STUDY OF THE MICROSCOPIC FERROELECTRIC PROPERTIES OF COPOLYMER P(VDF-TRFE) FILMS

By using a scanning tunnelling microscope (STM) we investigated the lo cal ferroelectric behaviour of copolymer P(VDF-TrFE) films of various compositions and crystallinity. By means of the STM we examined locall y the variation of the film thickness as a function of the poling volt age (a newly developed microscopic adaptation of the so-called ''butte rfly'' technique), achieving an accuracy of better than 1 Angstrom in height and a lateral resolution in the nanometer range. We could clear ly distinguish the different ferroelectric switching behaviour of the amorphous and crystalline domains. In addition, we were able to detect the switching of individual crystallites, the analogue to the Barkhau sen-effect in ferromagnetic materials, which has not been seen so far in ferroelectric systems, Finally, our observation of a spread-out but strong ferroelectric switching also in the amorphous regions of the s ample is not compatible with the current theoretical structural model of a strictly non-ferroelectric amorphous phase enclosing the ferroele ctric crystallites.