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Low Voltage Scanning Electron Microscopy (LVSEM), defined as operation in the energy range below 5keV, has become perhaps the most important single operational mode of the SEM. This is because the LVSEM offers advantages in the imaging of surfaces, in the observation of poorly conducting and insulating materials, and for high spatial resolution X-ray microanalysis. These benefits all occur because a reduction in the energy E0 of the incident beam leads to a rapid fall in the range R of the electrons since R ∼ k.E01.66. The reduction in the penetration of the beam has important consequences. Firstly, volume of the specimen that is sampled by the beam shrinks dramatically (varying as about E05 ) and so the information generated by the beam is confined to the surface of the sample. Secondly, the yield 8 of secondary electrons is increased from a typical value of 0.1 at 20keV to a value that may be in excess of 1.0 at 1keV.

The high performance of single-pixel microcalorimeter EDS (μ,cal EDS) has been shown to be very useful for a variety of microanalysis cases. The primary advantage of jxcal EDS over conventional EDS is the factor of 25 improvement in energy resolution (∽3 eV in real-time). This level of energy resolution is particularly important for applications such as nanoscale contaminant analysis where it is necessary to resolve peak overlaps at low x-ray energies. Because μcal EDS offers practical solutions to many microanalysis problems, several companies are proceeding with commercialization of single-pixel μal EDS technology. Two drawbacks limiting the application of uxal EDS are its low count rate (∽500 s−1) and small area (∽0.04 mm for a bare single pixel, ∽5 mm2 with a polycapillary optic). We are developing a 32x32 pixel array with a total area of 40 mm2 and with a total count rate between 105 s−1 and 106 s−1.

There is increasing interest in performing x-ray microanalysis of uncoated insulators while operating in unconventional SEM operating modes such as “low voltage” scanning electron microscopy (LVSEM), where the accelerating voltage is ≤ 5 kV and the pressure is low (-4 Pa), or variable pressure environmental SEM (VP-ESEM), where a selected gas is maintained at pressures in the range of 1 Pa -1000 Pa. LVSEM and VP-ESEM as microscopy techniques have proven to be extremely successful for imaging uncoated insulators through various charge dissipation mechanisms that are not available under conventional SEM operating conditions (accelerating voltage ≥ 10 kV and pressure < 10-3 Pa). in LVSEM, surface charging of insulators can often be controlled by careful choice of the accelerating voltage, sample tilt, and scan rate, while in VP-ESEM the charged species in the relatively dense gas (ions, secondary electrons) form a self-neutralizing plasma to provide an additional route for discharging the specimen.

Atmospheric aerosols are often investigated in order to gain insight into their effects on the global radiative heat budget, optical properties of the atmosphere, and their effects on human health. Characterizing the seasonal behavior of these aerosols is fundamental in understanding their climatological and air quality impacts. As part of a larger program to study the present and recent history of chemical species transported to Greenland, we analyzed a seasonal cycle of total aerosol matter scavenged from the air by surface snow.During a “winter-over” experiment in Summit, Greenland, extending from June 1997 through March 1998, kilogram quantities of surface snow were collected, melted, and filtered onto high-purity quartz fiber filters in the field. Upon the receipt of these filters at NIST, the total particulate matter was removed from the filters and transferred to boron substrates with protocols involving resuspension, centrifugation, and filtration.’ Previous techniques that quantified multi-element particles used several different substrates.

Chemical analysis in the scanning electron microscope and electron microprobe is performed by measuring the energy and intensity distribution of the x-ray signal generated by a focused electron beam. The subject of x-ray production has already been introduced in the chapter on electronbeam-specimen interactions (Chapter 3), which describes the mechanisms for both characteristic and continuum x-ray production. This chapter is concerned with the methods for detecting and measuring these signals as well as converting them into a useful form for qualitative and quantitative analysis.

Nonconducting samples invariably need some sort of treatment before they can be examined and analyzed under optimal conditions in electron-beam instruments that rely on an emitted signal to provide information. The treatment is necessary to eliminate or reduce the electric charge that builds up rapidly in a nonconducting specimen when it is scanned by a beam of high-energy electrons. Figs. 4.63a–c and 4.64a–c show examples of pronounced and minor charging as observed in the SEM. In addition to charging phenomena, which result in image distortion, the primary beam also causes thermal and radiation damage, which can lead to a significant loss of material from the specimen. In many situations the specimen may acquire a sufficiently high charge to decelerate the primary beam, and the specimen may even ultimately act as an electron mirror (see Fig. 4.62).

