二次离子质谱分析

一、引言 二次离子质谱(Secondary Ion Mass Spectrometry)是一种用于分析固体材料表面组分和杂质的分析手段。通过一次离子溅射,SIMS可以对样品进行质谱分析、深度剖析或成二次离子像。SIMS具有很高的元素检测灵敏度以及在表面和纵深两个方向上的高空间分辨本领,所以其应用范围也相当广泛,涉及化学、生物学和物理学等基础研究领域及微电子、催化、新材     

1998年国际二次离子质谱学研讨会暨第二届全国二次离子质谱学学术会议在京举行

1998年国际二次离子质谱学研讨会［1998InternationalSymposiumonSecondaryIonMassSpectrometry（IS－SIMS’98）］暨第二届全国二次离子质谱学学术会议［SecondaryChinessNationalConferenceonSecondaryIonMassSpectrometry（SIMSⅡ，China）］于1998年4月6－10日在北京清华大学举行。这是首次在我国召开的国际SIMS会议，同时是1993年我国成功地召开了第一届全国SIMS会议（SIMS　Ⅰ，China）后，首次与香港和台湾合作召开的中国SIMS会议。会议由北京清华大学与香港科技大学、台湾新竹清华大学和中国二次离子质谱学会议组…     

MCs~ -SIMS技术及其应用

强烈的基体效应一直是造成二次离子质谱（SIMS）难以定量分析和解释的主要原因。受其影响，常规SIMS，即M±－SIMS（检测原子型二次离子M＋或M－，M是要分析的元素）的适用范围受到了很大的限制。近几年来，上述状况已经通过一种新技术开发得到明显改善，这就是MCS＋－SIMS技术，即在CS＋一次离子轰击下检测分子型二次离子MCS＋而不是M±。由于该技术能明显减小甚至消除基体效应，从而开辟了SIMS定量分析的新途径。在综述MCS＋－SIMS技术的由来、发展、特点和应用以及MCS＋的生成机理的基础上，介绍了该技术的扩展思路。     

四极SIMS仪器的检测灵敏度

本文讨论了四极SIMS(二次离子质谱仪)的检测灵敏度及其主要影响因素,评述了目前一些商品仪器在给出仪器灵敏度和检测极限时所存在的问题,对SIQMS-1型仪器的灵敏度、本底以及本底信号比这三个指标提出了明确的定义并进行了测试。与其它表面分析技术相比,SIMS的一个突出优点是它对许多元素及化合物具有很高的检测灵敏度。但在目前众多的商品四极SIMS仪器中,如何正确反映检测灵敏度的问题尚未完全解决。我们在研制SIQMS-1型仪器的过程中对这个问题进行了一些探讨。     

高分辨率钼/硅纳米多层膜TOF-SIMS和Pulsed-RF-GDOES深度谱的定量分析

飞行时间二次离子质谱（TOF-SIMS）和脉冲射频辉光放电发射光谱（Pulsed-RF-GDOES）是两种重要的深度剖析技术，前者广泛应用于半导体工业的质量控制，后者主要应用于工业涂层及表面氧（氮）化层的分析。Mo/Si纳米多层膜由于其出色的反射特性被广泛应用于纳米光刻、极紫外显微镜等领域。本文利用原子混合-粗糙度-信息深度（MRI）模型分辨率函数，通过卷积及反卷积方法分别对Mo(3.5nm)/Si(3.5nm)多层膜的TOF-SIMS和Pulsed-RF-GDOES深度谱数据进行了定量分析，获得了相应的膜层结构、膜层间界面粗糙度及深度分辨率等信息。结果表明：GDOES深度剖析产生了较大的溅射诱导粗糙度，SIMS的深度分辨率优于GDOES。     

分子束外延生长GaAs中δ掺杂研究

利用二次离子质谱（SIMS）和电化学剖面C－V方法研究了生长温度对GaAs中理想Siδ掺杂结构的偏离和掺杂原子电激活效率的影响。实验发现，外延生长Siδ掺杂GaAs时，随着生长温度的升高，Si掺杂分布SIMS峰非对称展宽，表面分凝作用加强，但不影响Si原子的扩散。另外，Si施主电激活效率随着生长温度的提高而增大。     

