Insight into excitation wavelength and hotspot effect of noble metal nanoparticles dimer

A proper excitation wavelength and strong hot-spot effect are of great importance for the application of surface-enhanced Raman spectroscopy (SERS) in the field of biochemistry. As a popular SERS substrate, noble metal nanoparticles dimer is analyzed systematically in this paper. The hot-spot effect and the resonance peak position with varying geometric parameters of metal nanoparticles are investigated. Moreover, the excitation wavelength of bimetallic structure is discussed as well. The conclusions can provide reference for the selection of metal material at different excitation wavelengths.     

Design process for Web applications

Applying software engineering principles to Web application development can improve application quality. A case study involving development of a retail sales Web application uses a design model based on object-oriented interface design methods and cognitive science to enhance usability and meet user requirements     

Real-time vessel segmentation and tracking for ultrasound imaging applications

A method for vessel segmentation and tracking in ultrasound images using Kalman filters is presented. A modified Star-Kalman algorithm is used to determine vessel contours and ellipse parameters using an extended Kalman filter with an elliptical model. The parameters can be used to easily calculate the transverse vessel area which is of clinical use. A temporal Kalman filter is used for tracking the vessel center over several frames, using location measurements from a handheld sensorized ultrasound probe. The segmentation and tracking have been implemented in real-time and validated using simulated ultrasound data with known features and real data, for which expert segmentation was performed. Results indicate that mean errors between segmented contours and expert tracings are on the order of 1%-2% of the maximum feature dimension, and that the transverse cross-sectional vessel area as computed from estimated ellipse parameters a, b as determined by our algorithm is within 10% of that determined by experts. The location of the vessel center was tracked accurately for a range of speeds from 1.4 to 11.2 mm/s.     

Gadolinium-based metal oxide for nonvolatile memory applications

In this study, the memory characteristic of a gadolinium (Gd)-based oxide charge storage layer was demonstrated. The metal/oxide/high-k/oxide/silicon (MOHOS)-type memories were fabricated by using two different charge storage layers. The Gd₂O₃ nanocrystal (Gd₂O₃-NC) was used as a charge storage layer due to the discrete nodes, while the HfGdO high-k material was used as a charge storage layer due to the existence of discrete traps. In the case of Gd₂O₃-NC memory, a combination of X-ray photoelectron spectroscopy (XPS) and ultraviolet (UV)–visible spectrophotometer analysis was used in this study to extract the valence band location and the band-gap of the Gd₂O₃-NC layer. The retention characteristic was also analyzed to extract the trapping level in Gd₂O₃-NC, based on the relationship between trapping energy and discharging time. A band diagram was created to characterize the memory effect of the Gd₂O₃-NC memory. In the case of HfGdO SONOS-type memory, the electrical and physical studies were conducted for HfGdO charge-trapping layers deposited by a dual-sputtered method for silicon–oxide–nitride–oxide–silicon (SONOS)-type nonvolatile memory. The Hf/Gd dual-sputtered power ratio and the Ar/O₂ gas flow ratio were optimized. It was observed that the nonstoichiometric GdO (2 0 0) structure may be the main charge-trapping site for the memory. The memory samples with Hf/Gd = 150/150 and Ar/O₂ = 20/5 exhibited better electrical performance. A physical model is proposed to further explain the retention mechanism.     

Evaluation of metal mirrors for high power applications by multithreshold damage analysis

Development of damage-resistant mirrors for high power, pulsed infrared laser applications depends on accurate identification of dominant failure modes and their origin. Previous work indicates that metal surfaces are usually subject to plastic deformation, pitting, or Other effects which may degrade reflective properties long before laser-induced melting occurs. Here we examine file relationship between mirror preparation and thresholds for the various types of damage. Surface finishing methods such as polishing, precision diamond-turning and sputter-cleaning in ultrahigh vacuum are evaluated. Examples of different materials, fabrication methods, and the effects of oxidation and contamination are also included.     

