微细电铸电流参数设计与实验研究

研究了镍的直流电铸和脉冲电铸的不同形式电流及其参数,同时,结合铸层表面形貌的影响分析,发现脉冲电铸在采取相对较大电流密度时,电铸质量和效率均优于直流电铸,实验优化后得到的占空比为10%,频率为1000Hz,平均电流密度为4A/dm2。最后,利用优化的电流参数实现了不同微结构的电铸成型。

An improved ASM-HEMT model for kink effect on GaN devices

With the analysis of experiment and theory on GaN HEMT devices under DC sweep,an improved model for kink effect based on advanced SPICE model for high electron mobility transistors(ASM-HEMT)is pro⁃posed,considering the relationship between the drain/gate-source voltage and kink effect.The improved model can not only accurately describe the trend of the drain-source current with the current collapse and kink effect,but also precisely fit different values of drain-source voltages at which the kink effect occurs under different gatesource voltages.Furthermore,it well characterizes the DC characteristics of GaN devices in the full operating range,with the fitting error less than 3%.To further verify the accuracy and convergence of the improved model,a load-pull system is built in ADS.The simulated result shows that although both the original ASM-HEMT and the improved model predict the output power for the maximum power matching of GaN devices well,the im⁃proved model predicts the power-added efficiency for the maximum efficiency matching more accurately,with 4%improved.

Formation mechanism of nanopores in dense films of anodic alumina

Constant-current anodization of pure aluminum was carried out in non-corrosive capacitor working electrolytes to study the formation mechanism of nanopores in the anodic oxide films.Through comparative experiments,nanopores are found in the anodic films formed in the electrolytes after high-temperature storage(HTS)at 130°C for 240 h.A comparison of the voltage-time curves suggests that the formation of nanopores results from the decrease in formation efficiency of anodic oxide films rather than the corrosion of the electrolytes.FT-IR and UV spectra analysis shows that carboxylate and ethylene glycol in electrolytes can easily react by esterification at high temperatures.Combining the electronic current theory and oxygen bubble mold effect,the change in electrolyte composition could increase the electronic current in the anodizing process.The electronic current decreases the formation efficiency of anodic oxide films,and oxygen bubbles accompanying electronic current lead to the formation of nanopores in the dense films.The continuous electronic current and oxygen bubbles are the prerequisites for the formation of porous anodic oxides rather than the traditional field-assisted dissolution model.

Interface engineering of advanced electrocatalysts toward alkaline hydrogen evolution reactions Author links open overlay panel

Developing efficient,stable,and low-cost electrocatalysts toward alkaline hydrogen evolution reactions(HER)in water electrolysis driven by renewable energy sources has always been discussed over the past decade.To reduce energy consumption and improve energy utilization efficiency,highly active electrocatalytic electrodes are essential for lowering the energy barrier of the HER.Catalysts featuring multiple interfaces have attracted significant research interest recently due to their enhanced physicochemical properties.Reasonable interface modulation can optimize intermediate active species’adsorption energy,improve catalytic active sites’selectivity,and enhance intrinsic catalytic activity.Here,we provided an overview of the latest advancement in interface engineering for efficient HER catalysts.We begin with a brief introduction to the fundamental concepts and mechanisms of alkaline HER.Then,we analyze and discuss current regulating principles in interface engineering for HER catalysts,focusing particularly on optimizing electron structures and modulating microenvironment reactions.Finally,the challenges and further prospects of interface catalysts for future applications are discussed.

Current efficiency of recycling aluminum from aluminum scraps by electrolysis

Extracting aluminum from aluminum alloys in AlCl3-NaCl molten salts was investigated. Al coating was deposited on the copper cathode by the method of direct current deposition using aluminum alloys as anode. The purity of the deposited aluminum is about 99.7% with the energy consumption of 3-9 kW＆#183;h per kg Al, and the current efficiency is 44%-64% when the deposition process is carried out under 100 mA/cm2 for 4 h at 170 ＆#176;C. The effects of experimental parameters, such as molar ratio of AlCl3 to NaCl, cathodic current density and electrolysis time, on the current efficiency were studied. The molar ratio of AlCl3 to NaCl has little effect on the current efficiency, and the increase of deposition temperature is beneficial to the increase of current efficiency. However, the increase of current density or electrolysis time results in the decrease of current efficiency. The decrease of current efficiency is mainly related to the formation of dendritic or powder deposit of aluminum which is easy to fall into the electrolyte.

