title: Electron Beam-Induced Deposition for Atom Probe Tomography Specimen Capping Layers.
abstract: 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.
authors.affiliation: 1Department of Metallurgical and Materials Engineering,Colorado School of Mines,Golden,CO 80401,USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Diercks
authors.affiliation: 1Department of Metallurgical and Materials Engineering,Colorado School of Mines,Golden,CO 80401,USA.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Gorman
authors.affiliation: 2FEI Electron Optics,5600 KA Eindhoven,The Netherlands.
authors.forename: Johannes J L
authors.initials: JJL
authors.lastname: Mulders
keywords: atom probe tomography; dicobalt octacarbonyl; diiron nonacarbonyl; electron beam-induced deposition; evaporation field