基于CMOS的高响应度太赫兹探测器线阵

本文提出了一种基于CMOS 0.18μm工艺的改进型高响应度太赫兹探测器线阵,各探测像素单元由高增益片上天线、高耦合度差分自混频功率探测电路和集成电压放大器组成。其中,差分探测电路利用源极差分驱动场效应管的交叉耦合电容,将太赫兹差分信号耦合至场效应管的栅极与源极,增强场效应管沟道内自混频太赫兹信号的强度,实现高响应度。其次,该探测器配备高增益片上环形差分天线与集成电压放大器,可有效放大混频后的信号,进而提高系统信噪比,最终达到增强探测器响应度的目的。探测器1×3线阵系统充分利用CMOS工艺多层结构的特点,将电压放大器布置在天线地平面下方,提高了芯片面积的利用率,有效降低了制作成本,整个系统的面积为0.5 mm^(2)。测试结果表明,当场效应管的栅极偏置为0.42 V时,该探测系统对0.3 THz辐射信号的电压响应度(Rv)最大可达到43.8 kV/W,对应的最小噪声等效功率(NEP)为20.5 pW/Hz^(1/2)。动态测试结果显示该探测器可对不同材质的隔挡物进行区分。

宽光谱范围高响应度的InGaAs/InP光电探测器

报道了一种在0.6～1.65μm波段使用的InGaAs/InP光电探测器。该探测器使用的是外延在InP衬底上的InGaAs材料,探测器结构采用PIN结构通过选择性扩散的方法制作,通过调整掩模尺寸和控制扩散条件,可以制备出具有不同光敏面尺寸及光电特性的探测器。封装后光电探测器在0.6～1.0μm波段的响应度大于0.2A/W,其中,在1.0μm～1.65μm波段的响应度超过0.8A/W,5V偏压下的暗电流小于2nA。经过老化试验,探测器的寿命可以超过105h,器件的可靠性和稳定性已经达到商用标准。由于出色的工艺稳定性和器件性能的一致性,该探测器可做成适用于多通道甚短距离光传输用的探测器阵列。

基于0.18μm CMOS工艺的300GHz高响应度探测器

基于0.18μm CMOS工艺设计了一种300 GHz高响应度探测器。该探测器集成了双馈差分天线和双场效应管(FET)对称差分自混频电路。双馈差分天线较单馈天线有更高的精确度及更优的抗干扰性。差分自混频电路能有效地抑制共模信号,减小噪声输入。双场效应管后增加一级放大电路,将自混频电路输出的微弱信号进一步放大以增大响应度。天线与电路间的匹配网络实现了信号的最大功率传输。在全波电磁场仿真软件HFSS下对双馈天线进行建模与仿真优化,并与电路进行联合仿真。结果显示探测器在栅源电压为0.43 V、输入功率为-40 dBm时,最大响应度为11.25 kV/W,最小噪声等效功率为115pW/√Hz。

高响应NaTaO3/SnO2湿度传感器的制备及性能研究

本文采用水热法制备NaTaO3/SnO2纳米材料,系统地研究了其湿度传感性能。实验结果表明,NaTaO3/SnO2复合材料比表面积比纯NaTaO3更大,这使得复合材料表面吸附更多的水分子,增强了NaTaO3/SnO2湿度传感器的性能。NaTaO3/SnO2复合材料表面氧空位含量明显提升,使其吸附大量水分,促进水分子分解为导电离子,提高NaTaO3/SnO2湿度传感器的响应和恢复速度。该NaTaO3/SnO2湿度传感器电阻达到3个数量级,在11%~95%相对湿度范围内具有高响应度(303,959%)、良好的线性度、低的湿滞(1.99%)、长期稳定性和快的响应和恢复时间(分别为15 s和13 s)。通过对NaTaO3/SnO2湿度传感器的复阻抗谱分析,对其传感机理进行了解释。NaTaO3/SnO2复合材料的成功制备也为具有高湿敏性能的NaTaO3基电阻传感器的设计开辟了新的方向。

