双势垒磁性隧道结的磁电阻效应及其在自旋晶体管中的应用

利用磁控溅射方法沉积双势垒磁性隧道结多层膜, 其中Al-O势垒层由等离子体氧化1 nm厚的 金属铝膜方式制备，然后采用深紫外光曝光和Ar离子刻蚀技术、微加工制备出长短轴分别为 6和3 μm大小的椭圆形双势垒磁性隧道结（DBMTJ），并在室温和低温下对其自旋电子输运 特性进行了研究. DBMTJ的隧穿磁电阻(TMR)比值在室温和42 K分别达到27％和423％， 结电阻分别为136 kΩ·μm²和175 kΩ·μm²，并在实验中观 察到平行状 态下存在低电阻态及共振隧穿效应，反平行态下呈现高电阻态以及TMR随外加偏压或直流电 流的增加而发生振荡现象. 由此，设计了一种基于这种双势垒磁性隧道结隧穿特性的自旋晶 体管. 关键词： 双势垒磁性隧道结 隧穿磁电阻 共振隧穿效应 自旋晶体管     

MoS2/MoTe2垂直异质结的电荷传输及其调制

二维材料异质结器件具有纳米级厚度及范德瓦耳斯接触表面,因而表现出独特的光电特性.本文构建了栅压可调的MoS₂/MoTe₂垂直异质结器件,利用开尔文探针力显微镜(KPFM)技术结合电输运测量,揭示了MoS₂/MoTe₂异质结分别在黑暗和532 nm激光照射条件下的电荷输运行为,发现随着栅压的变化异质结表现出从n-n⁺结到p-n结的反双极性特征.系统地解释了MoS₂/MoTe₂异质结的电荷输运机制,包括n-n⁺结和p-n结在正偏和反偏下条件下的电荷输运过程、随栅压变化而发生的转变的结区行为、接触势垒对电荷输运的影响、n-n⁺结和p-n结具有不同整流特征的原因、偏压对带间隧穿的重要作用及光生载流子对电学输运行为的影响等.本文所使用的方法可推广到其他二维异质结体系,为提高二维半导体器件性能及其应用提供了重要的参考和借鉴.     

V2O5电极修饰对C60/Pentacene双层异质结场效应晶体管性能的影响

制备了用过渡金属氧化物V₂O₅修饰Al源、漏电极的C₆₀/Pentacene双层异质结有机场效应管.该构型器件与未修饰器件相比,呈现出典型的双极型晶体管传输特性.电子迁移率和空穴迁移率分别达到8.6×10^-2cm²/V·s^-1和6.4×10^-2cm²/V·s^-1,阈值电压分别为25 V和-25 V.器件性能改善的原因主要是由于插入V₂O₅修饰层后,可以明显降低Al电极与Pentacene之间的接触势垒,提高空穴的有效注入,从而使电子和空穴的注入接近平衡.研究表明,采用V₂O₅修饰电极方法,是制备低成本、高性能的双极型有机场效应管并实现其商业应用的有效途径.     

金属-绝缘体-半导体(Au-SiO2-Si)隧道结的负阻现象与发光特性

制备了Au-SiO_{2-Si结构MIS隧道发光结.测试并分析了该结的发光特性及电流-电压(I-V)特性.指出结的发光是由各膜层界面激发的表面等离极化激元(Surface Plasmon Polariton.SPP)与膜层表面粗糙度相互耦合的结果.观察到MIS结I-V特性中存在的负阻现象,采用SPP对电子的束缚模型对这一现象进行了初步分析.利用原子力显微镜(AFM)对结的表面形貌进行了观测,由此讨论了MIS隧道结的发光与电子在结内的隧穿输运特性之间的内在关系. 关键词：}     

硅基双势垒金属-绝缘层-金属-绝缘层-半导体隧道发光结

讨论了硅基双势垒金属－绝缘层－金属－绝缘层－半导体（MIMIS）隧道发光结的结构、制备方法及发光特性。所制备的样品最大发光亮度达到1．9cd/m^2、光谱的峰值波长移到了蓝绿光区，表明双势垒MIMIS隧道发光结的性能优于单势垒金属－绝缘层－半导体（MIS）隧道发光结。利用量子力学的共振隧穿效应对它作了较好的解释。     

