SOME REMARKS ON FITTING STANDARD-RESOLUTION AND HIGH-RESOLUTION C1S AND O1S X-RAY PHOTOELECTRON-SPECTRA OF PMMA

Thin PMMA films were investigated by high- and standard-resolution XPS and variable-angle NEXAFS. The results of fitting of the respective C 1s and O 1s XP spectra are compared with the latest literature data. It is found that using a non-constrained ''1 : 1 : 1 : 2'' fitting str ategy good agreement between standard-resolution C 1s spectra and high -resolution spectra can be achieved with regard to BE shifts and trend s in intensity and FWHM of the spectral C 1s components. A non-constra ined fit of standard-resolution O 1s spectra reveals the same characte ristic BE differences as well as non-stoichiometric relative component intensities and FWHM as observed in high-resolution XPS experiments. Comparison of the XPS results obtained with low-energy (380 eV) photon s with those obtained with MgKalpha X-ray photons supported by inspect ion of the C K-edge NEXAFS spectrum reveals that there should be an ou termost PMMA film layer dominated by methyl groups. O 1s NEXAFS spectr a also suggest a non-isotropic orientation of the molecules in the sur face region.