Study On Fatigue Recovery Characteristics Of Organic Ferroelectric Thin Films

Ferroelectric polymers, such as poly(vinylidene fluoride)(PVDF) and its copolymer with trifluoroethylene P(VDF-TrFE), have attracted much attention for their application in nonvolatile memories due to their high flexibility, low cost, ease of production, and integrability with mainstream silicon technology. Transparent and/or flexible ferroelectric memories, such as ferroelectric field effect transistor (FeFET) and capacitor memories, have been realized in many laboratories using oxide semiconductors, such as IGZO. However, polarization fatigue phenomenon in organic ferroelectrics severely restricting the application to memories. How to restore those degraded polarization as well as how to improve fatigue endurance has been attracting much attention. Meanwhile, oxide semiconductor formation by the sol-gel route requires an annealing step at relatively high temperature, which has prevented the incorporation of these materials with the polymer substrates used in high performance flexible electronics. It’s important to study how to prepare IGZO films at room temperature.In the work, we report the influence of ultraviolet(UV) irradiation on electrical fatigue in ferroelectric polymers. Experiments indicate that ferroelectric polymer films exposed to UV irradiation show degraded fatigue endurance. However, simultaneous application of UV light and bias voltage (Vb,as) can partially recover the electrical polarization in fatigued films, which is dependent on both electrical polarity of DC bias and the UV intensity. The influence of the value of Vbias on polarization restoration is also reported. Repeated fatigue and restoration measurements are also conducted. Based on fatigue mechanism in ferroelectric polymer films, UV-induced restoration is discussed.We report a general method for forming oxide semiconductors at room temperature, by deep-ultraviolet (main peaks at184.9nm (10%) and253.7nm (90%)) photochemical activation of sol-gel films. Deep-ultraviolet irradiation induces efficient condensation and densification of oxide semiconducting films by photochemical activation at low temperature. However, the performance of the devices photo-annealed in air is rather poor and unstable, which need us to do further research.