离子作为探束的表面分析技术(一)

本讲座介绍表面分析技术中的一个重要分支——以离子作为探束的表面分析技术。对离子散射谱(ISS)和二次离子质谱(SIMS)作较详细的说明。离子与表面相互作用常可得到最表层的信息,有最高的灵敏度,信息十分丰富,因而,它在表面分析技术中占有重要的位置。但离子与表面相互作用的过程很复杂,还有很多问题有     

覆氧条件下砷化镓表面二次离子发射机理的研究

研究了高真空分析室中砷化镓表面覆氧对二次离子产额的影响。通过 X 射线光电子谱(XPS)、二次离子质谱(SIMS)、俄歇电子谱(AES)研究比较了室温下长期暴露大气的砷化镓、高真空分析室中充氧后砷化镓表面以及离子轰击条件下砷化镓表面上氧的化学状态。并对覆氧对二次离子产额的作用机理进行了探讨。     

电子诱导脱附的F~ 及其特性

本文通过俄歇电子谱(AES)、二次离子质谱(SIMS)和电子诱导脱附离子质谱(ESDMS)的测量与分析,论证了电子诱导脱附的质荷比M/e=19的正离子是F~ 而不是H_3O~ 。实测表明在某些情况下ESD法检测氟(F)的灵敏度比AES高10~3,与SIMS法相当。由于使用电子束作探针,其空间分辨率高,对表面损伤小。因此,预期它在检测表面氟或氟化物的污染方面可成为一个极有用的方法。     

砷化镓中掺硅元素的SIMS定量分析

通过对体均匀掺硅和离子注入硅样品的二次离子质谱（ＳＩＭＳ）深度剖面分析，采用均匀体标样法、剖面二次离子强度积分法和ＬＳＳ理论关系计算获得了比较一致的、且与手册值接近的ＧａＡｓ中硅元素相对灵敏度因子值。将相对灵敏度因子法应用于双能量、双剂量硅离子注入ＧａＡｓ样品及分子束外延多层ＧａＡｓ膜渗硅的ＳＩＭＳ定量分折中。从实验结果初步讨论了ＧａＡｓ中氧和碳元素的存在对２８Ｓｉ－、１０３ＳｉＡｓ－二次离子信号强度的影响，２８ＳｉＡｓ－和１０３Ｓｉ－二次离子信号强度的线性关系和可靠性。     

C60 secondary ion Fourier transform ion cyclotron resonance mass spectrometry

Secondary ion mass spectrometry (SIMS) has seen increased application for high spatial resolution chemical imaging of complex biological surfaces. The advent and commercial availability of cluster and polyatomic primary ion sources (e.g., Au and Bi cluster and buckminsterfullerene (C(60))) provide improved secondary ion yield and decreased fragmentation of surface species, thus improving accessibility of intact molecular ions for SIMS analysis. However, full exploitation of the advantages of these new primary ion sources has been limited, due to the use of low mass resolution mass spectrometers without tandem MS to enable enhanced structural identification capabilities. Similarly, high mass resolution and high mass measurement accuracy would greatly improve the chemical specificity of SIMS. Here we combine, for the first time, the advantages of a C(60) primary ion source with the ultrahigh mass resolving power and high mass measurement accuracy of Fourier transform ion cyclotron resonance mass spectrometry. Mass resolving power in excess of 100?000 (m/Δm(50%)) is demonstrated, with a root-mean-square mass measurement accuracy below 1 part-per-million. Imaging of mouse brain tissue at 40 μm pixel size is shown. Tandem mass spectrometry of ions from biological tissue is demonstrated and molecular formulas were assigned for fragment ion identification.     

