Vibrational study of methylene radical interaction on the Cu(111) surface

Methylene interaction on Cu(lll) has been investigated with XPS, AES, TDS, LEED and HREELS at various exposures. CH2 and CD2 radicals are generated through a high-temperature nozzle source with the corresponding ketene gases. The presence of methylene in the chemisorbed state is confirmed by the characteristic vibrational frequencies in the HREELS spectra. A striking observation is the formation of aromatic species even at submonolayer coverages at 300 K. Apparently, the radical can aggregate and react to form complex species on the metal. The adlayer starts to desorb and decompose at about 400 K to produce methylidyne. Above 850 K, all hydrocarbon spectral characteristics disappear, and some residual carbon is left on the surface. (C) 1998 Elsevier Science B.V. All rights reserved.