High-Responsivity ZnS Schottky Barrier Photodiode Array for Ultraviolet Imaging

A different approach,using the molecular beam epitaxy (MBE)-grown ZnS-based Schottky photodiode technology,is applied to fabricate an 8×8 photodiode array.The micro-processing procedures of this photodiode array including standard photolithography,a number of metallisation,wet-chemical etching and SiO_2 deposition for insulation are developed.The detector is characterized to have a cutoff wavelength at 340 nm and the photo-responsivity measurements on the pixels result an ultraviolet (UV) response as high as 0.15 A/W,corresponding to an external quantum efficiency of 55% in the visible-blind spectral ranging from 400 down to 250nm.Imaging tests indicate that this array is able to capture the intensity profile of a given UV light source with reasonably good capability.

Response of upper ocean currents to typhoons at two ADCP moorings west of the Luzon Strait

We deployed two ADCP mooring systems west of the Luzon Strait in August 2008,and measured the upper ocean currents at high frequency.Two typhoons passed over the moorings during approximately one-month observation period.Using ADCP observations,satellite wind and heat flux measurements,and high-resolution model assimilation products,we studied the response of the upper ocean to typhoons.The first typhoon,Nuri,passed over one of the moorings,resulting in strong Ekman divergence and significant surface cooling.The cooling of surface water lagged the typhoon wind forcing about one day and lasted about five days.The second typhoon,Sinlaku,moved northward east of the Luzon Strait,and did not directly impact currents near the observation regions.Sinlaku increased anomalous surface water transport exchange across the Luzon Strait,which modulated the surface layer current of the Kuroshio.

Flexural response of reinforced concrete beams strengthened with post-poured ultra high toughness cementitious composites layer

Four-point bending tests were conducted up to failure on eleven reinforced concrete (RC) beams and strengthening beams to study the effectiveness of externally pouring ultra high toughness cementitious composites (UHTCC) on improving the flexural behavior of existing RC beams.The strengthening materials included UHTCC and high strength grade concrete.The parameters,such as thickness and length of strengthening layer and reinforcement in post-poured layer,were analyzed.The flexural behavior,failure mode and crack propagation of composite beams were investigated.The test results show that the strengthening layer improves the cracking and ultimate load by increasing the cross section area.Introducing UHTCC material into strengthening not only improves the bearing capacity of the original specimens,but also disperses larger cracks in upper concrete into multiple tightly-spaced fine cracks,thus prolonging the appearance of harm surface cracks and increasing the durability of existing structures.Compared with post-poured concrete,UHTCC is more suitable for working together with reinforcement.The load?deflection plots obtained from three-dimensional finite-element model (FEM) analyses are compared with those obtained from the experimental results,and show close correlation.

Characteristics of Schottky Barrier Junction Based on Hexagonal Microtube ZnO

Hexagonal microtube ZnO was firstly grown on single crystal p-Si (111) substrates by hydrothermal method, and fabricated Ag/n-ZnO and Au/n-ZnO Schottky junction. Schottky effective barrier heights were calculated by I-V measurement. It is confirmed that the presence of a large amount of surface states related possibly to lattice imperfections existed near the surface leads to the pinning of the surface Fermi level at 0.35eV below the conduction-band edge. Then the fabricated Schottky barrier junctions are evaluated for their use as UV photodetectors.

Leaching of copper from chalcopyrite concentrate by using ammonium persulphate in an autoclave:Determination of most suitable impeller type by using response surface methodology

Some effective parameters on the copper extraction from Kiire chalcopyrite concentrate were optimized by using response surface methodology （RSM）. Experiments designed by RSM were carried out in the presence of ammonium persulfate （APS） and different types of impeller in an autoclave system. Ammonium persulfate concentration and leaching temperature were defined numerically and three types of impellers were defined categorically as independent variables using experimental design software. The optimum condition for copper extraction from the chalcopyrite concentrate is found to be ammonium persulfate concentration of 277.77 kg/m3, leaching temperature of 389.98 K and wheel type of impeller. The proposed model equation using RSM has shown good agreement with the experimental data, with correlation coefficients R2 and RaZaj for the model as 0.89 and 0.84, respectively.

