硅紫外光伏探测器件响应度的研究

分析了硅紫外光伏探测器件的响应度与器件使用模式之间的关系．研究了包括网格结构在内的３种版图设计及所对应的响应度．结果表明，网格结构对改善紫外响应度的实际作用只是减小了串联电阻．细致讨论了光伏器件串联电阻的主要来源，给出了串联电阻对紫外响应度发生显著影响时所对应的估算数值．     

关于实李普希兹映射的lshikawa迭代的收敛率和加速收敛问题

本文研究使用Ｉｓｈｉｋａｗａ迭代格式求实李普希兹映射的不动点，指出该迭代格式仅具线性收敛率；对于参变量序列｛αｎ｝、｛βｎ｝所取的不同的值，比较了迭代格式的收敛速度．在给出加速因子定义的基础上，本文给出了加速收敛的一个充分条件．     

Thermo-poroacoustic acceleration waves in elastic materials with voids

A model for coupled elasto-acoustic waves, thermal waves, and waves associated with the voids, in a porous medium is investigated. Due to the use of lighter materials in modern buildings and noise concerns in the environment such models for thermo-poroacoustic waves are of much interest to the building industry. Analysis of such waves is also of interest in acoustic microscopy where the identification of material defects is of paramount importance to industry and medicine. We present a model for acoustic wave propagation in a porous material which also allows for propagation of a thermal wave. The thermodynamics is based on an entropy inequality of A.E. Green, F.R.S. and N. Laws and is presented for a modification of the theory of elastic materials with voids due to J.W. Nunziato and S.C. Cowin. A fully nonlinear acceleration wave analysis is initiated.     

新型复合盖层延伸波长InGaAs红外探测器结构优化设计

设计并模拟计算了延伸波长至2.6 μm的复合盖层材料PIN结构In_0.82Ga_0.18As红外探测器,即PNN型盖层、PIN结构的In_0.82Ga_0.18As红外探测器。研究了不同厚度及载流子浓度的PNN盖层对探测器性能的影响。研究结果表明:在In_0.82Al_0.18As厚度为200 nm且载流子浓度为2E18、InAs_0.6P_0.4 厚度为50 nm且载流子浓度为2E17、In_0.82Ga_0.18As厚度为50 nm且载流子浓度为2E16时,探测器表现出最佳的性能。与传统PIN结构探测器相比,其相对光谱响应度仅降低10%,暗电流降低了1个数量级。计算分析了不同工作温度下的暗电流,结果显示:在120~250 K时,暗电流主要为缺陷隧穿电流;在250~300 K时,暗电流主要为带间隧穿电流;当温度大于300 K时,暗电流主要为产生-复合电流和扩散电流。     

Trapped charge‐induced pyroelectric‐like transient response in single high‐resistivity Sb2Se3 nanowires

Dynamic scanning photocurrent microscopy was applied to Sb₂Se₃ crystalline single nanowires (NWs) to analyze their transient photocurrent responses. These NWs exhibited switching behavior with rapid rise and decay times upon illumination by laser pulses. The estimated spectral responsivity and external quantum efficiency for a freshly‐prepared NW at a bias voltage of 0.3 V and excitation wavelength of 488 nm were ～16.9 mA/W and ～42.9%, respectively. A pyroelectric‐like current transient was observed with reduced spectral responsivity when nonpolar Sb₂Se₃ single‐crystalline NWs were excited by laser pulses. Because Sb₂Se₃ NWs were nonpyroelectric or ferroelectric, the pyroelectric‐like current could possibly be attributed to temperature dependent nonlinear space‐charge distributions. Defects produced by the external electrical bias generated and re‐distributed space charges in the NWs. As a result, the temperature dependent inhomogeneous electric field led to nonlinear expansions or contractions of the lattice (electrostriction) that can produce pyroelectric current. We obtained a lower bound of equivalent pyroelectric coefficient α ≥ 60.09 μC/m² K from these materials by fitting the electrical transients. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Study on synthesis of poly(N‐isopropylacrylamide) grafted carbon black and temperature‐dependence conductivity of grafted carbon black/epoxy composites

