电子倍增器歧视效应和质量分馏效应的修正及其应用

文章介绍了电子倍增器测量引入的质量相关偏差和离子束流强度相关偏差的修正方法,给出了正确的计算公式;叙述了用同位素比值对关系线归一法修正样品蒸发和电离引入的质量分馏效应的方法,给出了计算分馏效应修正因子和计算修正值的公式。用上述方法分别对天然镁和天然锗样品的同位素丰度比值或同位素丰度进行修正后,天然镁同位素的丰度比值为:~(26)Mg/~(24)Mg=0.13938,~(25)Mg/~(24)Mg=0.12660;天然锗的同位素丰度为:~(70)Ge=20.50,~(72)Ge=27.48,~(73)Ge=7.76,~(74)Ge=36.51,和~(76)Ge=7.75。天然样品的分析结果与文献标定值相符。     

热表面电离源同位素丰度测量的理论模型

根据对热表面电离源同位素丰度测量过程中样品蒸发的微观研究 ,提出如下三条假设 :(1 )未被外层原子覆盖的原子才能蒸发 ;(2 )被外层原子覆盖的原子只能扩散不能蒸发 ;(3 )同位素原子的扩散几率与蒸发几率成正比。根据这三条假设建立了样品原子数的微分方程及边界条件 ,推导出了不同扩散系数的样品原子数的理论公式 ,从理论上讨论了熔融态、固态样品以及蒸发分解同时发生的样品同位素丰度比与样品消耗量间的关系。研究表明 :扩散系数 >1 0 -15m2 / s的样品同位素丰度比与样品消耗量的关系与 H.Kanno得出的结论相同 ,扩散系数 <5× 1 0 -2 1m2 / s的样品同位素丰度比与样品消耗量无关 ,等于实际值 ;蒸发分解同时发生的样品同位素丰度比与分解率蒸发率之比有关     

镝原子量测量-热电离质谱法的应用

用已知化学纯度的 16 2 Dy、16 4Dy两种浓缩同位素通过化学计量 ,配制人工合成校准样品 ,测量质谱计系统误差校正系数 K,校正用该仪器测量的来自地球不同地域矿物和试剂样品镝 ( Dy)元素天然同位素丰度比 ,求出自然界 Dy同位素丰度的真值。用该真值和它的核素质量 ,计算 Dy原子量 1 62 .4 995 ( 1 7)。上述测量经 IUPAC国际原子量委员会 ( UPAC-CAWIA)评审确认推荐报告中提供的测量值为 Dy原子量新的国际标准值 ,测量方法评为最佳测量     

镉新原子量测定计量学与 MC-ICP-MS测定水稻中的镉含量(英文)

天然镉是与铜矿共生的高挥发性元素 ,含有 8个稳定同位素。测量其同位素丰度的不确定度只能达到 0 .9%～ 4.8%。因此 ,必须按国际理论和应用化联合会原子量和同位素丰度分会 ( IUPACCAWIA)的要求来测定天然丰度镉的新镉原子量。IUPAC CAWIA要求的条件和步骤是采用高真空蒸馏法纯化浓缩镉和天然镉样品 ,测量和计算这些样品中杂质元素的含量 ,用计量学称重法制备同位素混合样品 ,用多接收电感耦合等离子体质谱 ( MC-ICP-MS)和热电离质谱 ( TIMS)测定镉的同位素比值 ,计算镉原子量并评估相关的不确定度。一些国家实验室用 MC-ICP-MS获得了稻米中镉的含量 ,可用作对照的关键参考值是 1 4 .48± 0 .0 87nmol·g- 1。     

多接收双聚焦等离子体质谱法测定高精度同位素比

采用 VG Axiom型多接收双聚焦等离子质谱仪 ( MC-ICPMS)测定 Nd、Pb、U同位素比值 ,应用指数公式对测定的结果进行质量歧视校正。结果表明 :测定参考物质 Ames Nd获得的钕同位素比值为 14 3 Nd/14 4 Nd=0 .5 1 2 1 44± 0 .0 0 0 0 1 5 (确认值为 0 .5 1 2 1 3 5 )、14 5Nd/14 4 Nd=0 .3 4841 7± 0 .0 0 0 0 1 9(确认值为 0 .3 4841 8) ;测定参考物质 NIST SRM981获得的铅同位素比值为 2 0 8Pb/2 0 4Pb=3 6.71 1 4± 0 .0 0 81、2 0 7Pb/2 0 4Pb=1 5 .4886± 0 .0 0 3 8、2 0 7Pb/2 0 6Pb=0 .91 44 5 6± 0 .0 0 0 0 3 9、2 0 6Pb/2 0 4Pb=1 6.93 82± 0 .0 0 3 1、2 0 8Pb/2 0 6Pb=2 .1 660 1± 0 .0 0 0 1 6;测定参考物质 NIST SRM 0 1 0获得的铀同位素比值为 2 3 4 U/2 3 8U =0 .0 0 0 0 5 46±0 .0 0 0 0 0 0 3 (确认值为 0 .0 0 0 0 5 46)     

RPQ-IC检测系统测量低丰度铀同位素

介绍了采用 Finnigan MAT 2 62热电离质谱计检测 NBS U 0 1 0、浓缩 2 3 3 U硝酸溶液 ( IRMM-0 40 a)。采用阻滞电位四极杆 ( RPQ) -IC装置测量低丰度铀 2 3 4 U、2 3 5U、2 3 6U的同位素丰度比 ,并与 Faraday(法拉第杯 )检测的数据进行比较。采用偏转法对 RPQ产额进行了校正。实验表明 :所得结果在误差范围内 ,RPQ-IC测量结果比 RPQ-FAR测量结果偏高 0 .1 4% ;RPQ-IC测量低丰度铀同位素的内精度比法拉第杯测量结果高 ,外精度比 FAR杯测量结果也高 ;RPQ产额变化比较大 ,但只要注意产额校正 ,可以得到满意的结果     

校准质谱法测定铕原子量

使用有确定化学纯度的高纯同位素~(151)Eu_2O_3和~(153)Eu_2O_3以配制标准溶液,并由此配制6种混合溶液,用来测定一台固体源热电离质谱计的质量岐视效应,从而校准天然铕的同位素丰度比。引用确知的有关核素质量,计算得出铕原子量为151.964±0.003,与国际现行值很好地符合。     

用校正质谱法测量铕同位素丰度的研究

用确定化学纯度的151Eu、153Eu两种浓缩同位素配成9个混合样品，用来测量质谱计系统误差的校正系数，以校正用该仪器测出的矿样和试剂样中铕同位素丰度比，求出铕同位素丰度的绝对值分别是47．810（42）at．％151Eu和52．190（42）at．％153Eu。用该值和已知的铕的核素质量，计算得到铕的原子量为151．9644（9），被定为新的国际标准值。     

自贡锂的同位素丰度研究

本文自制纯~6Li_2CO_3并用纯~7Li_2CO_3,经校准质谱测量求得质谱计的质量歧视效应的校正因数,从而对我国自贡锂测得其同位素的绝对丰度为:7.50(±0.08)原子%~6Li和92.50(±0.08)原子%~7Li,而锂原子量为6.9409±0.0007。     

MC-ICP-MS测量Ru同位素丰度比值的质量歧视校正

采用MC-ICP-MS测量Ru同位素丰度比时,存在较大的质量偏倚。利用IsoprobeMC-ICP-MS测量了RuCl3中Ru同位素丰度比值,并利用幂、指数以及通用幂校正规律(GPL)对Ru同位素丰度比值测量的质量偏倚进行了校正。结果表明,以100Ru/102Ru、104Ru/102Ru作为内标,采用GPL校正质量偏倚,得到的Ru同位素丰度更接近于天然值,与天然值的偏差在(20～650)×10-6之间。     

