Liquid crystal over silicon device characteristics for holographic projection of high-definition television images

We discuss some fundamental characteristics of a phase-modulating device suitable to holographically project a monochrome video frame with 1280 x 720 resolution. The phase-modulating device is expected to be a liquid crystal over silicon chip with silicon area similar to that of commercial devices. Its basic characteristics, such as number of pixels, bits per pixel, and pixel dimensions, are optimized in terms of image quality and optical efficiency. Estimates of the image quality are made from the noise levels and contrast, while efficiency is calculated by considering the beam apodization, device dead space, diffraction losses, and the sinc envelope.     

Controlling optical gain in semiconducting polymers with nanoscale chain positioning and alignment

We control the chain conformation of a semiconducting polymer by encapsulating it within the aligned nanopores of a silica host. The confinement leads to polarized, low-threshold amplified spontaneous emission from the polymer chains. The polymer enters the porous silica film from only one face and the filling of the pores is therefore graded. As a result, the profile of the index of refraction in the film is also graded, in the direction normal to the pores, so that the composite film forms a low-loss, graded-index waveguide. The aligned polymer chains plus naturally formed waveguide are ideally configured for optical gain, with a threshold for amplified spontaneous emission that is twenty times lower than in comparable unoriented polymer films. Moreover, the optimal conditions for ASE are met in only one spatial orientation and with one polarization. The results show that nanometre-scale control of semiconducting polymer chain orientation and position leads to novel and desirable optical properties.     

Low-cost and nanoscale non-volatile memory concept for future silicon chips

Non-volatile 'flash' memories are key components of integrated circuits because they retain their data when power is interrupted. Despite their great commercial success, the semiconductor industry is searching for alternative non-volatile memories with improved performance and better opportunities for scaling down the size of memory cells. Here we demonstrate the feasibility of a new semiconductor memory concept. The individual memory cell is based on a narrow line of phase-change material. By sending low-power current pulses through the line, the phase-change material can be programmed reversibly between two distinguishable resistive states on a timescale of nanoseconds. Reducing the dimensions of the phase-change line to the nanometre scale improves the performance in terms of speed and power consumption. These advantages are achieved by the use of a doped-SbTe phase-change material. The simplicity of the concept promises that integration into a logic complementary metal oxide semiconductor (CMOS) process flow might be possible with only a few additional lithographic steps.     

Side-coupled nanoscale photonic crystal structure with high-Q and high-stability for simultaneous refractive index and temperature sensing

In this paper, we propose a single-mode double-cavity photonic crystal (PhC) sensor for simultaneous detection of ambient refractive index (RI) and temperature. L3 cavity and L4 cavity are cascaded on both sides of the photonic crystal W1 waveguide. Two 0th-order modes generated by the two cavities with Q-factors over 16,330.80 and 8358.21 are used for sensing, which have a strong constraint on photons than the higher-order modes. By simulating the refractive index and temperature of the PhC structure, the sensing matrix can realize simultaneous sensing of two parameters. The maximum crosstalk of the two cavities is very low and can increase the accuracy of the detection. And the structure shows a good fabrication tolerance considering the deviation of the hole radius. The application of the PhC to dual-parameter sensing with high accuracy is proposed, which provides an idea for dual-parameter sensing.     

车辆-轨道非线性耦合动力学的精细积分法及其应用

提出精细积分法求解移动质量与结构相互作用的新的计算方法。分析焊接接头不平顺和轨枕悬空对轮轨力和轨道部件之间相互作用力的影响。该方法采用非齐次项的Duhamel积分的精细积分算法,避免状态空间下系统矩阵求逆。通过Lagrange插值多项式获得移动质量与结构相互作用的载荷项外插公式,无需迭代求解移动质量和结构非线性相互的动态响应。系统矩阵具有时不变性,无需反复计算指数矩阵。在每个积分步内,利用Euler梁的形函数分解移动载荷项,获得移动载荷与结构相互作用时间和空间连续变化的情况。计算结果表明,轮轨力的第一个峰值主要由于焊接接头不平顺造成,轨枕悬空主要影响轮轨力第二峰值。焊接接头不平顺区易出现轨枕悬空。轨枕悬空出现后,悬空区有扩大的趋势。     

