Induced current in a Bi2Sr2CaCu2Ox superconductor tube

Experiments were conducted to measure the induced current in a high-temperature Bi₂Sr₂CaCu₂O_x superconductor tube that was excited by an external coil driven by an AC sinusoidal voltage source. Experimental data were obtained for tests without and with an iron core inside the superconductor tube. All of the tests were conducted at 77 K and an excitation frequency of 60 Hz. The results showed that immediately after field penetration, the induced current (RMS value) decreased from the critical current, then began to recover, and eventually approached the critical current again at a high excitation current. Before field penetration, the induced current was mainly shielding current, which is 180 ° out of phase with the excitation current. After field penetration, the induced current consisted of two parts, a shielding current that led the excitation current by 180 ° and an inductive current (Faraday's law) that led the excitation current by 90 °. The presence of the iron core amplified the drop in induced current immediately after field penetration and delayed the growth of the inductive current after field penetration.     

High-voltage planar structure using SiO2-SIPOS-SiO2film

The BVCB0leakage current hFEwere studied for high-voltage planar transistors which had three kinds of passivation films; SiO2-semi-insulating polycrystalline silicon (SIPOS)-SiO2; SIPOS-SiO2; and SiO2-phosphosilicate glass (PSG)-SiO2. The SiO2-SIPOS-SiO2type had a lower leakage current (surface generation current) and higher hFEthan the conventional SIPOS-SiO2type. The SiO2-SIPOS-SiO2type also had the highest BVCB0due to the field-plate effect.     

Temporal stability of circulating current in thin film Tl2Ba2CaCu2O8 and YBa2Cu3O7

The temporal stability of trapped transport current in annular thin film Tl₂Ba₂CaCu₂O₈ (TBCCO) and YBa₂Cu₃O₇ (YBCO) wafers has been accurately measured and has been found to be of suitable quality for the stringent requirements of nuclear magnetic resonance (NMR) magnets. No detectable decay, to the limit of the experimental apparatus (2*10^-14 Ω), was detected in those wafers with transport current at or below the critical current density J_c. The critical current density, as previously determined from 12 μm meander lines, was confirmed in a wafer with a width of 1.9 cm. The profile of trapped magnetic field resulting from induced current was modeled in order to assess its effect on the uniformity of an NMR magnet     

2千瓦横向流动闭合循环CO_2激光器

本文报导了千瓦级横向流动闭合循环 CO_2激光器的组成,着重讨论了无弧光放电电极结构及放电特性。采用多针触发使较大放电电流时的辉光放电稳定性明显提高;主电源直流输出特性及限流电阻选择对放电稳定性及功率输出影响很大。放电区气流速度40米/秒,工作气压46毫米汞柱,激活区长度86厘米,获得2千瓦连续多模输出,电光效率达15%。     

A 2-ns detecting time, 2-μm CMOS built-in current sensingcircuit

Built-in current testing is known to enhance the defect coverage in CMOS VLSI. An experimental CMOS chip containing a high-speed built-in current sensing (BICS) circuit design is described. This chip has been fabricated through MOSIS 2-μm p-well CMOS technology. The power bus current of an 8×8 parallel multiplier is monitored. This BICS detects all implanted short-circuit defects and some implanted open-circuit defects at a clock speed of 30 MHz (limited by the test setup). SPICE3 simulations indicate a defect detection time of about 2 ns     

Electrothermal investigation of the switching effect in p-Type TllnSe2, TllnTe2, and TIGaTe2 chain chalcogenide semiconductors

Large p-type TlInSe₂, TlInTe₂, and TlGaTe₂ single crystals have been grown by the Bridgman-Stockbarger method, starting from stoichiometric melts. The first observations of the switching process in p-type TlGaTe₂ single crystal are reported. Current-voltage (I-V) characteristics of symmetrical In/p-TlInSe₂/In, In/p-TlInTe₂/In, and In/p-TlGaTe₂/In structures exhibit two distinct regions: an ohmic region at low current densities and nonlinear regions (S-shape) having negative differential resistance (NDR) at moderate and higher current densities. An electrothermal model was used to explain the nonlinear behavior. The nonlinear behavior of the I–V curves was studied at different ambient temperatures in the 100–340K region; the sample temperature and the threshold voltage of the NDR region were examined as a function of the current density and the ambient temperature, respectively. The electrothermal model is a satisfactory explanation.     