高角环形暗场成像方法测定负载型纳米贵金属催化剂的粒径

高角环形暗场(HAADF)像的衬度与样品中平均原子序数的平方成正比,并且具有原子尺度的分辨率,因此可以有效地区分贵金属颗粒和催化剂载体,非常适于测量负载型纳米贵金属催化剂中活性中心颗粒的粒径.本文以Pd/ZnO催化剂为例,介绍利用HAADF成像法测定负载型纳米贵金属催化剂中贵金属粒径的方法.     

Broadband scattering of the solar spectrum by spherical metal nanoparticles

Metal nanoparticles offer the possibility of improved light trapping in solar cells, but careful design is required to maximise scattering and minimise parasitic absorption across the wavelength range of interest. We present an analysis of the broadband scattering and absorption characteristics of spherical metal nanoparticles, optimized for either crystalline silicon (c‐Si) or amorphous silicon (a‐Si:H) solar cells. A random two‐dimensional array of optimally sized Ag spheres can scatter over 97% of the AM1.5 spectrum from 400 to 1100 nm. Larger particles are required for c‐Si devices than a‐Si:H due to the increased spectral range, with optimum particle sizes ranging from 60 nm for a‐Si:H to 116 nm for c‐Si. Positioning the particles at the rear of the solar cell decreases absorption losses because these principally occur at short wavelengths. Increasing the refractive index of the surrounding medium beyond the optimum value, which is 1.0 for a‐Si:H and 1.6 for c‐Si, shifts absorption to longer wavelengths and decreases scattering at short wavelengths. Ag nanoparticles scatter more of the solar spectrum than Au, Cu or Al nanoparticles. Of these other metals, Al can only be considered for a‐Si:H applications due to high absorption in the near‐infrared, whereas Au and Cu can only be considered for the rear of c‐Si devices due to high absorption in the ultraviolet (UV) and visible. In general, we demonstrate the importance of considering the broadband optical properties of metal nanoparticles for photovoltaic applications. Copyright © 2012 John Wiley & Sons, Ltd.     

MRI-guided focused ultrasound: methodology and applications

Focused ultrasound is very well suited for inducing noninvasive local hyperthermia. Since magnetic resonance imaging (MRI) may be employed to obtain real-time temperature maps noninvasively the combination of these two technologies offers great advantages specifically aimed toward oncological studies. Real-time identification of the target region and accurate control of the temperature evolution during the treatment has now become possible. Thermal ablation of pathological tissue, local drug delivery using thermosensitive micro-carriers and controlled transgene expression using thermosensitive promoters have recently been demonstrated with this unique technology. Based on these experiments combined focused ultrasound and MRI thermometry holds promise for future oncological diagnostics and treatment. In this paper, we review some of the recent methodological developments as well as experimental and first clinical studies using this approach.     

Integrated low-power CMFB-free variable-gain amplifier for ultrasound diagnostic applications

An integrated current-feedback variable-gain amplifier (VGA) suitable for low-power ultrasound diagnostic applications is presented in this paper, which provides variable gain to accommodate large input dynamic range of ultrasonic receiver. With a proposed active feedback technique, the amplifier maintains a constant bandwidth at different gain levels. Signal distortion due to the bandwidth shift is thus avoided. Compared to most Bipolar and BiCMOS counterparts, the proposed VGA is implemented in a low-cost CMOS process, without compromising the performance. In addition, it employs a resistive feedback network to automatically set the output DC voltage, without using any extra common-mode feedback (CMFB) circuits, making the design simple and effective. The proposed VGA was fabricated and tested with a standard 0.35-μm CMOS process, with an active die area of only 0.052 mm². The static power dissipation is 2.18 mW with a power supply of 3.0 V. The VGA exhibits a constant bandwidth of 4.5 MHz with a variable gain ranging from 0 to 46 dB. The system is well stabilized with a phase margin of 71.3° at the worst case. Comparisons to the state-of-the-arts demonstrate very competitive performance of this work.     

