Polymerization and decomposition of (formula presented) on pt(111) surfaces

The interaction of (Formula presented) with Pt(111) was investigated at submonolayer, monolayer, and multilayer coverages by Auger electron spectroscopy, x-ray photoelectron spectroscopy (XPS), UV photoelectron spectroscopy (UPS), high-resolution electron-energy-loss spectroscopy (HREELS), and low-energy electron diffraction studies. The Pt(111) surface strongly affects the thermal decomposition of (Formula presented) At submonolayer coverages, (Formula presented) is polymerized on Pt(111) at (Formula presented) as was evident from UPS spectra that show a 0.4–0.5 eV shift towards (Formula presented) for the VB features, in comparison to that of multilayer (Formula presented) films on Pt(111). The polymerization was most clearly evident in HREELS for (Formula presented) films on Pt(111) annealed to 700 K in the presence of O adatoms or Sn, as seen by the rise in intensity of the (Formula presented) derived mode at 1460 (Formula presented). As a result, annealing multilayer (Formula presented) films on Pt(111) to (Formula presented) leads to a (Formula presented) adlayer that is quite different from 1 ML (Formula presented) On annealing (Formula presented) films on Pt(111) to 900 K, graphite domains appear on the surface and complete fragmentation occurs at 1050 K. HREELS, XPS, and UPS results comparing the (Formula presented) monolayer to the multilayer were used to study charge-transfer interactions between (Formula presented) and Pt(111). For 1 ML (Formula presented) at 300 K, UPS spectra show that the (Formula presented) valence-band features are shifted by about 0.4–0.5 eV towards (Formula presented) while XPS studies show that the (Formula presented) core level is shifted by 0.4 eV to a lower binding energy and HREELS studies show that the (Formula presented) mode is shifted down by 20 (Formula presented) in comparison to multilayer coverages of (Formula presented) on Pt(111). Based on these shifts it was concluded that charge transfer of two electrons occurs from Pt(111) to monolayer (Formula presented) upon chemisorption. These charge-transfer interactions contribute to strong binding of the (Formula presented) monolayer and a low mobility for (Formula presented) molecules on the Pt(111) surface, which results in the growth of a disordered (Formula presented) film on Pt(111) at room temperature. Increased mobility of (Formula presented)-derived species on the surface at 900 K results in the growth of an ordered film with a hexagonal structure.