Measurement of residual stress in a multi-layer semiconductor heterostructure by micro-Raman spectroscopy

Si-based multilayer structures are widely used in current microelectronics. During their preparation, some inhomogeneous residual stress is induced, resulting in competition between interface mismatching and surface energy and even leading to structure failure. This work presents a methodological study on the measurement of residual stress in a multi-layer semiconductor heterostructure. Scanning electron microscopy（SEM）, micro-Raman spectroscopy（MRS）, and transmission electron microscopy（TEM） were applied to measure the geometric parameters of the multilayer structure. The relationship between the Raman spectrum and the stress/strain on the [100] and [110] crystal orientations was determined to enable surface and crosssection residual stress analyses, respectively. Based on the Raman mapping results, the distribution of residual stress along the depth of the multi-layer heterostructure was successfully obtained.

中煤级煤Micro-Raman结构对甲烷吸附的响应

煤与甲烷、二氧化碳等流体作用后的体积膨胀及其机制一直是煤层气地质学和煤与瓦斯突出防治研究中的重要课题之一。以往的研究主要集中在宏观吸附膨胀及变形,并从力学的角度解释其膨胀机制。实际上,煤作为由大分子构成的分子体系,与甲烷、二氧化碳的相互作用是一种分子现象,其膨胀变形的本质应该是分子体系发生了变化,因此揭示煤大分子结构对煤体吸附膨胀的响应特征是认识其机制的基础。应用显微-拉曼光谱法对吸附甲烷前后的8个中煤级煤样(镜质组最大反射率R_(o)=1.08%~1.80%)进行了结构表征,并运用Origin 8.5软件对煤样吸附甲烷前后的拉曼光谱曲线进行了分峰拟合,在此基础上计算了煤样吸附前后的拉曼光谱结构参数。结果表明:原煤和吸附煤的G峰与D峰的峰位差d(G-D)随着煤级的增加有增大趋势,G峰半峰宽(FWHM-G)呈减小趋势,表明在反射率1.08%~1.80%阶段,煤结构有序度和微晶尺寸随煤级增加而逐渐增加;大芳香环(≥6)的相对含量(A_(D)/A_(G))出现先增加后减小的趋势,这是以较大芳香环的生成为主转为向石墨结构生成为主的结果;随着煤级增加,原煤的大芳香环结构中“杂质”(A_(S)/A_(D))及氢化芳环上的C—C的含量(A_(S)/A_(total))均有减小的趋势,反映出煤结构中sp^(2)-sp^(3)杂化烷基碳或氢化芳环逐渐减少,有序度逐渐增加;当R_(o)>1.3%时,吸附煤相对原煤的d(G-D)及A_(D)/A_(G)减少,小芳香环相对含量(A_(GR+VR+VL)/A_(D)),A_(S)/A_(D),A_(S)/A_(total)和FWHM-G增加,表明甲烷吸附变形引起环数较大的芳香环和微晶结构破裂形成较小的芳香环。这一结果对于认识煤大分子结构与甲烷的相互作用机制提供了理论依据。

Comparison between Double Crystals X-ray Diffraction and Micro-Raman Measurement on Composition Determination of High Ge Content Si_(1-x)Ge_(x) Layer Epitaxied on Si Substrate

It is important to acquire the composition of Si1-xGex layer, especially that with high Ge content, epitaxied on Si substrate. Two nondestructive examination methods, double crystals X-ray diffraction （DCXRD） and micro-Raman measurement, were introduced comparatively to determine x value in Si1-xGex layer, which show that while the two methods are consistent with each other when x is low, the results obtained from double crystals X-ray diffraction are not credible due to the large strain relaxation occurring in Si1-xGex layers when Ge content is higher than about 20%. Micro-Raman measurement is more appropriate for determining high Ge content than DCXRD.

Development of in-situ Micro-Raman spectroscopy system for autoclave experimental apparatus

We developed a set of in-situ Micro-Raman spectroscopy system for autoclave experimental apparatus because of the scientific significance of in-situ Micro-Raman spectroscopy system under the high-pressure hydrothermal condition.We used this system to measure the Raman spectrum of water-fluid and quartz crystal at the temperature ranging from 125 to 420℃.The signal-tonoise ratio of the Raman signal is good.

