2ND-HARMONIC GENERATION SPECTROSCOPY AND HYPER-RAYLEIGH SCATTERING INLANGMUIR-BLODGETT-FILMS OF FULLERENES

Optical second-harmonic generation (SHG) spectroscopy and hyper-Raylei gh scattering (HRS) were studied in thin Langmuir-Blodgett films of fu llerenes. For films above five monolayers a coherent SHG signal was ob served, whereas a one-monolayer film only produced HRS. The HRS indica trices were measured, and a correlation length of the non-linear polar ization of about 100 nm was obtained. The increase in SHG intensity Fo r C-60-CN films in comparison with that of C-60 films is well pronounc ed, particularly at the blue end of the SHG spectra, and is attributed to a resonant surface electric-dipole contribution. (C) 1997 Elsevier Science B.V.