The energy dispersive spectrometer (EDS) of scanning electron microscope is an important tool for elemental composition analysis based on the interaction between electron beam and sample. Its principle and application can be summarized as follows:
principle
The core principle of EDS is to use an electron beam to bombard the surface of the sample, excite the inner layer electrons of the sample atoms to transition, and generate characteristic X-rays. The energy level structure of electrons outside the atomic nucleus of different elements is different, and the X-ray energy released during transitions has properties (i.e. characteristic energy). By detecting the energy distribution of these X-rays, qualitative analysis of elements can be achieved; The intensity of X-rays is related to the element content, and after calibration with standard samples, semi quantitative analysis can be further completed. The specific process is as follows: X-ray photons enter the detector and excite electron hole pairs in the silicon (Si) crystal, the number of which is proportional to the photon energy. By collecting these charge signals and converting them into voltage pulses, they are classified and counted by a multi-channel analyzer, and finally generate energy dispersive spectra (EDS spectra) to determine the types and relative contents of elements in the sample.
application
Materials Science: EDS can analyze the microscopic composition distribution of metals, ceramics, polymers, and other materials, such as detecting element segregation at metal grain boundaries, impurity phases in ceramic materials, or filler distribution in polymer composite materials.
Failure analysis: Revealing the cause of failure by locating element anomalies on the fracture surface or corrosion area. For example, analyzing the oxygen content of metal fracture can determine whether it is caused by oxidative corrosion.
Geology and Minerals: Quickly identify mineral composition, such as distinguishing quartz (SiO ₂) from feldspar (KAlSi ∝ O ₈), or detecting trace beneficial elements (such as gold and silver) in ores.
Biomedical: Analyze the elemental composition of biological tissues or medical implant surfaces, such as detecting calcium and phosphorus deposition on titanium alloy implant surfaces and evaluating bone integration effects.
Industrial quality inspection: Monitor the thickness and composition uniformity of surface coatings on products, such as detecting the gold (Au) content in electronic component coatings or analyzing anti-corrosion coatings on automotive components.
technical advantage
EDS combined with scanning electron microscopy (SEM) can achieve simultaneous morphology observation and composition analysis at the microscale (micrometer to nanometer level), with fast analysis speed (usually completed within a few minutes) and minimal damage to the sample. It is suitable for various forms of samples such as solids, powders, and films. Its limitation lies in the fact that quantitative accuracy is affected by factors such as sample conductivity and surface flatness, and needs to be improved by combining standard samples or calibration methods.