Low noise 80–115 GHz quasiparticle mixer with small Nb/Al-Oxide/Nb tunnel junctions

Millimeter-wave characterization of a heterodyne receiver using (2 μm²) Nb/Al-Ox/Nb Superconducting-Insulator-Superconducting (SIS) junctions arrays is reported. The fabrication of the Nb/Al-Ox/Nb SIS junction arrays as a heterodyne mixer is described. The leakage current of these junctions is below 2μA at 4.2K and unmeasurable at 2.5K. The receiver gave a noise temperature Double Side Band (DSB) between 63K and 187K over the frequency range 80 to 115 GHz at the first conversion peak. The results are comparable to those obtained with SIS receivers using well researched lead junctions. Contrary to the lead junctions, our mixer using all Nb junctions have proven remarkably stable with respect to thermal cycling, characteristics which are required for space applications. To our knowledge, this is the most reliable low noise receiver operating in this frequency range.     

Formation of Planar Field-Emission Devices Based on Carbon Nanotubes on Co–Nb–N–(O) Alloy

Semiconductors - Integrated field-emission devices and integrated circuits (ICs) based on them are a promising direction in microelectronics, which is associated with the use of low-voltage and...     

触摸极限：华硕W1Nb笔记本电脑

W1N曾获得了iF中国工业设计大奖，而W1Nb则是一款将全功能高性能进行到底的产品，如果价格不是影响你选择笔记本电脑的主要因素，那么它绝对是最OK的目标。     

Nb掺杂ZnO压敏电阻器的缺陷模型

对ＺｎＯ压敏电阻器高价Ｎｂ掺杂的缺陷模型进行了分析，据此模型对ＺｎＯ压敏电阻器的性质进行了讨论。     

块状Nb:KTP晶体及其蓝色激光器

在改性的K6体系中,用顶部耔晶熔盐法得到了重约60 g,透明区达15mm×17mm×14 mm的块状Nb:KTP晶体.在使用波段,透过率为85%.实现了1064nm的非临界相位匹配.晶体的Ⅱ型相位匹配的截止波长蓝移至937 nm.用不同掺杂浓度的Nb:KTP晶体倍频,分别获得了波长为468.5 nm,473nm和480 nm的蓝色激光.测量了7.5 mo1.-%Nb:KTP晶体的折射率,计算和测定了该晶体的截止波长,得到了该晶体的角度、温度和光谱接收带宽,结果表明它们分别约为KNbO3的2.6,24和3.4倍,因而在实现频率转换时将放宽对使用条件的要求,并改善输出蓝光的质量.     

Crystal growth in Bi–Sr–Ca–Cu–O system

We report growth of Bi₂Sr₂CaCu₂O_8+δ single crystals with dimensions of 6×2×0.03 mm³ using a melt and growth technique. The oxygen content is determined to be δ≈0.13 by iodometric titration. The crystal is shown to be homogeneous and close to stoichiometric cation ratio. The superconducting temperature with a sharp transition width (10–90% level) of 6–8 K was determined to be T_c=92 K from resistivity and dc susceptibility measurements. The predominant impurity phase is a Cu-free crystal, whose composition is identified as Bi₁₀Sr₁₁Ca₅O_x. The crystal structure of Bi₁₀Sr₁₁Ca₅O_x is monoclinic with a=11.108(1) Å, b=5.9487(1) Å; c=19.838 (3) Åand β=101.5° (P2_1/c space group).     

Optically-induced effects in Y–ba–cu–O Josephson junctions

We report our studies on light-induced changes in electrical properties of YBa₂Cu₃O_x (YBCO) grain-boundary Josephson weak links. We discuss the erasable process (photodoping), in which light-induced enhancement of junctions properties at low temperatures relaxes back above 250 K. Our studies are focused on the junction critical current versus time, light intensity, and magnetic field measurements. In tested few-μm-wide step-edge junctions, photodoping manifested itself as above 50% increase of the critical current and the decrease of the junction magnetic penetration depth, leading to reduction of the effective junction width. Contrary to the photodoping effect, the high-intensity laser modification of junctions led to permanent modification of their electrical characteristics that remained unchanged after subsequent room-temperature/helium thermal cycling of the sample. The laser-modified junctions exhibited up to 25% increase of the critical current times normal-state resistance product.     

