Energy-Dispersive X-ray Spectroscopy (EDX) is a method for determining the elemental composition of materials. It is of great value in various fields, including industry, geology, and medical science. At Sioux, we develop and produce the Ultra-X. This detection system for the Spectra Ultra S/TEM, a high-end transmission electron microscope from Thermo Fisher Scientific, represents the pinnacle of EDX technology.
Written by: Kees Kooijman and Marnix Tas, Senior System Architects at Sioux
EDX is not a new technology. Introduced in the late 1960s, it has since evolved into a sophisticated and widely used application for analysing materials. With EDX, the chemical elements in samples can be identified with great accuracy, determining, for example, the composition of alloys, minerals, and organic substances.
Significant value
EDX has numerous applications. These include analysing the positioning of elements such as silicon and nickel on semiconductors, as well as thin layers of materials deposited using atomic layer deposition (ALD) and other techniques, notably by manufacturers of next-generation batteries and solar panels. Another example involves determining the composition of stainless steel in the steel industry. In life sciences, EDX can map organic material such as proteins in viruses. Additionally, EDX is invaluable in forensic investigations, including the determination of gunpowder residues, and can even be used to ascertain the composition of pigments in old paintings.
Every element
How does EDX work? The first step is to fire electrons at a sample. These electrons interact with the atoms in the material. Electrons in the inner shell are ejected, and electrons from the outer shell take their place. This process emits X-rays with specific energies. For example, copper and iron emit X-rays with energies of 8 and 7 kilo-electron volts, respectively, and each element in the periodic table has its own characteristic signature. This radiation is measured by a detector that converts the X-rays into electrons. By analysing the energy spectrum, the composition of the material can then be determined.
Peak achievement
Sioux is a strategic partner of Thermo Fisher Scientific, the global leader in the development and manufacturing of electron microscopes. We collaborate on various R&D programs in areas such as software development, system integration, electron optics, and sample management. Our collaboration reached a peak with the development of the Ultra-X, a detection system for the Spectra Ultra S/TEM, a high-end transmission electron microscope. Sioux was responsible for the development of this EDX module, and we now also produce it.
‘Every electron counts’
The Ultra-X allows individual atoms to be irradiated with an electron beam. This enables elements in a sample to be imaged with a resolution of up to 50 picometers, showing their structure and position. Moreover, this can be done rapidly and under dynamic conditions. It is also an extremely sensitive detection device. Thermo Fisher Scientific's motto in developing electron microscopes is ‘every electron counts’. The Ultra-X lives up to this. X-rays generated in the module scatter in all directions. To detect them maximally, the surface of the small space is packed with sensors. This minimizes information loss.
Multiple disciplines
In 2021, the Ultra-X was awarded by Guinness World Records as the most sensitive X-ray detector on Earth. The following year, the detection system was recognized as one of the best microscopy innovations at the Microscopy Today Innovation Awards. With the development of the Ultra-X, Sioux, together with Thermo Fisher Scientific, has taken the ultimate step in EDX. It is practically impossible to capture more X-ray quanta from a sample within the electron microscope. Thus, the end of the technological roadmap in terms of sensitivity has almost been reached. This required the input of many disciplines within Sioux, including signal processing, mechanics, electronics, software, and mathematics.
Plug and play
The Ultra-X moves in and out of a vacuum chamber of the Spectra Ultra S/TEM. This occurs under very clean conditions to prevent contamination of the measurement results, and with micrometer precision. Furthermore, it is a plug-and-play module. Thermo Fisher Scientific engineers receive it fully assembled from Sioux. They essentially only need to slide it into the microscope, calibrate it, and it works. No further testing is required. This also makes the Ultra-X a mechanical masterpiece.
Factor 10
Sioux has also developed the Ultra-X’s control software. This is fully integrated into the microscope’s software, preventing collisions with other modules, which would lead to long downtimes and high costs. Additionally, this software ensures that the module can be rapidly inserted into the microscope using compressed air cylinders. Where this took half a minute in an earlier version, it now takes only a few seconds. Besides the reduction in measurement time due to the enormous sensitivity, the time savings are significant; images can be captured up to 10 times faster.
Plus or minus 2 electrons
The electronics developed for the Ultra-X are next-level. The measured X-rays arrive as very weak signals, barely distinguishable from noise. Using advanced signal processing, detection is accurate to 15 electrons, with an uncertainty of plus or minus 2 electrons. This also makes the Ultra-X an extremely sensitive detector. Our mathware specialists also made a significant contribution to optimizing the detection module; adjusting many parameters in the system for optimal performance. They also developed advanced algorithms that can detect very low energies hidden in the noise. Thus, no electron is lost.
Meticulous workflow
Sioux has been producing the Ultra-X since 2021. To ensure high-quality serial production, production machines were developed and built, a cleanroom was established, a meticulous workflow was set up, personnel were trained, and the supply chain was established. Much of the work is done manually. This requires extreme discipline from the assembly team, particularly in terms of cleanliness, sequence of operations, precision, and control.
Further Development
With the Ultra-X, we have set a new standard in the world of EDX analysis. A faster and more sensitive detection instrument than the Ultra-X does not exist. However, there are still steps to be taken in advancing this technology, especially in analysing sensitive biological samples and determining light elements. For example, bromine, beryllium, and lithium are still difficult to detect using EDX due to the weak X-ray radiation and thus low energy they emit. Sioux continues to invest in the further development of EDX, also with a focus on user-friendliness. Additionally, we are looking for new customers who wish to apply this technology in their specific market domains.
