HREEL SPECTROSCOPY OF THIN ION-BEAM DEPOSITED C-H(D) FILMS

Several monolayers thick C:H films, H/C ratio ca 0.5, have been prepar ed by ion beam deposition of hydrocarbons at a Pt(111)/C carrier. HREE L spectra of films deposited at 350 K exhibit a rich structure in the C-H stretch region around 3000 cm(-1) and fingerprint region below 160 0 cm(-1). The spectra confirm the presence of CH, groups at carbon in sp, sp(2), and sp(3) hybridization states in a graphitic network. Vibr ational spectra of deuterated films exhibit a normal isotope shift. Th e nature of the deposited ion: ethane, ethylene, acetylene, benzene, h as a negligible effect on the vibrational structure of the C:H films. Annealing of the films up to 1250 K successively destroys sp, sp(3), a nd sp(2) carbon related CH groups. Although the films are not crystall ine, the angular distribution of the elastically scattered electrons i s considerably peaked in the specular direction. The primary energy de pendence of the V(C-H) vibration losses exhibits a resonance at 5 eV w hich is considered as due to a marked impact mechanism contribution to the respective spectral features.