量子线中强耦合束缚磁极化子的电场效应

采用线性组合算符和幺正变换相结合方法研究了电场和温度对抛物量子线中强耦合束缚磁极化子性质的影响。计算了在电场和温度影响下抛物量子线中强耦合束缚磁极化子的基态能量、平均声子数和振动频率。数值计算结果表明：量子线中强耦合束缚磁极化子的基态能量随约束强度、回旋共振频率和电场强度的增强而增大,随耦合强度的增大和温度的上升而减小;平均声子数随回旋共振频率、约束强度和温度的增大而增加;振动频率随回旋共振频率的增大而增大,同时也随约束强度的增大而增大。     

钛酸钡晶体压电性能的分子动力学模拟

利用Tanaka对势函数,开展不同电场加载下单晶钛酸钡分子动力学方法模拟,研究外电场、温度等对单晶钛酸钡的压电应力常数(e33)的影响.结果表明,常温下,电场强度对e33影响不大;但随着电场强度增大,e31上升趋势较明显;温度在约275 K前,e33随温度升高迅速增大,此后基本呈缓慢走低的势头.     

混合电路制造中瓷介电容器的老化现象研究

瓷介电容器具有固有的老化和去老化现象，温度高于居里点会使电容器产生去老化现象；温度低于居里点后电容器将会发生容量随时间延长而下降的老化现象。本文叙述了试验分析的结果，并提供了设计和使用的数据。     

BaTiO3-Yb2O3-MgO系陶瓷居里点移动机理研究

通过在BaTiO3陶瓷中单独添加Yb2O3或复合添加MgO/Yb2O3,研究了不同含量Yb3 掺杂对Ba-TiO3陶瓷居里点的影响。研究表明,在BaTiO3陶瓷中单独添加Yb3 使陶瓷介电常数减小,介电常数温度特性改善,但不会影响居里温度。而同时添加Mg2 与Yb3 时,BaTiO3陶瓷的温度特性能满足X8R(-55~150℃,电容变化率ΔC/C≤±15%,)标准,且系统的居里点随Yb3 含量增大而升高,掺入Yb3 每增加1%(摩尔比)使居里点提高2℃。研究认为,BaTiO3居里点向高温方向移动是由于在具有壳-芯结构BaTiO3陶瓷中,Yb3 取代Ti4 使晶粒壳晶胞体积增大,对晶粒芯产生张应力所致。     

用椭园偏振法研究电磁场对完整单根横纹肌产生的收缩机理

当恒定电场或交变电场垂直作用于完整肌纤维时，发现其退偏率随电场强度的增加呈先下降后上升的趋势。这是由于电场能使肌纤维一侧的膜去极化，导致肌质网内钙离子的释放，促使肌动蛋白增加新的活化位置，使一部分弱结合桥向强结合过渡，另一部分自由横桥向结合横桥过渡，造成退偏率随电场强度的增大呈先下降的趋势。随着电场强度的进一步增加，钙离子的释放趋向饱和，而肌丝的电极化增强造成粗肌丝对横桥的静电吸引力增强，使退偏率     

硼轻掺杂对非晶硅薄膜光电性能的影响

用化学气相沉积法制备了厚度为 2 μm左右、掺杂比为 ( 2～ 6)× 1 0 -6的硼轻掺杂非晶硅半导体薄膜 ,测量了样品光电流随掺杂比、电压和光波长的变化。结果表明 ,非晶硅薄膜的光电流随掺杂比、电场强度和光功率密度的增大而增大 ,光电流灵敏度最高频谱范围随掺杂比和电场强度的增大而增大 ,掺杂比改变对光电流的影响比电场强度和光功率密度变化的影响更明显     

怎样选用元器件讲座（十三）：MZ2型PTC限流元件

PTC限流元件是一种具有恢复特性的正温度系数热敏电阻。PTC限流元件的主体材料是钛酸钡(BaTiO3),掺以能改善居里点温度的物质和极微量的导电杂质(如稀土元素镧),经研磨、挤压成型、高温烧结而成的复合钛酸盐的N型半导体陶瓷。图1为PTC限流元件的外型图。限流元件PTC在达到一个特定的温度前,电阻值随温度变化非常缓慢。当超过这个温度时,PTC的阻值急剧增大,发     

