Determination of the composition of Co-Pt thin films with quantitative electron-probe microanalysis

Quantitative electron-probe microanalysis (EPMA) with energy-dispersive (EDS) and wavelength-dispersive (WDS) X-ray spectroscopy was performed to determine the chemical composition of Co-Pt ferromagnetic thin films. The conventional “bulk” EPMA approach was applied and tested in detail by using several analytical set-ups with different combinations of Co and Pt spectral lines, beam energies and quantitative matrix-correction programs. The analyses with dedicated, thin-film EPMA programs were also made for comparison. The results were critically examined in order to assess their reliability and accuracy. The commonly used EDS analyses showed significant scatter between the set-ups and generally suffered from a poor analytical sensitivity. In contrast, the quantitative WDS analyses were fully consistent and practically independent of the analytical set-up. With the optimized WDS a high analytical precision, an improved sensitivity and an ultimate quantitative accuracy of better than 1% relative were achieved. The results confirmed that by using WDS microanalysis at low beam energies and by measuring the low-energy Co-Lα and Pt-Mα X-rays we were able to obtain the most accurate and reliable, quantitative, compositional analyses of Co-Pt thin films with thicknesses down to ≈ 100 nm.