Tuned Transport Path of Perovskite MAPbI3-based Memristor Structure

In this study, the features of resistive random access memory (RRAM) employing a straightforward Cr/MAPbI₃/FTO three-layer structure have been examined and clarified. The device displays various resistance switching (RS) behavior at various sweep voltages between 0.5 and 5 V. The RS effect has a conversion in the direction of the SET and RESET processes during sweeping for a number of cycles at a specific voltage. The directional change of the RS processes corresponds to the dominant transition between the generation/recombination of iodide ion and vacancy in the MAPbI₃ perovskite layer and the electrochemical metallization of the Cr electrode under the influence of an electric field, which results in the conductive filament (CF) formation/rupture. At each stage, these processes are controlled by specific charge conduction mechanisms, including Ohmic conduction, space-charge-limited conduction (SCLC), and variable-range hopping (VRH). By identifying the biased voltage and the quantity of voltage sweep cycles, one can take a new approach to control or modulate the pathways for effective charge transport. This new approach is made possible by an understanding of the RS characteristics and the corresponding mechanisms causing the variation of RS behavior in the structure.     

Synthesis of highly conductive EDOT copolymer films via oxidative chemical in situ polymerization

Poly(3,4‐ethylenedioxythiophene)s (PEDOT) represent a class of conjugated polymers that can be potentially used as an electrode material for flexible organic electronics due to their superior conductivity and transparency. In this study, we demonstrate that the conductivity of a PEDOT containing copolymer film can be further enhanced by the oxidative chemical in situ copolymerization of a liquid film spun coated from monomer mixture (3,4‐ethylenedioxythiophene (EDOT) and 3‐thienyl ethoxybutanesulfonate (TEBS)), oxidant (iron(III) p‐toluenesulfonate (Fe(OTs)₃)), weak base (imidazole), and solvent (methanol). We investigated that the effect of the processing parameters such as the molar ratios TEBS/EDOT, IM/EDOT, and Fe(OTs)₃/EDOT on the surface morphology, optical property, and the conductivity of the resulting copolymer films. These parameters have been optimized to achieve conductivities for the copolymer films as high as 170 S/cm compared with a conductivity of 30 S/cm for the pure PEDOT film synthesized using the same fabrication method. This conductivity enhancement for the copolymer films was found to be resulted from the fact that the addition of TEBS monomer reduces the copolymerization rate, leading to the formation of much more uniform film surface without defects and copolymers of higher molecular weight which increase the conductivity of the resulting copolymer film. The composition of two monomers in the copolymer film is not related to the variation of conductivity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1662–1673, 2008     

Theory and experiment of ultrahigh-gain gyrotron traveling waveamplifier

Physics and technology issues of importance to the high-gain gyrotron traveling wave amplifier (gyro-TWT) are investigated in theory and experiment. The gyro-TWT is known to be highly susceptible to spurious oscillations, especially in high gain operations. In the current study, oscillations of various origins are classified and characterized with detailed theoretical modeling. They are shown to be intricately connected to the interplay between the absolute/convective instabilities, circuit losses, and reflective feedback. Knowledge of these processes leads to the concept of an ultra high gain scheme which employs distributed wall losses for the suppression of spurious oscillations. A proof-of-principle Ka-band gyro-TWT experiment stable at zero drive has produced 93 kW saturated peak power at 26.5% efficiency and 70 dB gain, with a 3 dB saturated output power bandwidth of 3 GHz. The saturated gain is more than 30 dB beyond that previously achieved     

Poly(triarylamine): Its synthesis,properties, and blend with polyfluorene for white‐light electroluminescence

A new high‐molecular‐weight poly(triarylamine), poly[di(1‐naphthyl)‐4‐anisylamine] (PDNAA), was successfully synthesized by oxidative coupling polymerization from di(1‐naphthyl)‐4‐anisylamine (DNAA) with FeCl₃ as an oxidant. PDNAA was readily soluble in common organic solvents and could be processed into freestanding films with high thermal decomposition and softening temperatures. Cyclic voltammograms of DNAA and PDNAA exhibited reversible oxidative redox couples at the potentials of 0.85 and 0.85 V, respectively, because of the oxidation of the main‐chain triarylamine unit. This suggested that PDNAA is a hole‐transporting material with an estimated HOMO level of 5.19 eV. The absorption maximum of a PDNAA film appeared at 370 nm, with an estimated band gap of 2.86 eV from the absorption edge. Unusual multiple photoluminescence maxima were observed at 546 nm, and this suggested its potential application in white‐light‐emission devices. Nearly white‐light‐emission devices could be obtained with either a bilayer‐structure approach {indium tin oxide/poly(ethylenedioxythiophene):poly(styrene sulfonate)/PDNAA/poly[2,7‐(9,9‐dihexylfluorene)] (PF)/Ca} or a polymer‐blend approach (PF/PDNAA = 95:5). The luminance yield and maximum external quantum efficiency of the light‐emitting diode with the PF/PDNAA blend as the emissive layer were 1.29 cd/A and 0.71%, respectively, and were significantly higher than those of the homopolymer. This study suggests that the PDNAA is a versatile material for electronic and optoelectronic applications. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1727–1736, 2007     

非水电导滴定法测定磺化聚醚砜

在分析测试磺化聚醚砜时，包裹在ＳＰＥＳ中的自由硫酸常影响着测试结果。为此本文提出利用非水溶剂的区分效应和对ＳＰＥＳ的良好溶解性能，通过电导滴定分析ＳＰＥＳ和自由硫酸的混合产物。经过透析实验和采用不同碱式滴定剂进行非水滴定实验表明：电导滴定能简便，快速、准确地测出自由硫酸含量和磺化度。同时了相关实验和理论方面的讨论。     

Relationships between discrete-time and continuous-time algebraic riccati inequalities

The bilinear transformation is used to establish a direct relationship between a discrete-time algebraic Riccati inequality (DARI) and an associated continuous-time algebraic Riccati inequality (CARI). It is shown that under mild conditions, the DARI is solvable if and only if the corresponding CARI is solvable. The relationship between the DARI and the CARI is then used to translate the general solvability conditions for a CARI given by Scherer into analogous conditions for the DARI. It is shown how such conditions can be applied to determine the solvability of a discrete-time H_∞ control problem whose solution set is characterized by two DARIs.     

Low dielectric thermoset. IV. Synthesis and properties of a dipentene‐containing cyanate ester and its copolymerization with bisphenol A dicyanate ester

A 2,6‐dimethylphenol‐dipentene dicyanate ester ( DPCY ) was synthesized from the reaction of 2,6‐dimethylphenol‐dipentene adduct and cyanogen bromide. The proposed structure was confirmed by Fourier transform infrared (FTIR), elemental analysis, mass, and nuclear magnetic resonance (NMR) spectra. DPCY was then cured by itself or cured with bisphenol A dicyanate ester ( BADCY ). Thermal properties of cured epoxy resins were studied using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), dielectric analysis (DEA), and thermogravimetric analysis (TGA). These data are compared with those of BADCY . The cured DPCY exhibits a lower dielectric constant (2.61 at 1 MHz), dissipation factor (29.3 mU at 1 MHz), thermal stability (5% degradation temperature and char yield are 429 °C and 17.64%, respectively), glass transition temperature (246 °C by TMA and 258 °C by DMA), coefficient of thermal expansion (33.6 ppm before Tg and 134.1 ppm after Tg), and moisture absorption (0.95% at 48 h) than those of BADCY , but higher moduli (5.12 GPa at 150 °C and 4.60 GPa at 150 °C) than those of the bisphenol A system. The properties of cured cocyanate esters lie between cured BADCY and DPCY , except for moduli. Moduli of some cocyanate esters are even higher than those of cured BADCY and DPCY . A positive deviation from the Fox equation was observed for cocyanate esters. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3986–3995, 2004     

Synthesis and crystal structure of core-modified benziporphyrin: thia-p-benziporphyrin

The core-modified 5,20-phenyl-10,15-tolyl-thia-p-benziporphyrin (SBzP) can be prepared from the condensation of 1,4-bis(α-hydroxyl-benzyl)benzene with 5,10-ditolyl-16-thia-5,10,15,17-tetrahydrotripyrrin using BF₃·OEt₂ as catalyst. Spectroscopic studies suggest an aromatic macrocycle with a rapid flipping phenylene ring. SBzP exhibits a tilted phenylene ring and crystal packing shows dimeric structure with two SBzP rings linked by hydrogen bonding and π-π interaction. TFA acidified SBzPH₂²⁺ has a saddle-shaped dication porphyrin ring with two solvated trifluoroacetate and two solvated trifluoroacetic acid linked by hydrogen bondings.     

Effect of the repeated unit length of guest polymers on the molecular motion of polymer blends within a miscible window

The effect of the repeated unit length on the substantially increasing molecular motion and entropy change (?TΔS_m) of polymer blends was investigated with solid‐state ¹³C NMR and differential scanning calorimetry within a miscible window. The hydrogen‐bonding strength, from the formation of the phenolic–polyester interaction, was not high enough to overcome the breaking‐off of the self‐association of the phenolic. With respect to the increasing repeated unit length, the polyester resonance intensity of the solid‐state ¹³C NMR spectra was weakened because of the reduction in the cross‐polarization efficiency in highly mobile samples. The glass‐transition temperature of the blend and the proton spin–lattice relaxation time from NMR experiments were also reduced. The effect of the reduced hydrogen‐bonding strength on blending brought about a tendency of higher entropy (?TΔS_m) and higher molecular mobility of the blend. Accordingly, poly(decamethylene adipate) possessed the longest repeated unit length and exhibited the most mobile one in this phenolic/polyester blend family. The molecular segmental motion and entropy progressively increased while the repeated unit length of the guest polymers increased within a miscible window. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 679–686, 2003     

Array Waveguide Grating Based Fiber Lasers

Two array waveguide grating (AWGs) based fiber ring lasers are experimentally demonstrated. Either of them achieves wavelength discrete tuning of 32 nm, or yields simultaneously lasing up to four channels with -7 dBm output power for each channel.