Speaker
Description
While atom probe experiments to detect hydrogen are not new, special measures had to be taken to distinguish the H detected from the specimen from the contaminant unless molecular ion formation enabled identification. This is largely due to the residual hydrogen in conventional stainless steel atom probes. The distinction was mostly made by isotope, using deuterium or recently even tritium as tracers. This somewhat limits the scope of the experiments, but has certainly been a practical approach. However, especially for imaging, the tracer approach demands voltage pulsed APT experiments, since in laser pulsed experiments the formation of molecular H species renders interpretation of ionic identity from mass-to-charge very difficult. Many hydrogen embrittled materials however only yield relatively little data when using voltage pulsing.
In order to enable pulsed laser experiments to detect H, we have equipped our ultra-low H titanium atom probe with pulsed laser, with IR (1064), green (532) and DUV (266) wavelengths at a pulse duration of 400 fs and an unpicked pulse repetition rate of 400 kHz. The authors have already demonstrated that this instrument has a consitant improvement of H background of at least two orders of magnitude over conventional APT systems with stainless steel chambers, but was so far lacking a laser. This laser has now been installed and the optics are being built up. At the workshop we will present the status of the laser setup and some first experiments. These will hopefully show if the major improvement this instrument has brought in pulsed voltage mode can also be transferred to pulsed laser experiments.
