Characterization of Nanoporous Materials with Atom Probe Tomography

Abstract

A method to characterize open-cell nanoporous materials with atom probe tomography (APT) has been developed. For this, open-cell nanoporous gold with pore diameters of around 50 nm was used as a model system, and filled by electron beam-induced deposition (EBID) to obtain a compact material. Two different EBID precursors were successfully tested-dicobalt octacarbonyl [Co2(CO)8] and diiron nonacarbonyl [Fe2(CO)9]. Penetration and filling depth are sufficient for focused ion beam-based APT sample preparation. With this approach, stable APT analysis of the nanoporous material can be performed. Reconstruction reveals the composition of the deposited precursor and the nanoporous material, as well as chemical information of the interfaces between them. Thus, it is shown that, using an appropriate EBID process, local chemical information in three dimensions with sub-nanometer resolution can be obtained from nanoporous materials using APT.

Electron Beam-Induced Deposition for Atom Probe Tomography Specimen Capping Layers

“…Composition of the Co and Fe layers as measured by the two techniques agreed quite nicely. The Co deposition was shown to be 80 at% Co and roughly 10 at% each of C and O, which is in the range of values seen by others for this precursor (Utke et al, 2005; Fernández-Pacheco et al, 2009; Córdoba et al, 2010; Mulders et al, 2011; Pfeiffer et al, 2015). The Fe deposition was ~60 at% Fe and 40 at% O.…”

“…The Fe deposition was ~60 at% Fe and 40 at% O. These values are quite a bit different than previous reports using the same precursor, where ~15 at% C, 15 at% O, and 70 at% Fe was seen for deposition on a SiO 2 substrate (Lavrijsen et al, 2011) and~2 at% C, 2 at% O, and 96 at% Fe was seen for deposition on gold (Pfeiffer et al, 2015). This variability suggests that deposition conditions, particularly the substrate material, may exert a large influence over the final composition.…”

A Liquid Metal Encapsulation for Analyzing Porous Nanomaterials by Atom Probe Tomography

“…Many recent studies have sought to apply APT to porous materials (El-Zoka et al, 2017;Mouton et al, 2017;Barroo et al, 2019), nanoparticles (Li et al, 2014;Yang et al, 2019;Lim et al, 2020), and materials with cracks (Meisnar et al, 2015) or voids (Wang et al, 2020). Leaving these pores and cracks open introduces stress concentrators that make specimen preparation difficult and complicate the reconstruction of the analyzed specimens due to trajectory aberrations and premature fractures during analysis (Pfeiffer et al, 2015). To deal with this problem, the APT community has established the elimination of these pores/voids/cracks using foreign chemical methods, for instance, electrodeposition (El-Zoka et al, 2018a;Kim et al, 2020), electron beam-induced deposition (Barroo et al, 2020), atomic layer deposition (Larson et al, 2015), organic polymer resin deposition (Perea et al, 2016), and other physical or chemical vapor deposition methods (Felfer et al, 2014(Felfer et al, , 2015Taylor et al, 2019).…”

Atom Probe Tomography for Catalysis Applications: A Review

“…The first example consists of the analysis of Au 30 -Ag 70 materials dealloyed in HNO 3 by free corrosion [172], generating a nanoporous gold sample-npAu-with pores of~50 nm in diameter (Figure 13a-inset). Two precursors were used to fill the pores and get a compact material: Co 2 (CO) 8 and Fe 2 (CO) 9 , both precursors yielding relatively high purity metals as compared to more classical precursors (Pt-and W-based).…”