Self-polarized Poly(vinylidene fluoride) Ultrathin Film and Its Piezo/Ferroelectric Properties

Organic nonvolatile memory with ultralow power consumption is a critical research demand for next-generation memory applications. However, obtaining a large-area, highly oriented ferroelectric ultrathin film with low leakage current and stable ferroelectric switching remains a challenge for achieving low operation voltage in ferroelectric memory transistors. Here, an ideal ferroelectric neat PVDF ultrathin film with a high degree of orientation is fabricated by a melt-draw technique without post-thermal treatment and assisted stabilization process. The PVDF ultrathin film is self-polarized with predominantly vertical orientation of dipole moments, exhibiting a d₃₃ of 25 pm V^-1 and the ultralow coercive voltage of approximately 3 V characterized by piezoresponse force microscopy. A remnant polarization of 6.3 μC cm^-2 is identified based on a PVDF capacitor with an active layer formed by six layers of melt-drawn thin films. By employing a single-layer melt-drawn PVDF ultrathin film as an insulation layer, a bottom-gate-top-contact ferroelectric field-effect transistor is fabricated with a very low operation voltage of 5 V. It exhibits a memory window with an on/off current ratio of 10³ at zero gate bias and threshold voltage shift of around 2 V.