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Attenuation lengths in organic materials.

Seah, M P; Spencer, S J (2011) Attenuation lengths in organic materials. Surf. Interface Anal., 43 (3). pp. 744-751.

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Measurements are reported of attenuation lengths in overlayers of guanine, poly(styrene), poly(methyl methacrylate) and poly(2-vinylpyridine) in the energy range 800 eV to 1400 eV to evaluate the accuracy of theoretical computations and generic equations. The layers are deposited on gold, either by evaporation and condensation or by spin casting. Measurements are made by X-ray photoelectron spectroscopy for the substrate Au 4f, 4d and 4p peaks as well as the overlayer N 1s peak in guanine and poly(2 vinylpyridine). These measurements all correlate with the theory of Tanuma, Powell and Penn, to an RMS scatter of 14%. Correlations with the predictions using the generic equation known as TPP-2M exhibit a poorer RMS scatter of 23% and indicate that a search for an improved generic formula for organic materials may be required. Use of an "average" organic material for the inelastic mean free paths for the four materials leads to an unacceptable 46% RMS scatter. Additional data are also presented for Irganox 1010 that is increasingly used in reference samples for secondary ion mass spectrometry. Comparisons for 5 materials with the Gries G1 formula also give an RMS scatter of 19% but a small change to smooth between Gries' classes of organic materials, with H/C either being around 1 or 2, leads to a markedly reduced RMS scatter of 11%. This final version, G1-S, requires only the material density and chemical formula and is very simple to use for all organic materials if these are known or can be estimated.

Item Type: Article
Keywords: attenuation lengths, inelastic mean free paths, layers, organics, XPS, X-ray photoelectron spectroscopy
Subjects: Nanoscience
Nanoscience > Surface and Nanoanalysis
Identification number/DOI: 10.1002/sia.3607
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/4880

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