一种新的求解ULSI双介质互连电容的模拟电荷法

论述了一种模拟电荷法与镜像格林函数法相结合,对模拟电荷用DFP法进行最优设置的提取双介质ULSI互连电容参数的基本算法,并与其它互连电容模拟软件模拟的结果进行了比较,相对偏差小于10%,表明这种新的模拟电荷法是有效的和可行的．     

用光电灵敏度法研究a—Si：H中的电荷放大效应

测量了缝电极和梳形电极ａ－Ｓｉ：Ｈ样品的光伏安特性和光电灵敏度,撮由光电灵敏度计算电荷放大增益的方法,由此法测现的ａ－Ｓｉ：Ｈ的电荷放大增益,在１０＾５Ｖ／ｃｍ电场下,高达４．３×１０＾３、本文从能态图讨论了ａ－Ｓｉ：Ｈ中电荷放大效应的产生过程。由测量的增产佃值计算了电子迁移率与寿命之积。     

栅氧化层及界面电荷对SiC MOSFET阈值电压稳定性的影响

阈值电压不稳定是SiC MOSFET的一个主要问题，而栅氧化层及界面电荷是引起器件阈值电压不稳定的关键因素。结合三角波电压扫描法和中带电压法提取了SiC MOSFET中的栅氧化层陷阱电荷面密度、界面陷阱电荷面密度和可动电荷面密度随应力时间的变化量，总结了三种电荷面密度变化量在不同应力时间下的变化规律，分析了其对器件阈值电压不稳定性的影响，同时推测了长时间偏压作用下SiC MOSFET阈值电压稳定性的劣化机制。测试结果表明，栅氧化层陷阱电荷面密度、界面陷阱电荷面密度和可动电荷面密度在不同偏压温度下随应力时间的变化规律不同，常温应力下器件阈值电压稳定性劣化主要与栅氧化层陷阱电荷有关，而高温下，则主要与界面陷阱电荷有关。     

电荷陷阱对器件稳定性的影响和监测电荷陷阱密度方法

本文论述了电荷陷阱对器件稳定性的影响;认为在器件制造过程中监测电荷陷阱密度是很重要的.本文介绍了雪崩注入法测量电荷陷阱密度的方法,并给出了测量结果.     

减小VDMOS密勒电容和反向恢复电荷的研究

提出了在VDMOS FET中减小密勒电容和反向恢复电荷的一种新结构，该结构结合了肖特基接触和分段多晶硅栅的方法。数值分析仿真结果表明，在相同器件单元尺寸下，该结构优于常规VDMOS FET，密勒电容Cgd可减少73．25％，Qgd和导通电阻优值减小65．02％，显示出很好的Qgd*Rds（on）改善性能；同时，反向恢复电荷减少了40．76％。     

力学参数测量时由残余电荷导致的误差分析

分析了用静电牵引法测量悬臂梁结构力学参数时 ,由于绝缘层中残余电荷的存在 ,对测试结果带来的影响 ;并提出了利用C V特性曲线确定残余电荷数量的方法 ,将求出的残余电荷数量从静电力的角度进行等效 ,从而求出考虑残余电荷后带来的阈值电压测试误差。该分析方法既适于提高悬臂梁、桥等用来测量力学参数的精度 ,也适于对静电执行器等的精确分析     

力学参数测量时由残余电荷导致的误差分析

分析了用静电牵引法测量悬臂梁结构力学参数时,由于绝缘层中残余电荷的存在,对测试结果带来的影响;并提出了利用C-V特性曲线确定残余电荷数量的方法,将求出的残余电荷数量从静电力的角度进行等效,从而求出考虑残余电荷后带来的阈值电压测试误差.该分析方法既适于提高悬臂梁、桥等用来测量力学参数的精度,也适于对静电执行器等的精确分析.     

液晶面板PI层电荷累积和释放过程分析

液晶显示器的聚酰亚胺配向层(Polyimide,PI)电荷累积过程属于凝聚态物理的电介质理论范畴,由于电介质物理理论还不够完整,造成液晶显示器PI层电荷累积和释放过程机理不甚清晰。文章应用麦克斯韦方程组分析液晶PI层表面电荷累积过程,应用可将快慢效应分开的时域谱学理论分析慢电荷的释放过程,得出液晶面板PI层和液晶层接触面电荷累积与两者的介电常数和电导率的关系,以及累积慢电荷的释放时间常数与PI层厚度的关系。     

砷化镓声电荷输运的二维互作用模型

本文对砷化镓Ｓｃｈｏｔｔｋｙ－Ｎ结构的埋沟声电荷输运器件中的信号电荷包与声表面波非线性互作用建立了二维模型．研究了电荷包的声表面波输运特性，给出了包内信号电行密度分布，电荷包形状及电荷量随器件电荷加载、沟道常数等特性参量的变化特性．     

任意电压源输入下开关电容网络分析的回路电荷法

本文提出了一种适用于开关电容网络精确分析的回路电荷法。该网络包含电容、独立电压源,开关和零极子(nullors)。该方法适用于任意K相开关状态,能处理任意的连续时间和离散时间输入。用回路电荷法,还导出了用输入电压表示电容电压的精确表达式。     

Diffusion-Controlled Z-Scheme-Steered Charge Separation across PDI/BiOI Heterointerface for Ultraviolet,Visible, and Infrared Light-Driven Photocatalysis

Constructing heterojunctions is an efficient approach for enhancing charge separation to optimize photoreactivity. Although the aligned built-in electric fields across the heterointerface are generally considered as the main driving force for charge separation, diffusion-controlled charge separation also happens, which is poorly investigated in photocatalytic heterojunctions. Here, a perylene-3,4,9,10-tetracarboxylic diimide (PDI)–bismuth oxyiodide (BiOI) heterojunction is elaborately fabricated by in situ successive ion layer adsorption and reaction (SILAR) methods. Utilizing Kelvin probe force microscopy (KPFM), the local separation of photogenerated charge carriers across the heterointerface is directly mapped, which obeys a Z-scheme mechanism. Experimental results and theoretical simulations reveal that the differences of electron densities between PDI and BiOI enable a diffusion-controlled charge separation process, which overwhelm that of built-in electric fields across heterointerfaces. Benefiting from the effective charge separation driven by a diffusion-controlled driving force, this PDI/BiOI heterojunction exhibits superior photocatalytic activities even under infrared (IR)-light irradiation. These findings highlight the importance of diffusion-controlled charge separation, and also offer useful roadmaps for the design of high-performance heterojunction photocatalysts for down-to-earth applications.     

Quantification of Temperature-Dependent Charge Separation and Recombination Dynamics in Non-Fullerene Organic Photovoltaics

Transient optical spectroscopy is used to quantify the temperature-dependence of charge separation and recombination dynamics in P3TEA:SF-PDI₂ and PM6:Y6, two non-fullerene organic photovoltaic (OPV) systems with a negligible driving force and high photocurrent quantum yields. By tracking the intensity of the transient electroabsorption response that arises upon interfacial charge separation in P3TEA:SF-PDI₂, a free charge generation rate constant of ≈2.4 × 10¹⁰ s⁻¹ is observed at room temperature, with an average energy of ≈230 meV stored between the interfacial charge pairs. Thermally activated charge separation is also observed in PM6:Y6, and a faster charge separation rate of ≈5.5 × 10¹⁰ s⁻¹ is estimated at room temperature, which is consistent with the higher device efficiency. When both blends are cooled down to cryogenic temperature, the reduced charge separation rate leads to increasing charge recombination either directly at the donor-acceptor interface or via the emissive singlet exciton state. A kinetic model is used to rationalize the results, showing that although photogenerated charges have to overcome a significant Coulomb potential to generate free carriers, OPV blends can achieve high photocurrent generation yields given that the thermal dissociation rate of charges outcompetes the recombination rate.     

