Study On Electric Double Layer ZnO Thin-Film Transistors With Chicken Albumen Dielectric

Active Matrix Organic Light Emitting Diode Displays(AMOLED)and Active Matrix Liquid Crystal Displays(AMLCD)are the mainsteam products for current display,and Thin Film Transistor(TFT)is the dominted components of these display drivers.In the recent years,zinc oxide thin film transistors(ZnO-TFTs)have attracted many attentions due to their low preparation temperature,high carrier mobility,good chemical stability,large area eposition,environmental friendliness,and low manufacturing cost.However,the tranditional gate dielectric ZnO-TFT needs a high operating voltage,resulting in high power consumption,which restricts its application in portable mobile,and wearable electronic products.Considering that the electric double layer material,such as chicken albumen,it not only can be naturally degradable,but also can work under ultra low voltage.In this work,using electric double layer material chicken albumen as the ZnO-TFT gate dielectric,we made many ZnO-TFT devices with different process parameters.Besides,we had a further research on their electrical properties and stability.The main research contents and results are as follows:(1)Using chicken albumen as the gate dielectric material fabricated a bottom-gate structure Zn O-TFT on ITO glass substrate by spin coating method successfully.The ZnO film was deposited by spurrering at 120?.The electrical characteristics of the device were characterized.The device exhibited good electrical properties with a mobility of 8.27 cm~2/Vs,a threshold voltage of 1.74 V,a subthreshold swing of 0.489 V/decade,and a switching current ratio more than of 10~6,operating voltage as low as 3 V.(2)The bottom-gate structure ZnO-TFT on ITO glass substrate are fabricated with the gate dielectric layer spin coated with chicken albumen and the active layer made by ALD at the temperature of 120?.The device exhibited good electrical properties with a mobility of 26.64cm~2/Vs.Comparing with the different devices fabricated under the two methods,it can be found that the device under the ALD method exhibits generally better than the magnetron sputtering.The cause can be due to good uniformity and smooth surface of the ZnO film for ALD method.(3)The effects of active layer thickness(30 nanometer to 120 nanometer)on ALD-based ZnO-TFTs were systematically studied.According to the research,the subthreshold swing and the field-effect mobility were increased with the increased of the thickness of active layer,while the threshold voltage decreased with the increased of the thickness of active layer.As can be observed from these changes,they are mainly caused by the increase of the active layer thickness in this range and the increase of trap state in the active layer.(4)The effects of gate-bias and drain-bias voltage stress on the electrical characteristics of devices fabricated by ALD and magnetron sputtering methods were studied.We speculate the degradation of the device under gate-bias stress could be due to self-heating effect and hot carrier effect,and the degradation of the device under drain-bias stress is mostly on account of creating many new trap states between the active layer and the gate dielectric layer during the drain-bias stress stage.Finally,we studied the stability of the device fabricated under the two methods in the air,its electrical characteristics also have some degration,considering water and oxygen in the air to enter the active layer and creat a new defect state.