用大芯径石英玻璃光纤传输兆瓦级高能激光脉冲及其在双波长LA-LIBS技术中的应用

为了解决单脉冲激光诱导击穿光谱(LIBS)技术在元素分析时空间分辨本领与分析灵敏度之间的矛盾,本文利用一台双波长输出的Nd∶YAG激光器开展了双波长激光剥离-激光诱导击穿光谱(LA-LIBS)技术的研究。其中532 nm的二倍频激光用于剥离样品;1 064 nm的基频激光通过大芯径石英玻璃光纤传输并实现一定的延时后用于击穿被剥离的样品。两束激光采用正交几何配置以实现高空间分辨高灵敏的元素分析。实验研究了1 064 nm激光到光纤的耦合、光纤输出后的准直以及再聚焦时的一些关键技术问题。研究并得出了四种不同光纤对激光能量的传输能力。选择利用芯径为800 μm,数值孔径为0.39、长50 m的石英玻璃光纤成功传输了15 mJ的调Q激光脉冲并实现了250 ns的延时。并在此基础上开展了铜合金样品的双波长LA-LIBS分析,实验验证了基于一台Nd∶YAG激光器开展双波长LA-LIBS研究的可行性。该技术只需要一台激光器就可以完成相应的光谱分析,具有系统结构简单,便于小型化等优点,适合对不同样品开展原位的高空间分辨高灵敏的元素显微分析。     

Luminescence properties of InxGa1-xN（x～0.04） films grown by metal organic vapour phase epitaxy

In x Ga 1-x N (x ～ 0.04) films are grown by metal organic vapour phase epitaxy.For the samples grown on GaN directly,the relaxation of InGaN happens when its thickness is beyond a critical value.A broad band is observed in the luminescence spectrum,and its intensity increases with the increasing degree of relaxation.Secondary ion mass spectrometry measurement rules out the possibility of the broad band originating from impurities in InGaN.The combination of the energy-dispersive X-ray spectra and the cathodeluminescence measurements shows that the origin of the broad band is attributed to the indium composition inhomogeneity caused by the phase separation effect.The measurement results of the tensile-strained sample further demonstrate the conclusions.     

推导加速度合成公式的“牵连点跟踪法”1）

理论力学是大学工科各专业本科生的技术基础课,点的合成运动是重点与难点内容之一。部分学生对牵连（加）速度,特别是对（加）速度合成定理的推导需要较长时间才能理解和适应。很多教材（如文献[1,2]）都引入了“牵连点”的概念。牵连点的定义为：某瞬时与动点重合的动系上的点称为动点在该瞬时的牵连点。由于动点相对动系有运动,不同的瞬时动点与动系上不同的点重合,因此不同瞬时的牵连点是不同的。某瞬时的牵连（加）速度就是该瞬时的牵连点相对定系的（加）速度。牵连点的引入能较好地帮助学生理解牵连（加）速度。在定理推导的教学实践中,虽然用目前的教材中所采用的方法都能很好地证明该定理,但我们注意到,“两点”（即牵连点与动点）在时间点和空间位置上的“重叠性”会给学生带来理解和掌握的难度,学生容易在“重叠性”这一点上产生困惑。文献[3]就动系做定轴转动,采用了一种将动点从其重合点“拉开”的方式,对该定理进行了推导,对解决学生的困惑有一定帮助。以下,本文以文献[3]的方法为基础,补充引入“牵连点”、“绝对和相对导数”等重要概念,并就动系做一般运动对该定理进行推导,在表达方式上也做了一些调整。本文称这种推导方式为“牵连点跟踪法”。     

不同施肥处理对潮土胡敏酸结构特性的影响

研究了饼肥,绿肥,秸秆肥三种处理在等氮等磷条件下对胡敏酸结构特性的影响,采用元素分析,显微红外,固态13C-NMR三种分析方法进行结构解析,结果表明：不同施肥处理的胡敏酸在化学组成和结构上类似,但还有很多明显的差别。(1)饼肥处理的胡敏酸H和N含量最高,绿肥处理的胡敏酸含O量最大,秸秆肥处理的胡敏酸含C量最高 (2)红外分析显示,三种处理的胡敏酸均含有蛋白质及碳水化合物,饼肥处理的胡敏酸含氨基化合物最多,绿肥处理的胡敏酸含羟基,脂肪烃含量最大,秸秆肥处理的胡敏酸含醇,酚含量最高;(3)固态 13C-NMR数据表明饼肥处理的胡敏酸含有最多的羧基碳,绿肥处理的胡敏酸含有烷基碳,羰基碳最多。秸秆肥处理的胡敏酸烷氧基碳,芳香碳含量最大。     

On the influence of a TiN interlayer on DLC coatings produced by pulsed vacuum arc discharge: Compositional and morphological study