Photosynthetic and Growth Responses to Elevated [CO2] are Determined by Multiple Forest Ecosystem Conditions

The responses of photosynthesis and growth of forest trees to rising atmospheric carbon dioxide concentration [CO2] are modified by ecosystem conditions. With the exception of a few, the vast majority of empirical studies on the impact of future high CO2 levels on forest trees have focused on [CO2] alone or in combination with an environmental factor. This paper uses the case of CO2 × nutrient and CO2 × nutrient-related interactions to evaluate the relative value of single or multiple ecosystem factors in determining the responses of photosynthesis and growth to elevated [CO2]. A comprehensive literature search was conducted with Google Scholar. The findings show a consensus among studies that CO2 and nutrient availability have synergistic effects on photosynthesis and growth. However, combinations of nutrient availability with temperature or moisture modify the CO2 effect in ways different from nutrient availability alone. To increase the predictive power of empirical studies, it is recommended that conclusions on the responses of forest trees to elevated atmospheric [CO2] be based on interactions with multiple, rather than single, ecosystem conditions.

A high strength pH responsive supramolecular copolymer hydrogel

Constructing high strength pH sensitive supramolecular polymer hydrogel remains very challenging due to the unavoidable network swelling caused by ionization of acid or basic groups at a specified pH.In this work,we proposed a simple and very convenient approach to fabricate high strength pH responsive supramolecular polymer(SP) hydrogels by one-pot copolymerization of N-acryloyl glycinamide(NAGA) and 2-vinyl-4,6-diamino-1,3,5-triazine(VDT),two feature hydrogen bonding monomers.In these PNAGA-PVDT SP hydrogels obtained,the hydrogen bonding of NAGA was shown to play a dominant role in reinforcing strength,while the hydrogen bonding of diaminotriazine served as a pH sensitive moiety.At pH 3,the mechanical properties of PNAGA-PVDT hydrogels decreased to a different extent due to the breakup of hydrogen bonding;in contrast,the hydrogel resumed the original strength while pH was raised to 7.4 because of reconstruction of hydrogen bonding.Over the selected pH range,the PNAGA-PVDT hydrogels exhibited up to 1.25 MPa tensile strength,845% breaking strain,69 kPa Young's modulus and 21 MPa compressive strength.This novel high strength pH-responsive SP hydrogels may find applications in biomedical and industrial fields.

High-sensitivity shortwave infrared photodetectors of metal-organic frameworks integrated on 2D layered materials

Photodetectors operating in the shortwave infrared region are of great significance due to their extensive applications in both commercial and military fields.Narrowbandgap two-dimensional layered materials(2DLMs)are considered as the promising candidates for constructing nextgeneration high-performance infrared photodetectors.Nevertheless,the performance of 2DLMs-based photodetectors can hardly satisfy the requirements of practical applications due to their weak optical absorption.In the present study,a strategy was proposed to design high-performance shortwave infrared photodetectors by integrating metalorganic frameworks(MOFs)nanoparticles with excellent optical absorption characteristics and 2DLM with high mobility.Further,this study demonstrated the practicability of this strategy in a MOF/2DLM(Ni-CAT-1/Bi_(2)Se_(3))hybrid heterojunction photodetector.Due to the transfer of photo-generated carriers from the MOF to Bi_(2)Se_(3),the MOF nanoparticles integrated on the Bi_(2)Se_(3) layer can increase the photocurrent by 2-3 orders of magnitude.The resulting photodetector presented a high responsivity of 4725 A W^(−1) and a superior detectivity of 3.5×10^(13) Jones at 1500 nm.The outstanding performance of the hybrid heterojunction arises from the synergistic function of the enhanced optical absorption and photogating effect.In addition,the proposed device construction strategy combining MOF photosensitive materials with 2DLMs shows a high potential for the future high-performance shortwave infrared photodetectors.

