Low Energy Ion Scattering (LEIS) is a surface analysis technique almost exclusively sensitive to a topmost layer composition. We recently found out that in a rare selection of materials a contribution of second layer scattering is pronounced. This effect was observed before for very “open” crystal planes with low atomic density, but in our case the explanation is completely different and much more interesting. We believe it is connected to a high ion survival fraction in the material. To properly justify our theory ion fraction has to be measured on a number of different surfaces, composed of different elements. This is mostly a pure experimental task, which involves a healthy amount of challenge of systematically collecting LEIS spectra for different ion energies for every given surface. We expect that the data obtained in this bachelor project will be the experimental basis of a paper we plan to publish on this topic. Bachelor students are welcome to participate in the paper.
This project aims for the development of multilayer systems for the use as spectroscopic elements. These serve the purpose of analyzing soft x-ray emission spectra of materials e.g. upon excitation by x-rays or electrons. The analysis then allows the quantitative determination of the x-ray emitting elements in the materials, a technique which in the final application reaches great precision, preferably down to the ppb range. The desired wavelength range for this application is in the 10 to a few nm band, with emphasis on the range below 6 nm, including the so-called water window, below 4.4 nm. To reach substantial reflectivity, the multilayered optics need to have atomically sharp layer interfaces. To meet this extreme requirement, different approaches on layer growth manipulation will be applied: low-energy ion beams during the layer deposition process, thermalized particle deposition, unbalanced magnetron sputtering with high flux of low energy particles. Other new approaches are continuously being proposed and tested. A series of metrology techniques is to be applied: at-wavelength reflectometry, Cu-Kα-reflectometry and diffraction, low energy ion scattering, XPS, AES, AFM, STM, and TEM.
Synthesis of atomically thin multilayer structures with thermalized particles and low energy ions.
Graphene is a mechanically strong and optically transparent material suited for fabricating freestanding conductive see-through membranes for numerous applications such as filtration, sensor and optic applications. The challenge of graphene is to make it more chemical resistive, especially during plasma treatments. This could increase the lifetime of the graphene for several applications such as EUV optics, see also: https://doi.org/10.3990/1.9789036546577 and https://doi.org/10.1117/12.2280560.
Characterize the etching process of multi-layer graphene in harsh reactive environments such as H2 and O2 plasma as function of process power and time
Investigate to what extent a protective layer increases the chemical resistivity of graphene for these reactive plasma treatments
Work in the Nanolab cleanroom: attend necessary introductions/courses to work with plasma systems
Literature study on the chemistry of graphene surfaces which could lead to etching
Compose a project plan of the proposed research
Perform reactive plasma exposure test to graphene with and without protective layer
Characterize this etching process in terms of etch rate