The influence of a TiN interlayer on DLC coatings grown on silicon (1 0 0), 316 stainless steel and KCl by using the PAPVD pulsed arc discharge technique is presented in this paper. The structure of the coatings was determined by means of FTIR through observation of the absorption band modes of CH₂ between 3100 and 2800 cm⁻¹ and representation of the sp³ and sp² carbon bonds, respectively. The sp³/sp² bonds ratio was calculated by using the base line method and producing a value greater than 1 which was a good prediction of high hardness. XPS analysis of the films was made; the wide spectrum showed the elemental composition of the films (Ti, N, C). A narrow spectrum of C1s at binding energy of 284.48 eV was obtained, and its deconvolution showed peaks of sp³, sp² and Ti–C. Ti–C bonds were formed due to diffusion of carbon atoms into a TiN matrix. The concentration for the XPS spectra was calculated by using the area under the curve of sp³ and sp² peaks. The morphology of the bilayer, including roughness, grain size and thickness was studied through SPM techniques.     

Raman scattering studies of (GaP)n/(InP)n (n = 1, 1.7, 2) short‐period superlattice structures

We report Raman scattering from (GaP)_n/(InP)_n (n = 1, 1.7, 2) short‐period superlattice (SPS) structures to study the effect of lateral composition modulation (LCM) on the behavior of optical phonons. Cross‐sectional transmission electron microscope images revealed that LCM was formed with complex pattern in the n = 1.7 and n = 2 samples grown at 490 °C. Interestingly, both the InP‐ and the GaP‐like longitudinal optical (LO) phonon energies increased systematically as the number of monolayers was increased from n = 1 to n = 2. A significant broadening of the phonon line shapes was also observed for the n = 1.7 and n = 2 samples. In contrast, for samples grown at 425 °C, both the increase of the LO phonon energies and the broadening of the phonon line shapes were observed only when n = 1.7. Our results demonstrate that the optical phonons in the (GaP)_n/(InP)_n SPS structures are significantly affected in the occurrence of LCM related to the growth temperature and the number of monolayers.Copyright © 2009 John Wiley & Sons, Ltd.     

Low-temperature direct wafer bonding of GaAs/InP

An approach for low-temperature direct wafer bonding of GaAs/InP was presented. The bonding procedure was carried out at temperatures from 350 to 500 ^°C, and the bonded n-GaAs/n-InP specimens were obtained even at a temperature as low as 350 ^°C. The compositional profile on the GaAs/InP heterointerface was studied by X-ray photoelectron spectroscopy. The bonded interfacial properties were also characterized by current–voltage (I–V$I\text{–}V$) and bonding strength measurement. The experimental results revealed an InGaAsP (or/and InGaAs) interlayer formed at the bonded interface, which influences the electrical property as well as the bonding strength. For the specimen bonded at 350 ^°C, the transport of major carriers could be explained by a tunneling effect. But the carrier transport was described by the thermionic emission theory for the specimen bonded at 450 ^°C. Finally, the mechanism of GaAs/InP bonding was discussed.     

Analysis of oxide formation induced by UV laser coloration of stainless steel

Laser-induced coloration on metal surfaces has important applications in product identification, enhancing styles and aesthetics. The color generation is the result of controlled surface oxidation during laser beam interaction with the metal surfaces. In this study, we aim to obtain in-depth understanding of the oxide formation process when an UV laser beam interacts with stainless steel in air. The oxide layer is analysed by means of optical microscopy, scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometer (TOF-SIMS). TOF-SIMS results clearly show the formation of duplex oxide structures. The duplex structure includes an inner layer of Cr oxide solution and an outer layer of Fe oxide solution. The oxide layer thickness increased as the results of Fe diffusion to surface during multiple laser scanning passes.     

碲锌镉(Cd1-yZnyTe)晶体Zn组分的显微荧光光谱研究

利用激光显微Raman光谱仪测量了5块碲锌镉晶片的显微荧光光谱,通过对来自碲锌镉材料带隙的荧光峰进行拟合,得出碲锌镉材料Eg值,从而可以计算出材料的Zn组分值;利用激光显微Raman光谱仪的定峰位X-Y平面扫描技术,可以便捷和无损伤地给出碲锌镉晶片的Zn组分分布图。     

Y1-xCaxBa2Cu3O7-δ烧结样品的直流输运特性

本主要报道了对烧结样品YBa2Cu3O7—δ(Y-123)进行部分元素替代的初步实验结果．用Ca^2 部分替代Y^3 形成的Y1-xCaxBa2Cu3O7—δ(YCBCO)样品呈现出如下特征：样品的正常态电阻率ρ随Ca的替代浓度增加而依次降低,而超导临界温度Tc也依次下降．这一现象与通常情况下对铜氧化物超导材料进行元素替代所引起的行为截然不同．实验还显示：样品在低温下的临界电流密度Jc得到明显提高,掺Ca后烧结样品的临界电流受外磁场的影响明显减小．在弱磁场下,不同掺杂浓度样品的临界电流Ic随外磁场呈不同比例地线性下降,与一般颗粒多晶高温超导体临界电流Ic随外磁场行为明显不同．