Effect of oxide and fluoride addition on electrolytic preparation of Mg-La alloy in chloride molten salt

Mg-La alloys were prepared by constant voltage electrolysis in the molten salt system of MgC12-LaC13-KC1 at 750℃, with a graphite crucible as the anode and a tungsten rod as the cathode. The effect of oxide and fluoride addition on the electrolysis was investigated comprehensively. X-ray diffraction （XRD） was used to characterize some of the Mg-La alloy products and the sludges. As the content of MgO or La203 in the electrolyte increased, both the current efficiency and the mass of alloy product decreased, indicating that both MgO and La203 may take part in the reactions in the electrolyte. When the same mass of the oxide was added, compared with La203, MgO had a more pronounced effect on both the current efficiency and the mass of alloy product. XRD studies confirmed the formation of LaOC1 when MgO or LazO3 was added into the electrolyte. The formation of LaOCl sludge would be the main reason for the negative effect of the oxide addition on both the current efficiency and the mass of alloy. In the electrolytic system, the addition of CaF2 was not helpful to suppress the negative effect of MgO on the electrolysis, probably due to the complex reactions of the La compounds in the electrolyte.

Microstructures and electrochemical corrosion properties of Mg-Al-Pb and Mg-Al-Pb-Ce anode materials

Mg-Al-Pb alloy is a good candidate for the anode material of magnesium seawater battery. For improving the low current utilization efficiency of Mg-Al-Pb alloy, the influence of Ce on the microstructures and electrochemical corrosion properties in a 3.5% NaCl solution was investigated using scanning electron microscope and electrochemical measurements. The results indicate that Ce refines the grain structure of Mg-Al-Pb alloy. The formation of strip Al11Ce3 second phase promotes the uniform distribution of Mg17Al12 phase in Mg-Al-Pb-Ce alloy. The addition of cerium accelerates the discharge activity of Mg-Al-Pb alloy. Due to a large number of cathodic Al11Ce3 and MglyAla2 phases, Ce promotes the micro-galvanic corrosion and leads to larger corrosion current density and hydrogen evolution rate in Mg-Al-Pb-Ce alloy than those in Mg-Al-Pb alloy. However, Mg-Al-Pb alloy expresses smaller utilization efficiency than Mg-Al-Pb-Ce alloy because of grain detachment.

Electrical and mechanical properties of Cu-Cr-Zr alloy aged under imposed direct continuous current

The Cu-Cr-Zr alloys were aged at different temperatures for different time with different current densities. The results show that both the electrical conductivity and hardness are greatly improved after being aged with current at a proper temperature. The electrical conductivity increases approximately linearly with increasing current density while the hardness remains constant. The microstructure observation reveals that a much higher density of dislocations and nanosized Cr precipitates appear after the imposition of current, which contributes to the higher electrical conductivity and hardness. The mechanism is related with three factors： 1） Joule heating due to the current, 2） migration of mass electrons, 3） solute atoms, vacancies, and dislocations promoted by electron wind force.

