激光束诱导电流法提取HgCdTe光伏探测器的电子扩散长度

由于得到HgCdTe扩散长度L_p的标准测试结构会损伤p-n结单元,实验中广泛采用激光束诱导电流（LBIC）提取的等效扩散长度L来代替L_p.本文通过二维数值模拟,分析了等效扩散长度L和扩散长度L_p 的关系.二者的比例关系为L/L_p=1.1,该基本关系不受器件的关键参数如掺杂浓度、载流子寿命、载流子迁移率等的影响.最后将激光束 关键词： 碲镉汞 激光束诱导电流 扩散长度     

HgCdTe红外探测器离子注入剂量优化研究

在中波响应波段的p型Hg_0.709Cd_0.291Te(MCT)分子束外延生长薄膜上，利用材料芯片技术获得叠加注入不同硼离子剂量的系列大光敏元面积(500μm×500μm)的n-op-p结.通过测量液氮温度下不同离子注入剂量单元的电流-电压特性和对零偏微分电阻R₀分析，观测到p-n结的性能与硼离子注入剂量明显的依赖关系.在另一片薄膜材料(镉组分值为0.2743)上通过该方法获得R₀A优于现有常规数值的探测器单元. 关键词： p-n结 离子注入 碲镉汞薄膜     

Zn离子注入多晶Al的扩散研究

用离子注入技术制备Zn-Al扩散偶,在注入浓度小于溶解度的条件下,本文提出杂质原子在基体单相中扩散的理论模型。应用数值分析方法对这一模型求解,得到与实验相符的杂质原子扩散分布;利用离子注入产生的增强扩散现象,还求出沉积法难以得到的260—380℃温区内Zn原子在多晶Al中的扩散系数,弥补了传统方法的不足。 关键词：     

扩散序谱(DOSY)实验中扩散系数维数字分辨率的影响

核磁共振二维扩散序谱（DOSY）实验测定溶液中分子自扩散系数时,扩散系数维的数据点及其数字分辨率直接影响了测定值的精度.在较系统地确定了DOSY实验本身偏差范围的基础上,本文研究了扩散系数维不同的数字分辨率对测定值的影响,包括其引入偏差的来源以及形成偏差的大小.由于不同的溶液条件下分子扩散系数的改变可直接用于表征分子结构或状态的变化,本文提出的相对数字分辨率与扩散系数相对变化值的直接比较,可直观地表明数字分辨率对扩散系数测定值的影响.     

器件效应数值模拟中漂移扩散模型的误差分析

为了确定数值模拟过程中的误差来源,并针对误差来源改进软件,减小计算误差,对半导体器件数值模拟中的采用的漂移扩散模型进行了研究。结合自主开发的半导体器件效应软件GSRES,分析了软件中漂移扩散模型的理论近似,对计算模型中由于温度分布、载流子复合/产生率、载流子迁移率等项采取近似而导致的误差进行了分析。根据误差分析和数值模拟算例,认为误差主要来自于器件内部温度场分布和迁移率模型的近似,给出了软件的适用范围。结合半导体器件的研究热点和发展趋势,对该模型中需要进行改进的近似项进行了分析。     

扩散序谱(DOSY)实验测定缓冲体系中蛋白质表观分子量

液体核磁共振扩散序谱（DOSY）可以通过测定溶质分子的自扩散系数（D_t）来研究该分子在溶液中的表观分子量（M）.D_t与测试体系和分子本身性质相关,蛋白质体系较为复杂,从而增加了蛋白质自扩散系数（D_t-protein）测定的难度.本文以3-（三甲基硅基）丙磺酸钠（DSS）为内标,以蛋白质分子与DSS自扩散系数的比值（D_r）来表征蛋白质分子在溶液中的表观分子量（M_protein）,该方法降低了缓冲体系对M_protein的影响,使得M_protein主要由分子本身的性质决定.在此基础上,测定了不同分子量蛋白质分子相对于DSS的D_r,拟合得到了D_r与M_protein的相关关系：lgM_protein =-2.6488 lgD_r-0.7863,相关系数（R²）为0.997.最后测定了通过大肠杆菌表达纯化得到的SARS冠状病毒主蛋白酶C端结构域（M^pro-C）分子相对于DSS的D_r,并计算出与文献结果一致的M_protein,进一步验证了拟合公式的准确性和实用性.     

