Structure,impurity composition,and photoluminescence of mechanically polished layers of single-crystal silicon

The introduction of optically active defects (such as atomic clusters, dislocations, precipitates) into a silicon single crystal using irradiation, plastic deformation, or heat treatment has been considered a possible approach to the design of silicon-based light-emitting structures in the near infrared region. Defects were introduced into silicon plates by traditional mechanical polishing. The changes in the defect structure and the impurity composition of damaged silicon layers during thermal annealing (TA) of a crystal were examined using transmission electronic microscopy and x-ray fluorescence. Optical properties of the defects were studied at 77 K using photoluminescence (PL) in the near infrared region. It has been shown that the defects generated by mechanical polishing transform into dislocations and dislocation loops and that SiO₂ precipitates also form as a result of annealing at temperatures of 850 to 1000°C. Depending on the annealing temperature, either oxide precipitates or dislocations decorated by copper atoms, which are gettered from the crystal bulk, make the predominant contribution to PL spectra.     

Slanting propagation of stochastic electromagnetic twist anisotropic Gaussian–Schell model beams in turbulent atmosphere

Based on the extended Huygens–Fresnel diffraction integral and the unified theory of coherence and polarization, the slanting propagation properties of stochastic electromagnetic twist anisotropic Gaussian–Schell model (ETAGSM) beams in turbulent atmosphere have been investigated. Both numerical calculation and physical interpretation are obtained. The influence of the atmospheric turbulence and the source parameters on the polarization distribution, intensity distribution and coherence distribution has been studied in great detail. The investigation reveals that slanting propagation can weaken the influence of atmospheric turbulence on the spectral properties of stochastic ETAGSM beams more obviously. It is also shown that we can modulate the spectral degree of polarization in the output plane especially in the far field by simply controlling the coherence, the spot width or the twisty properties of the source beams. The distribution of the spectral degree of polarization and cross-polarization of the beams in the output plane is also given out.     

INTERACTION OF OXYGEN PRECIPITATES WITH STRUCTURAL DEFECTS IN CZ Si CRYSTALS

This paper ia dealing with the interaction between oxygen precipitates and structural defects in CZ Si crystals. Different lattice defects: dislocation loops, rod-like defects and stacking faults have been observed as a consequence of oxygen precipitation. In turn, these defects also promote the nucleation and growth of the oxygen precipitates. It is shown that the dislocation dipole is more efficient than single dislocation in enhancing the oxygen precipitate formation.     

Na5Er(WO4)4晶体的光谱参数

Na5Er(WO4)4是化学计量的基质发光晶体,含有很高浓度的Er,它的发光却没有明显的浓度猝灭.与Na5Er(WO4)4结构相同的Na5Nd(WO4)4单晶是良好的激光材料,已获得激光输出.而Er3+在YAlO3,Y3Al5O12和CaF2中也实现了激光输出[1],在ErP5O14[1],Y3Al5O12:Er3+[2]和掺Er3+磷酸盐玻璃[3]的光学参数和某些谱线出激光的可能性已有研究.     

The influence of heating on the spectral characteristics of pure alkali halide NaCl crystals

The influence of high-temperature heating on the spectral characteristics of pure natural NaCl crystals is studied. It is shown that defects changing spectral characteristics of crystals are formed in them when heated. Temperature dependences of the luminescence intensity growth for these defects are described by the hyperbolic function. The action of X-rays on heated crystals results in the formation of new defects luminescent in regions of 435 and 570–585 nm. The efficiency of formation of these defects is obtained as a function of the temperature of heat pretreatment. Regularities in variations of the location and the intensity of luminescence of the defects obtained under the action of ultraviolet radiation and on long storage are determined.     

高斯-谢尔模型光束在有色差的分数傅里叶变换系统中的光谱特性

基于柯林斯(Collins)积分公式,导出了高斯-谢尔模型(GSM)光束在有色差的分数傅里叶变换(FRFT)系统中的光谱传输表达式,并以Lohmann Ⅱ型系统为例,通过数值计算与分析,研究了色差大小、分数傅里叶变换阶数、以及相对横向坐标对输出面归一化光谱和相对谱移动的影响.研究表明,相对谱移动随FRFT阶数的变化而改...     

Spectral shifts and spectral switches of a pulsed Bessel–Gauss beam from a circular aperture in the far field

The far-field spectral characteristics of a broadband-pulsed Bessel–Gauss beam passing through a circular aperture are studied. Based on the expansion of a hard aperture function into a finite sum of complex Gaussian functions and starting from the Fresnel diffraction integral, the approximate analytical expression for the spectral distribution of the diffraction field is derived. The “aperture dispersion”, that is, the red and blue shifts of the spectral intensity maximum and the spectral intensity shape distortion and distribution under different conditions are studied and illustrated with numerical calculations. It is shown that the far-field, on-axis maximum spectral intensity always shifts to the right (blue shift) and the amount of the spectral shift is dependent on the source bandwidth only. However, for the cases of off-axis, when the observation angle θ approaches a critical value, a rapid spectral switch occurs.     

