Energy dispersive x-ray spectroscopy (EDS) is a chemical microanalysis technique performed in conjunction with a scanning electron microscope (SEM) . The technique utilizes x-rays that are emitted from the sample during bombardment by the electron beam to characterize the elemental composition of the analyzed volume. Features or phases as small as about 1µm can be analyzed.

When the sample is bombarded by the electron beam of the SEM, electrons are ejected from the atoms comprising the sample's surface. A resulting electron vacancy is filled by an electron from a higher shell, and an x-ray is emitted to balance the energy difference between the two electrons.

The EDS x-ray detector measures the number of emitted x-rays versus their energy. The energy of the x-ray is characteristic of the element from which the x-ray was emitted. A spectrum of the energy versus relative counts of the detected x-rays is obtained and evaluated for qualitative and quantitative determinations of the elements present in the sampled volume.

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Qualitative analysis-Elements with atomic numbers from that of beryllium to uranium can be detected. The minimum detection limits vary from about 0.1 weight percent to a few percent depending on the element and matrix.

Quantitative analysis-Quantitative results are readily obtained without standards. The accuracy of standardless quantitative analysis is highly sample dependent. Greater accuracy is obtained using known standards with similar structure and composition as the unknown sample.

Line profile analysis-The SEM electron beam is scanned along a preselected to line across the sample while x-rays are detected for discrete positions along the line. Analysis of the x-ray energy spectrum at each position provides plots of the relative elemental concentration for each element versus position along the line.

Elemental mapping-Characteristic x-ray intensity is measured relative to lateral position on the sample surface. Variations in x-ray intensity then indicate the relative elemental concentrations across the surface. Maps are recorded using image brightness intensity as a direct function of the local concentration of the element(s) present. Lateral resolution of about 1µm is possible.

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• Surface contamination analysis
• Corrosion evaluations
• Coating composition analysis
• Rapid material alloy identification
• Small component material analysis
• Phase identification and distribution

Model:Oxford Link ISIS

Samples up to 8 in. (200 mm) in diameter can be readily accommodated in the SEM. Larger samples, up to about 12 in. (300 mm) across can be loaded with limited stage movement. Sample height is limited to about 2 in. (50 mm). Samples must be compatible with moderate vacuum (pressures of 2 Torr or less).

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