New approaches to nanoparticle sample fabrication for atom probe tomography

Abstract

Due to their unique properties, nano-sized materials such as nanoparticles and nanowires are receiving considerable attention. However, little data is available about their chemical makeup at the atomic scale, especially in three dimensions (3D). Atom probe tomography is able to answer many important questions about these materials if the challenge of producing a suitable sample can be overcome. In order to achieve this, the nanomaterial needs to be positioned within the end of a tip and fixed there so the sample possesses sufficient structural integrity for analysis. Here we provide a detailed description of various techniques that have been used to position nanoparticles on substrates for atom probe analysis. In some of the approaches, this is combined with deposition techniques to incorporate the particles into a solid matrix, and focused ion beam processing is then used to fabricate atom probe samples from this composite. Using these approaches, data has been achieved from 10-20 nm core-shell nanoparticles that were extracted directly from suspension (i.e. with no chemical modification) with a resolution of better than ± 1 nm.

Acidity enhancement through synergy of penta- and tetra-coordinated aluminum species in amorphous silica networks

“…A drop of the diluted dispersed ASA nanoparticles in methanol (≈0.01 mol/L) was placed onto a Si flat wafer, which was covered by a 150-nm thick protective Cr layer in Leica EM ACE600. Needle-shaped APT specimens were prepared from the Si flat sample by a site-specific lift-out procedure using a FEI G4 CX focused ion beam (FIB)/scanning electron microscope 66 . The APT experiments were conducted on a CAMECA LEAP 5000 XR instrument equipped with an ultraviolet laser with a spot size of 2 µm and a wavelength of 355 nm.…”

Atom Probe Tomography: Development and Application to the Geosciences

“…However, a number of studies have successfully developed specimen preparation techniques based around electrophoresis (Tedsree et al ), encapsulation (Heck et al , Larson et al , Yang et al ) and agglomerated powder lift‐out (Xiang et al ). Each approach has benefits and disadvantages (see review by Felfer et al ) depending on the nature of the nanoparticles being analysed. Further work is needed in this area for optimisation of nanoparticulate analysis of geological materials.…”

Atomic worlds: Current state and future of atom probe tomography in geoscience

“…Further developments in specimen preparation will also enable a wider range of geological samples to be targeted, by providing robust methods for the analysis of nanoparticulate materials [33,64], or specimen preparation and coating methods to allow nanoporous or weakly-bonded materials to be analysed [64].…”