Fabrication of micropatterned ferroelectric gamma poly(vinylidene fluoride) film for non-volatile polymer memory

We describe a facile and robust method for fabricating ferroelectric γ-type poly(vinylidene fluoride) (PVDF) thin films useful for non-volatile polymer memory. Our method is based on heating and cooling rate-independent melt-recrystallization of a thin PVDF film confined under a surface-energy-controlled top layer that strictly forbids paraelectric α crystals. Thin and uniform PVDF films with ferroelectric γ crystals consisting of characteristic twisted lamellae are formed with versatile top layers including metals, oxides, and even polymers. Micropatterns of ferroelectric γ PVDF domains isolated by paraelectric α domains are readily developed when pre-patterned top layers are employed. Our ferroelectric films are conveniently incorporated into arrays of either capacitor or transistor-type non-volatile memory units. Arrays of ferroelectric transistors with vacuum deposited pentacene channels are fabricated with micropatterned γ PVDF films. Furthermore, arrays of bottom-gate ferroelectric transistor memories are demonstrated, in which our ferroelectric PVDF film is directly micropatterned during crystallization under the patterned poly(3-hexyl thiophene) active channels.