Photovoltaic Function and Exciton/Charge Transfer Dynamics in a Highly Efficient Semiconducting Copolymer

Exciton dissociation is a key step for the light energy conversion to electricity in organic photovoltaic (OPV) devices. Here, excitonic dissociation pathways in the high‐performance, low bandgap “in‐chain donor–acceptor” polymer PTB7 by transient optical absorption (TA) spectroscopy in solutions, neat films, and bulk heterojunction (BHJ) PTB7:PC₇₁BM (phenyl‐C₇₁‐butyric acid methyl ester) films are investigated. The dynamics and energetics of the exciton and intra‐/intermolecular charge separated states are characterized. A distinct, dynamic, spectral red‐shift of the polymer cation is observed in the BHJ films in TA spectra following electron transfer from the polymer to PC₇₁BM, which can be attributed to the time evolution of the hole–electron spatial separation after exciton splitting. Effects of film morphology are also investigated and compared to those of conjugated homopolymers. The enhanced charge separation along the PTB7 alternating donor–acceptor backbone is understood by intramolecular charge separation through polarized, delocalized excitons that lower the exciton binding energy. Consequently, ultrafast charge separation and transport along these polymer backbones reduce carrier recombination in these largely amorphous films. This charge separation mechanism explains why higher degrees of PCBM intercalation within BHJ matrices enhances exciton splitting and charge transport, and thus increase OPV performance. This study proposes new guidelines for OPV materials development.     

Mechanistic Investigation into Dynamic Function of Third Component Incorporated in Ternary Near‐Infrared Nonfullerene Organic Solar Cells

Organic solar cells (OSCs) consisting of an ultralow‐bandgap nonfullerene acceptor (NFA) with an optical absorption edge that extends to the near‐infrared (NIR) region are of vital interest to semitransparent and tandem devices. However, huge energy‐loss related to inefficient charge dissociation hinders their further development. The critical issues of charge separation as exemplified in NIR‐NFA OSCs based on the paradigm blend of PTB7–Th donor (D) and IEICO–4F acceptor (A) are revealed here. These studies corroborate efficient charge transfer between D and A, accompanied by geminate recombination of photo‐excited charge carriers. Two key factors restricting charge separation are unveiled as the connection discontinuity of individual phases in the blend and long‐lived interfacial charge‐transfer states (CTS). By incorporation of a third‐component of benchmark ITIC or PC₇₁BM with various molar ratios, these two issues are well‐resolved accordingly, yet in distinctly influencing mechanisms. ITIC molecules modulate film morphology to create more continuous paths for charge transportation, whereas PC₇₁BM diminishes CTS and enhances electron transfer at the D/A interfaces. Consequently, the optimal untreated ternary OSCs comprising 0.3 wt% ITIC and 0.1 wt% PC₇₁BM in the blend deliver higher J_SC values of 21.9 and 25.4 mA cm^‐2, and hence increased PCE of 10.2% and 10.6%, respectively.     

Enhancement of photoelectrochemical performance in ferroelectric films via the introduction of an Au buffer layer

The inefficient separation of photogenerated carriers has become a serious problem that limits the photoelectrochem-ical(PEC)performance of semiconductors.Herein,a sol-gel method was used to prepare BiFeO3 ferroelectric thin films with FTO and FTO/Au as substrates,respectively.The polarization electric field of the ferroelectric can more effectively separate the carriers generated in the photoelectrode.Meanwhile,the introduction of an Au buffer layer can reduce the resistance in the pro-cess of charge transfer,accelerate the carrier migration,and enhance the efficiency of the charge separation.Under light irradi-ation,Au/BiFeO3 photoelectrode exhibited an extraordinary improvement in PEC water splitting compared with BiFeO3.In addi-tion,the ferroelectric polarization electric field causes band bending,which further accelerates the separation of electrons and holes and improves the PEC performance of the photoelectrode.This work promotes the effective application of ferroelectric films in PEC water splitting.     

Charge Photogeneration for a Series of Thiazolo‐Thiazole Donor Polymers Blended with the Fullerene Electron Acceptors PCBM and ICBA

Photoinduced charge separation in bulk heterojunction solar cells is studied using a series of thiazolo‐thiazole donor polymers that differ in their side groups (and bridging atoms) blended with two acceptor fullerenes, phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) and a fullerene indene‐C60 bisadduct (ICBA). Transient absorption spectroscopy is used to determine the yields and lifetimes of photogenerated charge carriers, complimented by cyclic voltammetry studies of materials energetics, wide angle X‐ray diffraction and transmission electron microscopy studies of neat and blend film crystallinity and photoluminescence quenching studies of polymer/fullerene phase segregation, and the correlation of these measurements with device photocurrents. Good correlation between the initial polaron yield and the energetic driving force driving charge separation, ΔE_CS is observed. All blend films exhibit a power law transient absorption decay phase assigned to non‐geminate recombination of dissociated charges; the amplitude of this power law decay phase shows excellent correlation with photocurrent density in the devices. Furthermore, for films of one (relatively amorphous) donor polymer blended with ICBA, we observe an additional 100 ns geminate recombination phase. The implications of the observations reported are discussed in terms of the role of materials' crystallinity in influencing charge dissociation in such devices, and thus materials design requirements for efficient solar cell function.     

Modulating Charge Separation Efficiency of Water Oxidation Photoanodes with Polyelectrolyte‐Assembled Interfacial Dipole Layers

The charge separation efficiency of water oxidation photoanodes is modulated by depositing polyelectrolyte multilayers on their surface using layer‐by‐layer (LbL) assembly. The deposition of the polyelectrolyte multilayers of cationic poly(diallyldimethylammonium chloride) and anionic poly(styrene sulfonate) induces the formation of interfacial dipole layers on the surface of Fe₂O₃ and TiO₂ photoanodes. The charge separation efficiency is modulated by tuning their magnitude and direction, which in turn can be achieved by controlling the number of bilayers and type of terminal polyelectrolytes, respectively. Specifically, the multilayers terminated with anionic poly(styrene sulfonate) exhibit a higher charge separation efficiency than those with cationic counterparts. Furthermore, the deposition of water oxidation molecular catalysts on top of interfacial dipole layers enables more efficient photoelectrochemical water oxidation. The approach exploiting the polyelectrolyte multilayers for improving the charge separation efficiency is effective regardless of pH and types of photoelectrodes. Considering the versatility of the LbL assembly, it is anticipated that this study will provide insights for the design and fabrication of efficient photoelectrodes.     

共轭点电荷系在静电劈形问题中的应用

根据点-面情形电像解的规律提出共轭点电荷系概念,对不同类型的共轭点电荷系在半无限大导体平面上的感应电荷总量进行了计算,并应用到有一定对称性分布的静电劈形问题中。共轭点电荷系思想对π是夹角整数倍情形时的劈形角平分面上点电荷的电像解提供了一种新的解法和思路。     

Ionic Space‐Charge Depletion in Lithium Fluoride Thin Films on Sapphire (0001) Substrates

Lithium fluoride thin films with various thicknesses have been grown on c‐plane sapphire substrates by radio‐frequency sputtering. The thin films are granular with a preferential [111] orientation of the grains. Thickness‐dependent measurements allow the separation of bulk and interface conductions. The normalized conductance decreases linearly with decreasing LiF layer thickness with a negative extrapolated intercept. DC polarization, AC impedance spectroscopy and electromotive force measurement indicate depletion of lithium ion vacancies as majority charge carriers and hence a negative space‐charge potential. A generalized Mott–Schottky approach within the model of heterogeneous doping fully explains the entire boundary defect chemistry.     

Enhancing Charge Separation in Metallic Photocatalysts: A Case Study of the Conducting Molybdenum Dioxide

A new visible‐light responsive metallic photocatalyst, nanostructured MoO₂, has been discovered. The metallic nature of MoO₂ is confirmed by valance X‐ray photoelectron spectroscopy spectrum and theoretical calculations. However, MoO₂ itself shows only moderate activity due to the serious charge recombination, a general disadvantage of metallic photocatalysts. The findings suggest that its effective charge diffusion length L_p is smaller than 1.0 nm while the separation efficiency η_sep is less than 10%. Therefore, only the periphery of the metallic MoO₂ can effectively contribute to photocatalysis. This limitation is overcome by integrating MoO₂ in a hydrothermal carbonation carbon (HTCC) matrix (mainly contains semiconductive polyfuran). This simple chemical modification brings two advantages: (i) an internal electric field is formed at the interface between MoO₂ and HTCC due to their appropriate band alignment; (ii) the nanostructured MoO₂ and the HTCC matrix are intertwined with each other intimately. Their small size and large contact area promote charge transfer, especially under the internal electric field. Therefore, the separation rate of photoexcited charge carrier in MoO₂ is greatly enhanced. The activity increases by 2.4, 16.8, and 4.0 times in photocatalytic oxygen evolution, dyes degradation, and photoelectrochemicl cell, respectively. The new approach is helpful for further development of metallic photocatalysts.