Nb掺杂对ZnO压敏陶瓷电学性能的影响

研究了Nb2O5对ZnO压敏材料电学性能的影响。当x(Nb2O5)从0增加到1％时，ZnO压敏电阻的击穿电压从209V／mm降至0．70V／mm，40Hz时，样品电阻从0．21MΩ降至48．3Ω，1kHz时的相对介电常数从831增大到42200。晶界势垒高度测量表明：在实验范围内，Nb对势垒高度的影响较小。ZnO晶粒的变大是压敏电压急剧降低和介电常数增大的主要原因。对Nb掺杂量的增加引起样品阻抗减小的根源进行了解释。     

Nb—Si—N混合薄膜的HRTEM观察

Ｖｅｐｒｅｋ等[1] 在ＴｉＮ薄膜中加入Ｓｉ形成的由非晶Ｓｉ3 Ｎ4分隔的纳米晶ＴｉＮ薄膜 (记为ｎ ＴｉＮ ａ Ｓｉ3 Ｎ4) ,呈现出超高硬度而成为近年来超硬薄膜的研究热点之一。ＮｂＮ薄膜具有很高的硬度 ,高的耐磨性 ,耐腐蚀性[2 ] 和良好的热稳定性[3 ] 。ＮｂＮ薄膜中添加Ｓｉ元素也是改善其性能的途径之一。为了深入地研究Ｓｉ对ＮｂＮ薄膜微结构和力学性能的影响及其机理 ,本文采用多靶磁控反应溅射的方法制备了Ｎｂ Ｓｉ Ｎ系混合薄膜 ,研究了Ｓｉ在Ｎｂ Ｓｉ Ｎ系薄膜中的存在形式 ,及其对薄膜的微结构和力学性能的影响。实验所用Ｎ…     

基于Nb/Mc口的话音质量评估研究

随着移动通信日益普及,用户对服务品质和性能的要求也越来越高。话音业务作为用户最基本的业务,是评价用户感知质量的最重要方面。如何客观评估话音质量,高效地发现现网话音业务中存在的问题,定位问题的产生原因,都是移动通信网络维护面临的新课题。本文研究的内容,就是通过分析现网的话音媒体流,对用户通话的质量进行评估,定位话音降质的故障原因及故障点,并使媒体流的分析能够结合实际工作的需要,提供与话音质量相关的核心网、无线网支撑服务,即研究网络改造解决新方案。     

Lifetime of excess electrons in Cu–Zn–Sn–Se powders

The method of time-resolved microwave photoconductivity at a frequency of 36 GHz in the range of temperatures of 200–300 K is used to study the kinetics of the annihilation of charge carriers in Cu–Zn–Sn–Se powders obtained by the solid-phase method of synthesis in cells. The lifetime of excess electrons at room temperature is found to be shorter than 5 ns. The activation energy for the process of recombination amounted to E _a ~ 0.054 eV.     

The forward bias current density–voltage–temperature (J–V–T) characteristics of Al–SiO2–pSi (MIS) Schottky diodes

Metal–insulator–semiconductor Schottky diodes were fabricated to investigate the tunnel effect and the dominant carrier transport mechanism by using current density–voltage (J–V) and capacitance–voltage (C–V) measurements in the temperature range of 295–370?K. The slope of the ln?J–V curves was almost constant value over the nearly four decades of current and the forward bias current density J is found to be proportional to J_o (T) exp(AV). The values of N_ss estimated from J–V and C–V measurements decreased with increasing temperature. The temperature dependence of the barrier heights obtained from forward bias J–V was found to be entirely different than that from the reverse bias C–V characteristics. All these behaviours confirmed that the prepared samples have a tunnel effect and the current transport mechanism in the temperature range of 295–370?K was predominated by a trap-assisted multi-step tunnelling, although the Si wafer has low doping concentration and the measurements were made at moderate temperature.     

Photon-assisted capacitance–voltage study of organic metal–insulator–semiconductor capacitors

The results are reported of a detailed investigation into the photoinduced changes that occur in the capacitance–voltage (C–V) response of an organic metal–insulator–semiconductor (MIS) capacitor based on the organic semiconductor poly(3-hexylthiophene), P3HT. During the forward voltage sweep, the device is driven into deep depletion but stabilizes at a voltage-independent minimum capacitance, C_min, whose value depends on photon energy, light intensity and voltage ramp rate. On reversing the voltage sweep, strong hysteresis is observed owing to a positive shift in the flatband voltage, V_FB, of the device. A theoretical quasi-static model is developed in which it is assumed that electrons photogenerated in the semiconductor depletion region escape geminate recombination following the Onsager model. These electrons then drift to the P3HT/insulator interface where they become deeply trapped thus effecting a positive shift in V_FB. By choosing appropriate values for the only disposable parameter in the model, an excellent fit is obtained to the experimental C_min, from which we extract values for the zero-field quantum yield of photoelectrons in P3HT that are of similar magnitude, 10^?5 to 10^?3, to those previously deduced for π-conjugated polymers from photoconduction measurements. From the observed hysteresis we deduce that the interfacial electron trap density probably exceeds 10¹⁶ m^?2. Evidence is presented suggesting that the ratio of free to trapped electrons at the interface depends on the insulator used for fabricating the device.     

