The central element of electron microscopic investigations is the irradiation of the samples to be examined with a fine electron beam. If the energy of the electron beam used is high enough, X-ray quanta of different energies are produced in the sample material.
The energy of the individual X-ray quanta depends on which “atomic shell/s” of an excited sample element was/are excited. The EDX analytics detects these X-ray quanta and "sorts" them into narrow classes (channels) depending on their energy. If these energy channels are plotted against the number of X-ray quanta in the individual channels, an EDX spectra is obtained. Peaks in these spectra can be assigned to the characteristic energies of individual elements.
By further evaluating these spectra, it is possible to make qualitative and quantitative statements about the elemental composition of the sample. Element maps of the sample surface (EDX mapping) or line scans can also be carried out.
Depending on the atomic number of the element to be detected, the detection limit is approx. 0.1 to 0.2 w% (percent by weight). The energy resolution is around 120 to 130 eV.
EDX detectors are installed on all of our electron microscopes. If you have any further questions, please contact the person responsible for the respective device:
WDX (Wellendispersive Röntgenmikroanalytik)
Wave-dispersive X-ray microanalysis or spectroscopy (WDS) is based on the same physical processes in the examined sample as energy-dispersive X-ray microanalysis (EDX).
When detecting the X-ray quanta emitted by the sample, however, WDX does not use the different energy contents of the X-ray quanta directly, but rather their different wavelengths. Without going into detail about the complex measurement setup, it should be mentioned here that the detection limit is approx. 10x lower compared to EDX. Another advantage is the better energy resolution of approx. 7-10 eV compared to 120 to 130 eV (EDX).
A disadvantage is the greater time required for a WDX measurement, since all elements can only be measured sequentially, with EDX measuring all elements of a sample simultaneously.
A WDS system is only available on the Zeiss Supra. If you have any further questions, please contact the person responsible for the Zeiss Supras:
EBSD (Electron Backscatter Diffraktion)
Using the EBSD (Electron Backscatter Detector) method, it is possible to determine the crystal structure and orientation of the crystals (to the incident beam) in a sample.
A very good sample preparation (embedding, grinding and polishing) of the sample material to be examined is important for success.
The beam of electrons is diffracted on the sample surface, which is usually installed at an angle of 70°, and then hits a phosphor screen connected to a camera. When the electron beam is diffracted at the different lattice faces of the crystal, constructive interference occurs if the Bragg condition is fulfilled. The diffracted beam thus contains the information necessary to determine the crystal system and its orientation.
When the diffracted beam hits the phosphor screen, the information is converted into a two-dimensional interference pattern (Kikuchi pattern).
Finally, the crystal system and its orientation to the incident beam can be determined by evaluating the Kikuchi pattern. By scanning a specific sample area and the simultaneous recording and evaluation of the Kikuchi pattern, color-coded Euler angle maps are created that can be further evaluated, e.g. to be able to determine textures using pole figures.
EBSD is only available on the Zeiss Supra 55 VP. If you have any further questions, please contact the person responsible for the Zeiss Supra: