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Title: Mass fractionation of carbon and hydrogen secondary ions upon Cs{sup +} and O{sub 2}{sup +} bombardment of organic materials

Abstract

A phenomenon known as mass fractionation has been probed in organic materials using secondary ion mass spectrometry (SIMS). Mass fractionation occurs because two isotopes of a particular species (i.e., identical number of protons, but different number of neutrons) do not have identical secondary ion yields in a constant chemical environment. Two primary ion probes, Cs{sup +} and O{sub 2}{sup +}, have been utilized with detection of negative and positive secondary ions, respectively, using a magnetic sector mass spectrometer. These two analysis conditions have been found to yield considerably different mass fractionation effects as a result of different sputtering and ionization mechanisms. Also, as determined previously with SIMS analysis of inorganic materials, the lower molecular weight species carbon and hydrogen are particularly susceptible to mass fractionation effects. Because organic materials are primarily composed of carbon and hydrogen, and because isotopic labeling is often utilized to accurately analyze such materials, knowledge of these effects in organic materials is essential for quantitative SIMS analysis.

Authors:
; ; ; ;  [1];  [2];  [2];  [2]
  1. Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20979367
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films; Journal Volume: 25; Journal Issue: 3; Other Information: DOI: 10.1116/1.2718957; (c) 2007 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CARBON; CESIUM IONS; FRACTIONATION; HYDROGEN; ION BEAMS; ION MICROPROBE ANALYSIS; ION PROBES; IONIZATION; MASS; MASS SPECTRA; MASS SPECTROSCOPY; MOLECULAR WEIGHT; ORGANIC COMPOUNDS; ORGANIC MATTER; OXYGEN IONS; SPUTTERING