H2O2催化多孔硅的光致发光研究

采用H2O2催化的电化学法制备多孔硅,用原子力显微镜观察了样品的形貌,并测量了在不同电流密度下制得的多孔硅和在不同氧化时间高温氧化的多孔硅的光致发光谱。实验结果表明,采用H2O2催化的电化学法制备的多孔硅与常规电化学法制备的多孔硅相比,其表面更平整、细密、均匀。随着电流密度和氧化时间的增加,多孔硅的发光谱峰位蓝移。此实验结果符合量子限制模型。     

基于HfO2栅介质的Ga2O3 MOSFET器件研制

采用金属有机化学气相沉积(MOCVD)方法在(010) Fe掺杂半绝缘Ga2O3同质衬底上外延得到n型β-Ga2O3薄膜材料,材料结构包括400 nm的非故意掺杂Ga2O3缓冲层和40 nm的Si掺杂Ga2O3沟道层.基于掺杂浓度为2.0×1018 cm-3的n型β-Ga2O3薄膜材料,采用原子层沉积的25 nm的HfO2作为栅下绝缘介质层,研制出Ga2O3金属氧化物半导体场效应晶体管(MOSFET).器件展示出良好的电学特性,在栅偏压为8V时,漏源饱和电流密度达到42 mA/mm,器件的峰值跨导约为3.8 mS/mm,漏源电流开关比达到108.此外,器件的三端关态击穿电压为113 V.采用场板结构并结合n型Ga2O3沟道层结构优化设计能进一步提升器件饱和电流和击穿电压等电学特性.     

In2Ge2O7薄膜制备及其紫外光敏特性研究

以In2O3和GeO2为原料,采用碳还原法制备了In2Ge2O7多晶薄膜,利用XRD和SEM对薄膜的结构和形貌进行了表征。对基于In2Ge2O7薄膜的金属-半导体-金属(MSM)紫外探测器进行了紫外光电导特性测量,结果显示:在波长为250nm的紫外光照射下,在5V偏压下,器件的光电流为727μA(暗电流为12μA),光响应度达到262.9A.W-1,光响应上升时间约为67s,下降时间约为15s。分析认为较长的响应时间是由于内部的缺陷与位错造成的。初步研究结果表明:In2Ge2O7薄膜可以作为一种良好的日盲紫外探测材料。     

On the current conduction mechanisms of CeO2/La2O3 stacked gate dielectric

It was found that the electrical properties of CeO₂/La₂O₃ stack are much better than a single layer La₂O₃ film. A thin CeO₂ capping layer can effectively suppress the oxygen vacancy formation in the La₂O₃ film. This work further investigates the current conduction mechanisms of the CeO₂ (1 nm thick)/La₂O₃ (4 nm thick) stack. Results show that this thin stacked dielectric film still has a large leakage current density; the typical 1−V leakage can exceed 1 mA/cm² at room temperature. The large leakage current should be due to both the oxide defect centers as well as the film structure. Results show that at low electric field (<0.2 MV/cm), the thermionic emission induced current conduction in this stacked structure is quite pronounced as a result of interface barrier lowering due to the capping CeO₂ film which has a higher k value than that of the La₂O₃ film. At higher electric fields, the current conduction is governed by Poole–Frenkel (PF) emission via defect centers with an effective energy level of 0.119 eV. The temperature dependent current–voltage characteristics further indicate that the dielectric defects may be regenerated as a result of the change of the thermal equilibrium of the redox reaction in CeO₂ film at high temperature and the drift of oxygen under the applied electric field.     

Surface recombination current with a nonideality factor greaterthan 2

It is shown both theoretically and experimentally that under inverted surface conditions the surface recombination current of a bipolar transistor has an exponential nonideality factor >2. The behavior of the surface recombination current follows closely that of the excess leakage current in stressed-self-aligned silicon bipolar transistors at forward bias     

用La_2MoWO_9作固体电解质的极限电流型氧传感器

采用固相反应法,制备了氧离子导体La2MoWO9和混合导体La0.6Sr0.4Fe0.8Co0.2O3,并分别作为基体材料,制成了极限电流型氧传感器。利用两端子法,对氧传感器在500℃时不同氧分压下(pO2为(0~2.12)×104Pa)电流与电压的关系进行了测量。结果表明:用La2MoWO9作为氧传感器的固体电解质材料是可行的,即可以得到极限电流平台(pO2为1.70×104Pa,I为1.5mA),且极限电流与氧分压成线性关系。     

掺CeO2纳米MnO2非对称超级电容器的研究

采用化学共沉淀法制备出超级电容器用掺CeO2的MnO2电极材料,通过XRD、SEM对样品进行了表征,研究了掺杂量对MnO2电极稳定性能的影响。结果表明,产物主相为α-MnO2,粒度分布较均匀,在50～100nm;在6mol/L的KOH电解液中,该掺杂MnO2电极材料具有优良的电容行为和循环稳定性能。当掺CeO2量为10%(与MnO2的质量比)时,在电流密度为250mA/g时,比电容量达257.68F/g;循环500次,容量仅衰减1.18%。     

