Adsorption of triallylamine on Si(111) and its coadsorption with triethylgallium - A combined HREELS and XPS study

The adsorption of triallylamine [(C3H5)(3)N; TAA] on Si(111)-(7 x 7) under UHV conditions was studied by means of surface sensitive electron spectroscopy. The High-Resolution Electron Energy Loss Spectroscopy (HREELS) yields the spectrum of vibration modes of the adsorbed species. X-ray Photo-electron Spectroscopy (XPS) gives insight into the chemical environment and the relative concentrations in the near surface region. The tertiary amine TAA physisorbes at room temperature without dissociation. Successive annealing steps induce the dissociation of the physisorbed phase at temperatures above 400 degrees C. Further annealing leads to partial desorption of the allyl groups from the surface. At temperatures above 600 degrees C the remaining allyl groups are fully dissociated. Hydrogen leaves the surface and nitrogen and carbon start to diffuse into the substrate. The surface chemistry of triallylamine adsorbed on a heated substrate behaves in a very similar way. The coadsorption of TAA with triethylgallium [(C2H5)(3)Ga; TEG] in the temperature range between 500 and 800 degrees C induces no significant change of the surface reactions. Only a small amount of gallium could be detected at the surface. The nucleation of GaN has not been observed, neither on Si(111) not on Al2O3(0001) substrates.