Success or failure in obtaining comprehensive structural or chemical information from organic, polymeric, biological, and hydrated specimens examined by electron-beam instrumentation depends critically on the way the samples are prepared. This general statement is nowhere more important than in scanning electron microscopy and x-ray microanalysis.

The versatility of scanning electron microscopy and of x-ray micro-analysis is derived in large measure from the rich variety of interactions that the beam electrons undergo in a specimen. These interactions can reveal information on the specimen’s composition, topog­raphy, crystallography, electrical potential, local magnetic field, and other properties. The electron—specimen interactions can be divided into two classes.

Specimen preparation for SEM and EPMA is in many ways still as much of an art as a science. This chapter outlines a variety of procedures used to prepare inorganic materials for SEM and EPMA, and supplemented by laboratory exercises (Lyman et al., 1991), will provide the micros- copist and analyst with the starting point for most specimen-preparation problems for inorganic materials. This chapter specifically addresses the preparation of metals; ceramic and geological materials; sands, soils, and clays; electronic devices and packages; semiconductor materials; and particles and fibers. In addition, specimen preparation for both microstructural and microchemical characterization are discussed.

This chapter will consider the formation and interpretation of SEM images. One of the most surprising aspects of scanning electron microscopy is the apparent ease with which SEM images of three- dimensional objects can be interpreted by any observer, including young children with no prior knowledge of the instrument. This aspect of the SEM is often taken for granted, and yet it is one of the most important reasons for the great utility and wide acceptance of the instrument. SEM images are routinely presented in textbooks and popular scientific articles with little or no mention of the type of microscopy employed in preparing the image or of the complex way in which the image was constructed. It can safely be assumed that the reader will automatically perceive the true nature of the specimen without any instruction on the origin of the image. For this to be true, the SEM imaging process must in some way mimic the natural experience of human observers in visualizing the world around them. Such a situation is somewhat surprising in view of the unusual way in which the image is formed, which seems to differ greatly from normal human experience with images formed by light and viewed by the eye. In the SEM, high-energy electrons are focused into a fine beam, which is scanned across the surface of the specimen.

An overview of the basic principles and techniques used to determine chemical composition, on the micrometer scale, with the SEM and EPMA was presented in Chapter 8. We outlined the approach to quantitation, the need for matrix corrections, and the physical origins of the matrix effects. The x-ray production process and the use of φ(ρz) curves to describe x-ray production were introduced. Finally, we discussed the three major matrix effects, atomic number (Z), absorption (A), and fluorescence (F) and showed, on a conceptual basis, how they are calculated. This chapter presents the more detailed theory and equations which can be used to determine the three major matrix corrections for quantitative analysis of flat polished specimens. The two commonly used correction schemes, the ZAF and φ (ρz) methods, will be described separately although the two schemes are, in many ways, closely related.

As discussed in Chapter 6, qualitative analysis is based on the ability of a spectrometer system to measure characteristic line energies and relate those energies to the presence of specific elements. This process is relatively straightforward if.

The vast majority of applications of electron probe x-ray microanalysis takes place on specimens which deviate significantly from the ideal configuration. Classic quantitative x-ray microanalysis makes the tacit assumption that the only reason the unknown differs in emitted x-ray intensity from standards is that there is a difference in composition between them. While this seems trivial, it forces the analyst to eliminate a major non-compositional source of possible intensity differences, namely the geometric effects associated with surface roughness. An important early paper by Yakowitz demonstrated that deviations from an ideal flat surface due to surface topography could seriously degrade the accuracy of analysis. Yakowitz interrupted the grinding and polishing procedure on pure elements and alloys at various stages and measured the variance in the x-ray intensity as the probe was scanned across the surface as compared to the predicted distribution based on counting statistics.

