Realisation of Gas Electron Holography

Jes Ærøe Hyllested

Research output: Book/ReportPh.D. thesisResearch

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Magnetic nanoparticles is an important part of today’s technology. They are used to make fertilizers and used for water purification and in medicine. Improving the understanding of how these nanoparticles work is an important field of science.
This project aims precisely at learning how magnetic nanoparticles behave when they are ex-posed to certain gasses such as hydrogen, oxygen, nitrogen and others. To gain this knowledge, we need to image the nanoparticles in a controlled gas environment. In order to do this a new technique was realized by combining environmental TEM, a special TEM allows the presence of gasses and off-axis electron holography. The result of this synergy is a new, powerful magnetic imaging technique that we named ”gas electron holography”.
Electron holography provides add an extra layer of information on top of what we can see with electron microscopy: the electric and magnetic fields produced by the object under observation. To enable off-axis electron holography the microscope needs to be equipped with a device called ”electron biprism”. In a microscope that has gas inside there is a risk corroding the electron biprism, and since the electron biprism is very expensive, a part of this project has been to design and fabricate one that is hard to damage and yet cheap to replace. The electron biprism was designed by using physics models and computer simulations, and then realized using MEMS fabrication technology.
With the electron biprism added to the microscope, gas electron holography was used to study how the presence of gas changes the coherency of the electron beam. In the end gas electron holography was used to study magnetic nanoparticles in order to gain a deeper understanding of how their magnetic properties change when heated up in various gasses.
Original languageEnglish
PublisherDTU Nanolab
Number of pages145
Publication statusPublished - 2020


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