Citation Formats

Harton, Shane E., Zhu Zhengmao, Stevie, Frederick A., Griffis, Dieter P., Ade, Harald, Analytical Instrumentation Facility, North Carolina State University, Raleigh, North Carolina 27695, Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 and Analytical Instrumentation Facility, North Carolina State University, Raleigh, North Carolina 27695, and Department of Physics, North Carolina State University, Raleigh, North Carolina 27695. Mass fractionation of carbon and hydrogen secondary ions upon Cs{sup +} and O{sub 2}{sup +} bombardment of organic materials. United States: N. p., 2007. Web. doi:10.1116/1.2718957.
Harton, Shane E., Zhu Zhengmao, Stevie, Frederick A., Griffis, Dieter P., Ade, Harald, Analytical Instrumentation Facility, North Carolina State University, Raleigh, North Carolina 27695, Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 and Analytical Instrumentation Facility, North Carolina State University, Raleigh, North Carolina 27695, & Department of Physics, North Carolina State University, Raleigh, North Carolina 27695. Mass fractionation of carbon and hydrogen secondary ions upon Cs{sup +} and O{sub 2}{sup +} bombardment of organic materials. United States. doi:10.1116/1.2718957.
Harton, Shane E., Zhu Zhengmao, Stevie, Frederick A., Griffis, Dieter P., Ade, Harald, Analytical Instrumentation Facility, North Carolina State University, Raleigh, North Carolina 27695, Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 and Analytical Instrumentation Facility, North Carolina State University, Raleigh, North Carolina 27695, and Department of Physics, North Carolina State University, Raleigh, North Carolina 27695. Tue . "Mass fractionation of carbon and hydrogen secondary ions upon Cs{sup +} and O{sub 2}{sup +} bombardment of organic materials". United States. doi:10.1116/1.2718957.
@article{osti_20979367,
title = {Mass fractionation of carbon and hydrogen secondary ions upon Cs{sup +} and O{sub 2}{sup +} bombardment of organic materials},
author = {Harton, Shane E. and Zhu Zhengmao and Stevie, Frederick A. and Griffis, Dieter P. and Ade, Harald and Analytical Instrumentation Facility, North Carolina State University, Raleigh, North Carolina 27695 and Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 and Analytical Instrumentation Facility, North Carolina State University, Raleigh, North Carolina 27695 and Department of Physics, North Carolina State University, Raleigh, North Carolina 27695},
abstractNote = {A phenomenon known as mass fractionation has been probed in organic materials using secondary ion mass spectrometry (SIMS). Mass fractionation occurs because two isotopes of a particular species (i.e., identical number of protons, but different number of neutrons) do not have identical secondary ion yields in a constant chemical environment. Two primary ion probes, Cs{sup +} and O{sub 2}{sup +}, have been utilized with detection of negative and positive secondary ions, respectively, using a magnetic sector mass spectrometer. These two analysis conditions have been found to yield considerably different mass fractionation effects as a result of different sputtering and ionization mechanisms. Also, as determined previously with SIMS analysis of inorganic materials, the lower molecular weight species carbon and hydrogen are particularly susceptible to mass fractionation effects. Because organic materials are primarily composed of carbon and hydrogen, and because isotopic labeling is often utilized to accurately analyze such materials, knowledge of these effects in organic materials is essential for quantitative SIMS analysis.},
doi = {10.1116/1.2718957},
journal = {Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films},
number = 3,
volume = 25,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • Thin planar polymer films are model systems in a number of fields, including nano- and biotechnology. In contrast to reciprocal space techniques such as reflectivity or diffraction, secondary ion mass spectrometry (SIMS) can provide depth profiles of tracer labeled polymers in real space directly with sufficient depth resolution to characterize many important aspects in these systems. Yet, continued improvements in characterization methods are highly desirable in order to optimize the trade-offs between depth resolution, mass resolution, detection sensitivity, data acquisition time, and artifacts. In this context, the utility of a magnetic sector SIMS instrument for amorphous polymer film analysis wasmore » evaluated using model polymer bilayer systems of polystyrene (PS) with poly(methyl methacrylate) (PMMA), PS with poly(2-vinylpyridine), and poly(cyclohexyl methacrylate) (PCHMA) with PMMA. Deuterium-labeled polystyrene embedded in PS or PCHMA at concentrations ranging from 5% to 20%(v/v) was used as tracer polymer. Analysis conditions for a magnetic sector SIMS instrument (CAMECA IMS-6f) were varied to achieve a depth resolution of {approx}10 nm, high signal/noise ratios, and high sensitivity, while minimizing matrix effects and sample charging. Use of Cs{sup +} and O{sub 2}{sup +} primary ions with detection of negative and positive secondary ions, respectively, has been explored. Primary beam impact energy and primary ion species have been shown to affect matrix secondary ion yields. Sputtering rates have been determined for PS and PMMA using both primary ion species and referenced to values for intrinsic (100) silicon (Si) under identical analysis conditions.« less
