FOURIER-TRANSFORM SURFACE-ENHANCED RAMAN-SCATTERING OF LANGMUIR-BLODGETT MONOLAYERS ON COPPER AND GOLD ISLAND SUBSTRATES

Fourier transform surface-enhanced Raman scattering (FT-SERS) for a single Langmuir-Blodgett (LB) monolayer on a gold island film and on a copper island film using near-IR excitation at 1064.1 nm is reported here for the first time. FT-SERS was also observed for a thin vacuum-evaporated film of vanadyl phthalocyanine (VOPc) on a copper substrate. Similar attempts to obtain FT-SERS from vacuum-evaporated VOPc on GaAs and Ga0.7Al0.3As semiconductor substrates were not successful. The types of LB monolayers used were copper tetra-tert-butylphthalocyanine (CuTTPc), a mixed monolayer of arachidic acid/asymmetrically substituted diphthalocyanine (PcLuPc(t)), and N-pentyl-N-ethyl-3,4:9,10-perylene-tetracarboxylic diimide (PPTCDE). For comparison, surface-enhanced resonance Raman scattering (SERRS) spectra were obtained using visible laser excitation in resonance with both an electronic absorption of the LB material and the surface plasmons of either the copper or gold metal island films. In all cases, the LB material was physisorbed on the metal with the electromagnetic mechanism, leading to FT-SERS. The results illustrate the FT-Raman application to submicrometer thin solid films.