Bandgap modulation of carbon nanotubes by encapsulated metallofullerenes

Motivated by the technical and economic difficulties in further miniaturizing silicon-based transistors with the present fabrication technologies, there is a strong effort to develop alternative electronic devices, based, for example, on single molecules. Recently, carbon nanotubes have been successfully used for nanometre-sized devices such as diodes, transistors, and random access memory cells. Such nanotube devices are usually very long compared to silicon-based transistors. Here we report a method for dividing a semiconductor nanotube into multiple quantum dots with lengths of about 10nm by inserting Gd@C82 endohedral fullerenes. The spatial modulation of the nanotube electronic bandgap is observed with a low-temperature scanning tunnelling microscope. We find that a bandgap of approximately 0.5eV is narrowed down to approximately 0.1eV at sites where endohedral metallofullerenes are inserted. This change in bandgap can be explained by local elastic strain and charge transfer at metallofullerene sites. This technique for fabricating an array of quantum dots could be used for nano-electronics and nano-optoelectronics.     

Compact, stable and efficient all-fibre gas cells using hollow-core photonic crystal fibres

Gas-phase materials are used in a variety of laser-based applications--for example, in high-precision frequency measurement, quantum optics and nonlinear optics. Their full potential has however not been realized because of the lack of a suitable technology for creating gas cells that can guide light over long lengths in a single transverse mode while still offering a high level of integration in a practical and compact set-up or device. As a result, solid-phase materials are still often favoured, even when their performance compares unfavourably with gas-phase systems. Here we report the development of all-fibre gas cells that meet these challenges. Our structures are based on gas-filled hollow-core photonic crystal fibres, in which we have recently demonstrated substantially enhanced stimulated Raman scattering, and which exhibit high performance, excellent long-term pressure stability and ease of use. To illustrate the practical potential of these structures, we report two different devices: a hydrogen-filled cell for efficient generation of rotational Raman scattering using only quasi-continuous-wave laser pulses; and acetylene-filled cells, which we use for absolute frequency-locking of diode lasers with very high signal-to-noise ratios. The stable performance of these compact gas-phase devices could permit, for example, gas-phase laser devices incorporated in a 'credit card' or even in a laser pointer.     

Self-assembled monolayer organic field-effect transistors

The use of individual molecules as functional electronic devices was proposed in 1974 (ref. 1). Since then, advances in the field of nanotechnology have led to the fabrication of various molecule devices and devices based on monolayer arrays of molecules. Single molecule devices are expected to have interesting electronic properties, but devices based on an array of molecules are easier to fabricate and could potentially be more reliable. However, most of the previous work on array-based devices focused on two-terminal structures: demonstrating, for example, negative differential resistance, rectifiers, and re-configurable switching. It has also been proposed that diode switches containing only a few two-terminal molecules could be used to implement simple molecular electronic computer logic circuits. However, three-terminal devices, that is, transistors, could offer several advantages for logic operations compared to two-terminal switches, the most important of which is 'gain'-the ability to modulate the conductance. Here, we demonstrate gain for electronic transport perpendicular to a single molecular layer ( approximately 10-20 A) by using a third gate electrode. Our experiments with field-effect transistors based on self-assembled monolayers demonstrate conductance modulation of more than five orders of magnitude. In addition, inverter circuits have been prepared that show a gain as high as six. The fabrication of monolayer transistors and inverters might represent an important step towards molecular-scale electronics.     

Subwavelength-diameter silica wires for low-loss optical wave guiding

Silica waveguides with diameters larger than the wavelength of transmitted light are widely used in optical communications, sensors and other applications. Minimizing the width of the waveguides is desirable for photonic device applications, but the fabrication of low-loss optical waveguides with subwavelength diameters remains challenging because of strict requirements on surface roughness and diameter uniformity. Here we report the fabrication of subwavelength-diameter silica 'wires' for use as low-loss optical waveguides within the visible to near-infrared spectral range. We use a two-step drawing process to fabricate long free-standing silica wires with diameters down to 50 nm that show surface smoothness at the atomic level together with uniformity of diameter. Light can be launched into these wires by optical evanescent coupling. The wires allow single-mode operation, and have an optical loss of less than 0.1 dB mm(-1). We believe that these wires provide promising building blocks for future microphotonic devices with subwavelength-width structures.     

