Electron dispersive X-ray spectroscopy

AlAs/GaAs. Sample preparation and laser melting techniques are found in reference [62], Images of Al, Ga, Si, and O were sequentially recorded with a resistive anode encoder as the sample was depth profiled with Cs" and positive secondary ions in a Cameca IMS 5f in the microscope mode of operation. Two-dimensional cross sections of the Al, Ga, Si, and O images from a 60 pm rectangular slice centered around the 4 pm laser stripe were then computer generated and are shown in Fig. 4.30a. Depth profiles of Al, Ga, and O from selected 4 pm areas were also generated in the non laser-striped area in Fig. 4.30b and in the laser-striped area in Fig. 4.30c. Samples similar to the one in Fig. 4.30 have been analyzed with TEM, SEM, and electron dispersive X-ray spectroscopy (EDS) in addition to SIMS for full characterization [62]. 

With modern detectors and electronics most Enei -Dispersive X-Ray Spectroscopy (EDS) systems can detect X rays from all the elements in the periodic table above beryllium, Z= 4, if present in sufficient quantity. The minimum detection limit (MDL) for elements with atomic numbers greater than Z = 11 is as low as 0.02% wt., if the peaks are isolated and the spectrum has a total of at least 2.5 X 10 counts. In practice, however, with EDS on an electron microscope, the MDL is about 0.1% wt. because of a high background count and broad peaks. Under conditions in which the peaks are severely overlapped, the MDL may be only 1—2% wt. For elements with Z < 10, the MDL is usually around 1—2% wt. under the best conditions, especially in electron-beam instruments. 

Fig. 4.21. Schematic diagram of spectrometer arrangements for wavelength-dispersive and energy-dispersive X-ray spectroscopy (WDXS/EDXS) in electron microscopy.

The combined use of energy-dispersive X-ray spectroscopy and TEM/STEM is a routine method of analytical electron microscopy enabling both qualitative and quantitative chemical analysis of interfaces and interlayers with high lateral resolution. Reso-... 

Linear absorption measurements can therefore give the first indication of possible alloy formation. Nevertheless, in systems containing transition metals (Pd-Ag, Co-Ni,. ..) such a simple technique is no longer effective as interband transitions completely mask the SPR peak, resulting in a structurless absorption, which hinders any unambiguous identification of the alloy. In such cases, one has to rely on structural techniques like TEM (selected-area electron diffraction, SAED and energy-dispersive X-ray spectroscopy, EDS) or EXAFS (extended X-ray absorption fine structure) to establish alloy formation. 

Hill, A. D., A. H. Lehman, H. Arm, and M. L. Parr (2007), Using scanning electron microscopy with energy dispersive x-ray spectroscopy to analyze archaeological materials, J. Chem. Educ. 84(5), 810-813. 

The Atomic emission spectrometry (ICP-AES) results on the solids confirm the chemical purity of Py, Cp, Qz, Cal and Dol samples. The Po sample contains calcium which, after conversion into calcite, gives approximately 10wt% of this mineral. Sid sample contains 10.3 wt% Mn and 1.86 wt% Mg, in agreement with measurements using a Scanning Electron Microscopy coupled to Energy Dispersive X-Ray Spectroscopy (SEM-EDS) analysis again this explains the difference between the measured and theoretical density of the Sid powder. 

In HRTEM, very thin samples can be treated as weak-phase objects (WPOs) whereby the image intensity can be correlated with the projected electrostatic potential of crystals, leading to atomic structural information. Furthermore, the detection of electron-stimulated XRE in the electron microscope (energy dispersive X-ray spectroscopy, or EDX, discussed in the following sections) permits simultaneous determination of chemical compositions of catalysts to the sub-nanometer level. Both the surface and bulk structures of catalysts can be investigated. 

To find the distribution of iron within the nanotube walls an energy dispersive x-ray spectroscopy (EDS) line scan was performed via scanning transmission electron microscopy (STEM), see Fig. 5. 55. The intensity of both the TiK and FeKa lines are maximum at the center of the wall due to its torus shape. Despite the presence of isolated hematite crystallites, a more or less uniform distribution of iron relative to the titanium can be seen across the wall. STEM line scans were performed across a number of walls, and while the average relative intensity of the TiK and FeKa lines varied from wall to wall the relative distribution across a single wall remained uniform. It appears that some of the iron goes into the titanium lattice substituting titanium ions, and the rest either forms hematite crystallites or remains in the amorphous state. 

Local chemical composition from areas less than 1 nm in diameter can be measured by energy dispersive X-ray spectroscopy (EDS) or electron energy loss spectroscopy (EELS). Such spectroscopic information may be presented in 2D maps showing the spatial element distribution in the specimen (13). Furthermore, information about the local density of unoccupied electron states of a specific element can be extracted from EELS data and used to estimate the oxidation state and the local coordination geometry of the excited atoms (14). In some favorable cases, electronic structure information with a resolution of about 1 eV from individual atomic columns has been attained (15,16). Recent developments of monochromators and spectrometers have brought the resolution down to 0.1 eV (17,18), and this capability may offer new opportunities to determine relationships between electronic structure information, the atomic arrangements and the catalytic activities of solids. 

Brodowski, S., Amelung, W., Haumaier, L., Abetz, C., and Zech, W. (2005). Morphological and chemical properties of black carbon in physical soil fractions as revealed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Geoderma 128, 116-129. 

Effects of Chemical Purity. Zirconia tubes from five different sources were analyzed at Pennsylvania State University using scanning electron microscopy, plasma emission spectroscopy, energy dispersive X-ray spectroscopy, and electron beam microprobe analysis. The sources for the tubes included several commercially available tubes as well as tubes fabricated by the Pennsylvania State University Ceramics Department. 

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