A precise time-step integration method by step-response and impulsive-response matrices for dynamic problems

In this paper, a precise time-step integration method for dynamic problems is presented. The second-order differential equations for dynamic problems are manipulated directly. A general damping matrix is considered. The transient responses are expressed in terms of the steady-state responses, the given initial conditions and the step-response and impulsive-response matrices. The steady-state responses for various types of excitations are readily obtainable. The computation of the step-response and impulsive-response matrices and their time derivatives are studied in this paper. A direct computation of these matrices using the Taylor series solutions is not efficient when the time-step size Δt is not small. In this paper, the recurrence formulae relating the response matrices at t=Δt to those at t=Δt/2 are constructed. A recursive procedure is proposed to evaluate these matrices at t=Δt from the matrices at t=Δt/2^m. The matrices at t=Δt/2^m are obtained from the Taylor series solutions. To improve the computational efficiency, the relations between the response matrices and their time derivatives are investigated. In addition, these matrices are expressed in terms of two symmetric matrices that can also be evaluated recursively. Besides, from the physical point of view, these matrices should be banded for small Δt. Both the stability and accuracy characteristics of the present algorithm are studied. Three numerical examples are used to illustrate the highly precise and stable algorithm. © 1997 John Wiley & Sons, Ltd.     

Highly-ordered supportless three-dimensional nanowire networks with tunable complexity and interwire connectivity for device integration

The fabrication of three-dimensional assemblies consisting of large quantities of nanowires is of great technological importance for various applications including (electro-)catalysis, sensitive sensing, and improvement of electronic devices. Because the spatial distribution of the nanostructured material can strongly influence the properties, architectural design is required in order to use assembled nanowires to their full potential. In addition, special effort has to be dedicated to the development of efficient methods that allow precise control over structural parameters of the nanoscale building blocks as a means of tuning their characteristics. This paper reports the direct synthesis of highly ordered large-area nanowire networks by a method based on hard templates using electrodeposition within nanochannels of ion track-etched polymer membranes. Control over the complexity of the networks and the dimensions of the integrated nanostructures are achieved by a modified template fabrication. The networks possess high surface area and excellent transport properties, turning them into a promising electrocatalyst material as demonstrated by cyclic voltammetry studies on platinum nanowire networks catalyzing methanol oxidation. Our method opens up a new general route for interconnecting nanowires to stable macroscopic network structures of very high integration level that allow easy handling of nanowires while maintaining their connectivity.     

Water-soluble-template-derived nanoscale silicon nanoflake and nano-rod morphologies: Stable architectures for lithium-ion battery anodes

Earth abundant and economical rock salt (NaCl) particles of different sizes (<3 μm and 5–20 μm) prepared by high energy mechanical milling were used as water-soluble templates for generation of Si with novel nanoscale architectures via low pressure chemical vapor deposition (LPCVD). Si nanoflakes (Si_NF) comprising largely amorphous Si (a-Si) with a small volume fraction of nanocrystalline Si (nc-Si), and Si nanorods (Si_NR) composed of a larger volume fraction of crystalline Si (c-Si) and a small volume fraction of a-Si resulted from modification of the NaCl crystals. Si_NF yielded first-cycle discharge and charge capacities of ～2,830 and 2,175 mAh·g^?1, respectively, at a current rate of 50 mA·g^?1 with a first-cycle irreversible loss (FIR loss) of ～15%–20%. Si_NR displayed first-cycle discharge and charge capacities of ～2,980 and ～2,500 mAh·g^?1, respectively, at a current rate of 50 mA·g^?1 with an FIR loss of ～12%–15%. However, at a current rate of 1 A·g^?1, Si_NF exhibited a stable discharge capacity of ～810 mAh·g^?1 at the end of 250 cycles with a fade rate of ～0.11% loss per cycle, while Si_NR showed a stable specific discharge capacity of ～740 mAh·g^?1 with a fade rate of ～0.23% loss per cycle. The morphology of the nanostructures and compositions of the different phases/phase of Si influence the performance of Si_NF and Si_NR, making them attractive anodes for lithium-ion batteries.

