PHOTOELECTRON SPECTRA OF SUBMONOLAYER C60F48 FILMS ON d-METAL SUBSTRATES

Abstract

Photoemission valence band spectra of submonolayer fullerene C 60 F 48 films, evaporated in situ on d-metal foils of Au, Pt, Ta, W, Ni, were acquired under He II (40.8 eV) excitation at 300 K. Spectral structure transformations versus film thickness and substrate material were under investigation. For coverage ~ 0.5–1.0 ML C 60 F 48 the main spectral features were found to be close to those measured for thick films: with a main peak at Eb ≈ 9 eV (F2p) and a broad peak at 11.4 eV (C2p or C2s). However, a new low intensity band with Eb ≈ 1.5 eV (FWHM ≈ 1.4 eV) was found to arise at a film thickness of about 0.4–0.5 ML and to decrease beyond 1 ML. It may be attributed to a strong ion-covalent bonding between d-metal and fullerene at low coverage. For coverages exceeding 0.3 ML the spectra were found to be weakly dependent on substrate material, except for Ni, where this new band was found at Eb = 2.2 eV and the main peak at Eb = 9.7 eV .