High-spatial-resolution energy dispersive

HR-EDS high-spatial-resolution energy dispersive spectroscopy... 

Further significant developments of the EXAFS technique are envisaged. Energy-dispersive X-ray absorption tine structure (DXAFS) allows collection of a spectrum in much less than 1 s, and its extension to the fj,s or even the ns time scale is not impossible. Polarisation-dependent total-reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) permits high spatial resolution and has been applied to the copper trimer Cus on a Ti(llO) surface. The use of time-and space-resolved XAFS observation for studies of dynamic aspects of the local structure at catalyst surfaces under working conditions is forseen . Note that the acronym XAFS is used, rather than EXAFS. 

XAS requires synchrotron radiation and a relatively large amount of material but no vacuum condition. On the other hand, EELS can be performed directly using an electron spectrometer fitted to a scanning transmission electron microscope (STEM). Here, the main advantage is the high spatial resolution attainable. (The incident electron beam can be as. small as I nm in diameter.) EELS can also be coupled with conventional transmission electron microscope (TEM) facilities and particularly high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS). 

In energy dispersive instruments, all the characteristic X-rays from the specimen are first detected by a high resolution solid state detector. The detector output consists of electrical pulses of amplitude proportional to the energy of the detected photons. These pulses, once linearly amplified, are electronically sorted according to their amplitude by means of a pulse height analyzer. An advantageous consequence of this detection mode is that analysis of all chemical elements can be performed simultaneously. Since it eliminates the use of crystal goniometers and the X-rays are not spatially dispersed, this type of spectrometer is also sometimes referred to as nondis-persive. 

Energy-dispersive X-ray (EDX) spectroscopy utilizes the characteristic spectrum of X-rays that is emitted by a sample, following initial excitation by the high-energy electron beam. Information about the elemental composition of the sample can be obtained, where the spatial resolution is determined by the probe size, any beam broadening occurring within the specimen, and the effects of any backscattered electrons on the specimen around the point of analysis. EDX is relatively simple and can be used to provide rapid qualitative microanalysis. Quantitative elemental analysis can also be achieved, with an... 

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