Surface modification of a ferroelectric polymer insulator for low-voltage readable nonvolatile memory in an organic field-effect transistor

摘要

We demonstrate that the sequential surface modification of a ferroelectric polymer insulator plays an essential role in both the enhancement of the carrier mobility and the shift in the turn-on voltage (V_on) in an organic ferroelectric field-effect transistor (FeFET) for nonvolatile memory. The surface of a ferroelectric polymer insulator, poly(vinylidene fluoride-trifluoroethylene), is physicochemically modified by the successive treatments of ultraviolet-ozone (UVO) and CF_4 plasma to understand how the surface morphology and the hydrophobicity affect the grain size, the mobility, and V_on in the FeFET. In a pentacene-based FeFET, the CF_4 plasma irradiation leads to the mobility enhancement by a factor of about 5 as well as the shift in V_on toward a positive voltage direction while the UVO treatment results in only the shift in V_on toward a negative voltage direction. It is found that the sequence of the two successive treatments is critical for tailoring interfacial interactions between the ferroelectric polymer insulator and the pentacene layer. The underlying mechanism for the mobility enhancement and the shift in V_on is described in terms of the surface morphology and the nature of the built-in electric field.