高纯锗中浅受主的光热电离光谱

在液氦温度附近, 运用傅里叶变换光谱以及与之相连的磁光光谱系统, 对室温电阻率约为50Ω·cm的p型高纯锗样品进行了高灵敏度的光热电离光谱的研究.从实验上确定了高纯锗样品中浅杂质光热电离的最佳温度范围, 在该温度范围内测量了样品的光热电离光谱, 指出该样品中主要杂质为浅受主硼与铝. 对杂质谱线发生分裂的两种原因, 补偿性杂质导致的快速复合以及随机应力等, 进行了分析讨论. 关键词： 高纯锗 光热电离光谱 元素半导体中的杂质和缺陷能级     

高纯硅中补偿性杂质的光热电离光谱

首先测量了高纯n型硅样品在接近液氦温度区域内随温度变化的光热电离光谱,确定了硅样品的最佳光热电离温度范围. 在该温度范围内,在有本征带隙光照射条件下,测量了样品的高分辨率光热电离光谱,同时观察到了来自主要浅杂质施主磷以及补偿性杂质硼的正信号. 随后,应用外加磁场,对硼的光热电离光谱进行了研究,发现来自硼的光热电离信号,在外加磁场作用下,发生了由正向负信号的转变. 通过对该现象进行分析讨论,排除了该现象是温度效应的可能,指出普遍用来解释补偿性杂质光热电离响应的Darken模型存在不足,而少数载流子快速复合模 关键词： 高纯硅 光热电离光谱 元素半导体中的杂质和缺陷能级 少数载流子快速复合     

高纯硅中补偿性杂质的光热电离光谱

首先测量了高纯n型硅样品在接近液氦温度区域内随温度变化的光热电离光谱，确定了硅样品的最佳光热电离温度范围. 在该温度范围内，在有本征带隙光照射条件下，测量了样品的高分辨率光热电离光谱，同时观察到了来自主要浅杂质施主磷以及补偿性杂质硼的正信号. 随后，应用外加磁场，对硼的光热电离光谱进行了研究，发现来自硼的光热电离信号，在外加磁场作用下，发生了由正向负信号的转变. 通过对该现象进行分析讨论，排除了该现象是温度效应的可能，指出普遍用来解释补偿性杂质光热电离响应的Darken模型存在不足，而少数载流子快速复合模     

半导体中浅杂质的傅里叶变换光热电离光谱

本文报道与快扫描傅里叶变换红外光谱仪相结合的光热电离光谱实验装置和测量系统。采用该系统高分辨率、高灵敏度地研究和测量高纯锗和高纯硅中的剩余浅杂质获得成功。在P型超纯Ge中发现浓度低达10⁸cm^-3的硼受主杂质的光热电离谱线,而探测灵敏度则至少可达10⁷cm^-3;在n型高纯Si中观测到Li-O复合型浅施主中心D(Li,O);施加本征激发光后在P型高纯Si中同时观察到B受主和P施主的跃迁谱线系。此外,在Si,Ge中均观察到 关键词：     

ZnSe:Al发光光谱的研究

本文用热扩散的方法在Zn饱和蒸气压下,把Al掺杂到高纯ZnSe单晶中,通过77K下的光致发光光谱研究了Al杂质的发光行为,讨论了施主一受主对发射强度、自激活中心发射强度随掺杂温度的变化规律以及与Zn饱和蒸气压的关系.本文首次报道了在300℃～900℃温度范围内进行Al掺杂的ZnSe的发光规律.     

发射光谱测定微量稀土杂质用的一种新的载体KBH4的研究

介绍了高纯稀土氧化物中微量稀土杂质的光谱测定方法，本工作用碳粉做缓冲剂，ＫＢＨ４做载体，用化学方法将大量稀土分离掉，而后对余下微量和稀土杂质进行光谱测定。只要取样量不少于１克，则可测定的纯度为９９．９９９９５％的稀土样品。     

井型高纯锗探测器体源样品无源效率刻度

采用蒙特卡罗程序MCNP建立物理模型,对井型高纯锗探测器的效率进行虚拟刻度。模拟计算在密度为0.4,1.2 gcm-3的6种不同成分环境样品中,探测器对射线的探测效率,当能量高于0.10 MeV时,体源样品的探测效率主要与样品密度、射线能量相关。以土壤、水和植物油样品为代表,结合所选取的函数模型,确定了密度范围0.1~1.6 gcm-3的固体源、密度1.0 gcm-3的水溶液和密度0.92 gcm-3的油溶液体源的效率函数及参数。实验采用标准源,对探测效率模拟结果进行了验证,探测效率的模拟值与实验值符合较好,二者误差均在3%以内。说明MCNP程序可以较为准确地模拟计算井型高纯锗探测器对射线的探测效率,验证了该无源效率刻度方法的准确性和可行性。     

应变Si1-xGex层中p型杂质电离常温和低温特性

本文采用解析的方法计算了应变Si1-xGex层中p型杂质电离度与Ge组分x、温度T以及掺杂浓度N的关系.发现常温时,在同一Ge组分下,随着掺杂浓度的升高,杂质的电离度的先变小,而后又迅速上升到1.在同一掺杂浓度下,轻掺杂时,杂质的电离度随Ge组分的增加先变大,而后几乎不变;重掺杂时,杂质电离能变为0后,杂质电离度为1.低温下,轻掺杂时,载流子低温冻析效应较为明显,杂质的电离度普遍较小,当掺杂浓度大于Mott转换点时,载流子冻析效应不再明显,电离率迅速上升到1.在同一Ge组分下,随着掺杂浓度的升高,杂质的电离度先变小,后变大,而后又迅速上升到1.在同一掺杂浓度下,轻掺杂时,杂质的电离度随Ge组分的增加变大;重掺杂时,杂质电离能变为0后,杂质电离度为1.     

