The pilot study P98 on quantitative surface analysis of alloy films was performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The aim of this pilot study is to ensure the equivalency in the measurement capability of national metrology institutes (NMIs) for the quantification of thin alloy films. Nine laboratories including five NMIs, three companies and one university participated in this pilot study. The majority of the participants used x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), which are useful methods for the quantitative analysis of thin alloy films or structured surfaces made of them. The compositions of the certified reference material and the other test samples were determined by inductively coupled plasma mass spectrometry (ICP-MS) using the isotope dilution method. The in-depth and lateral homogeneities of the composition were confirmed by secondary ion mass spectrometry (SIMS) using a C₆₀ ion source.

In this pilot study, the quantification of Fe–Ni alloy films has been proven to be a good candidate as a subject for a CCQM key comparison. The measured slope and offset values of participants' XPS, AES or EPMA data versus compositions obtained by ICP-MS are considered in detail. Data sets for the compositions obtained either by relative sensitivity factors (RSFs) determined from (a) pure metal films or by RSFs from (b) a certified reference alloy film are compared with the result that the average offset value is substantially reduced from 0.725 to 0.038 for the Fe51–Ni49 alloy film test sample. This result means that the RSFs obtained from an alloy film are much more appropriate than those RSFs from pure metals for the quantification of alloy films because a matrix effect can be successfully covered in the first case. This is the right way to improve the equivalency in the measurement capabilities of participants. Similar results have been observed in an analysis of data obtained with the Fe28–Ni72 and Fe78–Ni22 test films. The compositions measured by XPS using RSFs determined from an alloy film showed the minimum in deviation from the nominal values.

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The final report has been peer-reviewed and approved for publication by the CCQM Working Group on Surface Analysis.