Theoretical characterization of the adsorption configuration of pyrrole on Si(100) surface by x-ray spectroscopy

The possible configurations of pyrrole absorbed on a Si(100) surface have been investigated by x-ray photoelectron spectroscopy(XPS) and near-edge x-ray absorption fine structure(NEXAFS) spectra. The C-1s XPS and NEXAFS spectra of these adsorption configurations have been calculated by using the density functional theory(DFT) method and fullcore hole(FCH) approximation to investigate the relationship between the adsorption configurations and the spectra. The result shows that the XPS and NEXAFS spectra are structurally dependent on the configurations of pyrrole absorbed on the Si(100) surface. Compared with the XPS, the NEXAFS spectra are relatively sensitive to the adsorption configurations and can accurately identify them. The NEXAFS decomposition spectra produced by non-equivalent carbon atoms have also been calculated and show that the spectral features vary with the diverse types of carbon atoms and their structural environments.