X-ray microanalysis often must estimate limits of detection for specific specimen compositions to optimize analytical strategy and to adequately describe results. Several approaches are available which make use of experimentally measured spectra to obtain peak and local background intensities. One of the oldest and simplest involves the use of pure element spectra. However, such an estimate procedure does not take into account the matrix effects, particularly absorption, which can be quite important in defining limits of detection in a particular multi-element composition. If a microhomogeneous standard is available with the appropriate matrix that also contains the other constituent(s) of interest at a known level, ideally at a minor constituent level (0.01 to 0.1 mass fraction), then the limit of detection, CDL, can be estimated through the use of the expression

The commercial introduction of high-count-rate, near-room-temperature silicon drift detectors (presently available) and high-energy-resolution cryogenic microcalorimeters (forthcoming) is an exciting development in x-ray microanalysis, in which detector choices and capabilities have been essentially stable for many years. Both of these new energy-dispersive detectors promise improved capabilities for specific applications, e.g., faster EDS mapping (silicon drift detectors) and nanoscale particle analysis (microcalorimeters). In this paper, we briefly examine some of the important benefits and drawbacks of microcalorimeter EDS (μcal EDS) for x-ray microanalysis.The primary benefit of μcal EDS over conventional semiconductor EDS is the factor of ∼ 20 improvement in energy resolution (∼ 4 eV, real-time analog signal processing), as shown in Figure 1.

The development of the electron microprobe by Raymond Castaing provided a great stimulus to materials science at a critical time in its history. For the first time, accurate elemental analysis could be performed with a spatial resolution of 1 µm, well within the dimensions of many microstructural features. The impact of the microprobe occurred across the entire spectrum of materials science and engineering. Contributions to the basic infrastructure of materials science included more accurate and efficient determination of phase diagrams and diffusion coefficients. The study of the microstructure of alloys was greatly enhanced by electron microprobe characterization of major, minor, and trace phases, including contamination. Finally, the electron microprobe has proven to be a critical tool for materials engineering, particularly to study failures, which often begin on a micro-scale and then propagate to the macro-scale with catastrophic results.

Monte Carlo simulation of electron scattering in solids has proven valuable to electron microscopists for many years. The electron trajectories, x-ray generation volumes, and scattered electron signals produced by these simulations are used in quantitative x-ray microanalysis, image interpretation, experimental design, and hypothesis testing. Unfortunately, these simulations are often computationally expensive, especially when used to simulate an image or survey a multidimensional region of parameter space.Here we present techniques for performing Monte Carlo simulations in parallel on a cluster of existing desktop computers. The simulation of multiple, independent electron trajectories in a sample and the collateral calculation of detected x-ray and electron signals falls into a class of computational problems termed “embarrassingly parallel”, since no information needs to be exchanged between parallel threads of execution during the calculation. Such problems are ideally suited to parallel multicomputers, where a manager process distributes the computational burden over a large number of nodes.

2008 marked the 40th anniversary of the seminal paper “Solid-State Energy-Dispersion Spectrometer for Electron-Microprobe X-ray Analysis” by Ray Fitzgerald, Klaus Kiel, and Kurt Heinrich [Science (1968), 159, 528] that introduced the Si(Li) energy dispersive spectrometer (EDS) detector as a practical analytical tool to the electron microscope community. In recognition of that anniversary, the Microscopy Society of America and the Microbeam Analysis Society organized a symposium at the 2008 Microscopy and Microanalysis Conference in Albuquerque, New Mexico to review the remarkable progress in Si(Li) EDS that has made elemental analysis available on virtually any electron beam platform.

