Elemental line scans

There are three modes of analysis commonly used spectrum acquisition spatial distribution, or dot, mapping of the elements and elemental line scans. 

In addition to analysis by HAADF and elemental line scans, changes to the X-ray absorption near edge structure (XANES) may be investigated as a function of potential to investigate the structure of core-shell materials. Figure 19.4 shows results of these types of analysis for PtML/IrNi/C core-shell particles, where smaller changes in the XANES spectra vs. reference spectra at 0.41 V [plotted as (Ay — Aj o.4i)/Ay o.4i y axis. Fig. 19.4c] are observed for the core-shell compared to a Pt/C reference catalyst material. These data may be interpreted as a smaller change in Pt surface oxidation for the core-shell system, indicative of lower OH... 

Elemental line scans after diffusion annealing Aluchrom P (ThyssenKrupp VDM). 

The results shown in Figure 6 above are an example of this mode of analysis, but include additional information on the chemical states of the Si. The third most frequently used mode of analysis is the Auger mapping mode, in which an Auger peak of a particular element is monitored while the primary electron beam is raster scanned over an area. This mode determines the spatial distribution, across the surface, of the element of interest, rather than in depth, as depth profiling does. Of course, the second and third modes can be combined to produce a three-dimensional spatial distribution of the element. The fourth operational mode is just a subset of the third mode a line scan of the primary beam is done across a region of interest, instead of rastering over an area. 

Line Scanning. In order to examine the variation of chemical composition within a sample, one approach is to select the X-ray signal from the element of interest and to display its intensity as the point of incidence of the electron beam is moved along a chosen path (by moving either the beam or the specimen). The instantaneous count rate is measured, and a trace of composition versus beam position is obtained, as illustrated in Figure 5.9. 

It is possible to extend the line scanning method to two-dimensional scanning. In its simplest form, the display is made bright every time an X-ray photon is counted, thus generating a image of bright dots. The dot density provides a qualitative measure of the concentration of the element of interest. 

Figure 5.36 shows a line scan obtained for these elements, as well as for oxygen, zinc and sulphur. 

Analysis by the Detection of X-rays or y rays. EPMA is a fully qualitative and quantitative method of non-destructive analysis of micrometre-sized volumes at the surface of materials, with sensitivity at the level of ppm. All elements from Be to U can be analysed, either in the form of point analysis, from line scans and also as X-ray distribution maps. Current software allows the combination of elemental data in the latter, so that, for example, the digital data for those elements that corresponds to a selected phase will produce an X-ray map of the distribution of that phase in a given microstructure. 

Fig. 33 Two-photon fluorescent images of photosensitive films developed (via 350-nm broadband exposure, 4.4mW/cm ) using an Air Force resolution target mask, a Image recorded by channel 1, b image recorded by channel 2, and c fluorescence intensity by scanning an xy line across one set of three-membered elements (line across set 5)...

The evolution of the non-uniform spatial profile of the inorganic nanoparticles deposited, across the filter wall, can be seen in Fig. 15 along with a typical SEM line scan of the distribution of an element of the... 

Nanotubes represent the typical nano-objects and this presentation would not be representative without at least one example. The high resolution image on the left-hand side of Figure 5 represents a nanotube, the detailed composition of which cannot be deduced from the image or any technique other than EELS. By performing line scans, it was possible to quantify all the detected elements (B, C, N) as a function of the probe position. From the atomic ratios and the shape of the atomic distribution, Suenaga et a . [16] demonstrated that this particular nanotube was made of a succession of 3 carbon layers, 6 boron nitride layers and finally 5 carbon layers. 

The variation of CL intensity and its relation to the growth of forsterites in meteorites requires a detailed study of the chemical variation and the observed CL. Numerous line scans were described (Steele, I.M. Geochim. Cosmochim. Acta, accepted for publication) where spectra and composition were obtained at the same point for forsterites in the Ornans (C3) carbonaceous chondrite. Interpretation is complicated by the fact that some elements are strongly correlated and the effect on CL can not be attributed to any one element. The most important influence is found to be Fe which had different quenching effects on the blue and infrared CL emissions. The blue emission is effectively quenched for Fe concentrations above 0.75 wt.% FeO while the infrared emission is... 

Fig. 22 Top Modification of aqueous microgels by hydroxyapatite (HAp) nanocrystals, (a-d) TEM images of VCL/AAEM/VIm-HAp hybrid microgels containing different amounts of HAp (a) 0, (b) 7.9, (c) 34.2, and (d) 52.2 wt%. (e) EDX line scan of single microgel containing 52.2 wt% HAp with element distribution curves. Color of the lines in (e) corresponds to the color in the element distribution spectra. Reprinted from [149] with permission. Copyright 2008 American Chemical Society...

Both optical and mechanical line scans generate large data sets when used to construct a two-dimensional Raman image, but computer power and storage is inexpensive in the post-PC world. An advantage of such large data sets is the retention of complete spectra for each spatial element, with often high spectral... 

Wavelength dispersive X-ray spectrometry (WDS) for a more detailed elemental analysis of samples in the SEM. JEOL Four-Crystal Spectrometer attached to the JSM-35C SEM can be used for l-pm spot analysis, digital and analog line scans, and X-ray image mapping, elements detection from Be to U, minimum detection limit of 0.01% by weight, fully quantitative results by extended cp-p-z. 

The synthesized TiBj-Cu FGM samples were longitudinally cut, polished and observed with SEM. The distributions of element Ti and Cu were line-scanned and area-scanned with EDX. The densities of layers were measured with image-analysis method. 

The spatial distributions of catalytic metals and contaminant poisons in auto exhaust catalysts were delineated by electron probe line scans. Element concentrations were characterized by element sensitivities, i.e. in counts per second (cps). The electron probe microanalyses (EPM) were qualitative or semiqualitative in nature. Accurate correlation between element sensitivity and element concentration requires rather sophisticated instrument calibration. A quantitative evaluation of the EPM findings is beyond the scope of this paper. In general, it can be stated that element concentration is directly proportional to element sensitivity. Furthermore, the proportionality constant between element concentration and element sensitivity varies greatly from element to element. 

Fig. 13.6 Compositions profiles of different elements along the arrow in Fig. 13.5 by EDS line scan...

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