EFFECTS OF THICKNESS ON FERROELECTRICITY IN VINYLIDENE FLUORIDE AND TRIFLUOROETHYLENE COPOLYMERS

The effects of thickness on ferroelectricity in vinylidene fluoride an d trifluoroethylene copolymers have been investigated mainly through s witching measurements. Switching phenomena as a result of ultimately 1 80 degrees rotations of individual chain molecules around their axes w ere observed in the copolymer films with thicknesses in the range of 0 .03-1 mu m. With decreasing film thickness, the switching times increa se, the switching curve becomes,road and the permittivity at the Curie point decreases. However, the amount of reversed polarization is near ly independent of film thickness. These results are generally reproduc ible if we assume a surface layer with thickness less than 0.01 mu m l ow permittivity, and absence of ferroelectric switching even in the pr esence of an applied electric field.