Introduction Calcified deposits (CDs) in skin and muscles are common in juvenile dermatomyositis (DM), and less frequent in adult DM. Limited information exists about the microstructure and composition of these deposits, and no information is available on their elemental composition and contents, mineral density (MD) and stiffness. We determined the microstructure, chemical composition, MD and stiffness of CDs obtained from DM patients. Methods Surgically-removed calcinosis specimens were analyzed with fourier transform infrared microspectroscopy in reflectance mode (FTIR-RM) to map their spatial distribution and composition, and with scanning electron microscopy/silicon drift detector energy dispersive X-ray spectrometry (SEM/SDD-EDS) to obtain elemental maps. X-ray diffraction (XRD) identified their mineral structure, X-ray micro-computed tomography (μCT) mapped their internal structure and 3D distribution, quantitative backscattered electron (qBSE) imaging assessed their morphology and MD, nanoindentation measured their stiffness, and polarized light microscopy (PLM) evaluated the organic matrix composition. Results Some specimens were composed of continuous carbonate apatite containing small amounts of proteins with a mineral to protein ratio much higher than in bone, and other specimens contained scattered agglomerates of various sizes with similar composition (FTIR-RM). Continuous or fragmented mineralization was present across the entire specimens (μCT). The apatite was much more crystallized than bone and dentin, and closer to enamel (XRD) and its calcium/phophorous ratios were close to stoichiometric hydroxyapatite (SEM/SDD-EDS). The deposits also contained magnesium and sodium (SEM/SDD-EDS). The MD (qBSE) was closer to enamel than bone and dentin, as was the stiffness (nanoindentation) in the larger dense patches. Large mineralized areas were typically devoid of collagen; however, collagen was noted in some regions within the mineral or margins (PLM). qBSE, FTIR-RM and SEM/SDD-EDS maps suggest that the mineral is deposited first in a fragmented pattern followed by a wave of mineralization that incorporates these particles. Calcinosis masses with shorter duration appeared to have islands of mineralization, whereas longstanding deposits were solidly mineralized. Conclusions The properties of the mineral present in the calcinosis masses are closest to that of enamel, while clearly differing from bone. Calcium and phosphate, normally present in affected tissues, may have precipitated as carbonate apatite due to local loss of mineralization inhibitors.

In routine electron probe analysis involving sample targets that are electron opaque, flat, and conductive, the mechanisms describing the interaction of the beam electrons with the target atoms and the subsequent x-ray generation, absorption, and detection are well known. Various correction procedures are currently available for routine quantitative analysis that offer accuracies of 2 percent relative, as determined from studies of well-characterized, homogeneous standards [1].

Of all the techniques of electron probe microanalysis, the one that has undergone the least change over the history of the field is the technique of producing an image of the distribution of the elemental constituents of a sample, which can be termed compositional mapping. Even today with the dominance of computers for digital data collection and processing in the microprobe laboratory, most compositional mapping is still carried out with an analog procedure that is little changed from the “dot mapping” or “area scanning” technique described by Cosslett and Duncumb in 1956 [1]. The dot mapping procedure can be summarized as follows: (1) As in conventional scanning electron imaging, the beam on the cathode ray tube (CRT) is scanned in synchronism with the beam on the specimen. (2) When the beam is at a particular position on the specimen and an x-ray photon is detected with either a wavelength-dispersive (WDS) or an energy dispersive spectrometer (EDS), the corresponding beam location on the CRT is marked by adjusting the current to excite the phosphor to full brightness. (3) The white dots produced on the CRT display are continuously recorded by photographing the screen to produce the dot map.

Early Times of Electron Microprobe Analysis.- Strategies of Electron Probe Data Reduction.- An EPMA Correction Method Based upon a Quadrilateral ?(?z) Profile.- Quantitative Analysis of Homogeneous or Stratified Microvolumes Applying the Model "PAP".- ?(?z) Equations for Quantitative Analysis.- A Comprehensive Theory of Electron Probe Microanalysis.- A Flexible and Complete Monte Carlo Procedure for the Study of the Choice of Parameters.- Quantitative Electron Probe Microanalysis of Ultra-Light Elements (Boron-Oxygen).- Nonconductive Specimens in the Electron Probe Microanalyzer - A Hitherto Poorly Discussed Problem.- The R Factor: The X-Ray Loss due to Electron Backscatter.- The Use of Tracer Experiments and Monte Carlo Calculations in the ?(?z) Determination for Electron Probe Microanalysis.- Effect of Coster-Kronig Transitions on X-Ray Generation.- Uncertainties in the Analysis of M X-Ray Lines of the Rare-Earth Elements.- Standards for Electron Probe Microanalysis.- Quantitative Elemental Analysis of Individual Microparticles with Electron Beam Instruments.- The f(?) Machine: An Experimental Bench for the Measurement of Electron Probe Parameters.- Quantitative Compositional Mapping with the Electron Probe Microanalyzer.- Quantitative X-Ray Microanalysis in the Analytical Electron Microscope.

