Application Of Microanalysis Research Articles

Developments in Broad Ion Beam Milling Sample Preparation Instrumentation for Microscopy and Microanalysis Applications.

Developments in Broad Ion Beam Milling Sample Preparation Instrumentation for Microscopy and Microanalysis Applications.

Editorial

Traditionally microscopy has been separated into materials and biological applications, but these divisions break down in fields such as nanotechnology and tissue engineering where there is a need to understand actions of materials components at the cellular and intracellular level. Microanalytical techniques with their ability to identify elemental content at the nm scale offer considerable promise in these areas of research, but their application is not always straightforward. Routine procedures developed for specific applications in one field are not always appropriate when applied in another, and may cause misleading results. This issue of J Microsc. brings together a number of papers dealing with the application of microanalysis at the interface between materials science and biology. The subjects dealt with include the effects of standard fixation and embedding procedures on nanoparticle composition, (Cross et al.), the inadvisability of using standardless quantitation routines with biological specimens (Warley), problems encountered in SEM analysis of cells cultured on biocompatible substrates (Tylko) and correlation of results produced from FIB SEM with those from TEM to overcome sampling problems that occur in thin section TEM studies (Hondow et al.). Lawrence et al. present their results achieved using soft X-rays as the source of X-ray excitation, the advantage of this technique being that minimal specimen preparation is required. Whilst Zeitvogel et al. present a plug in for Image J to tackle the problem of extracting information from the large data sets that can be produced from microanalytical studies. Together these papers tackle different aspects of problems that may be encountered when undertaking analysis at the materials biology interface and should provide a very useful reference point for workers in the field.

Electrochemical Seed-Mediated Growth of Surface-Enhanced Raman Scattering Active Au(111)-Like Nanoparticles on Indium Tin Oxide Electrodes

In this article, a novel electrochemical seed-mediated method has been proposed for the fabrication of surface-enhanced Raman scattering (SERS) active gold nanoparticle films deposited on indium tin oxide electrodes. First, due to the fact that a high overpotential and a short time of potentiostatic transient are applied in the nucleation stage, the high controllability with the density and the size of gold nanoparticles on an indium tin oxide (ITO) electrode are realized. Second, due to the fact that AuCl4– ions will be preferentially reduced and deposited on the previously formed Au seeds in a subsequent cyclic voltammetrical process, we achieve the size-controlled gold nanoparticles which are enriched in Au(111) facet orientation (ca. 80.7%). With the growth of the nanoparticles, the gap between the adjacent nanoparticles gradually decreases, and thus plenty of “hot spots” are formed on the substrate for SERS applications. Third, by using 4-mercaptobenzoic acid as a probe molecule, the enhancement factor of the as-prepared substrate is estimated as ∼1.3 × 106, and its reproducibility and stability for SERS measurements are also evaluated. These works reveal its great potential in routine SERS applications for microanalysis. The protocol for the fabrication of such a SERS substrate is facile and cost-effective, without introducing any template or surfactant.

Practical X-ray Spectrometry with Second-Generation Microcalorimeter Detectors

X-ray spectroscopy is a widely used and extremely sensitive analytical technique for qualitative as well as quantitative elemental analysis. Typically, high-energy-resolution X-ray spectrometers are integrated with a high-spatial-resolution scanning electron microscope (SEM) or transmission electron microscope (TEM) for X-ray microanalysis applications. The focused electron beam of the SEM or TEM excites characteristic X rays that are emitted by the sample. The integrated X-ray spectrometer can then be used to identify and quantify the elemental composition of the sample on a sub-micron length scale. This combination of energy resolution and spatial resolution makes X-ray microanalysis of great importance to the semiconductor industry.

Identifying Weak Linear Features with the “Coalescing Shortest Path Image Transform”

The detection of line-like features in images finds many applications in microanalysis. Actin fibers, microtubules, neurites, pilis, DNA, and other biological structures all come up as tenuous curved lines in microscopy images. A reliable tracing method that preserves the integrity and details of these structures is particularly important for quantitative analyses. We have developed a new image transform called the "Coalescing Shortest Path Image Transform" with very encouraging properties. Our scheme efficiently combines information from an extensive collection of shortest paths in the image to delineate even very weak linear features.

