Some structural considerations for pyroelectric multilayer films

Some structural and pyroelectric properties of alternate-layer Langmuir-Blodgett films of 22-tricosenoic acid/1-docosylamine and 22-tricosenoic acid/4-octadecylaniline are reported. Reflection high energy electron diffraction experiments reveal that the acid/amine multilayer system possesses a structure similar to that of a fatty acid salt, with the long axes of the molecules oriented perpendicular to the substrate surface. In contrast, for acid/aniline films the molecules are tilted with respect to the substrate normal, resulting in a structure similar to that observed for a simple monocomponent fatty acid film. The pyroelectric coefficients of the acid/aniline multilayers are shown to depend upon the film thickness. It is suggested that this reflects some difference in structure for films possessing a small number of monolayers.