Sample substrates for x-ray microanalysis of particles should be chemically simple and composed of low atomic number elements. Substrates meeting these requirements will generate a minimum number of low energy x-ray peaks that should not interfere with spectra generated by the particles of interest. Elemental carbon fulfills these requirements and carbon planchets are used for the majority of work involving x-ray microanalysis of particles. When particles of interest are carbonaceous, alternate substrates must be sought. Beryllium planchets have traditionally been used for the analysis of carboncontaining particles. However, concerns about beryllium toxicity along with regulations from the Occupational Safety and Health Administration (OSHA) have resulted in diminished use of beryllium as a substrate material. These toxicity issues prompted us to explore the possibility of using elemental boron as a substrate for microanalysis of carbon-containing particles.Elemental boron is available from chemical supply houses and the material we purchased was in the form of irregularly shaped pieces, approximately 3 cm in the longest dimension.

A central theme of modern materials science has been the exploration of the relationship between the microstructure of a material and its macroscopic properties. Beginning in the late 19th century, the developing field of metallography permitted scientists to view the microstructure of metal alloys. Mechanical polishing followed by selective chemical etching produced differential relief on chemically distinct phases or at grain boundaries. With such specimens, reflection optical microscopy revealed structures with micrometer and even finer dimensions. The microstructural world that was found proved to be highly complex, and most alloys were observed to be chemically differentiated into two or more distinct phases. The answer to many materials science questions required knowledge of the specific composition of such fine scale phases. Castaing’s research was motivated by these considerations, as evidenced by the title of his first paper, “Application of electron probes to metallographic analysis”. The subsequent impact of Castaing’s electron probe microanalyzer (EPMA) has occurred across a broad range of the physical and biological sciences. Materials science has been one of the most active areas and chief beneficiaries, as well as a source of researchers who not only employed electron beam microanalysis to solve their problems but who also contributed innovations that advanced the microprobe field. For example, the abstracts of the First National Conference on Electron Probe Microanalysis contain numerous examples of advanced applications of the electron microprobe to materials science, including analysis of (1) refractory metal coatings (P. Lubllin and W. Sutkowski), (2) diffusion in the Ti-Nb system (D. Nagel and L. Birks), (3) Au-Al alloys (C. Nealey), (4) various steels (H. Nikkei), (5) Al-V-Mo-Ti alloys (R. Olsen), (6) corrosion of Ni-Co alloy (C. Spengler and R. Stickler), and (7) analysis of metal oxides and carbides (T. Ziebold). Integrated over 50 years, the impact of electron probe microanalysis on materials science has been so broad and varied, especially in its continued development and incorporation within scanning electron microscopy and analytical electron microscopy, that a suitably comprehensive review could consume the entire presentation time available for all topics to be covered in this conference! Instead, selected examples of critical applications will be presented to illustrate the impact in materials science.

Microanalysis performed at low electron beam energies (≤ 5 keV) is limited by the physics of x-ray generation and the performance of existing semiconductor energy dispersive spectrometry (EDS) and wavelength dispersive spectrometry (WDS). Low beam energy restricts the atomic shells that can be excited for elements of intermediate and high atomic number, forcing the analyst to consider using unconventional M- and N-shells for elements such as Sn and Au. Unfortunately, these shells have very low fluorescent yield, which results in inherently low spectral peak-to-background ratios. The modest energy resolution of semiconductor EDS leads to poor limits of detection for these weakly emitted photons. The situation is further complicated by the inevitable interferences with the much more strongly excited K-shell x-rays of the light elements, particularly carbon and oxygen. WDS has the spectral resolution to overcome the resolution limitations of semiconductor EDS. However, WDS has a low geometric efficiency, and because of its narrow instantaneous spectral transmission, spectral scanning is required to detect and analyze x-ray peaks. Moreover, the high resolution field-emission-gun scanning electron microscope (FEG-SEM) provides only a few nanoamperes of beam current.

