First principles study of structural,electronic and magnetic properties of SnGen(0,±1) (n =1-17) clusters

The structures,relative stability and magnetic properties of pure Gen+1,neutral cationic and anionic SnGen (n =1-17) clusters have been investigated by using the first principles density functional theory implemented in SIESTA packages.We find that with the increasing of cluster size,the Gen+1 and SnGen(0,±1) clusters tend to adopt compact structures.It has been also found that the Sn atom occupied a peripheral position for SnGen clusters when n ＜ 12 and occupied a core position for n ＞ 12.The structural and electronic properties such as optimized geometries,fragmentation energy,binding energy per atom,HOMO-LUMO gaps and second-order differences in energy of the pure Gen+1 and SnGen clusters in their ground state are calculated and analyzed.All isomers of neutral SnGen clusters are generally nonmagnetic except for n =1 and 4,where the total spin magnetic moments is 2μb.The total (DOS) and partial density of states of these clusters have been calculated to understand the origin of peculiar magnetic properties.The cluster size dependence of vertical ionization potentials,vertical electronic affinities,chemical hardness,adiabatic electron affinities and adiabatic ionization potentials have been calculated and discussed.     

Thermal analysis for fast thermal-response Si waveguide wrapped by SiN

A new type of Si waveguide wrapped by silicon nitride (SiN) is designed,and its optical and thermal analysis are presented.The thickness of SiN up-cladding should be larger than 1 μm in order to preven...     

A cluster-based analysis of propagation characteristics in MIMO relay channels based on wideband measurement

In this paper,the characteristics of clusters induced by a variety of propagation mechanisms in the link from the relay station(RS) to the mobile station(MS) are presented.Based on the results of high resolution channel parameter estimation,an automatic framework integrated with the manual intervention is utilized to perform the cluster identification and tracking.The power proportion and angular spread of clusters are investigated in both the line-of-sight(LOS) and non-line-of-sight(NLOS) scenarios.The measurement results indicate that the channel characteristics of clusters are different from the link from the base station to the MS due to the lower height of the RS antennas.     

Analysis of an improved Lyot depolarizer in terms of the multi-beam superposition treatment

In order to study the depolarization properties of an improved Lyot depolarizer with monochromatic light, the theory of multi-beam superposition is adopted. The dependences of degree of depolarization (D) on vibration azimuth angle (VAA) and total retardation (TR) are analyzed. The results show that D is ideal for any VAA when TR is δ=(N+1/2)π (N is an integer) on the basis of wedge angle large enough. And when δ=Nπ, VAA makes the most significant impact on D. When δ is assigned to the other values, the impact on D made by VAA is between the former two. Using a 405 nm semiconductor laser, experiments for measuring D of the sample with wedge angle of 6° are conducted. The theo-retical results are well verified by experiments. D is over 98.8% when TR is nearly δ=(N+1/2)π by changing the incident angle.     

The photoresponse and photoconductivity of micron-sized C60 whiskers and sub-millimeter-sized C60 clusters

The photoresponse and photoconductivity properties of micron-sized C60whiskers and sub-millimeter-sized C60clusters are successfully studied by the microfabrication technologies.According to the ultraviolet-visible-near infrared（UVVis-NIR）absorption spectroscopic study,a highly intense absorption is observed in the UV and visible light regions,which indicates probable applications in photoelectric devices.Furthermore,a large photocurrent is measured under the illumination of white light in nitrogen（N2）atmosphere.The micron-sized C60whiskers and the sub-millimeter-sized C60clusters have different photoresponse curves under the same condition of measurement.A quick transformation of photoelectric response is detected in parallel multi-arranged micron-sized C60whiskers,but the recovery of the photocurrent of self-assembly sub-millimeter-sized C60clusters is much slower.     

