Thickness Dependence of Ferroelectricity in Langmuir-Blodgett Multilayer Films of Hemicyanine Dyes

The thickness dependence of ferroelectricity in hemicyanine Langmuir-Boldgett multilayer films was reported in this paper. By the observed ferroelectric hysteresis loop, it was found that the coercive field decreased with increasing of film thickness monotonously and may be approximated by a power law Ec proportional to N-4/3 in the range from 30 to 200 nm, which is consistent with other conventional ferroelectric materials. The measurement of dielectric properties give the optimum thickness about 60 nm of hemicyanine LB films and their optimum value as ferroelectric storage-devices has the same order of magnitude as copolymer's P(VDF-TrFE) (70:30 mol%).