X-ray mapping is one of the most popular modes for displaying information obtained with x-ray spectrometry performed in the scanning electron microscope. This popularity arises from the ready accessibility and apparent simplicity of information presented in a pictorial fashion, especially when used in conjunction with other SEM imaging modes, such as backscattered, secondary, and specimen current electron images. Further, the rise of powerful, inexpensive computer systems capable of image processing and display has given the analyst a dedicated, on-line tool with the capacity and flexibility needed for problem solving. Figure 1 shows a typical example of mapping. Although the interpretation of x-ray images obtained with a modern digital control and recording system would seem to be straightforward and relatively trivial, there are significant pitfalls and limitations that can easily fool the unwary. In Figure 1, within an individual x-ray map, the observer can reasonably judge where the concentration is lower or higher, at least for a group of contiguous pixels. Can such judgments be made among a set of maps of the same region for different elements, or even for the same element from different regions of the same specimen? With current x-ray processing and display systems, the answers are generally no. In fact, problems that can influence interpretation can arise at each stage of x-ray generation/emission, x-ray spectral collection, processing, and display.

The purpose of this laboratory is to prepare samples of metals, ceramics, and geological and microelectronic specimens for examination and analysis in the transmission electron microscope (TEM) and analytical electron microscope (AEM). Material forms include bulk, thin films, and particles. To achieve suitable electron transparency, and meet various requirements for electron diffraction and microanalysis, the thin region of the specimen must be

The SE signal collection efficiency of the conventional E-T detector is limited by the asymmetry of the collection field resulting from the detector position and from the surface potential of rough specimens. Specimen biasing should be routinely applied to optimize signal collection for a given specimen and imaging situation. The voltage supply must be of extreme stability which can be provided by dry batteries such as 45-V farm batteries. Two batteries connected in series provide for an easy change of polarity. There is no rule to predict the effect of specimen biasing on signal collection. The bias modifies only the accelerating voltage of the probe and the collection field of the collector. Thus, SE components will still be collected. (Note: Only a grounded specimen grid which shields the specimen from all other biased surfaces allows establishment of a positive field between the grid and the specimen for the absorption of SE-I+II as described in experiments of Section 12.3.)

This laboratory is designed to give you a feel for the amount of care and time that must go into any measurement involving trace elements. The trace element concentration range is often defined as concentrations below 0.5 wt% for most elements and below 1 wt% for the light elements. The example used here is the measurement of small amounts of phosphorus (P) in FeNi alloys. More details on these techniques may be found in SEMXM, Chapters 7 and 8.

This laboratory demonstrates: (1) the two major types of contrast in SEM images, known as atomic number contrast and topographic contrast, (2) the factors affecting the quality of the image and how they ultimately limit the image resolution, and (3) the effects of electronic signal processing on the visibility of features in the image. More details and references may be found in SEMXM, Chapters 3 and 4.

This laboratory explores some of the principal phenomena observed at low beam energies. Images prepared at “conventional” beam energies, e.g., 15 keV and above, are compared with low-beam-energy images, e.g., 5 keV and below. The possibility of examining uncoated insulators by taking advantage of enhanced emission of secondary electrons at low energy is also examined.

Platinum and platinum-gold metallurgy was fully developed by smiths in the Esmeraldas-Tumaco Pacific coast area of present day Ecuador and Colombia long before the arrival of Europeans in South America and centuries before platinum metallurgy became practicable in the Western world. Using gold to sinter together nuggets of native placer platinum, then alternately working and annealing the resultant solid, these South American smiths produced hard, fairly homogeneous platinum-gold alloys of a range of colors for fabrication into items of adornment, and small tools, such as needles, tweezers, awls, and fishhooks.The microstructures and compositions of sintered Pt-Au objects from La Tolita, Ecuador, and of experimentally simulated Pt-Au alloy samples were analyzed using new electron microprobe microanalysis (EPMA) techniques and data from the Pt-Au phase diagram in an effort to determine the fabrication temperatures used by Pre-Hispanic South American smiths. A comparison of EPMA results from the simulated materials with the corresponding results from the La Tolita Pt-Au objects suggests that the Pt-Au objects were never heated as high as 1100°C and probably never contained a liquid phase. As illustrated by this comparison, the qualitative and quantitative information provided by these new digital acquisition and display techniques far exceeds what conventional line scan and x-ray dot maps could provide.

