Results of Inter-laboratory Tests among SASJ on Accurate Mass Scale Calibration of ToF-SIMS

Surface & Interface Analysis

et al. 2016

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The applicability of internal additives for mass scale calibration in time-of-flight secondary ion mass spectrometry (TOF-SIMS) was studied. Relation between the ions selected for mass scale calibration and the relative mass accuracy of the target molecular ions was investigated. Didecyldimethylammonium bromide (dC10DMA + Br À ), dioctadecyldimethylammonium chloride (dC18DMA + Cl À ) and tetradecyltrimethylammonium chloride (C14TMA + Cl À ) as target molecules and octadecyltrimethylammonium chloride (C18TMA + Cl À ) as an internal additive were prepared for positive TOF-SIMS spectra. Tinuvin 770 as a target molecule and sodium hexadecyl sulfate (C16OSO3 À Na + ) as an internal additive were used to evaluate negative TOF-SIMS spectra. In the case of dC10DMA + Br À , dC18DMA + Cl À and Tinuvin 770, the relative mass accuracy of the target molecular ions tends to be improved by mass scale calibration using the molecular ion of the internal additive. The relative mass accuracy of the molecular ion of the target ensured by the mass scale calibration using internal additives was less than approximately ±46 ppm. In some cases, however, internal additives highly effect on samples and change the sample properties because of coverage of the sample, removing a target molecule or causing matrix effects. It is necessary to evaluate the influence of the internal additive addition before applying internal additives. The detection of target ion peak should be especially confirmed after the addition of the internal additive. When samples are not influenced by internal additive addition, the internal additive method is effective for accurate mass calibration.

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Mass scale calibration of TOF‐SIMS spectra with molecular ions of internal additives

Kobayashi

Aoyagi²,

Surface & Interface Analysis

et al. 2016

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“…A practical mass‐scale calibration in TOF‐SIMS has been discussed by the TOF‐SIMS working group that was established in the Surface Analysis Society of Japan on June 2007 . A novel mass calibration method with internal additives is expected to be become more accurate than the conventional one.…”

Section: Introductionmentioning

confidence: 99%

Mass‐scale calibration of TOF‐SIMS spectra using quaternary ammonium ions

Kobayashi

Surface & Interface Analysis

Aoyagi

et al. 2014

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A novel method with quaternary ammonium salts as internal additives has been applied to the mass-scale calibration of timeof-flight secondary ion mass spectrometry (TOF-SIMS). Five kinds of quaternary ammonium salts, octyltrimethylammonium bromide (C8TMA), tetradecyltrimethylammonium chloride (C14TMA), octadecyltrimethylammonium chloride (C18TMA), cetylpyridinium chloride (CPC) and benzyldimethyltetradecylammonium chloride (Bzl) were diluted with NH 3 aqueous solution and were mixed in equal quantities. The mixed solution was covered on a Si wafer and was measured by TOF-SIMS. When molecular ions of C8TMA, C14TMA, and C18TMA were used for the mass-scale calibration, the relative mass accuracy of lowmass C X H Y fragment ions indicated negative values and depended on the carbon chain length and the degree of unsaturation. This result means that the conventional mass-scale calibration with frequently employed low-mass C X H Y fragment ions leads to degradation of the mass accuracy of high-mass molecular ions. To improve the mass accuracy of molecular ions of CPC and Bzl, ions should be selected for the mass-scale calibration in the following two ways: One way is for ions to consist only of molecular ions of C8TMA, C14TMA, and C18TMA, and the other way is for ions to include one of the molecular ions: C8TMA, C14TMA, and C18TMA, along with the C X H Y fragment ions. This novel mass-scale calibration method is promising for realizing the correct identification of unknown high-mass molecular ions. Those quaternary ammonium salts are powerful candidates of internal additives.

Results of Inter-laboratory Tests among SASJ on Accurate Mass Scale Calibration of ToF-SIMS

Abe

Itoh

2011

JSA

To evaluate the present errors in the calibration of the mass scale of time-of-flight secondary ion mass spectrometry (ToF-SIMS) in the practical field of Japanese industries, ToF-SIMS Working Group (WG) of Surface Analysis Society of Japan (SASJ) conducted the inter-laboratory studies among 14 instruments in 2007, 2008 and 2009. There was significant scatter over 200 ppm in the relative mass accuracy at the first inter-laboratory test in 2007. Clearly, this is poor compared with the requirement for identification. However, the great deviation in the mass accuracy has been dramatically decreased at the second and third inter-laboratory tests by the accumulating knowledge through the discussion among the WG. Based on the results obtained, a practical guide to analysts for mass scale calibration will be provided in near future.