Fabrication of Bistable Switching Memory Devices Utilizing Polymer–ZnO Nanocomposites

This work reports fabrication of bistable memory switching devices employing wet-chemically synthesized ZnO nanoparticles with polymethyl methacrylate and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] polymers. ZnO nanoparticle-embedded polymer layers were coated on conducting indium tin oxide (ITO) glasses using the spin-coating technique. Synthesized ZnO nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, energy-dispersive x-ray, and photoluminescence studies. These ZnO particles are 20?nm to 30?nm in size with hexagonal structure. Switching and memory effects of the devices fabricated employing the ZnO nanoparticle?Cpolymer composite films were investigated using current?Cvoltage (I?CV) characteristics. The I?CV measurements of both polymer devices showed electrical bistability. The ON to OFF current ratio of the bistable device was found to be ??10³. The observed current?Ctime response showed good memory retention behavior of the fabricated devices. The carrier transport mechanism of the devices has been described on the basis of I?CV experimental results and electronic structure.     

Self‐Powered,Room‐Temperature Electronic Nose Based on Triboelectrification and Heterogeneous Catalytic Reaction

Herein, a self‐powered electronic nose strategy with highly selective gas detection is described. The electronic nose is a two‐dimensional microarray based on the triboelectrification between ZnO nanowires and the dielectric layers, and the heterogeneous catalytic reaction occurring on the nanowires and on the NiO nanoparticles. These electronic noses show the ability to distinguish between four volatile organic compound (VOC) gases (methanol, ethanol, acetone, and toluene) with a detection limit of 0.1% at room temperature using no external power source.     

无催化剂气相沉积法直接制备用于紫外光检测的氧化锌纳米线网

对于环境检测和高速光通信而言,高性能紫外光电探测器是关键。利用气相沉积法在无催化剂条件下制备氧化锌纳米线网,在纳米线网上直接制备光电器件的性能得到了提高。结果显示,纳米线网光电探测器的光电流为60 A,大约是单根纳米线光电器件光电流的15倍。详细讨论纳米线网光电探测器的响应机制发现,在纳米线网内,纳米线与纳米线之间的结势垒高度决定了纳米线内部载流子的传输。当紫外光照射纳米线网光电探测器时,纳米线与纳米线之间结势磊高度的快速变低,从而提高光电器件的性能。     

Catalytic and Light‐Driven ZnO/Pt Janus Nano/Micromotors: Switching of Motion Mechanism via Interface Roughness and Defect Tailoring at the Nanoscale

The first models of mesoporous ZnO/Pt Janus micromotors that show fuel‐free and light‐powered propulsion depending on the interface roughness are shown. Two models of ZnO semiconducting particles with distinct surface morphologies and pore structures are synthesized by self‐aggregation of primary nanoparticles and nanosheets into nanoscale rough and smooth microparticles, respectively. The self‐assembled nanosheet model (smooth) provides a large surface for the formation of a continuous Pt layer with strong adherence, whereas the discontinuous Pt species take place inside the inter‐nanoparticles pores in the self‐assembled nanoparticle model (rough). The effects of the interface, surface porosity, defect, and charge transfer on the light‐powered motion for both well‐designed mesoporous ZnO/Pt Janus micromotors are investigated and compared to find the underlying propulsion mechanisms. The degradation of two model pollutants is demonstrated as a proof‐of‐concept application of these carefully engineered Janus micromotors. In this work, it is shown that by discreet material fabrication together with semiconductor/metal interface charge transport interpretation, it would be possible to develop new light‐driven Janus micromotors based on other photocatalysts containing active surfaces such as TiO₂.     

Nanocomposite Microcontainers with High Ultrasound Sensitivity

A water suspension of nanocomposite microcapsules with embedded ZnO nanoparticles in the capsule shell is reported. The microcapsule morphology is characterized by confocal microscopy, TEM, SEM, and AFM before and after ultrasound treatment. A remarkably high capsule sensitivity to ultrasound is evidenced, and it is observed to grow with increasing number of ZnO nanoparticle layers in the nanocomposite shell. This effect is correlated with the mechanical properties of microcapsules measured with AFM.     

Ordered Superparticles with an Enhanced Photoelectric Effect by Sub‐Nanometer Interparticle Distance

As the development in self‐assembly of nanoparticles, a main question is directed to whether the supercrystalline structure can facilitate generation of collective properties, such as coupling between adjacent nanocrystals or delocalization of exciton to achieve band‐like electronic transport in a 3D assembly. The nanocrystal surfaces are generally passivated by insulating organic ligands, which block electronic communication of neighboring building blocks in nanoparticle assemblies. Ligand removal or exchange is an operable strategy for promoting electron transfer, but usually changes the surface states, resulting in performance alteration or uncontrollable aggregation. Here, 3D, supercompact superparticles with well‐defined superlattice domains through a thermally controlled emulsion‐based self‐assembly method is fabricated. The interparticle spacing in the superparticles shrinks to ≈0.3 nm because organic ligands lie prone on the nanoparticle surface, which are sufficient to overcome the electron transfer barrier. The ordered and compressed superstructures promote coupling and electronic energy transfer between CdSSe quantum dots (QDs). Therefore, the acquired QD superparticles exhibit different optical properties and enhanced photoelectric activity compared to individual QDs.     

Data-centric optical networks and their survivability

The explosive growth of data traffic-for example, due to the popularity of the Internet-poses important emerging network requirements on today's telecommunication networks. This paper describes how core networks will evolve to optical transport networks (OTNs), which are optimized for the transport of data traffic, resulting in an IP-directly-over-OTN paradigm. Special attention is paid to the survivability of such data-centric optical networks. This becomes increasingly crucial since more and more traffic is multiplexed onto a single fiber (e.g., 160×10 Gb/s), implying that a single cable cut can affect incredible large traffic volumes. In particular, this paper is tackling multilayer survivability problems, since a data-centric optical network consists of at least an IP and optical layer. In practice, this means that the questions "in which layer or layers should survivability be provided?" and "if multiple layers are chosen for this purpose, then how should this functionality in these layers be coordinated?" have to be answered. In addition to a theoretical study, some case studies are presented in order to illustrate the relevance of the described issues and to help in strategic planning decisions. Two case studies are studying the problem from a capacity viewpoint. Another case study presents simulations from a timing/throughput performance viewpoint     

Optical accelerator of nanoparticles

A model of the optical nanoaccelerator that allows the acceleration of nanoparticles to velocities of several meters per second with the aid of low-intensity external fields is proposed. The system is based on the application of the plasmon resonator that exhibits a relatively high gain of local field, which leads to a significant increase in the gradient optical force that is exerted on the nanoobject. The conditions under which the nanoparticle is pushed out from the resonator by the gradient force, so that a shot effect is observed, are determined. The effect of the perturbation that is introduced by the nanoparticle in the field distribution in the resonator on the electromagnetic forces and the acquired energy is analyzed.     

金属纳米二聚体结构的局域表面等离子体激元共振特性研究

将金属纳米粒子二聚体结构作为光学谐振腔,采用 时域有限差分(FDTD)法仿真模拟了一种新型局域表面等离子体激光器(SPASER)。 使用洛伦兹复介电常数模型研究二聚体的增益介质特性,探讨了二聚体结构中 两个纳米局域表面等离子体激元共振(LSPR)以及相互作用机制,进一步研究了 LSPR相互作用对SPASER的局域场增强的影响。 模拟结果表明,相比较单纳米颗粒SPASER,LSPR的相互作用使得二聚体SPASER的局域电场显著 增强,增强因子最 大可以相差27倍。本文研究为纳米光学器件尤其是激光器件的设计提 供了依据。LSPR效应的 研究可以用于探索一些光与物质相互作用的极限效 应,从而为有源光子线路、生物传感以及量子信息处理等研究开辟道路。     

Coulomb Enhanced Charge Transport in Semicrystalline Polymer Semiconductors

Polymer semiconductors provide unique possibilities and flexibility in tailoring their optoelectronic properties to match specific application demands. The recent development of semicrystalline polymers with strongly improved charge transport properties forces a review of the current understanding of the charge transport mechanisms and how they relate to the polymer's chemical and structural properties. Here, the charge density dependence of field effect mobility in semicrystalline polymer semiconductors is studied. A simultaneous increase in mobility and its charge density dependence, directly correlated to the increase in average crystallite size of the polymer film, is observed. Further evidence from charge accumulation spectroscopy shows that charges accumulate in the crystalline regions of the polymer film and that the increase in crystallite size affects the average electronic orbitals delocalization. These results clearly point to an effect that is not caused by energetic disorder. It is instead shown that the inclusion of short range coulomb repulsion between charge carriers on nanoscale crystalline domains allows describing the observed mobility dependence in agreement with the structural and optical characterization. The conclusions that are extracted extend beyond pure transistor characterization and can provide new insights into charge carrier transport for regimes and timescales that are relevant to other optoelectronic devices.     