The Nuclear Microprobe

Nuclear microprobes are used in many accelerator laboratories for a range of applications in microanalysis and modification of a wide variety of different materials. They are used to focus MeV ion beams to small spot sizes containing currents ranging from femtoamperes to nanoamperes. While microprobes routinely achieve spatial resolutions of a few micrometers, recent breakthroughs in lens design and accelerator technology have achieved resolutions of less than 100 nanometers and a state-of-the-art value of about 35 nm. This article gives a brief overview of the current state-of-the-art of microprobe performance and recent applications in different disciplines in microanalysis, focused irradiation, and micromodification.

Experimental study of Cr∕Sc multilayer mirrors for the nitrogen Kα-emission line

The authors present an experimental study of Cr∕Sc multilayer mirrors optimized for the detection of the nitrogen Kα-emission line (λ=3.16nm) at a grazing incidence around 23°, for electron probe microanalysis applications. The multilayers were deposited onto silicon substrates using a dc magnetron sputtering system. They were characterized with grazing incidence copper Kα x-ray reflectometry and atomic force microscopy, as well as with at-wavelength reflectometry using synchrotron radiation. These various characterization methods pointed out that the interfacial roughness of these multilayers increases drastically with the number of bilayers. Growth parameters were then optimized, and it is shown that the structure and reflectivity of such multilayers can be considerably improved by optimizing the sputter gas pressure during the deposition process. Reflectivity higher than 37% were measured at 22.3° grazing angle for the nitrogen Kα-emission line.

Development of laser-induced breakdown spectroscopy for microanalysis applications

AbstractLaser induced breakdown spectroscopy is a fast non-contact technique for the analysis of the elemental composition of any sample. Our focus is to advance this technique into a regime where we use pulse energies below 100 µJ. This regime is referred to as micro-laser-induced breakdown spectroscopy or µLIBS. At present we have concentrated on two application areas : (1) The imaging of latent fingerprints and (2) the extension to laser ablation followed by laser-induced fluorescence (LA-LIF) for very high sensitivity analysis of contaminants in water. Preliminary pulse emission scaling of Na in latent fingerprints has been investigated for ~130 fs, 266 nm pulses with energies below 15 µJ. The lowest energy for reliable single shot detection of Na is approximately 3.5 µJ. A 2D map of a fingerprint on a Si wafer has been successfully demonstrated using 5 µJ pulses. In LA-LIF the detection sensitivity of micro-laser-induced breakdown spectroscopy (µLIBS) is improved by coupling it with a second resonant probe pulse. This technique was investigated for the detection of Pb at low concentrations when ablated by 266 nm, 170 µJ pulses. After a short delay the resulting plume was re-excited with a nanosecond laser pulse tuned to a specific transition of Pb. In the case of the resonant dual-pulse LIBS the limit of detection was found to be approximately 60 ppb for Pb in water for 1000 shots. It is expected that this result could be implemented with fiber or microchip lasers with multi-kHz repetition rates and fiber Bragg grating tuning elements. The results are promising for the development of portable µLIBS water monitoring systems and portable fingerprint scanners.

Applications of microanalysis in the cultural heritage field

Several case studies of microanalysis of objects of cultural heritage are reviewed. These objects, including paintings, metal artefacts, paper and archaeological glass, present a variety of research questions. In all cases, their analysis was complex due to the different problems raised by each material and the interpretation of the results.