Low-energy(40 keV) proton irradiation of YBa_2Cu_3O_(7-x) thin films:Micro-Raman characterization and electrical transport properties

To investigate the damage profiles of high-fluence low-energy proton irradiation on superconducting materials and related devices, Raman characterization and electrical transport measurement of 40-keV-proton irradiated YBa_2Cu_3O_(7-x)(YBCO) thin films are carried out. From micro-Raman spectroscopy and x-ray diffraction studies, the main component of proton-radiation-induced defects is found to be the partial transition of superconducting orthorhombic phase to the semiconducting tetragonal phase and non-superconducting secondary phase. The results indicate that the defects induced in the conducting CuO_2 planes, such as increased oxygen vacancies and interstitials, can result in an increase in the resistivity but a decrease in the transition temperature TCwith the increase in the fluence of proton irradiation, which is confirmed in the electrical transport measurements. Especially, zero-resistance temperature TC_0 is not observed at a fluence of 10^(15)p/cm^2.Furthermore, the variation of activation energy U_0 can be explained by the plastic-flux creep theory, which indicates that the plastic deformation and entanglement of vortices in a weakly pinned vortex liquid are caused by disorders of point-like defects. Point-like disorders are demonstrated to be the main contribution to the low-energy proton radiation damage in YBCO thin films. These disorders are likely to cause flux creep by thermally assisted flux flow, which may increase noise and reduce the precision of superconducting devices.

A polarized micro-Raman study of a 0.65PbMg_(1/3)Nb_(2/3)O_3-0.35PbTiO_3 single crystal

Polarized micro-Raman spectra of a 0.65PbMgl/3Nb2/303 0.35PbTiO3 （0.65PMN-0.35PT） single crystal poled in the [001] direction are obtained in a wide frequency range （50 2000 cm^-1） at different temperatures. The best fit to the Raman spectrum at 77 K is achieved using 17 Lorenzians to convolute into it, and this is proved to be a reasonable fit. According to the group theory and selection rules of overtone and combinational modes, apart from the seven Raman modes that are from first-order Raman scattering, the remaining ones are attributed to being from second-order Raman scattering. A comparison between the experimental results and theoretical predictions shows that they are in satisfactory agreement with each other. Our results indicate that at 77 K the sample belongs to the rhombohedral symmetry with the C^53v（R3m） space group （Z = 1）. In our study, on heating, the 0.65PMN 0.35PT single crystal undergoes a rhombohedral → tetragonal → cubic phase transition sequence. The two phase transitions occur at 340 and 440 K, which correspond to the disappearance of the soft mode near 106 cm-1 recorded in VV polarization and the vanishing of the band around 780 cm^-1 in VH polarization, respectively.

Study of Thermal Conductivity of Porous Silicon Using the Micro-Raman Method

In this work, we are interesting in the measurement of thermal conductivity (on the surface and in-depth) of Porous silicon by the micro-Raman spectroscopy. This direct method (micro-Raman spectroscopy) enabled us to develop a systematic means of investigation of the morphology and the thermal conductivity of Porous silicon oxidized or no. The thermal conductivity is studied according to the parameters of anodization and fraction of silicon oxidized. Thermal transport in the porous silicon layers is limited by its porous nature and the blocking of transport in the silicon skeleton what supports its use in the thermal sensors.

Micro-Raman and SEM Analysis of Minerals from the Darhib Mine, Egypt

The Darhib mine is one of the several talc deposits in the Hamata area of southeastern Egypt. Several specimens of minerals coming from this mine were subjected to complementary investigation by micro-Raman spectrometry and scanning electron microscopy. The difficulty in their identification is the appearance of most of them: they are all very small and only visible under the mineral binocular microscope(×10 - ×40). They appear as small crystals in fissures and holes and a visual determination on colour and crystal gives only a guess of what kind of mineral it could be. Therefore, only after analyzing them by micro-Raman and scanning electron microscopy it was possible to identify their structure and they can be divided in three main groups: one is quite generic and several minerals of different species were identified, such as quartz, talc, mottramite and chrysocolla, very common in the talc mine (these ones are Si-based minerals);the other one is constituted by four samples which are Zn and/or Cu rich, which means minerals of the rosasite or aurichalcite groups;the last group is constituted by two samples containing mainly Pb..