The Impact of Nanocomposite Materials on Lithium Ion Batteries

1 Results Lithiumion batteries have become the power source of choice for consumer electronic devices such as cell phones and laptop computers due to their high energy density and long cycle life. In addition,lithium-ion batteries are expected to be a major breakthrough in the hybrid vehicle field.Despite their successful commercial application,further performance improvement of the lithium ion battery is still required.Nanomaterials and nanotechnologies can lead to a new generation of lithium secondary...     

非晶硅薄膜晶体管中不饱和输出电流的数值仿真研究

采用medici软件，对非晶硅薄膜晶体管的输出特性进行了数值仿真，并对器件的不饱和输出电流的产生机理进行了探讨。仿真结果表明，在长沟道器件中，体电流传输机制的改变是产生不饱和输出电流的主要原因；而对短沟道器件而言，则还需要同时考虑DIBL效应的影响。     

Manipulation of elementary charge in a silicon charge-coupled device

The ultimate limit in the operation of an electronic device is the manipulation of a single charge. Such a limit has been achieved in single-electron tunnelling devices. However, these devices are based on multiple tunnel barriers and conductive islands, which are complex structures to fabricate. Here we demonstrate another type of device that can also manipulate elementary charge, but which is more suitable for large-scale integration. The device consists of two closely packed silicon wire-MOSFETs, which are commonly used building blocks of electronic circuits. We have developed a scheme to generate and store holes in the channels of either of these MOSFETs. Subsequently, holes can be transferred between the two MOSFETs at the level of an elementary charge, and their exact position can be monitored. This single-charge transfer device, which is operated at 25 K, is in effect a charge-coupled device. This is also the first realization of a silicon-based device that manipulates elementary charge.     

Analog Circuit Testability for Fault Diagnosis

In every field of engineering, testing is a fundamental step for the validation of design, being the most direct way to verify that a product meets its specifications. If the desired performance is not achieved, testing should identify all the causes of malfunctioning and indicate suitable corrective actions. Different algorithms relying on the symbolic approach have been presented in the past by the authors and in this work noteworthy improvements on these algorithms are proposed. However, how the testability is designed to maintain devices during its lifetime is discussed lack at present. Furthermore, this problem concerns needing more times on testing and fault diagnosis, and wasting more manpower and material resources. Especially in the army devices field, it is very important that maintenance and indemnificatory are advanced. In this paper, the parameters in testability design for fault detection and diagnosis will be given. The detailed contents of testability will be proposed, including the dividing of circuit module in equipment, technology material needed for detection and requirement of specifications used for testing.     

Electronic read-out of a single nuclear spin using a molecular spin transistor

Quantum control of individual spins in condensed-matter devices is an emerging field with a wide range of applications, from nanospintronics to quantum computing. The electron, possessing spin and orbital degrees of freedom, is conventionally used as the carrier of quantum information in proposed devices. However, electrons couple strongly to the environment, and so have very short relaxation and coherence times. It is therefore extremely difficult to achieve quantum coherence and stable entanglement of electron spins. Alternative concepts propose nuclear spins as the building blocks for quantum computing, because such spins are extremely well isolated from the environment and less prone to decoherence. However, weak coupling comes at a price: it remains challenging to address and manipulate individual nuclear spins. Here we show that the nuclear spin of an individual metal atom embedded in a single-molecule magnet can be read out electronically. The observed long lifetimes (tens of seconds) and relaxation characteristics of nuclear spin at the single-atom scale open the way to a completely new world of devices in which quantum logic may be implemented.     

