METHOD ARTICLE Hydrogen and deuterium charging of lifted-out specimens for atom probe tomography [version 2; peer review: 2 approved] Heena Khanchandani 1 , Se-Ho Kim 1 , Rama Srinivas Varanasi 1 , TS Prithiv 1 , Leigh T. Stephenson 1 , Baptiste Gault 1,2 1 Max-Planck-Institut für Eisenforschung, Max-Planck-Str. 1, Düsseldorf, 40237, Germany 2 Department of Materials, Royal School of Mines, Imperial College, Prince Consort Road, London, SW7 2BP, UK First published: 14 Oct 2021, 1:122 https://doi.org/10.12688/openreseurope.14176.1 Latest published: 21 Feb 2022, 1:122 https://doi.org/10.12688/openreseurope.14176.2 v2 Abstract Hydrogen embrittlement can cause a dramatic deterioration of the mechanical properties of high-strength metallic materials. Despite decades of experimental and modelling studies, the exact underlying mechanisms behind hydrogen embrittlement remain elusive. To unlock understanding of the mechanism and thereby help mitigate the influence of hydrogen and the associated embrittlement, it is essential to examine the interactions of hydrogen with structural defects such as grain boundaries, dislocations and stacking faults. Atom probe tomography (APT) can, in principle, analyse hydrogen located specifically at such microstructural features but faces strong challenges when it comes to charging specimens with hydrogen or deuterium. Here, we describe three different workflows enabling hydrogen/deuterium charging of site-specific APT specimens: namely cathodic, plasma and gas charging. All the experiments in the current study have been performed on a model twinning induced plasticity steel alloy. We discuss in detail the caveats of the different approaches in order to help future research efforts and facilitate further studies of hydrogen in metals. Our study demonstrates successful cathodic and gas charging, with the latter being more promising for the analysis of the high-strength steels at the core of our work. Keywords atom probe tomography, hydrogen embrittlement, hydrogen trapping sites, twinning induced plasticity steel, cryogenic transfer workflows Open Peer Review Approval Status 1 2 version 2 (revision) 21 Feb 2022 view view version 1 14 Oct 2021 view view Maria Auger , University of Oxford, Oxford, UK 1. Gregory Thompson, University of Alabama, Tuscaloosa, USA 2. Any reports and responses or comments on the article can be found at the end of the article. Open Research Europe Page 1 of 25 Open Research Europe 2022, 1:122 Last updated: 07 MAR 2022