Adsorption of nitrogen-containing aromatic molecules on S(111)-7x7

The adsorption configurations of pyrimidine and triazine on Si(111)-7 x 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(sp(2))-H and C (sp(3))-H stretching modes together with the observation of the unconjugated C=N(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 sigma-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. (c) 2006 Elsevier B.V. All rights reserved.