Atom probe instrument for the imaging of hydrogen in materials – laser pulsing / detector upgrade

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APT has been widely used to study a range of high-strength structural alloys, semiconductor materials and oxides. It is uniquely suited for the imaging and analysis of all chemical elements in a sample without bias and with equal sensitivity. At FAU we aim to be on the forefront of atom probe tomography research. This includes in-house developed systems with special capabilities. Up to recently, APT excluded the imaging and analysis of hydrogen due to contamination from the stainless-steel chambers used. The in-house developed systems include a high-end instrument with titanium interior and chamber, resulting in an ultra-low hydrogen background for direct detection of hydrogen1. This instrument is the first and currently only one world-wide to achieve this. It can provide imaging and analysis for all chemical elements with equal sensitivity. This is especially important for the research on materials for the hydrogen economy. In this proposal we seek the upgrade of this ultra-low H atom probe system to state-of-the-art laser assisted field evaporation with an adequate digital front-end detector. This will serve multiple purposes. Firstly, it will allow the analysis of hydrogen in non-conductive materials and greatly increase the data yield on conductive specimens. Secondly, it will improve the detection efficiency of non-random detector hits, which are especially prevalent in laser-assisted atom probe tomography and therefore increase the analysis accuracy. Thirdly, it will enable us to analyse non-conductive materials with high detection efficiency (> 80% of all atoms), complementary to our existing instrument, which provides < 40 % detection efficiency albeit at high mass resolution. The upgrade consists of: (i) a tuneable deep-UV fs laser with < 300 nm minimum wavelength, > 1000 pJ pulse energy and a pulse repetition rate > 200 kHz, including optics for diffraction limited focussing and spot positioning. (ii) A delayline detector (detector head, high voltage power supply and pre-amplifier) with at least one redundant delayline and direct digitization with ≥ 2.5 GSa/s/ch on at least one channel per delayline endpoint. The atom probe laser upgrade applied for here will used in a broad research environment of materials research at FAU. The starting point is the Institute for General Materials Properties (WW1), where the fascinating possibilities of the atom probe are used very profitably in different areas (e.g. lightweight construction materials, catalysis, particle technology) and together with our collaboration partners (TU Wien, MU Leoben / Uni Innsbruck, Paul Scherrer Institute, Oak Ridge National Lab and more). The atom probe upgrade will also continue to enrich research at important FAU institutes, such as the Central Institute for New Materials and Process Technology, ZMP, and the Helmholtz Institute Erlangen-Nuremberg, which focuses on materials research for renewable energies.