不同煤级煤纳米力学性能的Micro-Raman结构响应

煤的力学性质具有非均质性及多尺度效应,从纳米尺度认识煤力学性质及与其组成结构之间的关系,是理解煤储层的压裂改造机制及裂纹扩展机理的关键。利用原子力显微镜和显微拉曼对不同煤级煤的镜质组进行测试,获得煤样的力学和结构参数。结果表明:镜质组的弹性模量E在0.66~7.58 GPa之间,且弹性模量随镜质组最大反射率Ro的增加而增加;同时随着Ro的增大,拉曼结构参数呈现有规律的变化;将弹性模量E与拉曼结构参数建立关系,发现(G-D)峰位差、多环芳烃的相对含量与致弹性模量均呈现明显的正相关关系,FWHM-G与E呈现负相关关系,反映了结构有序度的增加会导致弹性模量增大,表明随着成熟度的增加,促使大分子结构排列紧密且分子间作用力增大,导致弹性模量也随之增大。

Micro-Raman Spectroscopy for Stress Evaluation of 3C-SiC Epitaxially Grown on Si Substrate by Hot Wall CVD

A series of cubic SiC single crystals were heteroepitaxially grown by the hot-wall chemical vapor deposition (CVD) using a HMDS-C3H8-H2 system on 2 inch silicon substrates with the orientations of (100), (111), (110) and (211), respectively. Even though an initial carbonization was carried out to reduce the large lattice mismatch, residual stress could not be completely relieved, partly also due to the difference of their thermal expansion coefficients. Raman scattering studies for the specimens were performed to estimate the internal stress in the SiC epilayer and the substrate. Raman spectra were mapped out on the sample surface as well as on the cross section using an automated x-y stage with a spatial resolution capable of 100 nm. For all the samples, two Raman peaks corresponding to the transverse optical (TO) and longitudinal optical (LO) phonon modes were observed, even though the intensity varied with the polarization configurations. In the SiC epilayers, tensile stresses decrease away from the interface, while compressive stresses exist in the substrate, with the magnitudes dependent on the growth orientation. The lattice strains were discussed in terms of the elastic deformation theory for the comparison.

The 2-axis stress component decoupling of {100} c-Si by using oblique backscattering micro-Raman spectroscopy

With the application of strain engineering in microelectronics,complex stress states are introduced into advanced semiconductor devices.However,there is still a lack of effective metrology for the decoupling analysis of the complex stress states in semiconductor materials.This paper presents an investigation on the 2-axis stress component decoupling of{100}monocrystalline silicon(c-Si)by using oblique backscattering micro-Raman spectroscopy.A spectral-mechanical model was established,and two practicable methods for actual stress decoupling analyses were proposed.The verification experiments demonstrated the correctness and applicability of the methods proposed in this paper.

Investigation on the laser ablation of SiC ceramics using micro-Raman mapping technique

Research on the laser ablation behavior of SiC ceramics has great significance for the improvement of their anti-laser ability as high-performance mirrors in space and lasers, or the laser surface micro-machining technology as electronic components in micro-electron mechanical systems (MEMS). In this work, the laser ablation of SiC ceramics has been performed by using laser pulses of 12 ns duration at 1064 nm. The laser induced damage threshold (LIDT) below 0.1 J/cm(2) was obtained by 1-on-1 mode and its damage morphology appeared in the form of 'burning crater' with a clear boundary. Micro-Raman mapping technique was first introduced in our study on the laser ablation mechanisms of SiC surface by identifying physical and chemical changes between uninjured and laser-ablated areas. It has been concluded that during the ablation process, SiC surface mainly underwent decomposition to the elemental Si and C, accompanied by some transformation of crystal orientation. The oxidation of SiC also took place but only in small amount on the edges of target region, while there was no hint of SiO2 in the center with higher energy density, maybe because of deficiency of O-2 atmosphere in the ablated area, elimination of SiO2 by carbon at 1505 degrees C, or evaporating at 2230 degrees C.

Using X-ray computed tomography and micro-Raman spectrometry to measure individual particle surface area, volume, and morphology towards investigating atmospheric heterogeneous reactions