This laboratory demonstrates: (1) election gun saturation and alignment; (2) the measurement of beam current, beam size, and beam convergence; (3) the concept of electron gun brightness; and (4) the effects of these parameters on depth-of-field and resolution. More details and references can be found in SEMXM, Chapter 2.

The purpose of this laboratory is to prepare samples of metallic, ceramic, polymeric, and biological specimens for examination and analysis in the SEM. The organization is such that under each type of material sample preparations are discussed for surface topography (e.g., fracture surface), microstructural analysis (e.g., phase morphology), and x-ray microanalysis. Special procedures for semiconductor devices, polymers, and biological samples are also considered. The objective is to provide a brief outline and enough general references to enable the reader to produce all of the specimens used in this workbook. The outlined methods should not be considered comprehensive, however, and the reader is strongly urged to consult the references listed. For further discussion, see SEMXM, Chapters 9–12.

There are two main objectives of this laboratory: (1) to study the differences observed in EDS and WDS x-ray spectra obtained from particles and rough surfaces as compared to bulk targets, and (2) to test the comparative accuracies of (a) conventional quantitative analysis methods, (b) the peak-to-background method, and (c) the particle ZAF method when applied to particles. More details may be found in SEMXM, Chapter 7.

The purpose of this laboratory is to demonstrate quantitative x-ray microanalysis as practiced on an electron column instrument equipped with an energy-dispersive spectrometer (EDS) and a computer-based multichannel analyzer (MCA). Although the difficult calculations of quantitative x-ray microanalysis are performed automatically in the MCA, the analyst must be aware of the responsibility to select operating conditions that optimize accuracy and precision. As with the WDS, increasing the accelerating voltage will improve the x-ray count rate and peak-to-background ratio and therefore the precision and sensitivity, respectively. However, increasing the beam voltage will also increase the absorption of lower-energy x-ray lines such as aluminum. More details may be found in SEMXM, Chapters 3, 5, and 7.

This first laboratory is designed to acquaint the beginning SEM operator with the steps for taking a micrograph. The steps are described without reference to a particular instrument. Please consult the manufacturer’s operation manual or an instructor before proceeding.

The objective of this laboratory session is to introduce the principal method of obtaining electron diffraction information from regions smaller than the limit of conventional selected area diffraction (SAD), about 0.5 μm in diameter. The technique is termed convergent beam electron diffraction (CBED). We will see that CBED patterns can be used to generate much more information than can be obtained from SAD patterns.

This laboratory is concerned with use of the digital computer to aid in the acquisition, display, and interpretation of various digital images obtained with the scanning electron microscope, e.g., secondary electron, backscattered electron, x-ray, etc. We will be concerned with all aspects of SEM imaging from the generation of the signal, when the electron beam interacts with the specimen surface, to the perception and interpretation of this information in the mind of the observer. Indeed, we will view all steps involved as an information channel which has certain imperfections and nonlinearities that must be examined. This aspect of microscopy is a rapidly developing area and consequently it is difficult to condense all of the important concepts into a single laboratory exercise. Nevertheless, the topics covered in the following experiments should give a sense of the power of this new tool for the microscopist. For more details see ASEMXM, Chapter 5, and references [1–4] at the end of the laboratory.

The light element regime traditionally defined as the elements Be through F (Z = 4 to 9) has posed many difficulties for the analyst. Poor detectability due to low count rates caused by insufficient beam current at low voltage and small spot sizes has made microanalysis very difficult Adequate matrix correction procedures are just being developed and quantification is difficult without very good standards. Contamination of the sample during analysis often makes the results questionable. These problems are slowly but surely being corrected in today’s modern electron microprobes. New WDS crystals and recent ultra-thin-window (UTW) have contributed to improved detectability; modern electron columns have much better low-voltage performance; and finally, today’s SEMs and microprobes are designed with anticontamination devices. However, with all these improvements, the measurement and subsequent quantification of light elements is far from routine. This laboratory will illustrate operational aspects of light element analysis background measurements, peak overlap problems, and quantitation techniques. More details may be found in SEMXM, Chapter 8.