Ion-probe analysis

Steele I. M. and Smith J. V. (1982). Ion probe analysis of plagioclase in three howardites and three eucrites. Geochim. Cosmochim. Acta, 42 959-971. 

Chemical compositions of chondrules have been determined from extracted samples using neutron activation analysis and by in situ analysis in polished sections using electron microprobe and ion probe analysis (see e.g., Gooding et al, 1980 Grossman et al, 1988 Alexander, 1995). Chondrules typically show flat refractory abundances that are relatively close to the mean chondrite value and abundances of moderately volatile elements that scatter more widely about the mean. Type II chondrules are relatively unfractionated with near-CI levels of refractories and moderately volatile elements. However, type I chondrules show systematic depletions of moderately volatile elements and a broader spread of refractory abundances with the silicon-rich type IB chondrules being poorer in refractories than the silicon-poor type IA chondrules (Figure 18). The source of the fractionations in type I chondrules is discussed below. 

Deloule E., Albarede F., and Sheppard S. M. F. (1991) Hydrogen isotope heterogeneities in the mantle from ion probe analysis of amphiboles from ultramafic rocks. Earth Planet Sci. Lett 105, 543-553. 

Analysis of solid surfaces in terms of elemental composition is an important problem in modern research. Mass spectrometry, as secondary-ion mass spectrometry (SIMS) or ion-probe analysis [17], can play a useful role. 

Jones, A.P, Smith, J.V. (1984) Ion probe analysis of H, Li, B, F and Ba in micas with additional data for metamor-phic amphibole, scapolite and pyroxene. Neues Jahrb. Min. Mon., 5, 228-240. 

The La and Ce data ate upper limits and ate not included in the regression. Although not shown, it is probable that this REE pattern will have a substantial negative Eu ano-maly at low f02 [96]. Although not shown, the study of [5], using ion probe analysis, confirms the pattern of [93] and extends it to the light rare earths (LREE). The low Sr partition coefficient of Beattie [5], 5 x 10-5 to 1.1 xlO, also confirms the presence of a Eu anomaly at low fo2. 

Lauchli, A., Spurr, A.R. Wittkop, R.W. (1970). Electron probe analysis of freeze substituted, epoxy resin embedded tissue for ion transport studies in plants. Planta, 95, 341-50. 

Ion Beam Analysis (IBA) utilizes high-energy ion beams to probe the elemental composition of the surface of a specimen in a non-destructive way. It can establish the composition as a function of depth to several microns, with a typical depth resolution of 10-20 nm. It is a fast and standardless technique which quantifies the absolute atomic ratios, and can also determine the film thickness. 

Figure 12. Class searches from solids probe analysis of ambient filter samplenegative ion CI(CH ) accurate mass fragmentograms...

In field ion microscopy, one would also like to know how the field distributes itself above an emitter surface. This information is important in the quantitative interpretation of many field ion emission phenomena and experiments. It is also important in calculating the ion trajectory to enable a proper aiming in an atom-probe analysis. Unfortunately, not only does each tip have its own particular shape, but the presence of lattice steps also complicates the situation immensely. There are so far no reliable calculations for the field distribution above an emitter surface, nor for predictng the ion trajectory, nor yet for where the probe-hole... 

Assuming that/A is 0.01, and we would like to determine this value with the atom-probe to an accuracy of 5% of fA, then the number of ions collected should be at least 39 600. This is already near an impractically large number in the atom-probe analysis. It quickly becomes impractical to determine accurately the concentration of a minority species with the atom-probe at a low counting rate if its concentration is smaller than —0.5%. The following statistical analysis points to a method with which this difficulty can be overcome. 

As one of the alloy species may not be imaged, either because it is completely field evaporated or from the lack of field ionization or both, it is possible to distinguish atoms of different alloy species from the field ion image alone without relying on atom-probe analysis. In fact this method can identify constituent atoms in an ordered alloy without the aiming error of the atom-probe. Misplaced atoms in an ordered alloy, i.e. atoms... 

Fig. 4.44 (a) The simplest method in atom-probe analysis is to fix the probe-hole to a spot near the center of the plane one intends to analyze. For an ordered AB alloy, the cumulative number of A and B ions detected will look like (u) if the plane is a fundamental plane. The volume sampled is shown in Hi). (b) Another method is having the probe-hole always aimed at the edge of the top layer. The volume sampled will be that shown in (if). 

Fig. 4.51 35 K helium field ion image of polycrystallinc tungsten silicide layers grown on a W emitter surface. Atom-probe analysis shows that the stoichiometry is WSi2. Images of a few crystal planes of WSi2 have also already been shown in Fig. 4.14. The dark area is the hole of the 45° mirror of the atom-probe.

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