Twin boundaries in antimony(V)-doped rutile titanium(IV) oxide

Titanium-antimony oxides formed by the calcination of precipitates at elevated temperatures contain low concentrations of antimony(V) within the rutile titanium(IV) oxide lattice. Electron microscopy has revealed the presence of planar defects which have been shown by electron diffraction to be twin boundaries. Energy dispersive X-ray analysis has not revealed any evidence for the segregation of antimony to these planar faults. No evidence has been found for the occurrence of crystallographic shear planes which are frequently found in rutile when doped with trivalent cations.     

空气—氩气冷却ICP：有机溶液分析的工作条件及检出限研究

研究了冷却气含50%空气的ICP中,MIBK溶液里金属元素不同性质谱线的信背比与入射功率、观察高度、冷却气流量及冷却气中空气含量等工作条件的关系。测定了8种元素12条谱线的检出限并与氩有机ICP中相同谱线的检出限进行比较。另外还测定了在引入MIBK溶液的情况下,空气-氩气ICP中心通道的激发温度。结果表明,具有中等激发能的谱线在含50%空气的空气-氩气有机ICP中的检出限优于氩气有机ICP中的检出限。     

超短脉冲经线性小孔阵列衍射时的光谱开关特性

研究了超短高斯脉冲光束经线性排列的矩形光阑阵列衍射后的远场光谱奇变现象。基于菲涅耳积分公式,通过将光阑函数展开为有限项复高斯函数的叠加,得到了超短脉冲光束经线性排列的小孔光阑阵列衍射后的谱强度解析表达式,并对衍射场的光谱红移和蓝移现象进行了数值计算和分析,分析了小孔间距和光阑半径对光谱强度的影响。研究表明:在衍射场的某些观测点,即在调制函数为零的位置附近,存在光谱开关现象。     

超短脉冲经线性小孔阵列衍射时的光谱开关特性

研究了超短高斯脉冲光束经线性排列的矩形光阑阵列衍射后的远场光谱奇变现象。基于菲涅耳积分公式,通过将光阑函数展开为有限项复高斯函数的叠加,得到了超短脉冲光束经线性排列的小孔光阑阵列衍射后的谱强度解析表达式,并对衍射场的光谱红移和蓝移现象进行了数值计算和分析,分析了小孔间距和光阑半径对光谱强度的影响。研究表明：在衍射场的某些观测点,即在调制函数为零的位置附近,存在光谱开关现象。     

非线性介质表面缺陷对激光光场的调制

以高斯光束为例,研究了非线性介质表面振幅调制型缺陷对光场的调制。基于广义惠更斯-菲涅尔衍射积分并采用泰勒级数展开方法,建立了高斯光束经过表面存在缺陷的非线性介质后的传输模型,得到了受缺陷调制光束经非线性介质后的光强分布解析式,研究了缺陷尺寸和光束在非线性介质中产生的附加相移大小对光强分布的影响,结果表明介质表面的缺陷尺寸越大,介质内产生的附加相移越大,光场受到的调制越严重。分别考虑了非线性折射率为正值和为负值的情况,研究发现相应的折射率值导致光束发生会聚或发散现象,并由于缺陷调制的作用,在光束传输过程中始终存在一光强极值点,且随着附加相移绝对值的增大光强极值点的峰值也随之增强。     

Propagation properties of ultrashort chirped pulsed Gaussian beams in the free space

Based on the Rayleigh diffraction integral and complex analytical signal representation, the free-space analytical propagation equation and its Fourier spectrum for ultrashort chirped pulsed Gaussian beams with constant diffraction length are derived. The effect of chirp parameter on the spatiotemporal and spectral properties is illustrated with analytical formulas and numerical calculation results. It is shown that the axial spectra of ultrashort chirped pulsed Gaussian beams become broadened with increasing chirp parameter. For single optical cycle, the transversal intensity distribution is affected by increasing chirp parameter, but almost not affected for several optical cycles. Moreover, the positive or negative sign of the chirp parameter has no effect on the spectral distribution and intensity distribution.     

Measurement of the differential and integral distribution of diffuse x-ray scattering intensity from defects in thin strained layers

Double-and triple-crystal diffractometry have been used to study structural perfection of a ∼1 μm-thick Ga_1−x In_xSb_1−y As_y epitaxial film (x=0.9, y=0.8) on GaSb. It is shown that scattering from samples of this system can be divided into coherent and diffuse. The arrangement of reciprocal-lattice points of the film and substrate in the two-dimensional intensity distribution for asymmetrical reflections argues for the absence of elastic-strain relaxation. No dislocation networks are formed, and the diffuse scattering is produced by Coulomb-type defects. Localization of diffuse scattering in reciprocal space suggests that these defects reside in the epitaxial film. The diffuse-scattering distribution in asymmetrical reflections is shown to be anomalous; namely, it extends in a direction parallel to the surface and is split into two maxima. Schemes have been proposed and realized for measuring integral distributions of diffracted intensity along the surface and perpendicular to it, and their potential for studying diffuse scattering from defects is explored. Fiz. Tverd. Tela (St. Petersburg) 39, 1188–1193 (July 1997)     

Contactless Spectroscopy of Deep Levels in Semiconducting Materials: Gaas

Abstract

The surface photo voltage (SPV) and photocurrent (PC) transients as a result of the excitation by the short high-intensity light pulses from semiconductor's intrinsic absorption spectral region are investigated in semi-insulating GaAs. It is shown that the mathematical convolution of SPV transients and arbitrary form double-pulse integrator (lock-in, double-boxcar) in a wide temperature range allows to receive the deep-level (DL) spectrum without the need to form electrical contacts to the crystal investigated. The use of such a procedure while scanning the crystal surface with a light spot at a temperature, corresponding to some DL maximum in the spectrum, makes possible the con tactless determination of this DL density distribution profile along the scanning direction.     

