Transfer of Electron Density and Formation of Dative Bonds in Chemisorption of Pyrrolidine on Si(111)-7 × 7

Abstract

The chemical binding of pyrrolidine on Si(111)-7 × 7 was studied using high-resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS), and DFT calculation, to obtain a thorough mechanistic understanding of the formation of dative bonds of nitrogen-containing organic molecules on semiconductor surfaces. This study focuses on the electronic and geometric structures of the surface reactive sites. XPS of a chemisorbed monolayer suggests two adsorbates (β1 and β2) associated with the formation of a N···Siad dative bond. At low exposure, the adsorbate β1 forms a dative bond as indicated by a higher N1s binding energy compared to the Si−N σ bond in the dissociated product formed at 250 K. At higher exposure, the formation of the second N···Siad dative bond in adsorbate β2 was evidenced by an obvious upshift of the N1s core-level in contrast to that observed for physisorbed molecules or Si−N σ-bonded molecules. Vibrational studies show a down-shift of the N−H stretching frequen...