器件效应数值模拟中漂移扩散模型的误差分析

为了确定数值模拟过程中的误差来源,并针对误差来源改进软件,减小计算误差,对半导体器件数值模拟中的采用的漂移扩散模型进行了研究。结合自主开发的半导体器件效应软件GSRES,分析了软件中漂移扩散模型的理论近似,对计算模型中由于温度分布、载流子复合/产生率、载流子迁移率等项采取近似而导致的误差进行了分析。根据误差分析和数值模拟算例,认为误差主要来自于器件内部温度场分布和迁移率模型的近似,给出了软件的适用范围。结合半导体器件的研究热点和发展趋势,对该模型中需要进行改进的近似项进行了分析。     

低能离子注入育种中次级效应影响的模拟研究

低能离子注入育种作为一种有效的育种方法在实践中进行了大量的尝试并取得了一系列重要成果,但其作用机理一直都存在着巨大的争议,特别是射程很短的低能重离子如何穿透到种子内部触发生物效应。本研究利用SRIM、CASINO、Geant4模拟程序对低能离子注入生物样品的离子注入深度进行模拟和定量分析,并对次级粒子可能产生的影响进行了定量模拟研究。结果显示,低能重离子本身射程一般都小于1 μm,选用轻离子、提高注入能量、采用干种子进行注入,都有利于增加穿透深度。次级过程中,反冲质子的最大射程比初级入射离子的稍大,不能显著提升穿透能力。次级过程产生的粒子中只有X射线可以明显提高穿透种子的深度,只要剂量足够大,总会有少量X射线穿透到很深的地方。The breeding method by low-energy ion implantation has been proved to be a valuable breeding method by a large number of practical attempts, but the mechanism of the method has always been in a large dispute. The most difficult thing to be understood is how the low energy heavy ion with such a short range (normally shorter than 1 μm) can penetrate into the inner part of seeds to trigger the biological effects. In this paper, simulations with quantitative analysis were performed for the low energy ion implantating into biological samples and the effects caused by the secondary particles using SRIM, CASINO and Geant4 simulation programs. The results showed that the ranges of low energy heavy ions are normally less than 1 μm. The ranges can become longer if dry seeds and light ions are used with a higher energy. The ranges of recoil protons are only a little longer than that of the primary ions. Among the secondary particles produced in the ion implanting process, only the X-ray can obviously increase the penetration depth in seeds. There always will be a small amount of X-rays which can penetrate into the deeper place in the seed if the ion dose is high enough.     

激光梯度场中荧光关联谱学的实验研究

研究了荧光关联谱(fluorescence correlation spectroscopy,简称FCS)在FCS测量中外加激光梯度场的影响.实验显示,微区内粒子的扩散时间随梯度场强度增加而增加,近似呈线性关系.同时,微区内平均粒子数目随梯度场相应地增加.粒子的极化率越大,相同条件下受到激光梯度场的影响就越大. 关键词： 荧光关联谱(FCS) 激光梯度场 扩散时间     

低杂波电流驱动中径向扩散效应的数值模拟

应用改进后的程序详细计算了不同径向扩散系数对低杂波电流驱动剖面分布的影响。通过计算发现:考虑径向扩散效应后,驱动电流分布变平展宽,电流驱动的分布随着扩散系数的增大逐渐向外层移动,由局域性分布演化成非局域性分布;驱动电流的大小和效率随着扩散系数的增大而降低。     

Investigations on the Diffusion of Boron in SiGe Mixed Crystals

By studying the quadrupolar interaction of ¹²B in silicon–germanium mixed crystals with the β-NMR method, the boron–germanium pair was identified and the saturation amplitudes for boron in differently composed crystals were measured. The relative saturation amplitudes agree with statistical predictions. At low temperatures boron is preferentially implanted into stable interstitial sites. These sites are converted into substitutional sites by diffusion processes which take advantage of reorientation jumps.     

