Geometric and electronic structures of pyrazine molecule chemisorbed on Si(100) surface by XPS and NEXAFS spectroscopy

Abstract

The geometric and electronic structures of several possible adsorption configurations of the pyrazine (C 4 H 4 N 2) molecule covalently attached to Si(100) surface, which is of vital importance in fabricating functional nano-devices, have been investigated using X-ray spectroscopies. The Carbon K-shell (1s) X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy of predicted adsorbed structures have been simulated by density functional theory with cluster model calculations. Both XPS and NEXAFS spectra demonstrate the structural dependence on different adsorption configurations. In contrast to the XPS spectra, it is found that the NEXAFS spectra exhibiting conspicuous dependence on the structures of all the studied pyrazine/Si(100) systems can be well utilized for structural identification. In addition, according to the classification of carbon atoms, the spectral components of carbon atoms in different chemical environments have been investigated in the NEXAFS spectra as well.

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

“…[16][17][18][19] In soft x-ray spectroscopies, x-ray photoelectron spectroscopy (XPS) and the nearedge x-ray absorption fine structure (NEXAFS) spectrum are often used to study the interfacial structure of organic molecular surfaces. [20,21] The XPS involves the ionization of electrons in the nuclear orbit, which can be used to detect the surface chemical composition and the chemical state of elements contained therein, [22,23] and to provide information about the nuclear orbit. NEXAFS involves that the nuclear orbital electrons are excited to the unoccupied orbit, which can offer unoccupied orbital information, and conduct the quantitative and qualitative analysis of the elements through the spectrum generated by the electron transition in the inner layer of the element.…”