Responsive polymer-based multicolor fluorescent probes for temperature and Zn^(2+) ions in aqueous media

We report on the fabrication of fluorescent and multicolor probes for Zn^2＋ ions and temperature from a mixture of three types of fluorophore-labeled responsive block copolymers in aqueous media. Quinoline-based Zn^2＋-recognizing fluorescent mono- mer ZQMA, red-emitting rhodamine B-based monomer RhBEA, and blue-emitting coumarin derivative Coum-OH, were syn- thesized first. A ZQMA-labeled well-defined double hydrophilic block copolymer （DHBC）, PEG-b-P（MEO2MA-co-ZQMA）, was synthesized via reversible addition-fragmentation chain-transfer （RAFT） polymerization of 2-（2-methoxyethoxy）ethyl methacrylate （MEOzMA） and ZQMA by utilizing a PEG-based macroRAFT agent. Following similar procedures, PEG-b-P（St-co-RhBEA） amphiphilic diblock copolymer and PEG-b-P（MEOzMA-co-Coum） DHBC were also synthesized, where P（St-co-RhBEA） was a RhBEA-labeled polystyrene （PS） block. At room temperature in aqueous solution, almost non- fluorescent PEG-b-P（MEOzMA-co-ZQMA） can effectively bind Zn2＋ ions, leading to prominent green fluorescence enhance- ment due to the coordination of ZQMA with Zn^2＋ ions. However, by mixing red-emitting PEG-b-P（St-co-RhBEA） and blue-emitting PEG-b-P（MEO2MA-co-Coum） with PEG-b-P（MEO2MA-co-ZQMA） at an appropriate ratio, three color transitions could be observed. In the absence of Zn^2＋ ions, a mixed pink fluorescent originating from Coum and RhBEA was ob- served; upon the addition of a certain amount of Zn^2＋ ions, the green fluorescence enhanced dramatically, leading to a white fluorescence readout. By further increasing the amount of Zn2＋ ions, the green fluorescence further enhanced and overwhelmed the blue and red emissions, leading to a green-dominant mixed-fluorescence emission. In addition, upon increasing the temperature, the fluorescence of Coum decreased considerably due to the fluorescence-resonance energy transfer （FRET） between Coum and ZQMA moieties. In this way, a ratiometric fluorescent thermometer can be constructed.

Contrasting Response Patterns of Rice Phyllosphere Bacterial Taxa to Elevated CO_2

A vast number of microorganisms colonize the leaf surface of terrestrial plants, known as the phyllosphere, and these microorganisms are thought to be of critical importance in plant growth and health. However, the taxonomic identities and ecological functions of the microorganisms inhabiting the rice phyllosphere remain poorly understood. Using a massive, parallel pyrosequencing technique, we identified the phyllosphere bacterial taxa of four different rice varieties and investigated the microbial response to elevated CO2 （eCO2） in a rice field of a free-air CO2 enrichment （FACE） facility located in Jiangsu Province, China. The results showed that the dominant phylotype, the Enterobacteriaceae family of Gammaproteobacteria~ accounted for 70.6%-93.8% of the total bacterial communities in the rice phyllosphere. The dominant phylotype was stimulated by eCO2, with its relative abundance increasing from 70.6%-75.2% at ambient CO2 （aCO2） to 86.5%-93.8% at eCO2 in the phyllosphere of rice varieties IIYou084 （TY-084）, YangLiangYou6 （YLY-6）, and ZhenXian96 （ZX-96）. The rare phylotypes, including the bacterial taxa of Sphingobacteriaceae, Xanthomonadaceae, Oxalobacteraceae, Clostridiaceae, and Pseudomonadaceae, were suppressed and their relative abundance decreased from 13.4%-23.0% at aCO2 to 1.47% 6.11% at eGO2. Furthermore, the bacterial diversity indices decreased at eCO2 in the phyllosphere of the rice varieties TY-084, YLY-6, and ZX-96. In contrast, an opposite response pattern was observed for the rice variety of YangDao8 （YD-8）. In the phyllosphere of this variety, the relative abundance of the dominant phylotype, Enterobacteriaceae, decreased from 94.1% at aCO2 to 81.4% at eCO2, while that of the rare phylotypes increased from 3.37% to 6.59%. In addition, eCO2 appeared to stimulate bacterial diversity in the rice variety YD-8. Our results suggest that the phyllosphere microbial response to eCO2 might be relative abundance-dependent in paddy fields.