Convergent beam electron diffraction extinction distance measurements for quantitative analysis of si(1-x),Ge(x)

A new method to determine the concentration of germanium in Si(1-x) Ge(x) single crystals is presented. It is based on extinction distance measurements by means of convergent beam electron diffraction (CBED). The two-beam condition CBED intensity oscillation (the so-called rocking curve) is measured for the 004 diffracted beam and compared with a numerical simulation. Using the two-beam dynamical diffraction approximation theory, this approach yields very precise values for both specimen thickness and effective extinction distance (Ultramicroscopy 87 (2001) 5). First a theoretical extinction distance zetag(x) for strain relaxed Si(1-x)Ge(x) is calculated assuming a solid solution and using tabulated atomic scattering factors of silicon and germanium atoms. It is found that for single crystals zetag(x) decreases from 156 nm in pure silicon to 90 nm in pure germanium. Measurements on calibrated strain relaxed SiGe layers with variable germanium concentrations show an excellent agreement between experimental and calculated extinction distances zetag(x). As a consequence the experimental extinction distance zetag(x) becomes an indirect measure of the germanium concentration with a 1-2 at % sensitivity. The method turns out to be insensitive to strain as experimental zetag(x) values obtained on strained SiGe layers fit the theoretical extinction distance curve calculated for strain relaxed SiGe.     

Materials science aspects of dielectric film compositions in the planar technology of Ge-based MIS structures

A new fabrication route for Ge based metal-insulator-semiconductor (MIS) transistors has been developed based on materials research of dielectric layer compositions. Unwanted impurities were encapsulated in the Ge substrate by using the gate-first process and a modified thermal GeO₂ layer with increased viscosity at the interface with the Ge substrate. Increasing the density of the oxide layer near germanium interaction with the deposited Si₃N₄ film hindered diffusion of the impurities adsorbed by the substrate surface into the transistor channel. This increased the electron mobility in the MIS transistor and prevented its decrease at cryogenic temperatures.     

Carbon-stimulated self-organization of Ge nanoislands during molecular beam epitaxy of Ge/CaF<Subscript>2</Subscript>/Si(111) heterostructures

The self-organization of germanium nanoislands on the surface of calcium fluoride was studied using atomic-force microscopy and reflection electron diffraction. A Ge/CaF₂/Si(111) structure was grown by molecular beam epitaxy. The surface of the calcium fluoride film was modified by submonolayer carbon coverage to stimulate the formation of germanium nanoislands. The parameters of an array of nanoislands were found to depend on the coverage.     

Preliminary characterization of an intrinsic germanium detector on a 400-keV microscope

An evaluation was made of an intrinsic germanium X-ray detector fitted to a 400-keV electron microscope. Its characteristics as a function of accelerating voltage, pulse processor settings and count rate were investigated. Comparisons are drawn between intrinsic Ge and Si(Li) detectors at both an experimental and theoretical level. The software requirements for the successful collection of spectra are discussed.     

Optical Ring Resonator Based Temperature Sensor

Temperature sensor based on optical ring resonator has been demonstrated with its constituent material as silicon (Si-fiber) and germanium (Ge-fiber) in this work. It has been done through optical delay line signal processing technique in Z-domain. The group indices of both the materials vary with the change in temperature due to the thermo-optic effect in materials. Thus temperature dependence of free spectral range forms the basis of modeling the sensors. Silicon (Si) fiber based optical sensor can sense the temperature in the range 30–500 °C and that for germanium (Ge) fiber the range is ?25 to 300 °C. Obtained temperature sensitivities for Ge and Si-fibers are 5.55 and 2.97 MHz/°C respectively.     

