A. Barranco, A. Yanguas-Gil, F. Yubero, A.R. González-Elipe
Journal of Applied Physics, 100 (2006) 033706 (1-7)
doi: 10.1063/1.2222043

Silicone-like SiOxCyHzSiOxCyHzpolymeric thin films with different COC∕O atomic ratios have been studied by x-ray absorption spectroscopy and resonant Auger electron spectroscopy. The energy of the onset of the SiKSiKabsorption edge varies with the film composition from the value observed in SiCSiC (i.e.,1840eV∼1840eV) to that in SiO2SiO2 (i.e.,1844eV∼1844eV). In the samples with a low COC∕O atomic ratio (i.e.,1∼1),the main band of the SiKSiKspectra depicts two well defined peaks that can be associated with the SiCSi-C and SiOSi-Obonds present in the samples. Their relative intensity can be used to assess the concentration of these two bond types. Resonant SiKLLSiKLL Auger spectra of the polymeric thin film have been measured using photon energies across the SiKSiKabsorption edge. A first Auger peak appearing at a high kinetic energy was recorded for photon energies around the onset of the absorption edge and the first peak/shoulder of the SiKSiKspectrum associated with the SiCSi-Cbonds. This resonant SiKLLSiKLL Auger signal depicts the typical behavior of a resonant Auger process, i.e., its intensity increases when increasing the photon energy, passes through a maximum and then decreases to disappear. In parallel with the evolution of this resonant spectrum, a “normal” SiKLLSiKLL Auger spectrum with a lower kinetic energy appeared for photon energies around the middle of the absorption curve. This spectrum is the only one prevailing at photon energies well above the absorption edge. An outstanding behavior of the SiKLLSiKLL resonant Auger peaks in the polymers with a high COC∕O atomic ratio (i.e., 4⩾4) is that they present a negative dispersion with photon energy, i.e., their kinetic energy decreases as the photon energy increases. This behavior is opposite to that generally found for resonant Auger peaks in most systems and particularly for SiO2SiO2. Although the origin of such behavior is still unclear, the study of the SiKSiKabsorption edge and the corresponding SiKLLSiKLL resonant Auger spectra results helpful for the structural and electronic characterization of SiOxCyHzSiOxCyHzpolymers.

Analysis of SiOxCyHzSiOxCyHz polymeric materials by x-ray absorption spectroscopy: Anomalous behavior of the resonant SiKLLSiKLL Auger spectra