Thermal behavior of silver nanoparticles for low-temperature interconnect applications

Low-temperature sintering behavior of Ag nanoparticles was investigated. The nano Ag particles used (∼20 nm) exhibited obvious sintering behavior at significantly lower temperatures (∼150°C) than the T_m (960°C) of silver. Coalescence of the nano Ag particles was observed by sintering the particles at 150°C, 200°C, and 250°C. The thermal profile of the nanoparticles was examined by a differential scanning calorimeter (DSC) and a thermogravimetric analyzer (TGA). Shrinkage of the Ag-nanoparticle compacts during the sintering process was observed by thermomechanical analysis (TMA). Sintering of the nanoparticle pellet led to a significant increase in density and electrical conductivity. The size of the sintered particles and the crystallite size of the particles increased with increasing sintering temperature.     

Photoabsorption analysis of metal nanoparticles by hybrid quantum/classical scheme

The hybrid quantum/classical scheme (HQCS) is used for the photoabsorption analysis of metal nanoparticles. The HQCS divides the structure of interest into quantum and classical subsystems. First, we calculate and report Lorentz parameters for gold (Au), silver (Ag), aluminum (Al), chromium (Cr), and nickel (Ni) permittivities used in the classical subsystem. Then, photoabsorption spectra were obtained from HQCS for the single nanoparticle structures with and without two sodium (Na) atoms. The Au, Ag, Al, Cr, and Ni show strong sensitivity to the presence of the atomic subsystem. This work could pave the way for how coupled plasmon modes between metal nanoparticles and atomic structures can be utilized for sensing devices.     

激光烧蚀技术制备液相金属纳米粒子的研究进展

金属纳米粒子以其尺寸相关的独特的光电子、化学特性在许多领域都有极其重要的应用价值。因而，制备尺寸可控的金属纳米粒子具有重大的研究意义。溶液中制备金属纳米粒子或团簇，有可能控制纳米粒子的形态和尺寸分布，从而获得具有一定大小和结构的功能分子。本文首先介绍了几种制备液相金属纳米粒子的化学方法，然后详细阐述了激光烧蚀制备液相金属纳米粒子的特点、动力学形成机制和国外最新发展状况。另外，展望了激光烧蚀技术用于制备液相金属纳米粒子的发展前景。     

A standard CMOS high-voltage transmitter for ultrasound medical imaging applications

A high-voltage (HV) transmitter for ultrasound medical imaging applications is designed using 0.18-µm CMOS (complementary metal oxide semiconductor) technology. The proposed HV transmitter achieves high integration by employing standard CMOS transistors in a stacked configuration with dynamic gate biasing circuit while successfully driving the capacitive output load with an HV pulse without device breakdown reliability issues. The HV transmitter, which includes the output driver and voltage level-shifters, generates up to 30-Vp-p pulses at 1.25 MHz frequency and occupies 0.035 mm² of layout area.     

负载型贵金属催化剂中活性组分非均匀型分布的研究

采用饱和浸渍法与涂覆法制备出负载于氧化铝载体上活性金属呈非均匀分布的贵金属催化剂,并采用活性组分显色,电子探针对活性组分在载体中分布进行表征研究。结果表明对催化剂进行显色处理和光学显微照相,及用电子探针微量分析（EPMA）仪分析表征Pd和Pt在剖面上的分布,可确定活性组分在载体中非均匀分布情况。采用浸渍法制备催化剂时,添加竞争吸附剂,可得到Pd或Pt在载体中呈蛋壳型、蛋白型、蛋黄型或均匀型几种不同分布结构;采用涂覆法制备催化剂时,可得到所需壳层厚度的蛋壳型贵金属催化剂,活性金属主要集中在载体外表面。     

Synthesis and optical properties of Ni-doped zinc oxide nanoparticles for optoelectronic applications

Nanocrystalline undoped and nickel doped zinc oxide (Zn1-xNixO, x=0.00, 0.01) powders are successfully synthesized by a simple and low-temperature "auto-combustion method". The microstructural and optical absorption and emission properties of the as-prepared samples are obtained using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infra-red spectrometer (FTIR), UV-visible and photoluminescence (PL). The structure study confirms the formation of the hexagonal wurtz...     