RLVIP制备Ge1－xCx薄膜的X射线光电子能谱研究

应用低压反应离子镀（Reactive Low Voltage Ion Plating：RLVIP）在Ge基底上沉积了Ge1-xCx薄膜。制备过程中,低压等离子源作为辅助等离子源,Ge作为蒸发材料,CH4作为反应气体,在相同的条件下以不同沉积速率制备了C含量( x )从0.23到0.78的Ge1-xCx薄膜。X射线衍射测试表明制备的Ge1-xCx薄膜为无定形结构。通过X射线光电子能谱研究了不同C含量下Ge1-xCx薄膜的化学键合变化。测试结果表明当 x > 0.78时,成键为C-H键;当x在0.53至0.62时,成键为C-C键;当x < 0.47时,成键为Ge-C键。     

原子荧光光谱法测定海洋沉积物中的微量锗

试验了灯电流、原子化器高度、介质浓度及硼氢化钾浓度对原子荧光测定锗的影响,分析确定了海洋沉积物样品分解程序,采用特制锗编码空心阴极灯作激发光源氢化物发生法直接测定海洋沉积物中微量锗,方法检出限0.004μg/g,精密度(RSD,n=12)为2.44%～4.37%,加标回收率平均为98.2%。经水系沉积物标样和海洋沉积物批量样品实验室间分析验证,方法可靠实用。     

Improvement of Local Surface Quality by Using Single Abrasive Abrasion Process

AFM-based wear process actually is single abrasive abrasion process. It is widely employed in the surface micro/nano machining for fabrication of structures at the nanometer scale exhibiting high removing ability of nanometer scale materials. In this study, application of AFM-based single abrasive abrasion process in the local surface quality (surface roughness) improvement was studied. Merged holes were fabricated using an AFM diamond tip with different wear parameters on the surface of germanium (Ge) machined by conventional ultra-precision diamond turning. Results showed that cracks left by diamond turning can be removed and the local surface quality can be improved. Also effects of the wear parameters on the surface roughness were investigated. The optimized parameters of the abrasion process for improving the surface quality were provided. It is verified that AFM-based single abrasive abrasion process is a novel approach to modify or repair local surface on the surface of parts manufactured by other methods.     

Segmented high-purity germanium detectors

Segmented planar high-purity germanium detectors were developed. Segmentation of p-n junction was performed by implantation of boron (for the n-type Ge) and mechanical grooving of the Li diffusion layer (for the p-type Ge). The electric and spectrometric characteristics of each individual segment and interactions between segments were investigated. The reliability and stability of the detectors were improved by using special passivation of the crystal surfaces.     

Improved quantitative electron probe X-ray microanalysis of biological cryosections using an EDS germanium detector and a super-atmosphere thin window (SuperATW)

A new Link energy-dispersive GEM detector with SuperATW window was tested for quantitative electron probe microanalysis of low calcium and sodium concentrations ([Ca], [Na]) in intracellular compartments of cardiac myocytes. We compare Ca profiles with high count statistics and similar peak area collected under the same conditions with either a Be-windowed Si and a Ge SuperATW detector. The height of the Ca peak was increased by 7%, the full width at half-maximum height was reduced by 9% with the Ge detector. The counts statistics of the Ca Kα peak improved by 9% and the partial overlap with the K Kβ peak was better deconvoluted. We calculate [Ca] and errors of the single measurement in mitochondria of guinea-pig cardiac myocytes from spectra acquired with a Si or Ge detector. For identical analysis conditions, the [Ca] were identical; however, with the Ge SuperATW detector, the calculated error of the single measurement was only 1/2.7 of that calculated from measurements with the Si detector. We compare the peak area of identical [Na] in spectra collected with the Be-windowed Si detector and Ge SuperATW detector. The peak area was significantly higher with the SuperATW Ge than with the Si detector and Be window, whereas the continuum in the range 4–10 keV was comparable, demonstrating the improved sensitivity for low atomic elements such as Na of the Ge SuperATW detector. [Na] and errors of the single measurement in mitochondria of quiescent guinea-pig cardiac myocytes were calculated from spectra acquired with the Si or the Ge detector. The use of the Ge SuperATW detector improved the detectability limit for sodium by more than 80% and reduced the error of the single measurement by a factor of 7–8.