超导量子器件片上皮法电容的制备及测量

片上集成电容是超导量子芯片上的核心器件,其数值一般在百飞法(fF)至皮法(pF)范围.采用常规微纳加工技术在蓝宝石基片上制备了铌-氧化硅-铝(Nb/SiO₂/Al)平行板电容.利用刻蚀工艺制备了平行板电容器的下极板Nb,利用剥离工艺制备平行板电容器的上极板Al和介电层SiO₂.室温下利用锁相放大原理和桥式电路原理测定电容大小,两种方法测定电容值基本一致,表明锁相放大原理测试pF级电容的可靠性.利用该电容与铝基约瑟夫森结组成谐振器,制备了中心频率位于4.35 GHz的约瑟夫森参量放大器.在稀释制冷机中10 mK温度下测定直流偏置谐振器的磁通-频率相位图,拟合数据获得的电容值与室温测定电容值接近,表明在mK、GHz条件下工作的片上集成电容可在室温、kHz条件下测定其数值大小.     

双电层氧化锌薄膜晶体管偏压应力稳定性

以环保可降解的天然生物材料制备功能器件越来越受到关注,利用天然鸡蛋清作为栅介质层,采用射频磁控溅射法在其上沉积ZnO薄膜有源层,制备低压双电层氧化锌基薄膜晶体管（ZnO-TFT）并对其电学特性进行了表征,研究了器件在栅偏压和漏偏压应力下电性能的稳定性及其内在的物理机制。该ZnO-TFT器件呈现出良好的电特性,载流子饱和迁移率为5.99 cm²/（V·s）,阈值电压为2.18 V,亚阈值摆幅为0.57 V/dec,开关电流比为1.2×10⁵,工作电压低至3 V。研究表明,在偏压应力作用下,该ZnO-TFT器件电性能存在一定的不稳定性,我们认为栅偏压应力引起的电性能变化可能来源于栅介质附近及界面处的正电荷聚集、充放电效应和新陷阱态的复合效应;漏偏压应力引起的电性能变化可能来源于焦耳热引起的氧空位及沟道中的电子陷阱。     

双电层交叠时微通道内流动的数值模拟

本文采用有限容积法数值模拟了在电动效应作用下微通道内流体的流动特性。分别采用Poisson方程和Nernst- Planck方程计算电动势和离子浓度分布。结果表明在双电层相互交叠的情况下,微通道内轴向的流动电势先减小后增大,并逐渐趋于定值,从而导致了轴向电动效应不断增强。     

基于双电层作用的环境湿度差发电机理研究

环境湿度分布不均在自然界中普遍存在,其中包含着大量可用能量。利用湿度差驱动纳米材料中的电子或自由离子的定向运动、从而产生电能是很有发展前景的。然而,自由离子在纳米材料内部通道中的传递过程尚不明确。为此,本文构建了考虑通道双电层作用的湿度驱动发电理论模型,通过Comsol Multiphysics软件数值求解并进行了实验验证。结果显示,纳米材料内部通道对流经通道的自由离子具有选择透过性,其表面电位越大,离子选择性越强,电压输出越大。同时,通道长度越大,湿度差驱动下的电压输出性能越大,与实际发电器件的运行结果一致。该模拟可通过分析纳米通道内的离子分布,以预测不同种类和尺寸纳米颗粒的电压输出,为后续研究中的材料选择和装配提供指导。     

石墨烯褶皱结构对双电层储能性能的理论研究

石墨烯因其出色的比表面积和单层结构而被广泛认为是一种理想的电极材料。然而,实验制备的石墨烯常因官能团、缺陷和位错的引入而出现褶皱和变形。针对这一问题,本文构建了一系列具有不同幅度褶皱（a = 0 ~ 6.6 ?）的石墨烯片,并运用分子动力学模拟来研究这些褶皱石墨烯表面的双电层结构。本研究旨在探讨不同褶皱高度和充电状态下双电层的变化规律,及其与超级电容器储能性能之间的关系。研究发现,褶皱石墨烯模型内部的离子浓度随电压的增加呈现多峰层状分布,而表面离子浓度与施加的电压正相关。此外,石墨烯的褶皱结构能够减少离子和水对电极电压响应的敏感性。在不同电压条件下,褶皱型石墨烯结构的面积比电容（CA）始终高于其平面对应区域,突出了其在提升双电层储能性能上的优势。本研究揭示了石墨烯褶皱结构在调节离子分布、降低电压敏感性,以及增强电化学储能性能方面的特有作用机制。     

测量空气的电容率

利用自制的可调间距的精密平行板电容器,配合交流电桥,通过一定的误差分析与数据处理,较为准确地测量了空气的电容率。     

测量电介质的电容率

简述了应用计算机技术改进测量电介质电容率的一种方法。     

SiO2固态电解质中的质子特性对氧化物双电层薄膜晶体管性能的影响

本文采用等离子体增强化学气相沉积技术(PECVD)在室温条件下制备了具有双电层效应的二氧化硅(SiO₂) 固体电解质薄膜, 并以此SiO₂薄膜作为栅介质制备了氧化铟锌(IZO)双电层薄膜晶体管. 本文系统地研究了SiO₂固体电解质中的质子特性对双电层薄膜晶体管性能的影响, 研究结果表明, 经过纯水浸泡的SiO₂固体电解质薄膜可以诱导出较多的可迁移质子, 因此表现出较大的双电层电容. 由于SiO₂固体电解质薄膜具有质子迁移特性, 晶体管的转移特性曲线呈现出逆时针方向的洄滞现象, 并且这一洄滞效应随着栅极电压扫描速率的增加而增大. 进一步对薄膜晶体管的偏压稳定性进行测试, 发现晶体管的阈值电压的变化遵循了拉升指数函数(stretched exponential function)关系.     

鞘层电容对快速扫描双探针伏安曲线的影响

建造了基于多偶极腔体热阴极放电形式搭建的500kHz不对称快速扫描双探针系统,以电容对测量结果的影响进行实验研究。对不同扫描频率下不同尺寸的快速扫描不对称朗缪尔双探针受离子饱和电流及鞘电流影响的结果进行了对比分析。这项研究对于不同扫描频率下快速扫描不对称双探针的选择应用有着参考和指导意义。     

薄膜材料电容率的测量

利用阻抗分析仪测量了金属-介质薄膜-半导体结构的C-V特性曲线. 由积累区电容得到所制备HfO2薄膜的电容为1.24 nF,计算得其相对电容率为12.49.     

巧用指针式多用电表的欧姆挡测电容

用欧姆表测量大容量电容器时,可通过监测指针的偏转情况了解电容的充电情况,从而测量电容器的电容.     

用模拟万用表测电容

介绍了用模拟万用表和秒表测量电容的简单方法，对测量结果的误差原因进行了分析，给出了提高测量精度的几点措施。     

激光羽烟透过率测试技术研究

为了准确评估固体推进剂的性能,研制了红外激光羽烟透过率测量系统。系统采用透射的方法:在发射端对激光信号采用内调制,由光学系统送入接收端,并将接收到的信号进行光电转换、信号处理和A/D转换后送入计算进行数据的处理和显示。现场测试结果表明该系统的精度、响应速度和稳定度达到设计要求。     

Comparative study of electrochemical capacitance of multi-walled carbon nanotubes before and after chopping

In the work, short multi-walled carbon nanotubes (S-CNTs) were synthesized by chopping conventional μm-long multi-walled carbon nanotubes (L-CNTs) under ultrasonication in H₂SO₄/HNO₃ mixed acids. A comparative electrochemical investigation performed in 6 M KOH solution demonstrated that a specific capacitance (SC) of ca. 14.6 μF cm⁻² was delivered by the S-CNTs with the specific surface area (SSA) of 207 m² g⁻¹, much larger than that of ca. 10.1 μF cm⁻² for the L-CNTs with the SSA of 223 m² g⁻¹, the reason for which was that S-CNTs with two open ends, due to good ion penetrability, provided more entrances for electrolyte ions to access the inner surface easily through their shorter inner pathway so as to enhance their SSA utilization and geometric SC. The surface structure disruption of S-CNTs, owing to ultrasonication and oxidation during chopping process, deteriorated their electronic conductivity and resulted in an inferior power property in contrast to L-CNTs.     

Quantum fluctuations of the antiferro-antiferromagnetic double-layer

This paper stuides the magnetization and quantum fluctuations of an antiferro-antiferromagnetic (AF-AF) double-layer at zero temperature. It is found that the exchanges and anisotropy constants affect the quantum fluctuations of spins. If the anisotropy exists, there will be no acoustic energy branch in the system. The anisotropy constant, antiferromagnetic intralayer and interlayer coupling have important roles in a balance of the quantum competition.     

Analysis of the effect of stray capacitance on a charge/discharge-based electrical capacitance tomography system

The measurement circuit of electrical capacitance tomography (ECT) system mainly includes CMOS switches, C/V conversion circuit and Data processing circuit. In order to improve the image reconstruction quality, conversion circuit is very necessary to the small capacitance measurement circuit. A charge/discharge measurement circuit is one of the most suitable for the C/V conversion circuit in ECT. The stray capacitance between the measurement electrodes and earth can be large and have an effect on the capacitance measurement. This paper analyzes this effect, taking into account the ON-resistance of the COMS switch, the unit gain frequency of op-amp, and gain error in the measurement circuit. Finally, it is shown that if the range of stray capacitance is 150 ± 60 pF, overall error would be estimated. Comparing the effects of the circuit parameters, this charge/discharge-based capacitance is effectively stray-immune. It is a more efficient analysis to C/V circuit in ECT and offers a great benefit to information processing.     

采用超薄双层靶提高质子束的单能性

利用1维粒子模拟程序,研究了超短超强激光脉冲与超薄双层靶(基底层和加速层厚度均为nm量级)相互作用产生准单能质子束的过程。研究表明,基底层厚度及加速层厚度对质子能谱的影响至关重要。减小基底层厚度,靶后静电场增强,质子的最大能量显著增大;减小加速层厚度,靶后静电场分布变得更加均匀,质子能谱中心能量变化不大,单能性变好。通过优化参数,获得了能散度为7%的准单能质子束。     

Nanoscale capacitance: A quantum tight-binding model

Landauer–Buttiker formalism with the assumption of semi-infinite electrodes as reservoirs has been the standard approach in modeling steady electron transport through nanoscale devices. However, modeling dynamic electron transport properties, especially nanoscale capacitance, is a challenging problem because of dynamic contributions from electrodes, which is neglectable in modeling macroscopic capacitance and mesoscopic conductance. We implement a self-consistent quantum tight-binding model to calculate capacitance of a nano-gap system consisting of an electrode capacitance $C^{\prime }$ and an effective capacitance $C_d$ of the middle device. From the calculations on a nano-gap made of carbon nanotube with a buckyball therein, we show that when the electrode length increases, the electrode capacitance $C^{\prime }$ moves up while the effective capacitance $C_d$ converges to a value which is much smaller than the electrode capacitance $C^{\prime }$. Our results reveal the importance of electrodes in modeling nanoscale ac circuits, and indicate that the concepts of semi-infinite electrodes and reservoirs well-accepted in the steady electron transport theory may be not applicable in modeling dynamic transport properties.     

Marx调制器单元设计和叠加测试

基于单元器件的成功研制,介绍了Marx调制器单元充放电回路、电压和电流的实时监测以及控制系统和连锁保护等功能的设计和实现。对IGBT固态开关的静态、动态均压进行分析和模拟,采用RCD缓冲电路实现IGBT的动态均压;对控制系统改进和优化,设计了专用电源转换模块;分压电路和电流霍尔采样回路分别实现调制器单元电压和电流的检测;连锁保护功能由控制系统和继电器控制完成。所有部件按照电气标准设计在调制器单元支架上。经过测试的4个单元进行了叠加试验,4个单元总输出24 kV,各器件在高压试验中工作正常。     

Differential capacitance between circular stacked quantum dots

We have investigated the differential capacitance between two stacked, circular quantum dots. An expression defining such differential capacitance has been derived on the basis of that for the self-capacitance of a single quantum dot. By means of a self-consistent simulation we have obtained numerical results showing that the differential capacitance between the two dots is strongly influenced by shell-filling effects, and that the classical limit of the parallel-plate capacitor is retrieved when the two dots are in close proximity. Our results represent a contribution to the effort for the definition of a capacitance matrix for a complex system of quantum dots.