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Measuring compositions in organic depth profiling: results from a VAMAS interlaboratory study.

Shard, A G; Havelund, R; Spencer, S J; Gilmore, I S; Alexander, M R*; Angerer, T B*; Aoyagi, S*; Barnes, J P*; Benayad, A*; Bernasik, A*; Ceccone, G*; Counsell, J D P*; Deeks, C*; Fletcher, J S*; Graham, D J*; Heuser, C*; Lee, T G*; Marie, C*; Marzec, M M*; Mishra, G*; Rading, D*; Renault, O*; Scurr, D J*; Shon, H K*; Spampinato, V*; Tian, H*; Wang, F Y*; Winograd, N*; Wu, K*; Wucher, A*; Zhou, Y F*; Zhu, Z H* (2015) Measuring compositions in organic depth profiling: results from a VAMAS interlaboratory study. J. Phys. Chem. B, 119 (33). pp. 10784-10797.

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We report the results of a VAMAS (Versailles Project on Advanced Materials and Standards) interlaboratory study on the measurement of composition in organic depth profiling. Layered samples with known binary compositions in each layer were manufactured in a single batch and distributed to more than 20 participating laboratories. The samples were analyzed using argon cluster ion sputtering and either X-ray Photoelectron Spectroscopy (XPS) or Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) to generate depth profiles. Participants were asked to estimate the volume fractions in two of the layers and were provided with the compositions of all other layers. Participants using XPS provided volume fractions within 0.03 of the nominal values. Participants using ToF-SIMS either made no attempt, or used various methods that gave results ranging in error from 0.02 to over 0.10 in volume fraction, the latter representing a 50% relative error for a nominal volume fraction of 0.2. Error was predominantly caused by inadequacy in the ability to compensate for primary ion intensity variations and the matrix effect in SIMS. Matrix effects appear to be more pronounced as the number of atoms in both the primary analytical ion and the secondary ion increase. Using the participants' data we show that organic SIMS matrix effects can be measured and are remarkably consistent between instruments. We provide recommendations for identifying and compensating for matrix effects. Finally we demonstrate, using a simple normalization method, that virtually all ToF-SIMS participants could have obtained estimates of volume fraction that were at least as accurate and consistent as XPS.

Item Type: Article
Subjects: Nanoscience
Nanoscience > Surface and Nanoanalysis
Identification number/DOI: 10.1021/acs.jpcb.5b05625
Last Modified: 02 Feb 2018 13:13
URI: http://eprintspublications.npl.co.uk/id/eprint/6779

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