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Single crystal growth,structure and properties of TlHgBr3

High-quality inclusion-free single crystals of ternary thallium mercury bromide, TlHgBr₃, were successfully grown by Bridgman–Stockbarger method. For the pristine surface of the TlHgBr₃ single crystal, X-ray photoelectron core-level and valence-band spectra were measured. The comparison on a common energy scale of the X-ray photoelectron valence-band spectrum of TlHgBr₃ and the X-ray emission Br Kβ₂ band, representing peculiarities of the energy distribution of the Br 4p states revealed that the main contribution of the valence Br p states, occurred in the upper portion of the valence band, with also their significant contributions in other valence band regions. It has been determined that TlHgBr₃ is a semiconductor with the bandgap energy value of E_g = 2.51 eV at 100 K. The E_g value decreased up to 2.44 eV when temperature increased to 300 K.     

Performances and limits of a parallel oscillator for electrochemical quartz crystal microbalances

This paper describes a driving circuit for an electrochemical quartz crystal microbalance (EQCM) adapted to a wide range of applications. The oscillator is a Miller-type parallel oscillator using an operational transconductance amplifier (OTA). A theoretical study of the oscillating circuit led to the analytical expression of the microbalance frequency as well as to an overestimation of the error on the mass measurement. The reliability of the EQCM was then experimentally verified through electrochemical copper deposition and dissolution. The limit of operation of the EQCM was also investigated, both analytically and experimentally. This work shows that parallel oscillators using few electronic components allow a very reliable EQCM to be obtained for mass measurements on metallic films, even if they are highly damped.     

Wetting of silicon single crystal by silver and tin,and their interfaces

A study of wetting of silicon single crystals and electrode metals was undertaken to investigate the wetting mechanisms and to clarify the interfaces between the silicon wafer and silver and tin. The experiments were performed using a high-temperature surface tension measuring equipment in vacuum and 5% H₂/Ar atmospheres (10⁵ Pa). The contact angles were measured by taking photographs through a telescope during the wetting experiment. Silicon was wetted by silver with a contact angle of 42°, whereas it was not wetted by tin in vacuum and in the 5% H₂/Ar atmosphere. However, heat treatment of silicon in vacuum or 5% H₂/Ar atmosphere prior to the wetting experiment reduced the contact angles compared to the cases with no heat treatment. The bonding interfaces between silicon and silver are also discussed.     

Epitaxial integration of the highly spin-polarized ferromagnetic semiconductor EuO with silicon and GaN

Doped EuO is an attractive material for the fabrication of proof-of-concept spintronic devices. Yet for decades its use has been hindered by its instability in air and the difficulty of preparing and patterning high-quality thin films. Here, we establish EuO as the pre-eminent material for the direct integration of a carrier-concentration-matched half-metal with the long-spin-lifetime semiconductors silicon and GaN, using methods that transcend these difficulties. Andreev reflection measurements reveal that the spin polarization in doped epitaxial EuO films exceeds 90%, demonstrating that EuO is a half-metal even when highly doped. Furthermore, EuO is epitaxially integrated with silicon and GaN. These results demonstrate the high potential of EuO for spintronic devices.     