Organic Light-Emitting Diodes by Doping Liq into an Electron Transport Layer

Organic light emitting diodes （OLEDs） incorporating an n-doping transport layer comprised of 8-hydroxy-quin- olinato lithium （Liq） doped into 4＇ 7- diphyenyl-1,10-phenanthroline （BPhen） as ETL and a p-doping transport layer that includes tetrafluro-tetracyano-quinodimethane （F4- TCNQ） doped into 4,4′, 4″-tris （3-methylphenylphenylamono） triphe- nylamine （m-MTDATA） are demonstrated. In order to examine the improvement in the conductivity of transport layers, hole-only and electron-only devices are fabricated. The current and power efficiency Of organic light-emitting diodes are improved significantly after introducing an n-doping （BPhen：33wt% Liq） layer as an electron transport layer （ETL） and a p-doping layer composed of m-MTDATA and F4- TCNQ as a hole transport layer （HTL）. Compared with the control device （without doping） , the current efficiency and power efficiency of the most efficient device （device C） are enhanced by approximately 51% and 89% ,respectively, while driving voltage is reduced by 29%. This improvement is attributed to the improved conductivity of the transport layers that leads to efficient charge balance in the emission zone.

Study on Methanol Oxidation at Pt and PtRu Electrodes by Combining in situ Infrared Spectroscopy and Differential Electrochemical Mass Spectrometry

Methanol oxidation reaction （MOR） at Pt and Pt electrode surface deposited with various amounts of Ru （denoted as PtxRuy, nominal coverage y is 0.17, 0.27, and 0.44 ML） in 0.1 mol/L HClO4＋0.5 mol/L MeOH has been studied under potentiostatic conditions by in situ FTIR spectroscopy in attenuated-total-reflection con guration and di erential electro-chemical mass spectrometry under controlled flow conditions. Results reveal that （i） CO is the only methanol-related adsorbate observed by IR spectroscopy at all the Pt and PtRu electrodes examined at potentials from 0.3 V to 0.6 V （vs. RHE）; （ii） at Pt0.56Ru0.44, two IR bands, one from CO adsorbed at Ru islands and the other from COL at Pt substrate are detected, while at other electrodes, only a single band for COL adsorbed at Pt is observed; （iii） MOR activity decreases in the order of Pt0.73Ru0.27〉Pt0.56Ru0.44〉Pt0.83Ru0.17〉Pt; （iv） at 0.5 V, MOR at Pt0.73Ru0.27 reaches a current e ciency of 50% for CO2 production, the turn-over frequency from CH3OH to CO2 is ca. 0.1 molecule/（site sec）. Suggestions for further improving of PtRu catalysts for MOR are provided.

Performance Analysis of RF Spiral Inductor with Gradually Changed Metal Width and Space

To decrease the metal losses of RF spiral inductor,a novel layout structure with gradually reduced metal line width and space from outside to inside is presented. This gradual changed inductor has less eddy-current effect than the conventional inductor of fixed metal width and space. So the series resistance can be reduced and the quality （Q） factor of the inductor relating to metal losses is increased. The obtained experimental results corroborate the validity of the proposed method. For a 6nH inductor on high-resistivity silicon at 2.46GHz,Q factor of 14.25 is 11.3% higher than the conventional inductor with the same layout size. This inductor can be integrated with radio frequency integrated circuits to gain better performance in RF front end of a wireless communication system.

Direct Tunneling Currents Through Gate Dielectrics in Deep Submicron MOSFETs

A direct tunneling model through gate dielectric s in CMOS devices in the frame of WKB approximation is reported.In the model,an im proved one-band effective mass approximation is used for the hole quantization, where valence band mixing is taken into account.By comparing to the experiments, the model is demonstrated to be applicable to both electron and hole tunneling c urrents in CMOS devices.The effect of the dispersion in oxide energy gap on the tunneling current is also studied.This model can be further extended to study th e direct tunneling current in future high-k materials.

Effectof Neutral Traps on Tunneling Current and SILC in Ultrathin Oxide Layer

The effect of neutral trap on tunneling currentin ultrathin MOSFETs is investigated by num erical analy- sis.The barrier variation arisen by neutral trap in oxide layer is described as a rectangular potential well in the con- duction band of Si O2 .The different barrier variation of an ultrathin metal- oxide- sem iconductor(MOS) structure with oxide thickness of4nm is numerically calculated.It is shown that the effect of neutral trap on tunneling cur- rent can not be neglected.The tunneling current is increased when the neutral trap exists in the oxide layer.This simple m odel can be used to understand the occurring mechanism of stress induced leakage current.