DC/DC电源模块高温失效原因

为了得到一款军品级模块因为导致高温失效的原因,通过对模块内部元件加热测试,观测模块电学参数的变化,并与模块整体加热电学参数变化的结果做比较。得到影响模块输出电学参数变化的最主要的元件,同时对该元件特性分析,获得元件随温度变化失效的原理。测得其输出电压随环境温度的上升,而缓慢下降的主要原因来自于光耦的温度特性。环境温度达到150℃左右时,模块内变压器磁芯温度将达到居里点附近,使模块输出电压几乎为零。     

掺磷a—Si：H红外薄膜电阻率及电阻温度系数研究

用等离子体增强化学气相沉积方法制备了掺磷氢化非晶硅薄膜材料，对薄膜的电阻率以及电阻温度系数进行了详细研究。结果表明，掺磷a-Si：H薄膜的电阻率随磷掺杂比（PH3/SiH4）的增大和气体温度的升高而降低，但随退火温度的升高而增大，掺磷a-Si：H薄膜的电阻温度系数随薄膜自身电阻率的增大而增大，但随环境温度的升高而降低。     

利用通用迁移率模型计算有机二极管的交流阻抗谱

推导出了有机二极管交流阻抗谱的公式,当迁移率为常数时的计算结果与文献中的解析公式相符合,表明推出的公式和编写的程序是正确的。进一步根据文献中与温度、载流子浓度和电场强度有关的通用迁移率模型,计算了NRS-PPV有机二极管的交流阻抗谱。结果表明阻抗的实部总是取正值,虚部总是取负值。阻抗的实部和虚部的绝对值在低频极限下的数值都是随温度和直流偏压增大而减小。实部总是频率的单调减函数,且减小的速率随温度和直流偏压增大而变慢;虚部绝对值在低温下是频率的单调减函数,在高温下将出现极大值,极值的峰高随温度和直流偏压增大而减小,极值位置相应地出现蓝移。     

A novel method for laser-induced periodic domain reversal in LiNbO3 [nonlinear optical waveguide]

An intense laser light in conjunction with a strong localized field is used to reverse the polarity of the ferroelectric domain at the location of a laser beam. The focus beam from an argon laser raises the temperature of a moving z-cut LiNbO₃ plate close to the Curie point when a bipolar square wave electric field is applied. This technique has been used to construct a nonlinear periodic optical waveguide structure. This waveguide can be used for quasi-phase-matched second-harmonic generation. The applications of such waveguides are well documented in the literature     

栅脉冲条件下GaN MESFET电子温度分布仿真

利用数值模拟仿真对GaNMESFET在栅脉冲条件下的电子温度分布进行了研究。结果表明,在器件的栅下靠近漏端一侧的沟道处电子温度最高,当栅脉冲电压为-18V时可达6223K,并且电子温度从最高点向四周逐渐降低最后与晶格温度(300K)达到一致。同时还发现,电子温度与电场方向和电子电流方向密切相关,电子温度的最高点并不在电场的极大值处,而是在电场方向与电子电流方向一致之处。     

掺Fe的钽铌酸钾钠晶体的电光及电控衍射性能

报道了掺铁(Fe)的钽铌酸钾钠(KNTN)晶体的电光及电控衍射性能。利用顶部籽晶助溶剂法生长了高质量的晶体,居里温度为15℃;利用单光束椭偏法测量了晶体的有效二次电光系数Reff,在居里温度附近,Reff高达1.05×10-15 m2/V2,电光调制能力相当于铌酸锂的19倍(利用LiNbO3的γ33=30.8×10-12 m/V,偏压为500V/mm),Reff随着温度的升高而减小。利用二波耦合实验装置测量了晶体的电控衍射性能,当施加在晶体上的电场从0增加到900V/mm时,晶体的衍射效率先增大后减小,并且在外加电场为700V/mm时达到最大值80%。结果表明,Fe:KNTN是一种优异的电光晶体和电控衍射晶体。     

Field-dependent dielectric properties of KTaxNb1-xO3

The dielectric properties of KTN under applied dc biasing fields were studied. Applications of fields caused the Curie temperature to shift toward higher temperatures and the value of the dielectric constant at the peak to be reduced. A field of 6 kV/cm resulted in a shift of the Curie point by 8°C. The loss tangent was similarly affected by the field. At the Curie temperature, the loss tangent was quite high, about 0.2. A field of 6 kV/cm reduced it by a factor of about 3.     