SOI MOSFET with an insulator region (IR-SOI): A novel device for reliable nanoscale CMOS circuits

Device performance in the electronic circuits degrades with elapsed time. Therefore it is important to design a new device to have a reliable performance. In this paper, we present the unique features exhibited by a novel nanoscale silicon-on-insulator (SOI) metal-oxide-semiconductor field effect transistor (MOSFET) in which the silicon active layer consists of an insulator region (IR-SOI). The high-K dielectric HfO₂ as an insulator material is located in the silicon active layer and drain region. Our simulation results demonstrate that this leads to improve the hot electron reliability of the IR-SOI in comparison with the conventional SOI-MOSFET (C-SOI). The insulator region HfO₂ considerably decreases the electric field in the channel and drain regions. Therefore, the degradation mechanism in the proposed structure is lower than that in the C-SOI structure because of reduction of hot carrier effect (HCE). Also using two-dimensional and two-carrier device simulation, we have investigated the improvement in device performance focusing on the HCE, off current, gate current and gate induced drain leakage (GIDL) which can effect on the reliability of the CMOS devices.     

Monitoring, diagnostic, and therapeutic technologies for nanoscale medicine

The advent of medically-relevant technologies forged at the interface of life science and engineering will undoubtedly play a major role in shaping the next-generation of experimental as well as clinical medicine. This review will explore the development of a suite of platform modalities that can be employed towards medical diagnostics and therapeutics. Their specific relevance and impact towards cardiovascular medicine will be realized through biotic-abiotic coalescence, or the bridging of biological materials such as cells and proteins with non-biological materials such as polymers or solid-state devices. These modalities include: (1) Real-Time Cellular Interrogation Technology, which enables real-time investigation, or examination of cellular signal transduction and gene expression as a response to environmental conditions; (2) Diagnostic Devices, which include the fabrication of micro/nano sensors for the targeting of molecules indicative of cellular disorders; and (3) Therapeutics, or the engineering of membrane mimetics, or biomolecule-functionalized thin films as strategies for synthetic biological regenerative medicine, as well as therapeutically-active polymers as biocompatible coatings for implants, to name a few. These approaches collectively represent a universally-applicable, and comprehensive diagnostic-treatment strategy whereby cardiovascular disorders, or medical diseases in general can be diagnosed, monitored, and fundamentally understood to unprecedented levels. In turn, these conditions can be therapeutically addressed using drug-releasing nanostructured polymers with minimal intrusion upon normal cellular behavior, or biologically-active hybrid membrane devices based upon the interface of proteins with robust biomimetic polymers.     

Blue phase liquid crystal: strategies for phase stabilization and device development

Abstract

The blue phase liquid crystal (BPLC) is a highly ordered liquid crystal (LC) phase found very close to the LC–isotropic transition. The BPLC has demonstrated potential in next-generation display and photonic technology due to its exceptional properties such as sub-millisecond response time and wide viewing angle. However, BPLC is stable in a very small temperature range (0.5–1 °C) and its driving voltage is very high (～100 V). To overcome these challenges recent research has focused on solutions which incorporate polymers or nanoparticles into the blue phase to widen the temperature range from around few °C to potentially more than 60 °C. In order to reduce the driving voltage, strategies have been attempted by modifying the device structure by introducing protrusion or corrugated electrodes and vertical field switching mechanism has been proposed. In this paper the effectiveness of the proposed solution will be discussed, in order to assess the potential of BPLC in display technology and beyond.     

Adaptive neuro-fuzzy module for inertial navigation system/global positioning system integration utilising position and velocity updates with real-time cross-validation

Recently, methods based on artificial intelligence (AI) have been suggested to provide reliable positioning information for different land vehicle navigation applications. The majority of these applications utilise both the global positioning system (GPS) and the inertial navigation system (INS). These AI modules were trained to mimic the latest vehicle dynamics so that, in case of GPS outages, the system relies on INS and the recently updated AI module to provide the vehicle position. Several neural networks and neuro-fuzzy techniques were implemented in real-time in a de-centralised fashion and provided acceptable accuracy for short GPS outages. It was reported that these methods provided poor positioning accuracy during relatively long GPS outages. In order to prevail over this limitation, this study optimises the Al-based INS/GPS integration schemes utilising adaptive neuro-fuzzy inference system with performing, in real-time, both GPS position and velocity updates. In addition, a holdout cross validation method during the update procedure was utilised in order to ensure generalisation of the model. The proposed system is tested using differential GPS and both navigational and tactical grades INS field test data obtained from a land vehicle experiment. The results showed that the effectiveness of the proposed system over both the existing Al-based and the conventional INS/GPS integration techniques, especially during long GPS outages. This method may have one limitation related to the unusual significant changes of the vehicle dynamics between the update and the prediction stages of operation which may influence the overall positioning accuracy.     

