Six precursors were evaluated for use as in situ electron beam-induced deposition capping layers in the preparation of atom probe tomography specimens with a focus on near-surface features where some of the deposition is retained at the specimen apex. Specimens were prepared by deposition of each precursor onto silicon posts and shaped into sub-70-nm radii needles using a focused ion beam. The utility of the depositions was assessed using several criteria including composition and uniformity, evaporation behavior and evaporation fields, and depth of Ga+ ion penetration. Atom probe analyses through depositions of methyl cyclopentadienyl platinum trimethyl, palladium hexafluoroacetylacetonate, and dimethyl-gold-acetylacetonate [Me2Au(acac)] were all found to result in tip fracture at voltages exceeding 3 kV. Examination of the deposition using Me2Au(acac) plus flowing O2 was inconclusive due to evaporation of surface silicon from below the deposition under all analysis conditions. Dicobalt octacarbonyl [Co2(CO)8] and diiron nonacarbonyl [Fe2(CO)9] depositions were found to be effective as in situ capping materials for the silicon specimens. Their very different evaporation fields [36 V/nm for Co2(CO)8 and 21 V/nm for Fe2(CO)9] provide options for achieving reasonably close matching of the evaporation field between the capping material and many materials of interest.

We demonstrate direct electron beam writing of a nano-scale Cu pattern on a surface with a thin aqueous layer of CuSO4 solution. Electron beams are highly maneuverable down to nano-scales. Aqueous solutions facilitate a plentiful metal ion supply for practical industrial applications, which may require continued reliable writing of sophisticated patterns. A thin aqueous layer on a surface helps to confine the writing on the surface. For this demonstration, liquid sample holder (K-kit) for transmission electron microscope (TEM) was employed to form a sealed space in a TEM. The aqueous CuSO4 solution inside the sample holder was allowed to partially dry until a uniform thin layer was left on the surface. The electron beam thus reduced Cu ions in the solution to form the desired patterns. Furthermore, the influence of e-beam exposure time and CuSO4(aq) concentration on the Cu reduction was studied in this work. Two growth stages of Cu were shown in the plot of Cu thickness versus e-beam exposure time. The measured Cu reduction rate was found to be proportional to the CuSO4(aq) concentration.

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.