Shear-Induced Ordering of Ferroelectric Crystals in Spin-Coated Thin Poly(vinylidene fluoride-co-trifluoroethylene) Films

摘要

We present a robust route for fabricating a thin ferroelectric poly(vinylidene fluoride-cotrifluoroeth^ylene) (PVDF-TrFE) film with both molecular and microstructural crystal ordering over the area of 1 x 1 cm2 . 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.