Energy-dispersive X-ray spectroscopy (EDS, also abbreviated EDX or XEDS) is an analytical technique that enables the chemical characterization/elemental analysis of materials. A sample excited by an energy source (such as the electron beam of an electron microscope) dissipates some of the absorbed energy by ejecting a core-shell electron. A higher energy outer-shell electron then proceeds to fill its place, releasing the difference in energy as an X-ray that has a characteristic spectrum based on its atom of origin. This allows for the compositional analysis of a given sample volume that has been excited by the energy source. The position of the peaks in the spectrum identifies the element, whereas the intensity of the signal corresponds to the concentration of the element.
As previously stated, an electron beam provides sufficient energy to eject core-shell electrons and cause X-ray emission. Compositional information, down to the atomic level, can be obtained with the addition of an EDS detector to an electron microscope. As the electron probe is scanned across the sample, characteristic X-rays are emitted and measured; each recorded EDS spectrum is mapped to a specific position on the sample. The quality of the results depends on the signal strength and the cleanliness of the spectrum. Signal strength relies heavily on a good signal-to-noise ratio, particularly for trace element detection and dose minimization (which allows for faster recording and artifact-free results). Cleanliness will impact the number of spurious peaks seen; this is a consequence of the materials that make up the electron column.
- Sensitive to low concentrations—minimum detection limits below 0.1% in the best cases
- Affords a high degree of relative precision—typically 2–4%
- Non-destructive in most situations
- Usually requires minimal sample preparation effort and time
- Delivers complete analyses of complex samples quickly, often in under a minute
Advanced and fully integrated EDS solutions are available on Thermo Scientific TEM, SEM and Desktop systems.