近红外光谱分析中温度影响的修正

样品温度变化会对模型预测结果产生影响,为解决这个问题,首先,对同一样品不同温度下的光谱与同一样品相同温度的光谱进行了比较。结果显示,不同温度下的光谱差异较大。然后研究了样品温度对玉米粗蛋白模型的预测结果的影响,对随机选取的粗蛋白含量为6.04%的样品不同温度采集光谱,对这些光谱进行预处理消除温度之外的因素对光谱的影响,将预处理后的光谱代入已建立好的模型中进行预测,结果显示,预测结果与实测值之间的差别随着光谱温度与建模温度相之间差别的增大而增大,最大的误差为1.12%。为了解决温度对模型预测结果的影响,进而分析了温度与不同温度下的光谱数据之间的关系,发现在去除了光谱两端噪声较严重的区域后,不同温度下,同一波长点处的光谱数据之间存在一定的线性关系。依据这一发现,文中提出了温度修正理论,以建模时的光谱为基准光谱,然后根据温度与光谱之间的线性关系使用线性回归算法对不同波长点的光谱进行一元线性回归,求出不同温度下的光谱与基准光谱之间的差,最后将不同温度下的光谱校正为基准光谱,通过该理论对光谱进行校正之后,不同温度下的同一样品的光谱之间的差别和修正之前相比已经有了很大改善,将修正后的光谱代入模型,大部分预测结果得到了提高,符合国家标准±0.5%以下的要求。最后使用和建模无关的34个不同含量的样品对该温度修正理论进行验证,光谱修正前后粗蛋白的模型预测值与标准理化值决定系数分别为0.910和0.982,均方根误差分别为0.558和0.172,平均相对误差分别为6.05%和1.75%。该温度修正理论从近红外光谱分析的本质上进行了温度修正,为其他样品的温度修正提供了参考,有利于手持式近红外光谱仪使用的推广。     

激光剥蚀-电感耦合等离子体质谱法测定高纯铪中10种杂质元素

高纯铪由于具有独特的理化性质,在核反应堆、等离子切割机、光学元件等方面有着重要的应用。高纯铪中杂质的种类和含量会影响高纯铪的物理化学性能,应用中对高纯铪纯度的要求也越来越高,这就对高纯铪的分析检测技术提出了更高的要求。激光剥蚀-电感耦合等离子体质谱法（LA-ICP-MS）是激光剥蚀进样技术与电感耦合等离子体质谱联用,可以直接分析固体样品,并且方法前处理简单,可以避免样品前处理过程中引入杂质,是一项高效、快速、精密的分析技术,在环境、地质、冶金、燃料能源、材料、生物医药、考古等领域广泛应用。所以,激光剥蚀-电感耦合等离子体质谱法（LA-ICP-MS）是高纯金属杂质元素最佳检测方法之一。还未见有应用LA-ICP-MS于高纯铪样品的报道。用LA-ICP-MS对高纯铪中10种杂质元素（Al,Sc,Ti,Fe,Ni,Cu,Mo,Ag,Sn,W）进行定量分析。为了降低激光剥蚀过程中元素的分馏效应,提高信号灵敏度和稳定度,对激光剥蚀参数进行优化实验。确定了激光剥蚀的最优仪器参数为：氦气流量600 mL·min-1,激光能量90%,剥蚀孔径150 μm,激光扫描速度60 μm·s-1,激光脉冲频率20 Hz。经实验优化后的ICP-MS仪器工作参数为：RF功率1 450 W,射频匹配电压1.8 V,载气流量0.85 L·min-1,冷却器流量0.85 L·min-1,采样深度7.5 mm。在最优参数条件下,利用内控标样建立工作曲线,各杂质元素标准曲线的线性相关系数为0.993 6～0.999 8。采集载气空白的信号强度,平行测定11次,以3倍空白信号的标准偏差所对应的含量作为元素的检出限,得到各元素的检出限为0.001~0.08 μg·g-1。将高纯铪制成尺寸合适的样品,用硝酸洗去样品表面的氧化物,将其装入剥蚀池中,运用线扫描剥蚀方式,在最佳仪器工作条件下,对三个高纯铪样品中的10种杂质元素进行定量分析。实验结果显示,杂质元素含量为0.17～36.76 μg·g-1,相对标准偏差为1.4%～20%,精密度良好。以184W为例,将LA-ICP-MS法和ICP-MS法的测定结果进行t检验,三个样品的t值分别为2.14,1.64和2.11,均小于显著性水平为0.05时的临界值（t_{0.05, 12}=2.18）,说明LA-ICP-MS法和ICP-MS法的测定结果在置信度为95%时没有显著性差异,即正确度良好。所以,该方法正确度和精密度良好,可用于高纯铪中杂质的定量分析。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.