Study Of Flexible Low-Voltage IGZO Thin-Film Transistors With Polymer Electret Gate Dielectrics

Oxide-based thin film transistors(TFTs)have obtained researchers'great attention due to their good electronical properties and easy fabricating methods,such as high motilities(>10 cm2V-1s-1),transparency,low-temperature process,low-cost fabrication,and large-area production.Particularly,oxide-based thin film transistors on flexible substrates,such as paper,polymer plastics and metal foils,have received considerable attention because of their potential for flexible electronics devices.However,no matter for traditional devices or flexible devices,both are facing large voltage operation and high-power consumption problems,and especially for flexible devices,obtaining stable mechanical properties is also the key to realizing their wide application in our daily life.In this paper,our main work was to fabricate a kind of low-voltage transistor and study its flexible functions.Given that a-IGZO has many advantages,such as high field effect mobility,good stability,suiting for current fabricating process and not sensitivity to structural deformation,it was chosen as channel material.And ITO glass substrate and paper coated with Ag were used as substrate and bottom gate to fabricate traditional and flexible TFTs respectively.Furthermore,we innovatively used polymer electret as gate dielectrics mainly due to its flexible characteristic and good electrostatic polarization effect which can resulting very high-density charge accumulation in semiconducting channel layer at low gate voltage.As for the experimental part,firstly,we fabricated a-IGZO TFTs with poly(vinyl alcohol)(PVA)one kind of polymer electret as gate dielectric on normal ITO glass to investigate the possibility and potential of these novel devices(using polymer electret dielectric material)and its corresponding mature manufacturing methods.This IGZO-based TFTs with PVA electret films as the gate dielectric on ITO glass substrate shows good low voltage operating characteristics,exhibiting a large field-effect mobility of 43 cm2V-1s-1,a low threshold voltage of 1.03 V and a low subthreshold swing of 132 mV/decade,and a large current ON/OFF ratio of 1.03×1 O6.It proved that polymer electret represented by PVA can be used as gate dielectric to make low-voltage TFTs.Next,we fabricated flexible low-voltage a-IGZO TFTs with graphene oxide(GO)enhanced PVA electret films as the gate dielectrics on paper substrates.High performances with higher current ON/OFF ratio of?1.8×107,lower subthreshold swing of 106 mV/decade,lower threshold voltage of 0.79 V and large field-effect mobility of?42 cm2V-1s-1 was obtained.Additionally,these flexible TFTs presented a good stability under different bending degree and bending times due to the reinforcement effect of graphene oxide.Finally,a resistor-loaded inverter and a dynamic action of the resistor loaded inverter were also experimental demonstrated.Our study and results showed that polymer electret and its polymer composite have great potential to make low-voltage oxide-based TFTs,even realize flexible functions on different substrates.Such devices are very promising in next generation low-cost flexible paper electronics.