Adsorption and thermal dissociation of pyrrole on Si(1 0 0)-2 × 1

Abstract

The adsorption and thermal reaction of pyrrole on Si(1 0 0)-2 × 1 have been studied using X-ray and ultra-violet photoelectron spectroscopies (XPS and UPS) and high resolution electron energy loss spectroscopy (HREELS). At low exposures, Pyrrole chemisorbs molecularly at 120 K with its ring parallel to the surface via the π-interaction. The increase in coverage causes tilting of chemisorbed molecules towards the surface normal, attributable to the adsorbate–adsorbate interactions. At ∼350 K, the N–H bond scission of the π-bonded species occurs, resulting in Si–H and vertically N-bonded pyrrolyl on the surface. The pyrrolyl species is thermally stable to 700 K. Compared to furan or thiophene on Si(1 0 0), this higher thermal stability is ascribed to the passivation effect of the H-atoms from N–H bond dissociation and the less strain within the pyrrolyl–substrate complex. Further annealing to 900 K results in the formation of silicon carbide and silicon nitride on the substrate.