Organization of Organic Molecules with Inorganic Nanoparticles: Hybrid Nanodiodes

A monolayer of inorganic nanoparticles and a monolayer of organic molecules have been electrostatically assembled in sequence. Such assemblies or organizations exhibit electrical rectification. When the sequence of the organization is reversed, the direction of rectification becomes opposite. In both n‐type ZnO/organic and organic/n‐ZnO assemblies, electron flow is favorable from the n‐ZnO nanoparticle to the (electron‐accepting) organic molecule. While the individual components do not show any rectification, substitutes of the organic molecule tune electrical rectification. Junctions between a p‐type ZnO nanoparticle and an electron‐donating metal phthalocyanine favor current flow in the nanoparticle‐to‐phthalocyanine direction. The rectification in a junction between a nanoparticle and an organic molecule is due to the parity between free carriers in the former component and the type of carrier‐accepting nature in the latter one. By observing electrical rectification with the tip of a scanning tunneling microscope, organic/inorganic hybrid nanodiodes or rectifiers on the molecular/nanoscale have been established.     

新一代智能城域光网络

本提出了一种标准化的光控制平面。阐明了开了用于光传输网的控制平面所遇到的选择与挑战。光控制平面被分解成邻居发现、服务发现、连接控制和拓扑、资源发现等几个基本的过程。不同的网络组织和分割导致了几个不同的自动配置模型：软性持久链路模型、用户接口模型和对等模型。这是构成以IP为中心的光传输网的控制和管理基础。同时也介绍了基于SDH光交换的新一代CIENA公司智能光网络，它具有大容量光交换能力和网络拓扑结构自动发现、端对端电路配置、带宽动态分配等功能及特点，将大大提高数据、电路业务的服务质量，新一代智能光网络是干线和城域网络交换传输最佳的选择。     

Composite materials based on nanostructured zinc oxide

Composites formed from ZnO nanorods in combination with CuO or Ag nanoparticles are produced by the deposition of CuO or Ag nanoparticles onto ZnO nanorod arrays grown by the hydrothermal technique. The CuO nanoparticles are synthesized by the vacuum thermal deposition of a Cu layer followed by vacuum annealing at a temperature of 350°C for 1 h. CuO particles covered with a layer of nanoneedles are obtained. The current-voltage characteristics of the ZnO/CuO layers are indicative of the formation of a p-n junction. The ZnO/Ag composites are produced by the electrical deposition of Ag nanoparticles synthesized in an aqueous solution of silver nitrate and sodium citrate. The surface morphology and the optical and electrical properties of the samples are studied.     

Three‐Dimensional Inkjet‐Printed Interconnects using Functional Metallic Nanoparticle Inks

Inkjet‐printed gold nanoparticle pillars are investigated as a high‐performance alternative to conventional flip‐chip interconnects for electronic packages, with significant advantages in terms of mechanical/chemical robustness and conductivity. The process parameters critical to pillar fabrication are described and highly uniform pillar arrays are demonstrated. More generally, this work underscores the impact of sintering on the electrical, mechanical, structural, and compositional properties of three‐dimensional nanoparticle‐based structures. Using heat treatments as low as 200 °C, electrical and mechanical performance that outcompetes conventional lead‐tin eutectic solder materials is achieved. With sintering conditions reaching 300 °C it is possible to achieve pillars with properties comparable to bulk gold. This work demonstrates the immense potential for both inkjet printing and metal nanoparticles to become a viable and cost‐saving alternative to both conventional electronic packaging processes and application‐specific integration schemes.     

ZnO as a dielectric for organic thin film transistor-based non-volatile memory

This paper demonstrates the novel application of d.c. sputtered zinc oxide (ZnO) as a charge trapping dielectric material for the application of an organic thin film transistor (OTFT) based non-volatile memory (NVM). The motivation of using ZnO as a dielectric is due to its chemical stability and optical transparency, enabling future development of transparent electronic devices. Unbalanced magnetron d.c. sputtering with Ar:O₂ ratio of 80:20 was used to obtained a ZnO dielectric of 50 nm thick. The ZnO has an optical band gap of 3.23 eV, resistivity and k-value of 5 × 10⁷ Ω-cm and 50, respectively. The ZnO sandwiched between two layers of low-k methyl-silsesquioxane (MSQ) sol–gel dielectric creates a triple layer dielectric structure for charge storage. A solution-processable pentacene, 13,6-N-Sulfinylacetamodipentacene, was used as an active layer of an OTFT-NVM. It has been successfully demonstrated that this OTFT-NVM can be electrically programmed and erased at a low voltage.     

A General Method: Designing a Hypocrystalline Hydroxide Intermediate to Achieve Ultrasmall and Well‐Dispersed Ternary Metal Oxide for Efficient Photovoltaic Devices

Solution‐process fine metal‐oxide nanoparticles are promising carrier transport layer candidates for unlocking the full potential of solution process in solar cells, due to their low cost, good stability, and favorable electrical/optical properties. However, exotic organic ligands adopted for achieving small size and monodispersion can mostly cause poor conductivity, which thus impedes their electrical application. In this work, a concept of constructing a hypocrystalline intermediate is proposed to develop a general method for synthesizing various ternary metal oxide (TMO) nanoparticles with a sub‐ten‐nanometer size and good dispersibility without exotic ligands. Particularly, a guideline is summarized based on the understandings about the impact of metal ion intercalation as well as water and anion coordination on the hypocrystalline intermediate. A general method based on the proposed concept is developed to successfully synthesize various sub‐ten‐nanometer TMO nanoparticles with excellent ability for forming high‐quality (smooth and well‐coverage) films. As an application example, the high‐quality films are used as hole transport layers for achieving high‐performance (stability and efficiency) organic/perovskite solar cells. Consequently, this work will contribute to the development of TMO for large‐scale and high‐performance optoelectronic devices and the concept of tailoring intermediate can leverage the fundamental understandings of synthesis strategies for other metal oxides.     

Zinc Oxide Nanoparticles with Defects

Zinc oxide in the form of nanoscale materials can be regarded as one of the most important semiconductor oxides at present. However, the question of how chemical defects influence the properties of nanoscale zinc oxide materials has seldom been addressed. In this paper, we report on the introduction of defects into nanoscale ZnO, their comprehensive analysis using a combination of techniques (powder X‐ray diffraction (PXRD), X‐ray absorption spectroscopy/extended X‐ray absorption fine structure (XAS/EXAFS), electron paramagnetic resonance (EPR), magic‐angle spinning nuclear magnetic resonance (MAS‐NMR), Fourier‐transform infrared (FTIR), UV‐vis, and photoluminescence (PL) spectroscopies coupled with ab‐initio calculations), and the investigation of correlations between the different types of defects. It is seen that defect‐rich zinc oxide can be obtained under kinetically controlled conditions of ZnO formation. This is realized by the thermolysis of molecular, organometallic precursors in which ZnO is pre‐organized on a molecular scale. It is seen that these precursors form ZnO at low temperatures far from thermodynamic equilibrium. The resulting nanocrystalline ZnO is rich in defects. Depending on conditions, ZnO of high microstructural strain, high content of oxygen vacancies, and particular content of heteroatom impurities can be obtained. It is shown how the mentioned defects influence the electronic properties of the semiconductor nanoparticles.     

The application of optical packet switching in future communicationnetworks

Telecommunication networks are experiencing a dramatic increase in demand for capacity, much of it related to the exponential takeup of the Internet and associated services. To support this demand economically, transport networks are evolving to provide a reconfigurable optical layer which, with optical cross-connects, will realize a high-bandwidth flexible core. As well as providing large capacity, this new layer will be required to support new services such as rapid provisioning of an end-to-end connection under customer control. The first phase of network evolution, therefore, will provide a circuit-switched optical layer characterized by high capacity and fast circuit provisioning. In the longer term, it is currently envisaged that the bandwidth efficiency associated with optical packet switching (a transport technology that matches the bursty nature of multimedia traffic) will be required to ensure economic use of network resources. This article considers possible network application scenarios for optical packet switching. In particular, it focuses on the concept of an optical packet router as an edge network device, functioning as an interface between the electronic and optical domains. In this application it can provide a scalable and efficient IP traffic aggregator that may provide greater flexibility and efficiency than an electronic terabit router with reduced cost. The discussion considers the main technical issues relating to the concept and its implementation     

Next-generation optical storage area networks: the light-trails approach

Multiple architectures, technologies, and standards have been proposed for storage area networks, typically in the WAN environment. The transport aspect of storage signifies that optical communications is the key underlying technology. The contemporary SAN over optical network concept uses the optical layer for pure transport with minimal intelligence. This leads to high cost and overprovisioning. Future optical networks, however, can be expected to play a role in optimizing SAN extension into the WAN. An essential characteristic of SAN systems is tight coupling between nodes in a SAN network. Nodes in a SAN system have two critical functions that are presently emulated by data layers and can be offloaded to the optical layer. First, nodes need to signal among each other to achieve tasks such as synchronous and asynchronous storage. Second, to benefit from an optimized network, nodes need to allocate bandwidth dynamically in real time. In this article we show how the optical layer can be furthered from just pure transport to creating opportunities in provisioning as well as providing the mirroring function of SAN systems (multicasting) and consequently lead to reduction in cost. We demonstrate that the light-trail model is one way of efficiently utilizing the optical layer for SAN.