Heterogeneous reactions on the aerosol particle surface in the atmosphere play important roles in air pollution, climate change, and global biogeochemical cycles. However, the reported uptake coefficients of heterogeneous reactions usually have large variations and may not be relevant to real atmospheric conditions. One of the major reasons for this is the use of bulk samples in laboratory experiments, while particles in the atmosphere are suspended individually. A number of technologies have been developed recently to study heterogeneous reactions on the surfaces of individual particles. Precise measurements on the reactive surface area, volume, and morphology of individual particles are necessary for calculating the uptake coefficient, quantifying reactants and products, and understanding the reaction mechanism better. In this study, for the first time we used synchrotron radiation X-ray computed tomography（XCT） and micro-Raman spectrometry to measure individual CaCO_3 particle morphology, with sizes ranging from 3.5–6.5 μm. Particle surface area and volume were calculated using a reconstruction method based on software threedimensional（3-D） rendering. The XCT was first validated with high-resolution fieldemission scanning electron microscopy（FE-SEM） to acquire accurate CaCO_3 particle surface area and volume estimates. Our results showed an average difference of only 6.1% in surface area and 3.2% in volume measured either by micro-Raman spectrometry or X-ray tomography. X-ray tomography and FE-SEM can provide more morphological details of individual Ca CO3 particles than micro-Raman spectrometry. This study demonstrated that X-ray computed tomography and micro-Raman spectrometry can precisely measure the surface area, volume, and morphology of an individual particle.

Determination of channel temperature for AlGaN/GaN HEMTs by high spectral resolution micro-Raman spectroscopy

Channel temperature determinations of A1GaN/GaN high electron mobility transistors （HEMTs） by high spectral resolution microRaman spectroscopy are proposed. The temperature dependence of the E2 phonon fre quency of GaN material is calibrated by using a JYT64000 microRaman system. By using the Lorentz fitting method, the measurement uncertainty for the Raman phonon frequency of 40.035 cm1 is achieved, correspond ing to a temperature accuracy of 43.2 ~C for GaN material, which is the highest temperature resolution in the published works. The thermal resistance of the tested A1GaN/GaN HEMT sample is 22.8 °C/W, which is in rea sonably good agreement with a three dimensional heat conduction simulation. The difference among the channel temperatures obtained by microRaman spectroscopy, the pulsed electrical method and the infrared image method are also investigated quantificationally.

Micro-Raman investigations on the structures of the surface and the inner of MgSO_4 droplets

Spherical MgSO4 droplets were deposited by a syringe on the hydrophobic Teflon substrate. Using micro-Raman technique, the laser beam was highly focused twice on the surface and in the center of spherical droplets. The Raman spectra for the surface and the inner of MgSO4 droplets were accord-ingly obtained, suggesting formation of a thin layer of gels on MgSO4 droplets at low relative humidity. The gel layer covered the surface and exhibited a significant delay in response to the change of ambi-ent relative humidity, resulting in the structural difference between the surface and the inner of MgSO4 droplets.

煤系石墨微晶结构各向异性和非均质性的拉曼光谱表征

煤对温度和压力等地质环境条件十分敏感,在构造应力驱动下煤中“石墨微晶”结构取向生长,物理化学和结构呈现各向异性。采用X射线衍射和拉曼光谱对不同石墨化程度样品进行表征,结果表明:在高温主导,剪应力作用参与下,煤层顺层滑动,构造变形使石墨微晶旋转、择优取向,随着沿C轴方向堆砌高度的增加。以堆砌度Lc≤5 nm划分为无烟煤阶段,为碳层随机定向或无规则排列的紊层结构,光学各向同性;以Lc≥30 nm时视为较完善石墨结构形成的标志,光学各向异性显著;在10~20 nm间属于石墨化结构不够完善的过渡态结构(半石墨阶段)。石墨阶段样品SXL100、SXL130层理面、边缘面和粉末的拉曼光谱中1350 cm^(-1)带(D_(1))、1620 cm^(-1)带(D_(2))都较明显,但是石墨边缘面拉曼光谱中D1峰半高宽、D_(1)与G峰强度比(I_(D1)/IG,R_(1))、D_(2)峰与G峰强度比(I_(D2)/IG,R_(3))显著高于层理面,显示强度比等拉曼参数依赖于煤系石墨边缘面的取向。D1峰强度依赖样品缺陷或无序程度,边缘面D_(2)峰具有非对称特征,双峰结构显著,并且D′1峰随D_(2)峰变化,亦显示边缘面缺陷的光谱行为。用煤系石墨缺陷密度或有序度表征指标R_(1)划分无烟煤(R_(1)≥1.0)、半石墨(1.0>R_(1)≥0.5)和石墨(R_(1)<0.5)等阶段,并评价煤系石墨均匀程度及不同石墨化程度组分的比例及分布,发现变质无烟煤CM130N样中超前演化达到半石墨结构占比达3.52%,半石墨BC210样中无烟煤结构占比46.40%,SXL130样整体石墨化,但其中无烟煤结构占比仍有3.84%,层理面和边缘面结构中仍存在缺陷,建立的方法在区分无烟煤、半石墨更具优势。在拉曼激光入射方向一定时,可利用R_(1)、R_(3)参数来探讨受构造应力影响的煤系石墨层理面拉曼光谱特征,分别评价了石墨化不均一性和石墨微晶取向。