Charakterisierung von Plasma‐ Polymerfilmen mittels Flugzeit‐ Sekundärionen‐Massenspektrometrie (ToF‐SIMS). Characterisation Plasma‐Polymerfilms by Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS)

Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS) is a surface sensitive analytical method which is utilised in many scientific and industrial branches. The area of application is the identification and localisation of all elements as well as organic and inorganic chemical compounds on arbitrary solid surfaces. The information on the surface is obtained from mass spectra. Due to the high mass resolution (m/Δm > 5.000) different chemical species of the same nominal mass can be clearly separated from each other. Furthermore, the lateral distribution of elemental and molecular species on the surface can be displayed with a lateral resolution < 1 μm. By multivariate modeling the complete information from the mass spectra can be correlated with physical surface properties such as wetting behaviour, elemental concentrations, tribological parameters etc. The outcome of this are decisive information about the functionality of the analysed surface structure. For this reason Time‐of‐Flight Secondary Ion Mass Spectrometry becomes an essential analysis tool in the development of functional surfaces which are the basis of novel and innovative products.     

Laser ablation coupled to a flowing atmospheric pressure afterglow for ambient mass spectral imaging

A plasma-based ambient desorption/ionization mass spectrometry (ADI-MS) source was used to perform molecular mass spectral imaging. A small amount of sample material was ablated by focusing 266 nm laser light onto a spot. The resulting aerosol was transferred by a nitrogen stream to the flowing afterglow of a helium atmospheric pressure glow discharge ionization source; the ionized sample material was analyzed by a Leco Unique time-of-flight mass spectrometer. Two-dimensional mass spectral images were generated by scanning the laser beam across a sample surface. The total analysis time for a 6 mm (2) surface, which is limited by the washout of the ablation chamber, was less than 30 min. With this technique, a spatial resolution of approximately 20 microm has been achieved. Additionally, the laser ablation configuration was used to obtain depth information of over 2 mm with a resolution of approximately 40 microm. The combination of laser ablation with the flowing atmospheric pressure afterglow source was used to analyze several sample surfaces for a wide variety of analytes and with high sensitivity (LOD of 5 fmol for caffeine).     

Auger electron spectroscopy and secondary ion mass spectrometry depth profiling with sample rotation

Recently, there has been a rapid increase in the application of multilayered structured materials, as opposed to bulk materials, in many areas of technological development. Accurate characterization of the structure and composition of advanced multilayers such as superlattices, quantum wells, contacts, and coatings is important for materials and device fabrication technology. Surface analysis techniques including Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy, and secondary ion mass spectrometry (SIMS) in conjunction with ion beam sputtering (sputter depth profiling) are at present the most widely used methods for characterization of modern multilayer thin film materials and devices. Ion-beam-induced surface topography, however, can limit depth resolution, and with SIMS, can also cause changes in the secondary ion yield. These changes are due to the high sensitivity of secondary ion yield to the local angle of incidence on sputter-roughened surfaces. Degradation of depth resolution and changes in secondary ion yields during sputter depth profiling have often limited studies of thin film interdiffusion, segregation, oxidation at interfaces, and impurity effects. Much theoretical and experimental work has been carried out to try to improve depth resolution including the use of low ion beam energy, high angle of incidence, and two ion guns. Recent studies of AES and SIMS with sample rotation have shown that depth resolution can be improved substantially and that constant secondary ion yields in SIMS can be achieved. We will first provide an overview of the studies made by various groups to improve depth resolution of metal multilayers using AES with rotation. Next we will review recent investigations of SIMS using sample rotation including studies of the effects of sample rotation on O₂⁺ ion-beam-induced topography, secondary ion yield, and the depth resolution of electronic, metallurgical and dielectric materials. The results presented demonstrate that SIMS with sample rotation provides constant secondary ion yield, and depth-independent depth resolution because sample rotation prevents ion-beam-induced roughness and reduces the effect of the inhomogeneity of low energy ion beams.     

