Study of rewritable thin-film memories using ferroelectric polymers

点击翻译按钮获取中文摘要

1. Ultra thin films of ferroelectric VDF/TrFE(vinylidene fluoride/ trifluoroethylene) copolymers were produced by use of spin-coating technique. We took aim at forming of submicron films whose polarization can be controlled by voltages less than about 10 V. The best condition for solvent, solution density and rate of rotation of spin coater was chosen by many tests. As the result, a thin film of 220 nm in thickness which exhibits a ferroelectric D-E hysteresis was obtained. This film can be used as a memory in an integral circuit. However, films of higher quality including higher ordered crystals are required to make a real memory, because the polarization reversal switching process observed in the submicron films described above is not so clear in comparison with those observed in films with the thickness more than 1μm.2. Memories have three elementary actions of writing, reading and initializing. About reading, we studied whether the change in the optical transmittance of the sample films can be used for the switching process of memories or not, in order to use them as the memory for optical circuit. We took up PDLC (polymer dispersed liquid crystal) composed of VDF/TrFE copolymer and nematic liquid crystal 5CB as a sample. The polarization of P(VDF/TrFE) was oriented by applying an external electric field to PDLC. The internal electric field originating from the ferroelectric polarization affected molecular orientation of the liquid crystal 5CB and changed the optical transmittance of PDLC. This result suggests that the changes in the optical transmittance can be used for the reading mechanism of the PDLC memory.From these results we conclude that the organic thin-film memory can be obtained using the ferroelectric properties of polymers.