Cryogenic ultra-high vacuum atom probe sample transfer solution

• Subject Area: Materials Science
• Term: Funded in 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 467717439

Atom probe tomography (APT) is a unique materials characterisation technique that can provide three-dimensional (3D) imaging and chemical composition measurements at the atomic scale. APT has been widely used to study a range of high-strength structural alloys, semiconductor materials and oxides. The applicant is currently leading her group to extend the application of APT to catalyst materials, e.g., catalyst nanoparticles, electrocatalysts and metal-organic frameworks that are important classes of materials used in sustainable energy conversion devices. These materials tend to be highly reactive with oxygen or humidity, or they contain light elements such as hydrogen, which is extremely mobile at room temperatures. Prior to APT analysis, these advanced materials can undergo an immense structural or elemental change during sample transfer under ambient environmental conditions, and this presents serious challenges when quantitatively characterising their 'native' state by APT. In this context, it is critical to ensure environmental protection during sample transfer. Therefore, the applicant will set up an 'atom probe sample transfer solution' that will enable the movement of samples between various sample preparation and analytical platforms under cryogenic and/or ultra-high vacuum (UHV) conditions. APT analysis generally utilises a dual beam scanning electron microscope/focused ion beam (FIB/SEM) to prepare a needle-like specimen from the bulk materials. Prior to specimen preparation, bulk materials sometimes require deposition of a metal layer in a sputter coater, which protects the surface from the energetic ion beam during specimen preparation. Transferring bulk materials to either a sputter coater or FIB/SEM, or transporting prepared APT specimens between FIB/SEM and APT, typically exposes samples to ambient environmental conditions. Thus, the following items of key equipment are requested to enable the transportation of environmentally sensitive samples under cryogenic and/or UHV conditions: (i) cryogenic UHV transfer suitcase, (ii) customised glovebox, (iii) special adaptations of the transfer suitcase on an existing FIB/SEM, sputter coater and atom probe, and (iv) a high-precision potentiostat that can be used to perform electrochemical treatments on the environmentally sensitive materials inside the glovebox. The proposed 'transfer solution' will enable the atomic-scale characterisation of air- or thermally-sensitive materials in their 'native' state. This transfer solution is urgently needed not only by the applicant's group to further expand the APT application in the new disciplines, but also for collaborative interdisciplinary research within Materials Research Department at Ruhr University Bochum (RUB).

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Kryogene Ultrahochvakuum-Transferlösung für Atomsonden-Proben
• Instrumentation Group: 8540 Tiefgefrieranlagen (flüssiger Stickstoff)
• Applicant Institution: Ruhr-Universität Bochum
• Leader: Professorin Tong Li, Ph.D.