  • Equilibrium isotope exchange reactions have been examined for transfer of H/sup +/(D/sup +/), H/sub 3/O/sup +/(H/sub 2/OD/sup +/, HOD/sub 2//sup +/, D/sub 3/O/sup +/), F/sup -/, and Cl/sup -/ among H/sub 2/O, HOD, and D/sub 2/O. In each case ions are found to be more favorably coordinated to H/sub 2/O rather then D/sub 2/O. These results are compared to similar data for ions in H/sub 2/O or D/sub 2/O solution. Statistical thermodynamic arguments are presented which imply that rotational effects play an important role in determination of the overall isotope effect, in addition to the more commonly considered zero-point energymore » effects. The important role of the inversion mode of H/sub 3/O/sup +/ on the isotope effect is considered. Implications for isotope fractionation in the interstellar medium are discussed.« less
  • Changes in secondary ion yields of matrix and dopant species have been correlated with changes in surface topography during O/sup +//sub 2/ bombardment of Si and GaAs. In Si, profiles were measured in (100) wafers at 6- and 8-keV impact energy. At 6 keV, a yield increase of about 70% occurred for Si/sup +/ over a depth range of 2.5 to 3.5 ..mu..m, with changes in other species ranging from a decrease of approx.20% for Si/sup +//sub 3/ to an increase of more than 25% for O/sup +/. The development of a rippled surface topography was observed in scanning electronmore » micrographs over the same depth range. Similar effects occurred over a 3--5 ..mu..m depth range for 8-keV ions, and in (111) silicon at a depth of 3 to 4 ..mu..m for 6-keV ions. No differences were noted between p- and n-type silicon, or implanted and unimplanted silicon. In GaAs, profiles were measured in (100) wafers at 2.5-, 5.5-, and 8-keV impact energies. At 8 keV, a yield increase of about 70% was found for GaO/sup +/ in the range 0.6--1.0 ..mu..m, with smaller changes for other matrix species. At 5.5 keV, similar effects were observed, but over a depth interval of 0.3 to 0.7 ..mu..m. No yield changes were detected at 2.5-keV impact energy. The yield changes at the higher energies were again correlated with the onset of changes in topography. No change in ion yield or surface topography was noted for Cs/sup +/ bombardment of Si or GaAs. The topography and ion yield changes are affected by the angle of incidence and, for Si, the oxygen coverage. The results show that the practice of normalizing secondary ion mass spectrometry dopant profiles to a matrix signal must be modified for situations where matrix yield changes occur.« less
  • The reaction of Re{sub 2}O{sub 7} with XeF{sub 6} in anhydrous HF provides a convenient route to high-purity ReO{sub 2}F{sub 3}. The fluoride acceptor and Lewis base properties of ReO{sub 2}F{sub 3} have been investigated leading to the formation of [M][ReO{sub 2}F{sub 4}] [M = Li, Na, Cs, N(CH{sub 3}){sub 4}], [K][Re{sub 2}O{sub 4}F{sub 7}], [K][Re{sub 2}O{sub 4}F{sub 7}]{center_dot}2ReO{sub 2}F{sub 3}, [Cs][Re{sub 3}O{sub 6}F{sub 10}], and ReO{sub 2}F{sub 3}(CH{sub 3}CN). The ReO{sub 2}F{sub 4}{sup {minus}}, Re{sub 2}O{sub 4}F{sub 7}{sup {minus}}, and Re{sub 3}O{sub 6}F{sub 10{sup {minus}} anions and the ReO{sub 2}F{sub 3}(CH{sub 3}CN) adduct have been characterized in the solidmore » state by Raman spectroscopy, and the structures [Li][ReO{sub 2}F{sub 4}], [K][Re{sub 2}O{sub 4}F{sub 7}], [K][Re{sub 2}O{sub 4}F{sub 7}]{center_dot}2ReO{sub 2}F{approximately}3}, [Cs][Re{sub 3}O{sub 6}F{sub 10}], and ReO{sub 3}F(CH{sub 3}CN){sub 2}{center_dot}CH{sub 3}CN have been determined by X-ray crystallography. The structure of ReO{sub 2}F{sub 4}{sup {minus}} consists of a cis-dioxo arrangement of Re-O double bonds in which the Re-F bonds trans to the oxygen atoms are significantly lengthened as a result of the trans influence of the oxygens. The Re{sub 2}O{sub 4}F{sub 7}{sup {minus}} and Re{sub 3}O{sub 6}F{sub 10}{sup {minus}} anions and polymeric ReO{sub 2}F{sub 3} are open chains containing fluorine-bridged ReO{sub 2}F{sub 4} units in which each pair of Re-O bonds are cis to each other and the fluorine bridges are trans to oxygens. The trans influence of the oxygens is manifested by elongated terminal Re-F bonds trans to Re-O bonds as in ReO{sub 2}F{sub 4}{sup {minus}} and by the occurrence of both fluorine bridges trans to Re-O bonds. Fluorine-19 NMR spectra show that ReO{sub 2}F{sub 4}{sup {minus}}, Re{sub 2}O{sub 4}F{sub 7}{sup {minus}}, and ReO{sub 2}F{sub 3}(CH{sub 3}CN) have cis-dioxo arrangements in CH{sub 3}CN solution. Density functional theory calculations at the local and nonlocal levels confirm that the cis-dioxo isomers of ReO{sub 2}F{sub 4}{sup {minus}} and ReO{sub 2}F{sub 3}(CH{sub 3}CN), where CH{sub 3}CN is bonded trans to an oxygen, are the energy-minimized structures. The adduct ReO{sub 3}F(CH{sub 3}CN){sub 2}{center_dot}CH{sub 3}CN was obtained by hydrolysis of ReO{sub 2}F{sub 3}(CH{sub 3}CN), and was shown by X-ray crystallography to have a facial arrangement of oxygen atoms on rhenium.« less