Li2Mo2O6多晶材料的结构与电性能的研究

本文用固相反应烧结制备出Li₂Mo₂O₆多晶材料。经X射线分析、红外光谱和电子顺磁共振谱(EPR)的研究,确定了它的结构是Li₂Mo₂O₄和MoO₂两个晶相组成的烧结体。钼离子以四价状态存在于MoO₂晶相结构中。采用交流阻抗谱分析了晶界与温度变化的相关性。测得了样品的ln(σ_总T)-1/T 曲线是由两段直线和一段曲线所组成;总电导率化能σ_27℃=1.36×10^-3(Ω·cm)^-1,σ_115℃=1.49×10^-3(Ω·cm)^-1,σ_300℃=9.71×10^-3(Ω·cm)^-1,σ_370℃=2.42×10^-3(Ω·cm)^-1;电导活化能E₁=0.043eV,E₂=0.235eV,E_平均=0.76eV。采用维格纳极化电池法测得电子电导率σ_e,σ_e27℃=2.240×10^-5(Ω·cm)^-1,σ_e300℃=4.476×10^-3(Ω·cm)^-1。实验证明,室温下材料为固体电解质,300℃附近为良好的离子与电子混合导体。 关键词：     

Au/(SiO2/Si/SiO2)纳米双势垒/n+-Si结构的电致发光研究

利用射频磁控溅射方法,在n⁺-Si衬底上淀积SiO₂/Si/SiO_{2纳米双势垒单势阱结构,其中Si层厚度为2至4nm,间隔为0.2nm,邻近n⁺-S i衬底的SiO2层厚度固定为1.5nm,另一SiO2层厚度固定为3nm.为了 对比研究,还制备了Si层厚度为零的结构,即SiO2(4.5nm)/n⁺-Si 结构.在经过600℃氮气下退火30min,正面蒸上半透明Au膜,背面也蒸Au作欧姆接触后,所 有样品都在反向偏置(n^＋-Si的电压高于Au电极的电压)下发光,而在正向偏压 下不发光.在一定的反向偏置下,电流和电致发光强度都随Si层厚度的增加而同步振荡,位 相相同.所有样品的电致发光谱都可分解为相对高度不等的中心位于2.26eV(550nm)和1.85eV (670nm)两个高斯型发光峰.分析指出该结构电致发光的机制是：反向偏压下的强电场使Au/( SiO2/Si/SiO2)纳米双势垒/n⁺-Si结构发生了雪崩击穿 ,产生大量的电子-空穴对,它们在纳米SiO2层中的发光中心(缺陷或杂质)上复 合而发光. 关键词： 电致发光 纳米双势垒 高斯型发光峰 雪崩击穿}     

金属-绝缘体-金属隧道发光结的电子隧穿和负阻现象

薄膜Au-Al₂O₃-Al隧道结(MIMTJ)在产生可见光发射的同时表现出了明显的负阻现象.这种负阻现象的物理机制是由于结中产生了作为发光中介作用的表面等离极化激元(SPP)对隧穿电子的阻挡作用.通过MIMTJ的电子输运的电路模拟和I-V特性的数值计算，揭示了SPP在I-V特性曲线中的负阻、隧道结发光中所起的关键作用. 关键词：     

Ga2S3-Sb2S3-Ag2S硫系玻璃和光纤的制备及性能研究

本工作确定了一种新型的Ga₂S₃-Sb₂S₃-Ag₂S硫系玻璃体系的玻璃形成区,研究了玻璃的热稳定性和光学性能、稀土离子掺杂玻璃的中红外发光特性以及玻璃的成纤性能,评估了该玻璃在中红外波段的应用潜力.实验结果表明,Ga₂S₃-Sb₂S₃-Ag₂S体系的玻璃形成区为～10%—30%Ga₂S₃,～60%—80%Sb₂S₃和～0—15%Ag₂S(均为摩尔分数);该玻璃具有较宽的红外透过范围(～0.8—13.5μm)、较高的线性折射率(～2.564—2.713@10μm)和较大的三阶非线性折射率(～9.7×10^-14—15.7×10^-14 cm²/W@1.55μm);使用1.32μm激光抽运,稀土离子Dy...     