Four-Dimensional Gallant–Lambert–Vanstone Scalar Multiplication

The GLV method of Gallant, Lambert, and Vanstone (CRYPTO 2001) computes any multiple kP of a point P of prime order n lying on an elliptic curve with a low-degree endomorphism Φ (called GLV curve) over $\mathbb{F}_{p}$ as $$kP = k_1P + k_2\varPhi(P) \quad\text{with } \max \bigl\{ |k_1|,|k_2| \bigr\} \leq C_1\sqrt{n} $$ for some explicit constant C ₁>0. Recently, Galbraith, Lin, and Scott (EUROCRYPT 2009) extended this method to all curves over $\mathbb{F}_{p^{2}}$ which are twists of curves defined over $\mathbb{F}_{p}$ . We show in this work how to merge the two approaches in order to get, for twists of any GLV curve over $\mathbb{F}_{p^{2}}$ , a four-dimensional decomposition together with fast endomorphisms Φ,Ψ over $\mathbb{F}_{p^{2}}$ acting on the group generated by a point P of prime order n, resulting in a proven decomposition for any scalar k∈[1,n] given by $$kP=k_1P+ k_2\varPhi(P)+ k_3\varPsi(P) + k_4\varPsi\varPhi(P) \quad \text{with } \max_i \bigl(|k_i| \bigr)< C_2\, n^{1/4} $$ for some explicit C ₂>0. Remarkably, taking the best C ₁,C ₂, we obtain C ₂/C ₁<412, independently of the curve, ensuring in theory an almost constant relative speedup. In practice, our experiments reveal that the use of the merged GLV–GLS approach supports a scalar multiplication that runs up to 1.5 times faster than the original GLV method. We then improve this performance even further by exploiting the Twisted Edwards model and show that curves originally slower may become extremely efficient on this model. In addition, we analyze the performance of the method on a multicore setting and describe how to efficiently protect GLV-based scalar multiplication against several side-channel attacks. Our implementations improve the state-of-the-art performance of scalar multiplication on elliptic curves over large prime characteristic fields for a variety of scenarios including side-channel protected and unprotected cases with sequential and multicore execution.     

Electron Microscopy Study of Ferroelectric Memory Based on Si–SiO2–Ti–Pt–PZT Multilayer Structure

Model Si–SiO₂–Ti–Pt–PZT multilayer structures obtained by chemical solution deposition at excessive (relative to the stoichiometric composition) amounts of lead in the starting film-forming solution (x= 0–30 mol %) were studied by TEM and X-ray microanalysis techniques. In the absence of excessive lead, the films crystallize largely into the metastable phase of pyrochlore, which does not have ferroelectric properties. With an excessive amount of lead added, PZT ceramic crystallizes into the ferroelectric phase of perovskite and has columnar grains 0.2 m in size. The thermal stability of the metallization system during the formation of the ferroelectric film was investigated. A 180-nm-thick transition layer between the Pt electrode and the adhesive titanium film was discovered. This layer, resulting from high-temperature synthesis, consists of fine-grain platinum, as well as metal oxides and silicides.     

Zn0.15Nb0.3Ti0.55-x(Co1/3Nb2/3)xO2陶瓷的微波介电性能研究

采用固相烧结法制备Zn0.15Nb0.3Ti0.55-x(Co1/3Nb2/3)xO2(x=0,0.05,0.15,0.25,0.35,0.4,0.45,0.55)陶瓷,研究了(Co1/3 Nb2/3)4+取代Ti4+对陶瓷的物相、微观形貌和微波介电性能的影响.实验结果表明,当(Co1/3 Nb2/3)4+取代量x≤0...     

Nb掺杂量对SrBiFeO基陶瓷NTC特性的影响

采用传统固相法,按化学式Sr0.65Bi1-xFe0.35NbxO3(x=0.01,0.02,0.05,0.10和0.20)制备了具有NTC特性的Nb掺杂SrBiFeO基陶瓷试样。研究了Nb掺杂量对其NTC特性的影响。结果表明:试样的ρ25和B25/85值随着Nb含量的增加都呈现增加趋势;在25~200℃的测试温区内,其电阻率–温度特性呈现近似的线性关系;当x为0.05时,线性关系较好,其中ρ25的值约为6700?·cm,B25/85值约为3540K。     

失效HP40+Nb乙烯裂解炉管的SEM分析

本工作是应用ＳＥＭ显微分析方法，对某厂意外破裂的离心铸造乙烯裂解炉管进行了失效分析。该炉管外径为１３５ｍｍ，壁厚为７．５ｍｍ，设计规定的使用温度≤１１１５℃，压力＝０．１８５ＭＰａ，使用寿命为５年。但实际使用不足１年即在装料运行中发生破裂事故，裂口位...     

Nb，Ti对钢的显微组织结构的影响

微合金钢是一类应用广泛、强度高、延性和韧性优良，可焊性和成形性好的新材料，工业上通常通过添Nb，Ti等微合金元素改善微合金钢的微观组织状态，以改善其综合性能。