Fabrication and characterization of SERS‐active silver clusters on glassy carbon

AbstractIn this article, a novel technique for the fabrication of surface enhanced Raman scattering (SERS) active silver clusters on glassy carbon (GC) has been proposed. It was found that silver clusters could be formed on a layer of positively charged poly(diallyldimethylammonium) (PDDA) anchored to a carbon surface by 4‐aminobenzoic acid when a drop containing silver nanoparticles was deposited on it. The characteristics of the obtained silver clusters have been investigated by atomic force microscopy (AFM), SERS and an SERS‐based Raman mapping technique in the form of line scanning. The AFM image shows that the silver clusters consist of several silver nanoparticles and the size of the clusters is in the range 80–100 nm. The SERS spectra of different concentrations of rhodamine 6G (R6G) on the silver clusters were obtained and compared with those from a silver colloid. The apparent enhancement factor (AEF) was estimated to be as large as 3.1 × 104 relative to silver colloid, which might have resulted from the presence of ‘hot‐spots’ at the silver clusters, providing a highly localized electromagnetic field for the large enhancement of the SERS spectra of R6G. The minimum electromagnetic enhancement factor (EEF) is estimated to be 5.4 × 107 by comparison with the SERS spectra of R6G on the silver clusters and on the bare GC surface. SERS‐based Raman mapping technique in the form of line scanning further illustrates the good SERS activity and reproducibility on the silver clusters. Finally, 4‐mercaptopyridine (4‐Mpy) was chosen as an analyte and the lowest detected concentration was investigated by the SERS‐active silver clusters. A concentration of 1.6 × 10−10 M 4‐Mpy could be detected with the SERS‐active silver clusters, showing the great potential of the technique in practical applications of microanalysis with high sensitivity. Copyright © 2006 John Wiley & Sons, Ltd.

Experimental secondary electron spectra under SEM conditions.

Secondary electron spectra have been collected from both pure elements and from compounds examined under conditions approximating those found in a scanning electron microscope. Despite the presence of substantial surface contamination these spectra are found to be reproducible and characteristic of the underlying material. Typically the peak in such spectra is found to be at an energy of about 5 eV, and 50% of the total secondary electron emission falls within the range 0-12 eV. These data may be of value for the design of detectors for scanning microscopy and might have applications for microanalysis.

Micro-Mining and Segmented Log File Analysis: A Method for Enriching the Data Yield from Internet Log Files

The authors propose improved ways of analysing web server log files. Traditionally web site statistics focus on giving a big (and shallow) picture analysis based on all transaction log entries. The pictures are, however, distorted because of the problems associated with resolving Internet protocol (IP) numbers to a single user and cross-border IP registration. The authors argue that analysing extracted sub-groups and categories presents a more accurate picture of the data and that the analysis of the online behaviour of selected individuals (rather than of very large groups) can add much to our understanding of how people use web sites and, indeed, any digital information source. The analysis is labelled `micro' to distinguish it from traditional macro, big picture transactional log analysis. The methods are illustrated with recourse to the logs of the Surgery Door (www.surgerydoor.co.uk) consumer health web site. It was found that use attributed to academic users gave a better approximation of the sites' geographical distribution of users than an analysis based on all users. This occurs as academic institutions, unlike other user types, register in their host country. Selecting log entries where each user is allocated a unique IP number can be particularly beneficial, especially to analyses of returnees. Finally the paper tracks the online behaviour of a small number of IP numbers, in an example of the application of microanalysis,

X-Ray Microanalysis in the Environmental SEM Using Mapping and Fourier Deconvolution Techniques

X-ray microanalysis of any type of specimen in its natural state without the use of conventional SEM specimen preparation techniques has immense potential in a wide range of scientific and industrial applications. This capability would be particularly useful in microanalysis applications where it is highly desirable to preserve the integrity of the specimen, for example in semiconductor failure analysis and forensic investigations. in principle, this X-ray microanalysis goal can be achieved in an environmental or variable pressure scanning electron microscope (VPSEM) because specimen charging and vacuum stability problems are negated by the presence of a gas in the specimen chamber. However, the accuracy and spatial resolution of X-ray microanalysis in the VPSEM is significantly degraded by the chamber gas as it scatters primary beam electrons, generating spurious X-rays far from the analysis point. to date, two different X-ray measurement strategies have been developed to facilitate X-ray microanalysis at high chamber pressure in the VPSEM.

Resonant laser ablation of copper and its application in microanalysis

Resonant laser ablation of copper and its application in microanalysis

Resonant laser ablation of copper and its application in microanalysis

Resonant laser ablation (RLA) is a two-step process, occurring within a pulse of a tunable laser, in which the leading edge of the laser pulse ablates a solid surface to produce neutral atoms or molecules that are then resonantly ionized by the trailing edge of the same laser pulse. The sensitivity and selectivity of RLA allow detection and quantitation at very low concentrations. In our preliminary RLA research, a sub-ppm detection level has been reached for copper in a standard aluminium sample. In addition, the threshold and saturation effects of RLA have been observed.