离子辐照对单晶Si中预注入B原子扩散的影响

室温下使用MeV能量级Si,F和O离子对5keV B离子预注入后的n-型单晶Si(100)进行了辐照,应用二次离子质谱仪测试分析了掺杂物B原子的分布剖面及其变化.结果表明,高剂量Si,F和O离子的附加辐照可以抑制热激活退火中B原子发生的瞬间增强扩散.在相同的辐照条件下,Si近表面区域中SiO₂层的存在更有助于限制B原子的瞬间增强扩散.结合卢瑟福沟道背散射分析和DICADA程序计算对实验结果进行了讨论.     

束旋转90°对束变换环孔腔输出性能的影响

 使用积分方法和差分方法结合的快速计算方法，在实际燃烧驱动氟化氢化学激光器增益介质沿径向分布不均匀的情况下，考虑在光束变换环形孔径激光谐振腔的紧束段引入光束旋转90°对其输出性能的影响。计算结果显示：在无腔失调的情况下，在紧束段引入光束旋转对束变换环孔激光谐振腔输出功率及光束质量的改善并不显著；在存在腔失调的情况下，紧束段光束旋转对于输出功率和光束质量的改善有显著效果。     

Effects of the structural order of canthaxanthin on the Raman scattering cross section in various solvents: A study by Raman spectroscopy and ab initio calculation

In this work,we measure the Raman scattering cross sections(RSCSs) of the carbon-carbon(CC) stretching vibrational modes of canthaxanthin in benzene,acetone,n-heptane,cyclohexane,and m-xylene.It is found that the absolute RSCS of CC stretching mode of canthaxanthin reaches a value of 10 24 cm 2 ·molecule 1 ·sr 1 at 8×10 5 M,which is 6 orders of magnitude larger than general RSCS(10 30 cm 2 ·molecule 1 ·sr 1),and the RSCSs of canthaxanthin in various solvents are very different due to the hydrogen bond.A theoretical interpretation of the magnetic experimental results is given,which is introduced in a qualitative nonlinear model of coherent weakly damped electron-lattice vibration in the structural order of polyene chains.In addition,the optimal structure and the bond length alternation(BLA) parameter of canthaxanthin are calculated using quantum chemistry calculation(at the b3lyp/6-31g(d,p) level of theory).The theoretical calculations are in good agreement with the experimental results.Furthermore,the combination of Raman spectroscopy and the quantum chemistry calculation study would be a quite suitable method of studying the structures and the properties of the π-conjugated systems.     

Design and fabrication of ultra broadband infrared antireflection hard coatings on ZnSe in the range from 2 to 16 μm

In conventional infrared multilayer antireflection coatings (MLAR) materials of fluoride and chalcogenide types are used, which are disadvantaged due to their low mechanical strength and poor stability against humidity and environmental impacts. In this paper, we show that high performance ultra broadband and hard infrared multilayer antireflection coatings on ZnSe substrates in the wavelength range from 2 to 16 μm can be designed and fabricated. Diamond-like carbon (DLC) hard coating as a mechanical and environmental protection layer was proposed and deposited onto MLAR surfaces (MLAR + DLC) using a pulsed vacuum arc ion deposition technique. The thickness of the high optical quality DLC can be optimized in the design simulation to achieve a practically best antireflection and surface protection performance. We show that a germanium thin film (15 nm) between the MLAR and DLC surfaces can be used as a transition layer for optical and material match. The average transmission of the fabricated MLAR+DLC surfaces was 93.1% in the wavelength range between 2 and 16 μm. The peak transmission was about 97.6%, close to the simulated values. The durability and stability against mechanical impacts and environmental tests was improved significantly compared with the conventional infrared windows.     

