Atom probe microscopy specimens can be damaged by exposure to various common environmental conditions (air, moisture, ambient temperatures) and, addressing this unintentional damage, various well-designed specimen transfer systems have been designed (University of Oxford [1], Universität Göttingen [2], Iowa State University [3], Friedrich-Alexander Universität [4], Pacific Northwest National Laboratory [5], Sydney University [6]). We have previously described our use of cryogenically-cooled ultra-high vacuum carry transfer suitcases [7], jointly developed by Ferrovac GmbH, MPIE and Cameca Instruments [8]. These suitcases allowed cryogenic transfer of specimens between two atom probes (LEAP 5000XS/XR), a cryogenically-equipped dualbeam Xe-plasma FIB (FEI Helios) and an N2 glovebox (Sylatec).
Transfer systems are sometimes combined with an environmental treatment hub for experiments designed to intentionally modify a specimen by controlled environmental exposure (gaseous mixtures, electrochemical cells, various temperature schedules). At MPIE, one approach in this direction was the development of the “ReactHub Module”, jointly designed by the institutions listed in the author summary. It allows for versatile experiments with controlled reactive gas delivery and precisely controlled laser heating. A specimen is seated in a standard atom probe puck and is mounted on a specially designed steel grid or is otherwise free-standing. It can then be exposed to mixtures of ultra-high purity gases (N2, O2, CO, H2) at controlled pressures as low as 10-6 millibar or as high as 1 atmosphere, the exact gas mixture being analysed by an online mass spectrometer. The ReactHub uses an innovative laser heating system with integrated optical targeting and pyrometry to allow calibrated temperature reading with an expected range of 250-1100°C and a cryo-stage that allows for immediate quenching to a minimum temperature of 45K. Following treatment, the specimen can be transferred via suitcase to the p-FIB or a LEAP. We shall here present the technical challenges and the latest atom probe experiments.