Influence of the Dosage of Surfactant on the Electrorheological Behaviors of Fluids

To investigate the influence of surface characteristics of particles on electrorheological (ER) fluids, water free complex strontium titanate particles were synthesized through the sol gel technique and different mass fraction of the surfactant was doped in particles and dispersed in silicon oil. The test shows that surface characteristics of particles have great influence on the behavior of ER fluids. Surface tension, surface polarity and interfacial polarization are strongly related to the surface status of the dispersed particles.

Gate breakdown of high-voltage P-LDMOS and improved methods

The failure experiments of the P-LDMOS （lateral double diffused metal oxide semiconductor） demonstrate that the high peak electrical fields in the channel region of high-voltage P-LDMOS will reinforce the hot-carrier effect, which can greatly reduce the reliability of the P-LDMOS. The electrical field distribution and two field peaks along the channel surface are proposed by Tsuprem-4 and Medici. The reason of resulting in the two electrical field peaks is also discussed. Two ways of reducing the two field peaks, which are to increase the channel length and to reduce the channel concentration, are also presented. The experimental results show that the methods presented can effectively improve the gate breakdown voltage and greatly improve the reliability of the P-LDMOS.

Influence of Device Narrowing on HALO-pMOSFETs' Degradation Under V_g= V_d/2 Stress Mode

The degradation characteristics of both wide and narrow devices under V _g= V _d/2 stress mode is investigated.The width-enhanced device degradation can be seen with devices narrowing.The main degradation mechanism is interface state generation for pMOSFETs with different channel width.The cause of the width-enhanced device degradation is attributed to the combination of width-enhanced threshold voltage and series resistance.

Numerical Study of Optimization of Layer Thickness in Bilayer Organic Light-Emitting Diodes

A numerical model for bilayer organic light-emitting diodes (OLEDs) is developed under the basis of trapped charge limited conduction.The dependences of the current density on the layer thickness,trap properties and carrier mobility of the hole transport layer (HTL) and emission layer (EML) in bilayer OLEDs of the structure anode/HTL/EML/cathode are numerically investigated.It is found that,for given values of the total thickness of organic layers,reduced depth of trap,total density of trap,and carrier mobility of HTL as well as EML,there exists an optimal thickness ratio of HTL to EML,by which a maximal quantum efficiency can be achieved.Through optimization of the thickness ratio,an enhancement of current density and quantum efficiency of as much as two orders of magnitude can be obtained.The dependences of the optimal thickness ratio to the characteristic trap energy,total density of trap and carrier mobility are numerically analyzed.

A Novel Empirical Model of I-V Characteristics for LDD MOSFET Including Substrate Current

A compact model for LDD MOSFET is proposed,which involves the hyperbolic tangent function description and the physics of device with emphasis on the substrate current modeling.The simulation results demonstrate good agreement with measurement,and show that deep submicron LDD MOSFET has larger substrate current than submicron device does.The improved model costs low computation consumption,and is effective in manifestation of hot carrier effect and other effects in deep submicron devices,in turn is suitable for design and reliability analysis of scaling down devices.

An SIT-BJT Operation Model for SITh in the Blocking State

A SIT-BJT model is proposed for static induction thyristors （SITh） operation in the blocking state. On the basis of the physical mechanism, this model is presented analytically in terms of governing equations that link the electrical parameters to the structural parameters. The model is verified by numerical simulation and theoretical analysis. Based on the model, the variations of the electrical parameters such as the potential barrier, the anode junction voltage drop, and the current amplification factor are studied and discussed.

Relationship Between Noise Figure and Equivalent Input Noise Current Spectral Density for Optical Receiver Design

Based on the equivalent circuit model of a two-port optical receiver front-end,the relationship between the equivalent input noise current spectral density and the noise figure is analyzed. The derived relationship has universal validity for determining the equivalent input noise current spectral density for optical receiver designs, as verified by measuring a 155Mb/s high-impedance optical receiver front.end. Good agreement between calculated and simulated results has been achieved.