Quantum-confined field-effect light emitters: device physics andexperiments

Extended experimental results on three-terminal quantum-confined field-effect light emitters with current injection and field control of luminescent characteristics in the quantum-well structure are reported. By incorporating superlattice buffer layers (SLBLs), the quantum efficiency of the device is dramatically improved and equivalently nonradiative recombination processes are sufficiently suppressed at room temperature. The red-shift of the emission spectra by the quantum-confined Stark effect assures that the electric field is effectively applied to the quantum well. The experimental data on the transient responses of emission intensity to input voltage pulses show fairly good correspondences with theoretical prediction and previous photoluminescence experiments. The authors discuss the ultimate capability of high-speed switching and point that an optical pulse with a duration as short as 30 ps and involving more than 100 photons can be generated by scaling down the size of the device with 1% external efficiency     

Ionic conductivity and dielectric relaxation in γ-irradiated TlGaTe2 crystals

The switching effect, field and temperature dependences of the permittivity and conductivity of TlGaTe₂ crystals subjected to various γ-irradiation doses are studied. Under rather low electric fields, the phenomenon of threshold switching with an S-shaped current-voltage characteristic containing a portion with negative differential resistance is observed in the crystals. In the region of critical voltages, current and voltage oscillations and imposed modulation are observed. Possible mechanisms of switching, ionic conductivity, disorder, and electrical instability in TlGaTe₂ crystals are discussed.     

交变外场下双结超导量子干涉器件的讨论

本文在a.c.Josephson结方程和直流超导量子干涉器件(d.c.SQUID)原理的基础上,讨论了在外加交流电场下,双结超导量子干涉器件环路的输出电流与待测磁通量的关系,得到了输出电流和待测磁通量关于时间的微分方程。并基于以上微分方程,提出了通过测定输出电流与时间的关系从而测量随时间发生微小变化的磁通量的构想。     

Off-state degradation with ac bias in PMOSFET

For the first time, the current failure of p-channel MOSFETs used for the sub-wordline driver of state-of-the-art DRAM chips was investigated during off-state switching cycles. With increasing switching speed for the sub-wordline driver, the subthreshold leakage current of p-channel MOSFETs increased, and resulted in serious stand-by current failure. The model proposed in this work suggested that the off-state degradation of p-channel MOSFETs with ac bias will intensify as the dimensions of devices decrease due to both the high electric field and the high operating frequency. The roles of various device parameters- such as gate length, gate-tab width, doping concentration at the source/drain extensions, operating temperature and operating frequency- on the degradation of p-channel MOSFETs were investigated.     

Ferroelectric Response and Induced Biaxiality in the Nematic Phase of Bent‐Core Mesogens

The still undiscovered fluid ferroelectric nematic phase is expected to exhibit a much faster and easier response to an external electric field compared to conventional ferroelectric smectic liquid crystals; therefore, the discovery of such a phase could open new avenues in electro‐optic device technology. Here, experimental evidence of a ferroelectric response to a switching electric field in a low molar mass nematic liquid crystal is reported and connected with field‐induced biaxiality. The fluid is made of bent‐core polar molecules and is nematic over a range of 120 °C. Combining repolarization current measurements, electro‐optical characterizations, X‐ray diffraction and computer simulations, ferroelectric switching is demonstrated and it is concluded that the response is due to field‐induced reorganization of polar cybotactic groups within the nematic phase. This work represents significant progress toward the realization of ferroelectric fluids that can be aligned at command with a simple electric field.     

The new switching effect in liquid selenium

Liquid selenium shows above 720°C a reversible switching from higher to lower conductance effected by an electric field. Below 720°C liquid selenium switches first to higher and then to lower conductance. After switching to low conductance, a voltage controlled negative resistance is observed. By means of a single pulse technique the current oscillograms of the switchings (switching to high conductance, to low conductance and multi-switching) are investigated. The influence of magnetic field upon the switching (delay time and threshold voltage) is investigated. An electronic explanation for the switching and the influence of the magnetic field on it is given.