Simulative investigation on the impact of laser-spectral width in single-tone radio-over-fiber transmission system using optical single side-band technique

In this paper, we analyzed the impact of laser-spectral width incorporating dual-electrode Mach–Zehnder modulator (DEMZM) in single-tone radio-over-fiber (RoF) transmission system by simulation setup. It is shown that an improvement in the measurement of received radio frequency (RF) power is achieved by reducing the laser line width from 100 MHz to 100 kHz, which further improves the BER rate and optical link by transmitting the information with low power. The results are calculated for 20 and 50 km optical single sideband (OSSB)–RoF transmission system by varying the chirp from 0 to −3 as it requires less bandwidth than optical dual sideband (ODSB)–RoF system and is tolerable for power degradation due to a chromatic fiber-dispersion, through a standard single-mode fiber (SSMF) carried by a continuous wave (CW) laser at 1550 nm of laser-spectral width varying from 100 MHz to 100 kHz with CW power of 10 mW that modulates a single RF channel of 20 GHz. Further, deployment of such lasers with OSSB scheme helps the telecom industry to reduce the designing cost of RoF communication systems.     

Role of chromium ion implantation on the corrosion behavior of zirconium in 1N H2SO4

In order to study the effect of chromium ion implantation on the aqueous corrosion behavior of zirconium, specimens were implanted by chromium ions with a dose range from 1×10¹⁶ to 1×10¹⁷ ions/cm², using MEVVA source at an extracted voltage of 40 kV. The valence and elements penetration distribution of the surface layer were analyzed by X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES), respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the micro-morphology and microstructure of chromium-implanted samples. The potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zirconium in a 1N H₂SO₄ solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zirconium compared with that of as-received zirconium. The mechanism of the corrosion resistance improvement of chromium-implanted zirconium is probably due to the addition of the chromium oxide dispersoid into the zirconium matrix.     

高阶效应对光纤系统中孤子和艾里脉冲传输特性影响的数值研究

以变系数耦合高阶非线性薛定谔方程为理论模型,采用分步傅里叶方法,讨论了孤子和艾里脉冲在光纤中的传输特性。研究表明三阶色散、自频移和自陡峭效应导致孤子和艾里脉冲所分离出的俘获孤子的中心位置发生偏移,且三阶色散会影响俘获孤子的强度,并讨论了两脉冲的中心位置及强度对艾里脉冲截断系数的依赖关系。     

Effect of Host Medium on the Fluorescence Emission Intensity of Rhodamine B in Liquid and Solid Phase

In this work, we study the effect of concentration, host medium, PH and phase states on the fluorescence emission from the laser dye Rhodamine B pumped by UV laser as exited source. The polymethylmethacrylate PMMA is used as a host medium in case of solid phase samples while, ethanol and Tetrahydrofuran (THF) are used in case of a liquid one. Laser Induced Fluorescence (LIF) technique was used to study the fluorescence properties of both cases of liquid and thin film solid-state samples. In addition, the Dual Thermal Lens (DTL) technique was used to study the quantum yield of these samples. The concentrations of Rhodamine B in ethanol as solvent between 2 × 10⁻² M and 5 × 10⁻⁶ M were studied. The maximum fluorescence emission is observed at concentration of Rhodamine B C = 3 × 10⁻⁴ M. Comparison studies were investigated for different host medium such as ethanol, THF, PMMA in liquid phase state and PMMA in solid phase state. The measurements revealed that, the behavior of both phases state was analogous. Rhodamine B/PMMA thin film sample by ratio of 4:1 and thickness 0.12 mm was found to have the best photostability sample with a quantum yield about ≈0.82.