Observation of FT-IR/Photoacoustic and FT-IR/Photoacoustic Reflection-Absorption Spectra of Langmuir-Blodgett Films on a Metal Substrate

Abstract

Recently, much attention has been paid to studies of the applications of thin films deposited on solid substrates for microelectronics. In order to clarify the properties and functions of thin films, researchers have developed many techniques. Vibrational spectroscopy, using Fourier transform infrared (FT-IR) instrumentation in particular, has been applied successfully to such films. For the determination of molecular orientation of films deposited on a flat metal substrate, reflection-absorption spectroscopy (RAS) is frequently used. Sometimes, the transmission spectrum is needed if detailed information about molecular orientation of the films is to be obtained. To obtain the transmission spectra of the thin films, one should deposit materials on a mid-IR transparent substrate with a flat surface, such as a ZnSe or a BaF2 window, under the same conditions used with the deposition on the metal substrate. Dote and Mowry have reported, however, that the adsorbate-surface bonding orientation of a Langmuir-Blodgett (LB) monolayer differs with different substrates.