A new tungsten gate process for VLSI applications

In spite of the growing demand for MOS gates and interconnections of higher conductivity, the refractory metal gate process has not received as much attention as those using silicides because it is incompatible with the Si-gate process. The metal gate cannot withstand oxidizing annealing ambients, and source-drain formation by ion implantation is difficult because of the channeling of doping ions through the gate metal during ion implantation. In a new process developed for use in MOS VLSI fabrication, tungsten (W) is used as a gate metal because degradation of SiO2by annealing the metal/SiO2/Si structure at around 1000°C can be minimized if the metal is W. Metal oxidation is prevented by using a H2/H2O ambient for this annealing, which also allows Si to be oxidized in the same ambient. The channeling mentioned above is stopped by forming a thin layer of PSG or WOxon the W. This gate process is believed to be a step forward toward the desired compatibility.     

Development of spin-on-glass process for triple metal interconnects

Spin-on-glass(SOG),an interlayer dielectric material applied in liquid form to fill narrow gaps in the sub-dielectric surface and thus conducive to planarization,is an alternative to silicon dioxide(SiO_2) deposited using PECVD processes.However,its inability to adhere to metal and problems such as cracking prevent the easy application of SOG technology to provide an interlayer dielectric in multilevel metal interconnect circuits,particularly in university processing labs.This paper will show that a thin...     

三层金属布线的SOG隔离工艺开发

摘要: SOG平坦化技术是一种采用液态介质材料填充CMOS后段布线工艺中金属间隙的工艺技术,它使得硅片表面平坦化,物理特性上它和PECVD淀积SiO2类似,二者具有相似的电特性,SOG材料的介电常数低,具有良好的绝缘特性,是一种常用的金属层间隔离材料。但SOG材料和金属间的粘附性差、容易开裂等问题都阻碍了SOG技术作为多层金属层间介质的应用,特别是在大生产工艺上。本文采用首先CVD淀积一层薄SiO2,接着进行SOG涂敷固化和反腐工艺,最后再淀积顶层SiO2,形成三明治介质机构,这样有利于提高粘附性、防止开裂和孔中毒等问题,同时用电扫描显微镜对采用此结构的三层布线工艺进行纵向剖面分析。这种结构在CMOS三层布线工艺中已成功开发,并在0.5m CMOS DPTM批量生产中得到应用和验证。     

射频溅射沉积SiO2膜的工艺及其结构性能研究

利用自制的磁控溅射沉积设备,针对影响SiO2薄膜沉积速率的氩气流量,氧气分压两个关键参数进行工艺研究,并通过扫描电子显微镜(SEM)对沉积完成的Si不O2薄膜表面、剖面结构质量进行表征,结果表明,射频溅射沉积的SiO2薄膜均匀、致密,具有良好的结构性能.     

Quantum efficiency of flourescence excited by photodissociation in metal halide vapors and applications

Interaction of ultraviolet radiation with diatomic and triatomic metal halide vapors is discussed. Patterns observed in ultraviolet absorption cross sections are noted. Measurements of quantum efficiency of fluorescence excited by photodissociation (QE = fluorescence photons out/ultraviolet photons in) are described. Results and their implications for 205 ± 15-nm deuterium, 213.9-nm-Zn resonance and deuterium VUV excitation are discussed. Applications of photodissociation in photodissociation lasers, electric discharge lamps, and collisional processes such as measurement of reactive and quenching cross sections are summarized.