Characterization of coatings

The variety of physical and chemical properties of coatings is determined by their thickness, structure and chemical composition. A fundamental understanding of coating properties, as well as of their reproducibility, therefore requires a good knowledge of these parameters.During the last few years great progress has been made in the field of chemical analysis (including depth distribution) of thin films and coatings. This progress is mainly the result of the combination of recently developed surface analytical techniques such as Auger electron spectroscopy (AES), photoelectron spectroscopy (UPS, XPS), ion scattering spectroscopy (ISS) and secondary ion mass spectroscopy (SIMS), on one hand, and controlled simultaneous surface etching by sputtering on the other.With these surface analytical techniques the chemical composition of the uppermost monolayers is detected by energy or mass analysis of ion- (ISS, SIMS), electron- (AES) or photon- (UPS, XPS) induced emission of ions (ISS, SIMS) or electron (AES, UPS, XPS), respectively. By combining these techniques with sputtering, the depth distribution of elements and compounds can also be determined with a lateral resolution of some microns.In order to recognize the capabilities and limitations of these techniques for coating analysis, the fundamental emission processes as they appear in the various analytical techniques, as well as the details of the sputtering process, have to be taken into account. The main features such as detection limits, isotope sensitivity, detection of compounds etc. of these techniques will be compared for some typical examples.Other methods, such as high energy ion backscattering and the detection of sputtered particles in the gas phase, will also be considered.     

Effect of local matrix crystal variations in matrix-assisted ionization techniques for mass spectrometry

Intense intact molecular ion signals have been obtained from phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, and phosphatidyiinositol using matrix-enhanced secondary ion mass spectrometry (ME-SIMS). It was found that the high-mass (m/z >500) regions of the ME-SIMS spectra closely resembled those obtained using matrix-assisted laser desorption/ionization (MALDI). Using high spatial resolution SIMS, a detailed investigation of dried-droplet samples was performed. Based on the detected Na+ and 2,5-DHB matrix signal intensities, different crystal types were distinguished, in addition to different sizes of crystals. Spatially mapping the pseudomolecular and fragment ions of the phospholipids revealed that the nature of the pseudomolecular ions formed, as well as the ratio of intact molecular to fragment ion, was dependent on the type and surface composition of the crystal. The observed chemical bias effects due to crystal heterogeneity and the resulting variation in desorption/ionization efficiency will complicate the interpretation of data obtained from matrix-assisted mass spectrometric (imaging) techniques and is an important factor in the "hot spot" phenomenon frequently encountered in MALDI experiments. In this respect, imaging SIMS was found to be a versatile tool to investigate the effects of the local physicochemical conditions on the detected molecular species.     

Nanoparticle-assisted laser desorption/ionization based mass imaging with cellular resolution

Today, two-dimensional mass spectrometry analysis of biological tissues by means of a technique called mass imaging, mass spectrometry imaging (MSI), or imaging mass spectrometry (IMS) has found application in investigating the distribution of moleculesMSI with matrix-assisted laser desorption/ionization (MALDI) and secondary ion MS (SIMS). However, the size of the matrix crystal and the migration of analytes can decrease the spatial resolution in MALDI, and SIMS can only ionize compounds with relatively low molecular weights. To overcome these problems, we developed a nanoparticle-assisted laser desorption/ionization (nano-PALDI)-based MSI. We used nano-PALDI MSI to visualize lipids and peptides at a resolution of 15 microm in mammalian tissues.     

Depth profiling of fullerene-containing structures by time-of-flight secondary ion mass spectrometry

A new variant of depth profiling for thin-film fullerene-containing organic structures by the method of time-of-flight (TOF) secondary ion mass spectrometry (SIMS) on a TOF.SIMS-5 setup is described. The dependence of the yield of C₆₀ molecular ions on the energy of sputtering ions has been revealed and studied. At an energy of sputtering Cs⁺ ions below 1 keV, the intensity of C₆₀ molecular ions is sufficiently high to make possible both elemental and molecular depth profiling of multicomponent (multilayer) thin-film structures. Promising applications of TOF-SIMS depth profiling for obtaining more detailed information on the real molecular composition of functional organic materials are shown.     

激光-分子束-表面散射装置的研制

介绍了自行设计和加工的激光-分子束-表面散射装置，并对超高真空转动密封结构作了详细描述。差分泵浦的超音速分子束对准样品中心，射入超高真空主室。样品架安放在主室中央，四极质谱检测器可绕样品转动，用来测量表面散射分子的平动能及角分布。三个石英窗口作为激光窗口，可用LIF或MPI方法来测量表面散射分子的内能态分布，也可用于研究表面光化学。最后给出了分子束发散角及室温时CH2I2在Ag（110）表面用308um激光光解碎片碘的TOF谱的测量结果。