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We present a robust route for fabricating a thin ferroelectric poly(vinylidene fluoride-cotrifluoroethylene) (PVDF-TrFE) film with both molecular and microstructural crystal ordering over the area of 1 Â 1 cm 2 . The method is based on the static mechanical shearing of the film under appropriate thermal conditions. The apparatus designed particularly for ultrathin PVDF-TrFE films with thickness of 200 nm or less allowed us to fabricate a thin film with ca. 25 nm thick crystalline lamellae globally ordered perpendicular to the shear direction. Grazing incident X-ray diffraction and polarized near edge X-ray absorption fine structure further revealed the molecular orientation of the crystals with c and a axes of the PVDF-TrFE crystals preferentially oriented parallel to shear direction and film surface normal, respectively. The shearing of a thin film at 135 °C gave rise to the best crystal orientation directly correlated with approximately 50% enhanced ferroelectric polarization observed in a metal/sheared PVDF-TrFE/metal capacitor.

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Abstract-The article presents the recent research development in polymer ferroelectric non-volatile memory. A brief overview is given of the history of ferroelectric memory and device architectures based on inorganic ferroelectric materials. Particular emphasis is made on device elements such as metal/ferroelectric/metal type capacitor, metalferroelectric-insulator-semiconductor (MFIS) and ferroelectric field effect transistor (FeFET) with ferroelectric poly(vinylidene fluoride) (PVDF) and its copolymers with trifluoroethylene (TrFE). In addition, various material and process issues for realization of polymer ferroelectric non-volatile memory are discussed, including the control of crystal polymorphs, film thickness, crystallization and crystal orientation and the unconventional patterning techniques.

Excellent retention of the initial remanent polarizations was observed in ca. 200 nm thick ferroelectric poly͑vinylidene fluoride-co-trifluoroethylene͒ film capacitors with the writing pulse amplitude and time width of Ϯ20 V and 1 ms, respectively, over 200 h at 80°C. The opposite state program turned out more sensitive to retention deterioration than the same state one in both switching and nonswitching mode when either writing pulse amplitude or time width decreases. Nonswitching retention in the opposite state mode is in particular one of the most critical properties for designing a ferroelectric polymer capacitor memory.