Determination of the composition and thickness of chromel and alumel thin films on different substrates by quantitative energy dispersive spectroscopy analysis.

Abstract

Thin films of two alloys (chromel and alumel), with thickness less than 100 nm, were obtained by plasma deposition technique, namely filtered cathodic vacuum arc (FCVA). The elemental analyses were performed by quantitative energy dispersive spectroscopy (EDS) microanalysis and Rutherford backscattering spectrometry (RBS). The applicability of EDS to such thin films as these was established by analysis of films deposited on substrates of different atomic numbers, specifically vitreous carbon, silicon, copper, and tin. We found that a substrate with atomic number similar to the mean atomic number of the film constituents is best for reliable EDS results, when compared to RBS. The compatibility between quantitative EDS measurements and RBS measurements, as well as comparison between the thin film elemental composition and the bulk material composition, was assessed by statistical analysis. Good consistency between EDS and RBS measurements was found for both chromel and alumel thin films when copper was used as substrate material. We observed severely overlapping peaks in the RBS output for the case of alumel films so that EDS analysis was crucial. We also compared thickness measurements determined by EDS and RBS, and we found good agreement for the case of alumel film on copper substrate, and 15% agreement for chromel film on copper substrate.