UHV sputter system with temperature variable UHV/ in-situ scanning tunneling microscope

• Subject Area: Materials Science
• Term: Funded in 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 554851635

Investigating the storage and embrittlement behaviour of materials (M) in interaction with hydrogen (H) is essential for their use in climate-neutral hydrogen technology. For more than 25 years, Prof. Pundt has been dedicated to studying the fundamental physical behaviour of M-H materials in defect-rich or nanoscale form. Purely linear elasticity over the entire H concentration range, mechanical stresses of -10 GPa and drastically changed phase stabilities as well as suppressed twophase regions are some results of these investigations, especially for ultra-thin layers. Tunneling microscopy has proven to be an extremely powerful method, as hydride formation is detected locally and sensitively by surface topography changes. Through the appointment of Prof. Pundt to the KIT, thermodynamic models are developed that consider the contribution of mechanical stresses and various defects. The proposed temperature-variable (VT) UHV-STM will allow the detection of phase transformations in nanomaterials at different temperatures, thus enabling the determination of postulated effects in the phase diagrams. A UHV background pressure is essential, as H-affine storage materials oxidize quickly. The samples must therefore be transferred directly after preparation under UHV conditions and analyzed in the UHV-STM with exposure to a hydrogen partial pressure. Through the appointment of Prof. Pundt to the KIT, test methods that require large-area or cylindrical samples are required for hydrogen research studies. Present aim is here, to adjust the H concentration in these large-area cylindrical samples. To do this, it is necessary to sputter-clean and coat the samples, by rotating the cylindrical specimen along its longitudinal axis. This allows to remove the natural oxide layer, coat it with a protective layer (Pd or Ni) that catalyzes H uptake and then analyse its mechanical behaviour. This process will also make it possible to carry out measurements on testing machines in a direct H environment. The proposed UHV sputtering system with temperature-variable UHV/in-situ STM will enable a wide range of investigations in both subject areas and beyond, thereby generating a large number of new basic research-oriented investigations. It will thus essentially expand the potential of the department of Prof. Pundt at KIT, in which a UHV sputtering system with a UHV (and hydrogen loading) tunneling microscope (built in 1998) is successfully used for nanomaterials, by the possibility of depositing even thick layers (in the µm range), cleaning and coating large-area samples and cylindrical samples and measuring thermodynamic and kinetic properties of systems in the STM under H environment and at different temperatures.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: UHV-Sputteranlage mit temperaturvariablem UHV/in-situ H-Rastertunnelmikroskop
• Instrumentation Group: 8330 Vakuumbedampfungsanlagen und -präparieranlagen für Elektronenmikroskopie
• Applicant Institution: Karlsruher Institut für Technologie
• Leader: Professorin Dr. Astrid Pundt