The three-dimensional atom probe (3DAP) is one of the ways to image materials three-dimensionally on atomic scale. However, some technical issues in 3DAP are still unresolved. One of them is the rupture of a specimen that sometimes occurs when the atoms are field-evaporated at the apex of a needle specimen. This is caused by the high electric stress around the tip of the needle specimen. One way to reduce the stress is to enlarge the taper angle of the needle specimen. In this study, adapting this idea to 3DAP, we estimated the appropriate values of not only the taper angle of the needle specimen but also its diameter, length, radius of curvature, and distance between the tip and local electrode by simulation. Furthermore, we calculated the average value of field-induced stress on each plane for z-direction in the specimen.
Three-dimensional atom probe (3DAP) equipped with a newly designed preset-type sample stage has been developed. This new type of sample stage can reduce the costs of constructing a 3DAP instrument, and this instrument consists of quite simple components because the complicated mechanism to make any desired adjustment is no longer required to be done in a vacuum. These advantages are expected to lead to the wider distribution of 3DAP.In addition, a wider range of applications is also expected in our equipment because the atoms can be field-evaporated by means of either high-voltage pulses or femto-second laser pulses. In this article, the performance of the pulse voltage mode and pulse laser mode are described and illustrated through the investigation of metals.
Three-dimensional atom probe (3DAP) has been developed in our laboratory. In our instrument, the position-sensitive detector with a diameter of 120 mm following a pair of microchannel plates (MCP) was set up at a distance of 110 mm in front of the apex of the sample. Our original preset-type sample stage with a local microelectrode was adopted. The pulse laser, or voltage pulse, was used as a trigger for field evaporation. The pulse width of the laser was 180 fs at a wavelength of 1030 nm. The pulse width of the voltage pulse was less than 10 ns. The performance of our instrument was widely tested with the pure tungsten samples fabricated by the electropolishing and focused ion beam methods. The flight path compensation of detected ions, including the small inclination of MCP assembly, led to the good mass resolution approximately 220 (FWHM). By this compensation, we realized full 0.75 sr acceptable angle 3DAP. The detection efficiency of emitted ions was estimated to be about 50% from the three-dimensional reconstruction images of samples.
This paper reports the evaluation and operation of laser pulse assisted three-dimensional atom probe (3DAP). With wide angle acceptance using femto second pulse laser, high speed time to digital converter, and newly designed sample-extraction electrode integrated sample holder, we can get high performance, easy to treat and wide angle 3DAP. The change of the resolution in the application to pure metals such as Mo was observed when the laser condition (laser polarization and implied voltage) was changed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.