Carbon black nanoparticle grafted with poly(N‐isopropylacrylamide) (CB‐g‐PNIPAAm) was synthesized by surface‐initiated atom transfer radical polymerization (SI‐ATRP). The temperature‐responsive behavior of CB‐g‐PNIPAAm was proved by temperature‐variable ¹H NMR. A temperature‐dependent conductive composite was prepared by blending CB‐g‐PNIPAAm with epoxy resin. The relationship between temperature and resistivity of the composite was studied: the composite exhibited a negative temperature coefficient (NTC) phenomenon. Possible mechanism for the NTC phenomenon was suggested. The results showed that resultant composites can be used in intelligent temperature‐switching. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1529–1535, 2008     

Shock tube spherical particle accelerating study for drag coefficient determination

An original particle accelerating technique has been developed for a shock tube. The trajectories of calibrated spherical particles and in diameter have been measured by the multiple exposure shadowgraph technique coupled with a high speed drum camera. Both particle velocity and acceleration, deduced from the experimental trajectories, allow the determination of the drag coefficients for different, subsonic and supersonic, flow regimes for the particle Reynolds numbers from to and the particle Mach numbers from 0.6 to 1.2. The drag coefficient values have been compared with different correlations found in the literature. Received 8 April 2002/ Accepted 17 June 2002 Published online 19 December 2002 Correspondence to: L. Houas (e-mail: Lazhar.Houas@polytech.univ-mrs.fr)     

Fermi Acceleration in driven relativistic billiards

We show numerical experiments of driven billiards using special relativity. We have the remarkable fact that for the relativistic driven circular and annular concentric billiards, depending on initial conditions and parameters, we observe Fermi Acceleration, absent in the Newtonian case. The velocity for these cases tends to the speed of light very quickly. We find that for the annular eccentric billiard the initial velocity grows for a much longer time than the concentric annular billiard until it asymptotically reach c.     

A fast iterative model for discrete velocity calculations on triangular grids

A fast synthetic type iterative model is proposed to speed up the slow convergence of discrete velocity algorithms for solving linear kinetic equations on triangular lattices. The efficiency of the scheme is verified both theoretically by a discrete Fourier stability analysis and computationally by solving a rarefied gas flow problem. The stability analysis of the discrete kinetic equations yields the spectral radius of the typical and the proposed iterative algorithms and reveal the drastically improved performance of the latter one for any grid resolution. This is the first time that stability analysis of the full discrete kinetic equations related to rarefied gas theory is formulated, providing the detailed dependency of the iteration scheme on the discretization parameters in the phase space. The corresponding characteristics of the model deduced by solving numerically the rarefied gas flow through a duct with triangular cross section are in complete agreement with the theoretical findings. The proposed approach may open a way for fast computation of rarefied gas flows on complex geometries in the whole range of gas rarefaction including the hydrodynamic regime.     

Influence of the spectral power distribution of a LED on the illuminance responsivity of a photometer

The measurement accuracy in the photometric quantities measured through photometer head is determined by the value of the spectral mismatch correction factor (c(S_t,S_s)), which is defined as a function of spectral power distribution of light sources, besides illuminance responsivity of the photometer head used. This factor is more important when photometric quantities of the light-emitting diode (LED) style optical sources, which radiate within relatively narrow spectral bands as compared with that of other optical sources, are being measured. Variations of the illuminance responsivities of various V(λ)-adopted photometer heads are discussed. High-power-colored LEDs, manufactured by Lumileds Lighting Co., were used as light sources and their relative spectral power distributions (RSPDs) were measured using a spectrometer-based optical setup. Dependences of the c(S_t,S_s) factors of three types of photometer heads (f₁′=1.4%, f₁′=0.8% and f₁′=0.5%) with wavelength and influences of the factors on the illuminance responsivities of photometer heads are presented.