Transistor characteristics with Ta2O5 gatedielectric

As the gate oxide thickness decreases below 2 nm, the gate leakage current increases dramatically due to direct tunneling current. This large gate leakage current will be an obstacle to reducing gate oxide thickness for the high speed operation of future devices. A MOS transistor with Ta₂O₅ gate dielectric is fabricated and characterized as a possible replacement for MOS transistors with ultra-thin gate silicon dioxide. Mobility, I_d-V_d, I_d-V_g, gate leakage current, and capacitance-voltage (C-V) characteristics of Ta₂O₅ transistors are evaluated and compared with SiO₂ transistors. The gate leakage current is three to five orders smaller for Ta₂O₅ transistors than SiO₂ transistors     

The Physical Background of JUNCAP2

A new physics-based junction model for CMOS, called JUNCAP2, is presented. It contains new single-piece formulations for the Shockley–Read–Hall generation/recombination current and the trap-assisted tunneling (TAT) current, which are valid both in forward and reverse mode of operation. Moreover, the TAT model extends the existing model (IEEE Trans. Electron Devices, vol. 39, p. 2090, 1992) to the high electric fields encountered in today's CMOS technologies. Furthermore, the model contains expressions for junction capacitance, ideal current, band-to-band tunneling current, avalanche breakdown, and junction shot noise. The parameter extraction is also discussed in this paper.     

LC—2A型离子注入设备的某些改进

本文叙述了弗里曼(Freeman)离子源体联接在LC-2A型中能离子注入机上的应用;表明了弗里曼离子源体与LC-2A型中能离子注入机光路系统相吻合后,可以茯得较大束流;这样,满足了我所半导体集成电路研制工艺中高剂量离子注入掺杂要求;文章还讨论了LC-2A型离子注入机束流增大后引起的诸如离子流的污染、磁分析器扁管防“穿通”、以及样品热聚积效应问题。     

DC machine models for SPICE2 simulation

A four-level computer model is proposed for DC machine simulation using SPICE2 to meet different simulation requirements. The most complex model takes account of magnetic saturation, armature reaction, current dependence of winding circuit parameters, and eddy current effects. The models have been developed to enable designers to simulate the static and dynamic characteristics of a complete converter drive system including the DC machine more simply, practically, and reliably in one simulation run. Some simulations have been investigated to demonstrate the benefits of the SPICE2 machine models     

Investigation of electron transport properties in Li2CO3-doped Bepp2 thin films

The admittance spectroscopy investigations showed that doping lithium carbonate (Li₂CO₃) into bis[2-(2-hydroxyphenyl)-pyridine] beryllium (Bepp₂) greatly improved the electron mobility compared with the pure Bepp₂ film. The electron mobility reaches the orders of ∼10⁻⁴ cm² V⁻¹ s⁻¹, almost independent of the electric field. The trap states at low frequencies were clearly observed by capacitance–frequency measurement. The current–voltage and current–thickness characteristics indicated the electron conduction of space-charge-limited current (SCLC) with discrete trap distributions in the intermediate voltage and the SCLC with exponential trap distribution at the higher voltage in the Li₂CO₃-doped Bepp₂ film. We further estimated the density of trap states to be about 4.54 × 10¹⁷ cm⁻³ by the temperature dependent current density characteristics. The investigation of ultraviolet photoemission spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS) found that there occurs complicated chemical reaction between Bepp₂ and Li₂CO₃, and the Bepp₂ traps more electrons after Li₂CO₃ doping. This is an effective charge transfer between Bepp₂ and Li₂CO₃, which greatly reduces the electron injection barrier and significantly enhances the electron mobility.     

Sb掺杂SnO2修饰双电层电容活性炭电极的研究

应用sol-gel浸渍与热处理工艺相结合,在活性炭表面包覆Sb掺杂的SnO2薄膜对电极进行修饰,构成AC-SnO2/KOH/AC-SnO2双电层电容器,测试结果表明,400 mA/g电流密度条件下,修饰后的双电层电容器在0.001～1.5 V相对较高电压区间的放电容量,比AC/KOH/AC双电层电容器在0.001～1.0 V电压区间高36%,但AC-SnO2的单电极比电容仅为AC单电极比电容的91.9%;当电流密度大于400 mA/g,两种电极的大电流性能相当。     

2×2有机聚合物的全内反射型热光光开关

利用有机聚合物材料的负性热光效应 ,设计并研制成功了 2× 2全内反射型光开关。所研制的无阻塞 2× 2光开关 ,具有 >2 7dB的消光比 ,全内反射状态下 ,器件驱动功率约为 132mW (驱动电压约 3V×驱动电流约 4 4mA) ,这一驱动功率值可以降至 5 0～ 6 0mW ,同时给出器件插入损耗的测试结果。