Adsorption of nitrogen-containing aromatic molecules on Si(1 1 1)-7 × 7

The adsorption configurations of pyrimidine and triazine on Si(1 1 1)-7 × 7 were investigated using high-resolution electron energy loss spectroscopy (HREELS) X-ray photoelectron spectroscopy and density functional theory calculations. The HREELS spectra of chemisorbed monolayer show the coexistence of the C(sp2)–H and C (sp3)–H stretching modes together with the observation of the unconjugated CN(C) vibrational feature suggesting that the carbon atom and its para-nitrogen atom of pyrimidine and triazine directly participate in binding with the surface to form Si–C and Si–N σ-linkages. The core levels of the C-atom and its opposite nitrogen atom directly binding with Si-atoms experience a down-shifting by 1.8–1.9 and 1.4–1.6 eV, respectively. These experimental findings are consistent with the density functional theory calculations indicating that the carbon atom and its para-nitrogen atom favorably link with the adjacent adatom and rest atom pair to form C–Si and N–Si linkages.