高温^(107)Ag^(5+)离子辐照后核石墨的截面微区拉曼表征与缺陷演化规律研究

在第四代反应堆中,核石墨作为慢化体和反射体材料服役于高温和高通量的快中子辐照环境中。快中子辐照会在核石墨中产生大量的弗伦克尔缺陷对。这些缺陷经过湮灭、扩散、最终形成更大的缺陷团簇,从而改变核石墨的微观结构,进而改变核石墨的宏观性能。因此,研究核石墨在高温辐照条件下的缺陷演化行为和机理对提高反应堆安全性具有重要意义。本研究采用30 MeV的^(107)Ag^(5+)离子在420℃下辐照IG-110核石墨来模拟核石墨在快中子辐照过程中的缺陷演化行为。通过微区拉曼光谱对IG-110核石墨截面结构进行表征,并对比不同深度处的拉曼光谱特征参数和辐照损伤剂量之间的关系,研究IG-110核石墨微观结构随辐照损伤剂量(Displacements Per Atom,DPA)的演化行为。研究结果表明,随着注量的增加,核石墨拉曼光谱的特征参数D峰高度与G峰高度比值(I_(D)/I_(G))、G峰半高宽(Full Width at Half Maximum of the G peak,FWHM(G))以及G峰的偏移量都显著增加。与^(58)Ni^(5+)辐照样品相比,相同辐照损伤剂量下,^(107)Ag^(5+)辐照的石墨拉曼光谱的I_(D)/I_(G)和FWHM(G)更大。相同的FWHM(G)下,^(107)Ag^(5+)辐照的石墨拉曼光谱的I_(D)/I_(G)比^(58)Ni^(5+)辐照样品大。这些结果说明更重的重离子辐照会在核石墨中引起更高速率的缺陷积累,从而更快地导致石墨晶粒尺寸变小,并促进纳米晶化进程。

基于显微共聚焦拉曼光谱结合机器学习方法对粉底液的分类研究

为建立一种快速检验粉底液样品的方法,运用显微共聚焦拉曼光谱和机器学习对不同品牌、色号、价格的粉底液进行分类研究。首先将收集到的50个粉底液样品的拉曼光谱数据利用Savitzky-Golay平滑和归一化算法进行预处理;其次通过主成分分析法进行特征值提取,提取前2个主成分用于后续研究;采用K-Means聚类法将50个样品分成5类,系统聚类法验证分类结果;最后以40个样品为训练集,10个样品为测试集搭建支持向量机(SVM)分类模型。结果表明在Linear核函数下的SVM模型训练集和测试集的准确率可达90%。说明该方法能够实现区分粉底液品牌和价格自动化,为公安机关物证检验、定罪处罚提供新思路。

水环境中微塑料的来源分布及其分子光谱检测技术的研究进展

随着社会发展和人类日常活动的不断增加,水体中的微塑料污染问题日益严重,对水生生物及人类健康构成潜在威胁。为了有效监测和控制水环境中的微塑料污染,需要发展一种快速、准确和高效的检测技术。分子光谱技术作为一种无损检测方法,具有高灵敏度、高分辨率和高精度等优点,是检测和分析微塑料最常用方法之一,在水环境中微塑料含量和组成检测方面具有广阔的应用前景。因此对水环境中微塑料的来源分布及分子光谱技术在微塑料检测方面的应用研究进展进行综述,重点介绍显微红外光谱、拉曼光谱等技术在水环境中微塑料识别和定量分析方面的优势和局限性,并探讨未来研究的发展方向。

基于显微-表面增强拉曼光谱的烟碱半定量筛查方法研究

结合显微拉曼技术和SERS技术,提出了电子烟油中的烟碱半定量筛查方法。显微拉曼技术筛查对象是电子烟油本身,无需样品稀释。SERS技术筛查对象是电子烟油稀释溶液,操作过程中只需将电子烟油配制溶液,滴入SERS芯片后筛查测试。不同烟碱含量和不同烟碱浓度的SERS特征谱峰强度随浓度呈正比关系。实现了电子烟油中烟碱的快速筛查,该方法具有识别性、快速、方便和高灵敏度等特点。