Electrical conduction through DNA molecules

The question of whether DNA is able to transport electrons has attracted much interest, particularly as this ability may play a role as a repair mechanism after radiation damage to the DNA helix. Experiments addressing DNA conductivity have involved a large number of DNA strands doped with intercalated donor and acceptor molecules, and the conductivity has been assessed from electron transfer rates as a function of the distance between the donor and acceptor sites. But the experimental results remain contradictory, as do theoretical predictions. Here we report direct measurements of electrical current as a function of the potential applied across a few DNA molecules associated into single ropes at least 600 nm long, which indicate efficient conduction through the ropes. We find that the resistivity values derived from these measurements are comparable to those of conducting polymers, and indicate that DNA transports electrical current as efficiently as a good semiconductor. This property, and the fact that DNA molecules of specific composition ranging in length from just a few nucleotides to chains several tens of micrometres long can be routinely prepared, makes DNA ideally suited for the construction of mesoscopic electronic devices.     

电力储能技术发展概述

长期以来,电能的储存一般采用小规模电池储能和抽水储能电站,直到最近二三十年,科技工作者发明了超导储能和飞轮储能等技术。这些原理和方式各畀的储能装置还都处在研究阶段．存在着技术难点需要解决本文对各种储能方式及其发展做出概括介绍.     

Influence of nanostructure on the device performance and charge recombination dynamics of P3HT:PCBM solar cells

In this paper,we investigated the recombination dynamics of photogenerated charge carriers in a poly(3-hexylthiophene)(P3HT):[6,6]-phenyl-C 61-butyric acid methyl ester(PC 61 BM) blend system with donor-acceptor ratio of 1:1 before and after solvent annealing treatment.The technique of transient photocurrent and photovoltage measurements were used,and charge carriers were photogenerated by a 7 ns laser pulse at room temperature(298 K).In transient photocurrent measurement,we observed some differences in the saturation extracted charge in P3HT:PCBM solar cells with different power efficiencies.In addition,the bimolecular recombination coefficient is found to be 3.5×10-13 cm 3 s-1 for annealed devices,while 9.5×10-12 cm3 s-1 for as-cast devices.In the transient photovoltage measurement,we found that the photovoltage decay can be fitted by power-law equation at long time scale.The exponent parameter is 2.6 for annealed devices,which can be described as trap-free bimolecular recombination;is 1.76 for as-cast device due to the trap-limited bimolecular recombination.These experimental results indicate that the nanomorphology of active layer indeed have influence on charge carriers dynamics in P3HT:PCBM blend systems.     

Laser-induced ultrafast spin reorientation in the antiferromagnet TmFeO3

All magnetically ordered materials can be divided into two primary classes: ferromagnets and antiferromagnets. Since ancient times, ferromagnetic materials have found vast application areas, from the compass to computer storage and more recently to magnetic random access memory and spintronics. In contrast, antiferromagnetic (AFM) materials, though representing the overwhelming majority of magnetically ordered materials, for a long time were of academic interest only. The fundamental difference between the two types of magnetic materials manifests itself in their reaction to an external magnetic field-in an antiferromagnet, the exchange interaction leads to zero net magnetization. The related absence of a net angular momentum should result in orders of magnitude faster AFM spin dynamics. Here we show that, using a short laser pulse, the spins of the antiferromagnet TmFeO3 can indeed be manipulated on a timescale of a few picoseconds, in contrast to the hundreds of picoseconds in a ferromagnet. Because the ultrafast dynamics of spins in antiferromagnets is a key issue for exchange-biased devices, this finding can expand the now limited set of applications for AFM materials.     

先进能源储存和转换材料专刊社论

The ever-increasing environmental problems and energy challenges have called urgent demand for utilizing green, ef-ficient, and sustainable energy, thus promoting the develop-ment of new technologies associated with energy storage and conversion systems. Amongst a wealth of energy storage devices, Li/Na/K/Zn/Mg ion batteries, metal-air batteries, and lithium–sulfur/all-solid-state batteries together with su-percapacitors as advanced power sources have attracted con-siderable interest due to their conspicuous merits of high en-ergy density, long cycle life, and good rate capability. In the energy conversion systems, solar cells and fuel cells can be considered as mainstream renewable energy resources once their manufacturing cost has decreased to an affordable level. However, the developments of advanced power sources de-pend critically on advances in materials innovation. There-fore, to promote the practical applications of these promising systems, developing high-performance electrode materials has been taken into the center stage in current research areas from chemistry, physics, and materials science fields.     