量子棒中强耦合氢化杂质束缚磁极化子基态性质的磁场和温度依赖性

Magnetic field and temperature dependence of the properties of the ground state of the strong-coupling bound magnetopolaron in quantum rods(QRs) with hydrogenic impurity is studied by means of the Huybrechts-Lee -Low-Pines transformation method and the quantum statistical theory.The expressions for the ground-state energy and the mean number of phonons of the magnetopolaron are derived.Results of the numerical calculations show that the bound state of the magnetopolaron cannot be formed when the value of the aspect ratio of the QR,the dielectric constant ratio,the electron-phonon coupling strength or the temperature parameter is small.The larger the deviation of the value of aspect ratio e’from 1 is,the more it is unfavorable to the stability of the ground state of the magnetopolaron.When the magnetopolaron is in the bound state,the absolute value of its ground-state energy and its mean number of phonons increase with an increase of the dielectric constant ratio and confinement strength of QRs,but decrease with an increase in the cyclotron frequency of the external magnetic field and the temperature. The absolute value of the ground-state energy and the mean number of phonons of the magnetopolaron decrease with decreasing e’when e’<1,but decrease with increasing e’when e’>1.They get the maximum value at e’=1.     

COHERENT RADIATION OF MILLIMETER WAVES GENERATED BY AN INTENSE ROTATING ANNULAR RELATIVISTIC ELECTRON BEAM

Properties of coherent radiation of millimeter waves generated by an intense rotating annularrelativistic electron beam(E-layer)which is from a cusp magnetic field are investigated.The linearizedVlasov-Maxwell equations are used to analyze the interaction between E-layer and resonators of themagnetron.The dispersion relation is deduced and numerical calculation is made.The results show that thefrequency of microwave radiation is ω_r(ω_r=lΩ〃 where Ω〃 is the electron relativistic cyclotron frequencyin the axial magnetic field;l is the azimuthal mode number,l=n+mN;N is the number of sideresonators,n=0,1,2,……N/2,m is any integer).The growth rate of radiation is still large enough even ifl is large.It is good for generating a millimeter wave radiation at low axial magnetic field.If the modes canbe controlled well,a tunable,high power millimeter wave device can be made.     

A New Base—6 FFT Algorithm

A new FFT algorithm has been deduced, which is called the base-6 FFT algorithm. The amount for calculating the DFT of complex sequence of N =2 r by the base-6 FFT algorithm is M r( N )=14/3· N log 6 N -4 N +4 for multiplication operation of real number and A r( N )=23/3· N log 6 N -2 N +2 for addition operation of real number. The amount for calculating the DFT of real sequence is a half of it with the complex sequence.     

Organic light-emitting devices based on 4,4’-bis(2,2’- diphenyl vinyl)-1,1’-biphenyl as a spacer between dual ultrathin layers

White organic light-emitting devices (WOLEDs) were fabricated by using a highly blue fluorescent dye of 4,4’-bis(2,2’-diphenyl vinyl)-1,1’-biphenyl (DPVBi) and a red fluorescent dye of 5H-benzo[ij] quinolizin-9-yl) ethenyl]-4H-pyran-4-ylidene] propane-dinitrile (DCM2), together with a green fluorescent dye of 10-(2-benzothiazolyl)- 2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-(1)-benzopyroyran-o(6,7-8-i,j) quinolizin-11-one (C545T). The multilayer WOLEDs does not involve the doping process. The structure of the device is indium tin oxide (ITO)/ 4,4’,4’’-tris{N,-(3-methylphenyl)-N-phenylamin}triphenylamine (m-MTDATA) (55 nm)/ N,N’-bis-(1-naphthyl)- N,N’-diphenyl-1,1’-biph-enyl-4,4’-diamine (NPB) (10 nm)/ DPVBi (8 nm)/ C545T (x nm)/ DPVBi (5 nm)/ DCM2 (y nm)/ tris- (8-hydroxyquinoline) aluminum (Alq3) (60nm)/ LiF (1 nm)/ Al, where the DPVBi is introduced as a spacer. By changing the thicknesses of dual ultrathin layers of C545T and DCM2, the WOLED is obtained. When x=y=0.05, the Commission Internationale de 1’Eclairage (CIE) coordinates of the device change from (0.262 6, 0.351 4) at 4 V to (0.214 7, 0.269 3) at 12 V that are well in the white region. Its maximum luminance is 41400 cd/m2 at 13 V, and the maximum current efficiency and the maximum power efficiency are 7.95 cd/A at 6 V and 5.37 lm/W at 5 V, respectively.     

A fast algorithm for discrete hartley transform of arbitrary length

DHT of length p~lq(p is odd and q is arbitrary) is turned into p~l DHTs of length qand some additional operations, while the additional operations only involves the computation ofcos-DFT and sin-DFT with length p. If the length of a DHT is p_1~(l_1)…P_N~(l_N)2~l(P_1…,P_N are oddprimes), a fast algorithm is obtained by the similar recursive technique. Therefore, the algorithmcan compute DHT of arbitrary length. The paper also Proves that operations for computingDHT of length N by the algorithm are no more than O(Nlog_2N), when the length is N=p~l,operations of the algorithm are fewer than that of other known algorithms.     

