SPECTROSCOPIC STUDIES OF THE INTERACTION OF C-60 AND C-70 FILMS WITH METAL SUBSTRATES

The interaction of fullerenes C60 and C70 films with metal substrates Au, Ag, In and Sn has been studied by UV-visible absorption spectra, IR, Raman, photoluminescence and second-order nonlinear optics. The absorption spectra show new bands for films on Au, Ag, In and Sn film substrates. For C60 on Au and Ag, new bands appear, peaking at 723 and 566 nm, respectively. For C60 film on Sn, several new bands are found at 975.4, 1218, 1557, 2000 and 3570 nm in the NIR and IR regions. Raman spectra reveal an additional peak at 350 cm-1 for C60 film on Au and five new peaks at 350, 532, 564, 1692 and 1850 cm-1 for the film on Sn. An enhancement of the Raman peak intensity is observed in the latter case. A peak blue shift of photoluminescence band from 749 to 735 nm for C60 on Sn has also been found. Moreover, a second-order nonlinear optics study at 1.06 mum yields a ten times greater secondary harmonic generation signal intensity for C60 films on Ag than that of Ag, while no signal is observed for C60 film on glass. For C70 on Sn, UV absorption bands broaden and new bands are found at 747, 984 and 1738 nm. The above results suggest a structural distortion of C60 and C70 molecules, induced by charge transfer from these metals to the molecules.