Bulk crystal growth,spectral, optical,thermal, electrical and third-order NLO properties of benzylidene malononitrile derivative single crystal: a promising material for nonlinear optical device applications

Bulk organic intramolecular charge transfer nonlinear optical single crystal of 2-(2,4-dimethoxybenzylidene) malononitrile (DMM) with the sizes of 24?×?18?×?13 mm³ have been successfully grown by slow evaporation solution growth technique at 35 °C using acetone as the solvent. The lattice parameters of the grown DMM crystal was evaluated by single crystal X-ray diffraction analysis. The optical transmittance (T) data was taken from the well-polished crystal of DMM, and cut-off wavelength (λ?=?483 nm) was identified by UV–Vis spectral studies. Thermal stability and melting point (145.78 °C) were studied with TGA–DSC analysis. The low value of the dielectric constant (ε_r) of DMM suggests that the crystal can be used in the microelectronics industry. The laser-induced damage threshold experiment shows that the grown DMM bulk crystal possess an excellent resistance to laser radiation with a high threshold up to 1.75 GW/cm², much larger than those of several known organic and inorganic NLO materials. The DMM crystal exhibits positive optical non-linearity and reverse saturation absorption. It also exhibited a nonlinear refractive index (n₂) in the order of 10^?11 m²/W, a nonlinear absorption coefficient (β) in the order of 10^?5 m/W, third order non-linear susceptibility (χ⁽³⁾) in the order of 10^?5 esu and a second-order molecular hyperpolarizability (γ) in the order of 10^?33 esu. All the above results indicate that DMM has a potential application as a useful NLO candidate.     

Growth and characterization of 2-aminopyridinium malonate single crystal for photonic device applications

An organic conjugated chromophore 2-aminopyridinium malonate (2APM) single crystal was synthesized and grown-up by means of slow solvent evaporation method. The unit cell parameters were assessed from single-crystal X-ray diffraction analysis. The various characteristic fundamental vibration frequencies were identified by FTIR spectroscopic studies. Optical parameters like nature of transmittance, lower cut-off wavelength, and band gap (E_g) were found using UV–Vis–NIR spectrum. The mechanical property like microhardness of the 2APM sample was studied using a Vickers microhardness tester. The thermal stability nature of the grown crystal was determined using differential scanning calorimeter examination. The dielectric behavior of the 2APM crystal was studied at various frequencies and temperature. A Z-scan technique was used to investigate the third-order NLO response in 2APM.

     

ℋ︁∞ filtering with secure eigenvalue calculation and precise integration

Based on the analogy between structural mechanics and optimal control, interval mixed variable energy and the corresponding variational method are introduced to transform the induced norm γ of an ℋ︁_∞ filter into the fundamental eigenvalue γ⁻²_cr of a self‐adjoint operator, which can itself be expressed as a generalized Rayleigh quotient of the variational principle with two kinds of variable, i.e. the state vector x and the co‐state vector λ . These vectors correspond, respectively, to the displacement and internal force vectors in the theory of structural mechanics. The interval matrices Q , G and F of the mixed variable energy are introduced in a natural way, based upon which the precise integration of a time invariant system is proposed and then combined with the extended Wittrick–Williams algorithm to solve the eigen‐value problem, enabling the optimal eigenvalue parameter γ⁻²_cr to be computed with high precision. Copyright © 1999 John Wiley & Sons, Ltd.