Cadmium Arachidate Multilayers Research Articles

Order–disorder transitions in Langmuir–Blodgett films. III. Polarized Raman studies of cadmium arachidate using integrated optical techniques

Polarized Raman measurements of Langmuir–Blodgett (LB) multilayers of cadmium arachidate (CdA) have been obtained through the application of integrated optical techniques. Excitation of either the transverse electric (TE) or transverse magnetic (TM) mode of an asymmetric slab waveguide was alternately used to produce Raman scattering in the CdA multilayers deposited on its surface. Analysis of the 90° scattered light with a polarizer placed at two mutually perpendicular positions for both the TE and TM modes of the waveguide produced a set of four measurements which were used to determine the orientation and lateral order of the CdA monolayer components. The extent of order in the LB film was then investigated as a function of temperature and compared with that of bulk CdA. The temperature of the order–disorder transition was found to be similar in both cases and consistent with that found previously from infrared studies.

Variable-Temperature Raman Studies of Langmuir-Blodgett Multilayers Using Integrated Optical Techniques

A unique integrated optical device has been constructed which allows the study of submicron films and Langmuir-Blodgett multilayers at both elevated (100°C) and cryogenic (−125°C) temperatures by Raman spectroscopy. The two-stage coupler maintains a constant pressure on the prism used for coupling the incoming laser light into the thin film whose spectrum is desired. A Raman study of L-B multilayers of cadmium arachidate (CdA) in the −125°C to 100°C illustrates the versatility of the integrated optical technique.

Negative resistance in organic monomolecular layers: Experiments on triodes

The work on low frequency differential negative resistance (DNR) in monomolecular multilayers of cadmium arachidate is extended to three-electrode (M-I-M-I-M) devices. If the conductivity and DNR between the outer electrodes is well developed, most of the applied voltage is dropped between the central electrode and one of the outer electrodes, depending on the individual triode. When the applied voltage is reversed, the potential drop remains in the same region and DNR still occurs without significant change.