长距离输电线路故障精确计算的程序实现

用复矩阵特征模量分解方法在计及线路分布参数及换位条件下精确计算长距离输电线路的故障，给出有关公式的推导和程序实现框图，完成了全部程序设计．     

小高层结构屋顶不同的TMD设置方式减震对比分析

根据屋顶水箱和保温层对房屋整体结构减震的作用,建立采用铅芯橡胶支座的3种不同屋顶的TMD控制装置的小高层结构模型,即单水箱屋顶TMD、双水箱屋顶TMD和屋顶保温层TMD.在此基础上运用有限元分析和动力时程分析方法对控制装置的减震效果进行计算对比.对比结果表明,3种屋顶TMD控制装置均有明显的减震效果;当质量比控制在3%以内时,质量越大,屋顶TMD荷载分布越均匀,减震效果越好;屋顶保温层TMD减震效果最好,双水箱屋顶TMD的减震效果次之,单水箱屋顶TMD的减震效果最差.本项研究成果可以为TMD的后续研究和设计提供理论依据.     

可穿戴传感器进展、挑战和发展趋势

 可穿戴传感器是近年来高速发展的传感器技术。其功能、原理和形态各异,并已经广泛应用于国民生活和生产的多个方面。本文结合大量商业化和处于研究阶段的可穿戴产品和器件,简述了可穿戴传感器的主要形式,列举了可穿戴设备的常用测量方法。根据可穿戴传感器及人体的接触方式,将其划分为皮肤接触式传感器、非直接接触式传感器和植入式传感器,结合现有商业化产品及实验室中研究成果,展示了现今可穿戴设备在日常健康、医疗、运动科学、工业和军事等方面的广泛应用。认为可穿戴传感器技术将会在未来同大数据与精准医疗实现更高程度的结合,更好地服务于长期动态的人体信息和环境信息的采集。     

人体动能驱动的可植入式电磁感应供电方法研究

当前,随着医学技术的飞速发展,满足各类治疗和诊断需求的可植入人体式医用器件日益增多,如何为其提供长期、稳定和高效的电能是一个关键问题.本研究分析了人体运动动能的量级,提出一种可植入式电磁发电装置,可适时捕捉人体动能并将其转化为电能.通过理论分析、模拟及在体实验,证实了新方案可于人体运动中收集到足够的电能来对植入式医疗器件供电,并就各种影响发电的因素,如发电装置内的动态电磁场强度、运动幅度以及不同植入部位的影响进行了全面评估,在此基础上讨论了发电器件微型化的问题.对于今后研究微型植入式医疗器械的永久性充电问题具有重要参考价值.     

Pushing the limits of lithography

The phenomenal rate of increase in the integration density of silicon chips has been sustained in large part by advances in optical lithography--the process that patterns and guides the fabrication of the component semiconductor devices and circuitry. Although the introduction of shorter-wavelength light sources and resolution-enhancement techniques should help maintain the current rate of device miniaturization for several more years, a point will be reached where optical lithography can no longer attain the required feature sizes. Several alternative lithographic techniques under development have the capability to overcome these resolution limits but, at present, no obvious successor to optical lithography has emerged.     

Rare Earth Doped Polymer Waveguide Materials and Devices

1 Results Rare earth doped waveguide amplifiers and devices have been demonstrated in silica, crystal and other glass hosts. These rare earth doped optical waveguide devices are based on inorganic materials. Many processing steps are required and can lead to long fabrication time and low yield.Polymer materials offer many distinct properties compared to inorganic materials, such as ease of fabrication, low production costs, simple processing steps, and compatibility with micro-fabrication technologies. ...