处理具有任意形状势垒的磁性隧道结中电子输运的一个简单方法

在Slonczewski自由电子模型的基础上,提出了一个可用于处理具有任意形状势垒的磁性隧道结中磁电子输运的简单方法,并以三种常见构形的势垒,即梯形势垒,计入了镜像势的梯形势垒和抛物线势垒为例,讨论了势垒形状对隧穿磁电阻及其随偏压变化的影响. 关键词： 磁性隧道结 隧穿磁电阻 任意形状势垒 非零偏压     

Significant Fowler–Nordheim tunneling across ZnO – Nanorod based nanojunctions for nanoelectronic device applications

We demonstrate significant Fowler–Nordheim (FN) tunneling across Al/Al₂O₃/ZnO metal–insulator–semiconductor (MIS) and Ag/ZnO metal–semiconductor (MS) nanojunctions. The transport properties of ZnO nanostructures in the form of urchins and randomly distributed nanorods were investigated in terms of various conduction mechanism. The minimum voltage necessary for triggering Fowler–Nordheim (FN) tunneling, under forward biasing, was ～1.2 V and ～3.4 V; respectively, below which only direct tunneling and thermionic emission events were evident. Mediated through Al₂O₃ layer, the FN tunneling was more prominent across MIS junction than MS one. The weak FN tunneling across MS junction was owing to interfacial charge transfer process through the atomic scale gapping between adjacent nanostructures. The extent of such type of tunneling is found to be nanostructure morphology dependent and largely rely on the free electrons donated by the native donor defects in the crystal structure of ZnO. The significant FN tunneling across the MIS and MS junctions has a direct relevance in designing nanoscale field emission devices/components working at low voltage with high throughputs.     

Differential conductance in normal-metal/insulator/metal/d-wave superconductor junction carrying a supercurrent

This paper applies the Bogoliubov--de Gennes equation and the Blonder--Tinkham--Klapwijk approach to study the oscillatory behaviour of differential conductance in a normal metal/insulator/metal/d-wave superconductor junction carrying a supercurrent I_s. We find that (i) a three-humped structure appears at a nearly critical supercurrent I_s and z ≈ 0.5 for the normal metal/insulator/metal/d_x² + y²-wave superconductor junction; (ii) the zero-bias conductance peak splits into two peaks with sufficiently large applied current for the normal metal/insulator/metal/d_xy-wave superconductor junction; (iii) the conductance spectrum exhibits oscillating behaviour with the bias voltage and the peaks of the resonances are suppressed by increasing supercurrent I_s.     

ZnSe-ZnS应变超晶格的光致发光

本文讨论了使用常压金属氧化物化学汽相沉积(MOCVD)技术生长的ZnSe-ZnS应变超晶格的发光特性。ZnSe-ZnS应变超晶格的发射光谱,在高密度激发下通常仅存在一个发射峰;在低密度激发下除带边发射之外,还存在深中心的发射;与低密度激发相比,高激发下发光峰值红移且其半高宽展宽,高质量的ZnSe-ZnS应变超晶格在低激发下,带边发光很强,而深中心发射能被大大抑制,我们观测到一个新的激子发射峰,考虑应变效应与量子限制效应,本文将这一新的发射峰归结为与n=1的轻空穴激子有关的复合发光。 关键词：     

The Dependence of Benzo-15-Crown-5 Ether-Containing Oligo Paraphenylene Vinylene (CE-OPV) Emission Upon Complexation with Metal Ions in Solution

The effects of metal salts (NaCl, CaCl₂·2H₂O, EuCl₃·6H₂O and Eu(OAc)₃) on the steady state and time resolved fluorescence behaviour of poly(para phenylene vinylene) oligomers containing benzo-15-crown-5 ether units (CE-OPV) have been investigated. The presence of EuCl₃ causes a significant (8–9 fold) increase in the fluorescence emission intensity of the OPV segments, as compared to pure CE-OPV, in 99:1 methanol/chloroform solution and a small (9 nm) red shift in the emission maximum. The presence of Na⁺ or Ca²⁺ results in less marked increases in fluorescence intensity compared to Eu³⁺. In the presence of Eu³⁺ and Na⁺, the fluorescence intensity increases approximately linearly with metal ion concentration up to a metal ion/CE-OPV molar ratio of 10. The emission enhancement is not related to a simple 1:1 (CE-OPV:metal ion) complex formation process. In contrast, in acetonitrile, CE-OPV shows complex fluorescence quenching behaviour as a function of EuCl₃ concentration. This solvent dependence suggests that the emission changes with metal concentration are related to the formation of charge-transferred complexes. The marked changes in fluorescence quantum yield of the PPV backbone due to complexation with metal ions makes CE-OPV a sensitive fluorescent probe for metal ions, or may be exploited for improving the quantum yield of PPV-based devices.     

Sol-gel derived Y2O3 as an efficient bluish-white phosphor without metal activator ions

In this paper, Y₂O₃ powder phosphors without metal activators were successfully prepared by the sol-gel method. The obtained sample shows an intense bluish-white emission (ranging from 350 to 600 nm, centered at 416 nm) under a wide range of UV light excitation (235-400 nm). The chromaticity coordinates of the sample are x=0.159, y=0.097, and the quantum yield is as high as 64.6%, which is a high value among the phosphor family without metal activators. The luminescent mechanisms have been ascribed to the carbon impurities in the Y₂O₃ host.     

Si中Pt的复合行为

本文在不同本底掺杂浓度的n-Si与p-Si的扩Pt深扩散结样品中,利用暗电容瞬态法观察到了零偏压偏置结的耗尽区内,在E_F以上kT范围的深能级处的电子发射与俘获瞬态过程。这类瞬态行为满足该处不同起始条件的深能级的电子变化率方程的解。本文并对发射瞬态的产生提出了一种机理,认为它的存在是与深扩散结的结构密切有关,至于俘获瞬态则与不同杂质的俘获特性密切有关。 关键词：     

Electronic structure,magnetic properties,and microstructural analysis of thiol-functionalized Au nanoparticles: role of chemical and structural parameters in the ferromagnetic behaviour

The present work describes the field emission characteristics of nanocrystalline metal clusters decorated multi walled carbon nanotubes (MWNT) field emitters fabricated over flexible graphitized carbon cloth. MWNT have been synthesized by catalytic chemical vapour decomposition (CCVD) of acetylene over Rare Earth (RE) based AB₂ (DyNi₂) alloy hydride catalyst. Fine powders of RE based AB₂ alloy hydride catalysts have been prepared by hydrogen decrepitation technique. The as-grown carbon nanotubes (CNTs) are purified by acid and heat treatments and characterized using XRD, SEM and TEM. Purified MWNT have been decorated with nanocrystalline Pd, Pt and Pt–Ru metal clusters using a simple chemical reduction method. The characterization of metal decorated CNTs were done by using XRD, SEM, TEM, HRTEM and EDX. Nanocrystalline Pd, Pt and Pt–Ru metal clusters decorated MWNT field emitters have been fabricated over graphitized carbon fabric using spin coating method. The field emission characteristics have been studied using an indigenously fabricated set up and the results are discussed. The samples show excellent emission properties with a fairly stable emission current over a period of 4 h. As the presence of the graphitic layer provides strong adhesion between the nanotubes and carbon cloth, the use of graphitized carbon cloth as substrate opens new possibilities for CNT field emitters.     

Evaluation of nanoparticle emission for TiO<Subscript>2</Subscript> nanopowder coating materials

In this study, nanoparticle emission of TiO₂ nanopowder coated on different substrates including wood, polymer, and tile, was evaluated in a simulation box and measured with a Scanning Mobility Particle Sizer (SMPS) for the first time. The coating process for the substrate followed the instructions given by the supply company. In the simulation box, UV light, a fan, and a rubber knife were used to simulate the sun light, wind, and human contacting conditions. Among the three selected substrates, tile coated with TiO₂ nanopowder was found to have the highest particle emission (22 #/cm³ at 55 nm) due to nanopowder separation during the simulation process. The UV light was shown to increase the release of particle below 200 nm from TiO₂ nanopowder coating materials. The results show that, under the conditions of UV lamps, a fan and scraping motion, particle number concentration or average emission rate decreases significantly after 60 and 90 min for TiO₂/polymer and TiO₂/wood, respectively. However, the emission rate continued to increase after 2 h of testing for TiO₂/tile. It is suggested that nanoparticle emission evaluation is necessary for products with nanopowder coating.     

n-GaAs表面全息光栅的形成及表面等离振子电磁耦子发光测定

本文讨论n-GaAs表面采用H₂O₂-H₂SO₄系光加速腐蚀形成衍射光栅的方法,以及Ag/n-GaAs肖脱基势垒二极管表面等离振子电磁耦子发光的测定。 关键词：