用微硅层析法制作的微型硅传感器

主要介绍1种用硅的微机械加工技术研制的硅电容式传感器，采用电容层析法(ECT)技术可检测尺寸为50μm左右的微小粒子。其中的主要技术有硅材料的微机械加工技术，特厚光刻胶的匀胶曝光技术，微集成电镀技术。     

Silicon CREATiONS

正About SilicoN Creations Silicon Creations provides world class silicon IP for precision and general purpose timing(PLLs),SerDes and high-speed differential IOs.We have a deep commitment to our customer's success and to providing complete support.Our careful development procedures and strong QA result in robust and correct designs.And in our labs we comprehensively test all key blocks.As a     

Silicon Microrefrigerator

We fabricated a silicon microrefrigerator on a 500-$mu$m-thick substrate with the standard integrated circuit (IC) fabrication process. The cooler achieves a maximum cooling of 1$^circ$C below ambient at room temperature. Simulations show that the cooling power density for a$hbox40times hbox40 muhboxm^2$device exceeds 500$hboxW/cm^2$. The unique three-dimensional (3-D) geometry, current and heat spreading, different from conventional one-dimensional (1-D) thermoelectric device, contribute to this large cooling power density. A 3-D finite element electrothermal model is used to analyze non-ideal factors inside the device and predict its limits. The simulation results show that in the ideal situation, with low contact resistance, bulk silicon with 3-D geometry could cool$sim hbox20 , ^circhboxC$with a cooling power density of 1000$hboxW/cm^2$despite the low thermoelectric figure-of-merit (ZT) of the material. The large cooling power density is due to the geometry dependent heat and current spreading in the device. The non-uniformity of current and Joule heating inside the substrate also contributes to the maximum cooling of silicon microrefrigerator, exceeding 30% limit given in one–dimensional thermoelectric theory$DeltaT_max=hbox0.5hboxZT_c^2$, where$T_c$is the cold side temperature. These devices can be used to remove hot spots on a chip.     

Silicon optics

Arroyo Optics, a flexible wavelength management solution manufacturer, and Lightcross Inc, a manufacturer of integrated, silicon-based optical products for telecoms equipment have agreed to merge. Arroyo Optics, the resulting company, will comprise technologies and products developed with over $50m of combined R&D capital provided by private equity investors. Both companies focus on products targeting fibre optics infrastructure applications.Visit www.three-fives.com for the latest advanced semiconductor industry news     

Silicon Photonics

After dominating the electronics industry for decades, silicon is on the verge of becoming the material of choice for the photonics industry: the traditional stronghold of III-V semiconductors. Stimulated by a series of recent breakthroughs and propelled by increasing investments by governments and the private sector, silicon photonics is now the most active discipline within the field of integrated optics. This paper provides an overview of the state of the art in silicon photonics and outlines challenges that must be overcome before large-scale commercialization can occur. In particular, for realization of integration with CMOS very large scale integration (VLSI), silicon photonics must be compatible with the economics of silicon manufacturing and must operate within thermal constraints of VLSI chips. The impact of silicon photonics will reach beyond optical communication-its traditionally anticipated application. Silicon has excellent linear and nonlinear optical properties in the midwave infrared (IR) spectrum. These properties, along with silicon's excellent thermal conductivity and optical damage threshold, open up the possibility for a new class of mid-IR photonic devices     

硅光子学

硅光子学有六个主要研究领域,包括产生光、在硅中选择地引导和传输光、编码光、探测光、包装器件和智能地控制这一切光子功能。综述了以上各领域的研究进展。     

标准单元ASIC／FPGA的权衡与结构化ASIC

看来您已认定,采取购买并组装现成的专用标准产品(ASSP),如嵌入式控制器、外设芯片等,然后再编写您自己的软件这种做法将不能使您设计的产品与您竞争对手的产品有足够大的差别.因此,您会决定选择芯片级设计.两大硅平台竞争对手及其各自的折衷方案已经在各种工业论坛上引起广泛的争论.不过如果您刚涉足这场争论,则很有必要了解下述有关争论的概要.