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Argon cluster ion beams for organic depth profiling: results from a VAMAS inter-laboratory study.

Shard, A G; Havelund, R*; Seah, M P; Spencer, S J; Gilmore, I S; Winograd, N*; Mao, D*; Miyayama, T*; Niehuis, E*; Rading, D*; Moellers, R* (2012) Argon cluster ion beams for organic depth profiling: results from a VAMAS inter-laboratory study. Anal. Chem., 84 (18). pp. 7865-7873.

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The depth profiling of organic materials with argon cluster ion sputtering has recently become widely available with a number of manufacturers of surface analytical instrumentation producing sources suitable for surface analysis. In this work, we assess the performance of argon cluster sources in an inter-laboratory study under the auspices of VAMAS (Versailles project on advanced materials and standards). The results are compared to a previous study which focused on C60q+ cluster sources using similar reference materials. Four laboratories participated using time of flight secondary ion mass spectrometry for analysis, three of them using argon cluster sputtering sources and one a C60+ cluster source. The samples used for the study were organic multilayer reference materials consisting of a ~400 nm thick Irganox 1010 matrix with ~1 nm marker layers of Irganox 3114 at ~50, 100, 200 and 300 nm depths. In accordance with a previous report, argon cluster sputtering is shown to provide constant sputtering yields through these reference materials. The work additionally demonstrates that molecular secondary ions may be used to monitor the depth profile and depth resolutions approaching 5 nm FWHM can be achieved. The participants employed energies of 2.5 keV and 5 keV for the argon clusters and both the sputtering yields and depth resolutions are similar to those for C60+ cluster sputtering. In contrast to C60+ cluster sputtering however, a negligible variation in sputtering yield with depth was observed and the repeatability of the sputtering yields was better than 1%. We observe that, with argon cluster sputtering, the position of the marker layers may change by up to 3 nm depending upon which secondary ion is used to monitor the material in these layers, an effect not previously encountered with C60+ cluster sputtering. We also note that electron irradiation, used for charge compensation, can induce molecular damage to areas of the reference samples well beyond the analyzed region that significantly affects the molecular secondary ion intensities for tens and, in some cases, hundreds of nanometres in the depth profiles.

Item Type: Article
Subjects: Nanoscience
Nanoscience > Surface and Nanoanalysis
Identification number/DOI: 10.1021/ac301567t
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/5614

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