Spectroscopic studies of the interaction of C60 and C70 films with metal substrates

Abstract

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,μm 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.