercaptan

We have conducted a study of the compositional control of epitaxial ZnS_ySe_1-y grown by photoassisted metal organic vapor phase epitaxy (MOVPE) (250 torr, 340°C, UV=14 mW/cm²) on GaAs (100) substrates. We have achieved lattice matched ZnSSe films on GaAs substrates using photoassisted growth using dimethylzinc (DMZn), dimethylselenide (DMSe), and tertiary-butylmercaptan (t-BuSH) as precursors. In addition, we have obtained sulfur compositions (y), ranging from 0.023 to unity (ZnS). The growth rate of the ZnS was 1 μm/h, which was previously unattainable by our group using diethylsulfur. The closely lattice matched sample (y=0.07 as determined by high resolution x-ray diffraction) showed a near band edge peak intensity (NBE) to deep level emission intensity (DLE) ratio of 77 to 1, as determined by room temperature photoluminescence measurements. We have examined the sulfur incorporation as a function of source mole fractions, UV intensity, and growth temperature and found that optimized growth conditions (optimized for range of compositions possible, and NBE/DLE ratio) are X_DMZn=1.5 × 10⁻⁴, X_DMSe=3×10⁻⁴, UV=14 mW/cm², growth temperature=340°C. X_DMZn and X_DMSe are the mole fractions of DMZn and DMSe, respectively. We have found the growth rate to be 1 μm/h for y=0.023 to 0.24 for these optimized conditions. It was found that to achieve sulfur compositions of less than 0.9, the t-BuSH mole fractions had to be kept low. Higher UV intensities increased the incorporation of selenium, while also lowering the material quality (NBE/DLE ratios). We have shown that the optical material qualities of ZnSSe films grown with t-BuSH are much better than ZnSSe films grown with DES.     

Defective 2D Covalent Organic Frameworks for Postfunctionalization

Defects are deliberately introduced into covalent organic frameworks (COFs) via a three‐component condensation strategy. The defective COFs (dCOF‐NH₂‐Xs, X = 20, 40, and 60) possess favorable crystallinity and porosity, as well as have active amine functional groups as anchoring sites for further postfunctionalization. By introducing imidazolium functional groups onto the pore walls of COFs via the Schiff‐base reaction, dCOF‐ImBr‐Xs‐ and dCOF‐ImTFSI‐Xs‐based materials are employed as all‐solid‐state electrolytes for lithium‐ion conduction with a wide range of working temperatures (from 303 to 423 K), and the ion conductivity of dCOF‐ImTFSI‐60‐based electrolyte reaches 7.05 × 10^?3 S cm^?1 at 423 K. As far as it is known, it is the highest value for all polymeric crystalline porous material based all‐solid‐state electrolytes. Furthermore, Li/dCOF‐ImTFSI‐60@Li/LiFePO₄ all‐solid Li‐ion battery displays satisfactory battery performance under 353 K. This work not only provides a new methodology to construct COFs with precisely controlled defects for postfunctionalization, but also makes them promising candidate materials as all‐solid‐state electrolytes for lithium‐ion batteries operate at high temperatures.     

High-contrast top-emitting organic light-emitting diodes with AlO1.086 dark-and-conductive electrodes

To improve the poor contrast of conventional organic light-emitting diodes (OLEDs) resulting from highly reflective metal electrode, a dark-and-conductive electrode with an average reflectance of 28.1% and a resistivity of 4.6 × 10⁻⁴ Ω/cm was fabricated by fine-tuning O₂/Ar flow ratio on aluminum electrode sputtering. X-ray photoelectron spectroscopy analysis indicates pure aluminum and aluminum oxide coexist in the fabricated dark-and-conductive electrodes. With the proposed dark-and-conductive AlO_1.086 electrodes, top-emitting OLEDs exhibit significantly improved contrast, whereas maintain moderate luminous efficiency. The demonstrated AlO_1.086 dark-and-conductive electrodes can potentially replace the circular polarizers for high-contrast OLED display applications.     

Facile Design of Sulfide-Based all Solid-State Lithium Metal Battery: In Situ Polymerization within Self-Supported Porous Argyrodite Skeleton

All solid-state batteries holds great promise for superiorly safe and high energy electrochemical energy storage. The ionic conductivity of electrolytes and its interfacial compatibility with the electrode are two critical factors in determining the electrochemical performance of all solid-state batteries. It is a great challenge to simultaneously demonstrate fantastic ionic conductivity and compatible electrolyte/electrode interface to acquire a well-performed all solid-state battery. By in situ polymerizing poly(ethylene glycol) methyl ether acrylate within a self-supported 3D porous Li-argyrodite (Li₆PS₅Cl) skeleton, the two bottlenecks are tackled successfully at once. As a result, all solid-state lithium metal batteries with a 4.5 V LiNi_0.8Mn_0.1Co_0.1O₂ cathode designed by this integrated strategy demonstrates a high Coulombic efficiency exceeding 99% at room temperature. Solid-state nuclear magnetic resonance data suggest that Li⁺ mainly migrates along the continuous Li₆PS₅Cl phase to result in a room temperature conductivity of 4.6 × 10⁻⁴ S cm⁻¹, which is 128 times higher than that of the corresponding polymer. Meanwhile, the inferior solid–solid electrolyte/electrode interface is integrated via in situ polymerization to lessen the interfacial resistance significantly. This study thereby provides a very promising strategy of solid electrolyte design to simultaneously meet both high ionic conductivity and good interfacial compatibility towards practical high-energy-density all solid-state lithium batteries.     

Chemically Resistant,Shapeable, and Conducting Metal‐Organic Gels and Aerogels Built from Dithiooxamidato Ligand

Metal‐organic gels (MOGs) appear as a blooming alternative to well‐known metal‐organic frameworks (MOFs). Porosity of MOGs has a microstructural origin and not strictly crystalline like in MOFs; therefore, gelation may provide porosity to any metal‐organic system, including those with interesting properties but without a porous crystalline structure. The easy and straightforward shaping of MOGs contrasts with the need of binders for MOFs. In this contribution, a series of MOGs based on the assembly of 1D‐coordination polymer nanofibers of formula [M(DTA)]_n (M^II: Ni, Cu, Pd; DTA: dithiooxamidato) are reported, in which properties such as porosity, chemical inertness, mechanical robustness, and stimuli‐responsive electrical conductivity are brought together. The strength of the M? S bond confers an unusual chemical resistance, withstanding exposure to acids, alkalis, and mild oxidizing/reducing chemicals. Supercritical drying of MOGs provides ultralight metal‐organic aerogels (MOAs) with densities as low as 0.03 g cm^?3 and plastic/brittle behavior depending on the nanofiber aspect ratio. Conductivity measurements reveal a semiconducting behavior (10^?12 to 10^?7 S cm^?1 at 298 K) that can be improved by doping (10^?5 S cm^?1). Moreover, it must be stressed that conductivity of MOAs reversibly increases (up to 10^?5 S cm^?1) under the presence of acetic acid.