With EDS, the elemental composition of samples can be determined (including quantitatively). All elements from atomic number 4 (beryllium) can be detected.

A central component of electron microscopic investigations is the irradiation of the samples to be examined with a fine electron beam. If the energy of the applied electron beam is high enough, the atoms of the sample are excited and emit X-rays. The atoms of a chemical element emit X-rays with an energy characteristic of that element (fingerprint).

EDS analysis detects these X-ray quanta and "sorts" them into narrow classes (channels) based on their energy. Plotting these energy channels against the number of X-ray quanta in each channel results in an EDS spectrum. Peaks in these spectra can be assigned to the characteristic energies of individual elements.

Further evaluation of these spectra makes it possible to make qualitative and even quantitative statements about the elemental composition of the sample. Our EDS software also allows for the creation of elemental maps of the sample surface (EDS mapping) or so-called line scans.

The detection limit of EDS analysis, depending on the atomic number of the element to be detected, is approximately 0.1 to 0.2 wt% (weight percent). The energy resolution is about 120 to 130 eV.

The lateral resolution of EDS analysis is limited, in analyses within an SEM, by the excited volume of the sample and is in the range of a few micrometers, depending on the sample material and excitation energy. Due to the very thin samples in a TEM, the lateral resolution here is in the range of 1 to 10 nm.

EDS analysis is installed on all our electron microscopes.

Using the HEED method, the crystal structure of very thin crystalline samples can be analysed in the TEM.

If very thin crystalline samples/sample areas are irradiated with an electron beam of high-energy electrons (acceleration voltage e.g. 200kV), the electrons are diffracted due to the periodic arrangement of the atoms in the crystal. The prerequisite is that the wavelength of the electrons is of the same order of magnitude as the atomic spacing in the crystal.   This diffraction follows the laws of Bragg's equation and results in characteristic diffraction patterns. From the diffraction patterns, conclusions can be drawn about the lattice parameters and the symmetry of the crystalline lattice of the sample. It is interesting in this context that the diffraction pattern corresponds to the 2D Fourier transformation of the real lattice.

The elemental composition of a sample can be determined qualitatively and quantitatively using WDX. Compared to an EDX measurement, WDX is much more complex, but the energy resolution is higher and the detection limit is lower.

Wave-dispersive X-ray microanalysis (WDX) is based on the same physical processes in the sample to be examined as energy-dispersive X-ray microanalysis (EDX). When detecting the X-ray quanta emitted by the sample, WDX does not directly use the different energy contents of the X-ray quanta, but rather their different wavelengths. For each suspected element, the measuring apparatus is set up so that the characteristic wavelengths are reflected onto a suitable crystal and directed into the detector.

A measurement therefore takes considerably longer than an EDX measurement, but the detection limit is also around 10 times lower (0.01 w% to 0.1 w%) and the energy resolution is also higher, around 7-10 eV, compared to 120 to 130 eV (EDX).

The disadvantage is that a WDX measurement takes more time, as all elements can only be measured sequentially, whereas with EDX all elements of a sample are measured simultaneously. A WDX system is only available on the Zeiss Supra.