Utveckling av metod för bestämning av fotojoniseringstvärsnitt vid XPS-mätning med Al-och Ga Kα-strålning

Sammanfattning

A method based on previous work in litterature was developed iteratively for a more general determination of relative photoionization cross sections during XPS-measurement with Al K𝛼 and Ga K𝛼 respectively. The developed method was used for pure Ta with Ga and Al K𝛼 as well as Cr samples with Al K𝛼. Measurements with Al K𝛼 were carried out with two different spectrometers to test the reproducibility of the method. It was possible to determine cross sections relative to gold reference samples. The determined cross sections generally differed significantly from interpolations of theoretical values from litterature. Cross sections determined with different instruments did not match. The reasons for this are discussed. Several correction factors have to be applied to the peak intensity in order to obtain cross sections relative to gold. The attenuation length, atomic density and photoemission anisotropy were calculated using data from the simulation software SESSA provided by the National Institute of Standards and Technology (NIST). The transmission function, photon flux, illuminated area and detector efficiency were assumed to be constant according to the arguments put forth in this report. Common practice during analysis of XPS-data is to obtain peak intensity from integration intervals, which are not well defined. To improve the reproducibility of the data analysis, a quantitative method that systematically defines the integration intervals of peaks was developed. It had a low fail rate for symmetric peaks and failed to quantify half of the asymmetric peaks.