Cryogenic high-resolution X-ray spectrometers for SR-XRF and microanalysis.

Experimental results are presented obtained with a cryogenically cooled high-resolution X-ray spectrometer based on a 141 x 141 micro m Nb-Al-Al(2)O(3)-Al-Nb superconducting tunnel junction (STJ) detector in an SR-XRF demonstration experiment. STJ detectors can operate at count rates approaching those of semiconductor detectors while still providing a significantly better energy resolution for soft X-rays. By measuring fluorescence X-rays from samples containing transition metals and low-Z elements, an FWHM energy resolution of 6-15 eV for X-rays in the energy range 180-1100 eV has been obtained. The results show that, in the near future, STJ detectors may prove very useful in XRF and microanalysis applications.

Two types of ion gun equipped sputter-initiated resonant ionization and time-of-flight mass spectroscopy and its application in microanalysis of minerals

An apparatus, based on sputter-initiated resonant ionization spectroscopy and combined with time-of-flight mass spectroscopy, has been recently developed for microanalysis of mineral samples and other solid materials. This equipment has two kinds of ion gun, which make it possible to do more convenient and accurate microanalysis of complicated mineral samples. With this apparatus, detection and size measurement of fine gold grains trapped in pyrite at low concentrations have been carried out. The detection limit of this apparatus for gold is 73 ppb. The apparatus also has the function of secondary electron imaging. This gives very helpful information for geologists to evaluate the inborn state of gold in mineral samples and to improve the extraction rate of gold from minerals.

Imaging focused x-rays from glass capillaries

Recent developments of glass capillaries allow x-ray probes to be focused down to micrometer sizes. These probes show promise for microanalysis applications, if they can reliably deliver high intensity, well formed x-ray beams to a specimen. We have developed an optical bench for viewing and evaluating the focused x-rays emitted from these capillaries. The optical bench allows pulse counting, direct viewing of the x-ray probe spatial distributions, and energy pass band by using exchangeable detectors. Our results are used to determine the probe forming capabilities of the lenses and to indicate problems and directions for improving the manufacturing of the x-ray optics.The x-ray optical bench is shown in a schematic diagram in figure A. It consists of a conventional CuKα x-ray diffraction tube joined to an optical table. An optical rail extends across them. A shielded box with a hinged side covers the source and the optical rail. The x-ray optic and exchangeable detector system are located on computer controlled stages to allow fine adjustments in all necessary translation and tilt directions. This optical bench permits measurements to be devised, performed, and changed with a minimum of difficulty. The optical bench allows for maximum flexibility in sample positioning, detector positioning, source size, and source collimation. The quantities that we evaluate in each optical element include focal spot size, spot uniformity, total spot flux, spot aberrations, diffuse scattered radiation, and depth of field or convergence.

Applications of micro-analysis to individual environmental particles.

An overview is given of the recent applications of micro-analytical techniques to single particle environmental research performed at the University of Antwerp since 1990. Automated electron probe X-ray micro-analysis, laser microprobe mass spectrometry and micro-particle induced X-ray emission are the techniques most used for aerosol, aqueous suspension and sediment characterisation. Other techniques like scanning transmission electron microscopy, electron energy loss spectroscopy, Fourier transform infra red microscopy and secondary ion mass spectrometry have only recently been implemented into environmental research.

Theoretical and Practical Aspects of Nuclear Microprobe Analysis of Solid Surfaces and Bulk Solids

The aim of this paper is first to describe the nuclear microprobe and to present the analytical capabilities of the different methods involved in nuclear microanalysis resulting from the interactions between the incident ion beam and the solid target, such as proton induced X-ray emission, proton induced gamma-ray emission, Rutherford backscattering spectrometry, non-Rutherford scattering, elastic recoil detection and nuclear reaction spectrometry. The respective analytical performances are also discussed. The second purpose of this paper is to illustrate some aspects of nuclear microanalysis applications from materials sciences to earth sciences and life sciences, using recently published data. Thirdly, both recent developments and further progresses in nuclear microprobe technology are detailed regarding as well ion sources, beam focussing as associated microscopic techniques, detection devices and data processing.