Theoretical identification of pyrimidine on Si(100) by means of X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectra

The C 1s and N 1s X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure structure (NEXAFS) spectroscopy of 11 possible configurations of pyrimidine molecules adsorbed on the Si(100) surface have been studied by the first principle method. These structures for pyrimidine adsorbed on the silicon surface have also been predicted and theoretically characterised. Our results show that the XPS and NEXAFS spectra of these adsorption configurations are structurally dependent. In contrast to the XPS spectra, it is found that the NEXAFS spectra are significantly dependent on the structures of pyrimidine absorbed on the Si(100) surface, which can effectively identify different molecular structures. In addition, since spectra vary with the local environment of carbon atoms, the NEXAFS spectra are useful to investigate the relationship between spectra and the structures of carbon atoms.