Normal-incidence infrared absorption spectra of C60 films deposited on silver islands have been measured. The spectra exhibit bands at 1429 and 1180 cm-1· due, respectively, to the infrared active T1u(4) and T1u(3) modes of C60 in multilayers. These bands increase in intensity rather rapidly until 20 nm thickness: the intensity increase involves an enhancement of absorption due to the excitation of the transverse collective resonance of valence electrons in the silver islands. Additionally two bands appear at 1442 and 1370 cm-1, both of which abruptly increase in intensity until 2 nm and saturate 10 nm thickness. These bands decrease in intensity and shift to higher wave numbers when oxygen is preadsorbed on the silver islands. The 1442 cm-1 band is caused by the activation of the infrared inactive Ag(2) mode via electron transfer from the silver to adsorbed C60, whereas the 1370 cm-1 band is assigned to the T1u(4) mode redshifted by the charge transfer. The results reveal that both the charge transfer and the collective electron resonance contribute to the IR absorption enhancement of C60 on silver islands.
|ジャーナル||Physical Review B - Condensed Matter and Materials Physics|
|出版ステータス||Published - 2002 11 15|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics