Study On Performance And Thin Film Devices Structural Optimization Of P(VDF-TrFE)

Ferroelectric materials as a kind of functional material,have many other electrical properties,such as pyroelectric,dielectric,electro-optic effects,piezoelectric,acousto-optic effects and non-linear optical effects besides unique ferroelectricity.Normally,ferroelectric materials are used in various electronic products by the forms of thin films.In recent years,with the improvement of thin film preparation technology,the research of ferroelectric thin film materials in non-volatile memory,sensors,capacitors,energy harvesting and so on,has become more and more mature.These functional electronic products have tremendous application potential in the automotive industry,information technology,aerospace,ship heavy industry and other high-end technology fields.Compared with inorganic ferroelectric materials,organic ferroelectric materials become a research hot spot due to many advantages,such as good flexibility,easily formed film,low-voltage switching,strong compatibility and so on.Poly(vinylidene fluoride)(PVDF)and its copolymer Poly(vinylidene fluoride-trifluoroethylene)(P(VDF-TrFE))are the most typical organic ferroelectric materials.In this paper,based on the organic ferroelectric thin film capacitors with different structures,the performance mechanism of P(VDF-TrFE)ferroelectric ultrathin films,such as polarization,fatigue and domain switching,was analyzed,which were affected by the structure effect of electrodes,thickness,electroactive interface layer and temperature.The fatigue phenomena in polarization switching process of P(VDF-TrFE)ferroelectric thin films is mainly introduced.The ferroelectric domain fatigue machine is analyzed by theoretical model.In addition,the effects of probe resistance(R_P),leakage resistance(R_L),interfacial layer resistance(R_I)and interfacial layer capacitance(C_I)on the switching speed of ferroelectric ultrathin film capacitors were analyzed in RC model.The contents of this paper are as follows.(1)Ferroelectric film capacitors with different electrode structures were used to study the effect of structural on the properties of P(VDF-TrFE)ferroelectric thin films.The results show that polarization and fatigue properties of P(VDF-TrFE)ferroelectric thin films can be effectively improved by using the line electrode structure.The reason for the improvement of properties of P(VDF-TrFE)ferroelectric thin films is explained by the charge compensation mechanism model.In the polarization switching process,the structure effect of the line electrode offer to enough charge to keep the ferroelectric domain active,which improves the fatigue polarization performance remarkably.(2)The performance of capacitor with 70 nm thickness spin coating P(VDF-TrFE)ferroelectric films was analyzed with different electrode height and width.The results show that the change trend of polarization is basically the same with different electrode height and the increase of polarization shows an"S"curve change with the increase of voltage.However,the polarization rate reaches the maximum value decreases with the increase of electrode thickness.The relative polarization value show a decreases with the increases of electrode height.Further,when the electrode width is the same,the driving voltage value decreases with the increases of electrode height.(3)In this work,the influence of the change of probe resistance(R_P),leakage resistance(R_L),interfacial layer resistance(R_I)and interfacial layer capacitance(C_I)on the switching speed of ferroelectric ultrathin film capacitors was further analyzed in RC model.The results show that more free charges are pinned and bound to form trap charges under larger R_P values,which leads to the decrease of device switching ability and the increase of switching time.The larger the leakage resistance,the smaller the leakage current,the more obvious the rectangular characteristics of the hysteresis loop is showed.The faster reads and writes of device make it have the better performance.In addition,with the increase of interfacial layer resistance R_I value,the speed of device reading and writing is inhibited;however,the larger of interfacial layer capacitance C_I value is,the larger U_F will be due to voltage dividing effect,which will promote faster reading and writing.