啁啾脉冲参数对合成光束的远场光强的影响

光束合成是提高激光功率及光束质量的一种有效方法,啁啾脉冲高斯光束的各参数都会影响合成的效果。利用夫琅禾费衍射积分公式导出了两束啁啾脉冲高斯光束合成的远场光强的解析式,得知远场光强与啁啾参数、脉宽及谱宽等参数有关。对远场光强进行了数值模拟,结果表明:对甚多束光束合成而言,单元激光间的啁啾参数增大、脉宽差值减小或者谱宽差值增大,均有利于轴上光强的增大及远场光强分布集中于传输轴附近。     

啁啾脉冲参数对合成光束的远场光强的影响

光束合成是提高激光功率及光束质量的一种有效方法,啁啾脉冲高斯光束的各参数都会影响合成的效果。利用夫琅禾费衍射积分公式导出了两束啁啾脉冲高斯光束合成的远场光强的解析式,得知远场光强与啁啾参数、脉宽及谱宽等参数有关。对远场光强进行了数值模拟,结果表明:对甚多束光束合成而言,单元激光间的啁啾参数增大、脉宽差值减小或者谱宽差值增大,均有利于轴上光强的增大及远场光强分布集中于传输轴附近。     

背景扣除和强度校正对激光诱导等离子体光谱参数的影响

激光诱导击穿光谱技术以其无需样品预处理、分析速度快、能实现多元素同时检测和远程分析等优点已经被广泛应用于诸多领域的物质成分定性或定量分析。该技术的理论基础是激光诱导等离子体。对等离子体光谱参数(如光谱谱线强度、等离子体温度等)的准确测量是利用该技术进行定性或定量分析的前提条件。实际的实验系统中,由于仪器本身固有的性能限制,会造成采集光谱信号的失真,从而限制等离子体光谱参数的精确测量或计算。为了克服仪器固有性能的影响,分析了实验系统所用中阶梯光栅光谱仪和传输光纤的固有性能缺点对光谱信号背景噪声和元素谱线绝对强度的影响,然后采用剥峰法对光谱信号中存在的锯齿状背景噪声进行扣除,利用辐射定标光源的标准光谱数据对谱线绝对强度进行校正,并对比了背景扣除和强度校正对等离子体谱线强度和等离子体温度的影响,实验表明谱线强度校正对合金钢等离子体380 nm以下的光谱信号具有较大影响,通过背景扣除和强度校正后,等离子体温度由13 401.75 K降低至8 980.72 K,玻尔兹曼平面法求解等离子体温度的拟合决定系数由0.60提高至0.91。因此在光谱数据处理之前对测量光谱进行背景扣除和强度校正是十分必要的,为提供可靠地光谱数据进行物质成分定性或定量分析奠定了基础。     

Al-4%Ag合金中Ag原子偏析的低温正电子湮没参数研究

分别研究了823 K淬火处理和20%形变量的Al-4%Ag低温下Ag析出物对正电子的捕获行为的变化。采用正电子湮没寿命谱(PALS)技术和符合多普勒展宽能谱(CDBS)在温度范围10~293 K内对其进行表征。多普勒展宽能谱结果表明2种样品中均存在Ag析出物。正电子寿命谱的解谱结果中的各组分给出了Ag析出物随测量温度的变化规律。在170 ~273 K之间,正电子湮没行为具有较强的温度依赖性。但对于两个具有不同类型缺陷的样品,在低于170 K时观察到样品中Ag析出物捕获正电子能力出现了差异。随着测量温度的降低,淬火样品中的Ag析出物的正电子寿命和强度基本不变。在低于170 K的测量中,形变样品中的Ag析出物对正电子的捕获能力仍旧存在着较强的温度依赖性,但是变化幅度在逐渐减弱。当测量温度提升到室温(273~293 K),越来越多的正电子从Ag析出物中逃逸,逐渐回到自由状态或被其他深陷阱所捕获,失去了对温度的依赖性。     

有振幅调制和相位畸变光束的远场光谱移动与光谱开关

基于瑞利衍射公式,研究了被光阑衍射的具有振幅调制和相位畸变光束的远场光谱变化规律。结果表明,有振幅调制和相位畸变光束在远场也会出现光谱异变现象和光谱开关效应,光阑截断参数、光束的相位畸变参数、振幅调制参数、光强调制参数对远场光谱的跃迁量和光谱开关产生影响。通过数值计算结果分析讨论了光阑截断参数及光束各参数影响远场光谱的规律。