The Effect Of The Interface Modification On Properties Of ZnO Based TFT Devices

The main content of this thesis is research the active layer of ZnO thin film transistor (ZnO-TFT) prepared by zinc oxide thin films. We research zinc oxide thin film transistor's electrical properties from the point of thickness of ZnO thin films, interfacial modification of the use of different materials, and organic-inorganic compound.First, we use the method of magnetron sputtering, we obtained the best film-forming conditions of preparation the ZnO thin films with purity of 99.99% zinc as a target, by controlling the different ratio of argon and oxygen, and adjust the sputtering power. Through XRD and AFM tests, we found the best film-forming conditions are Ar:O2 is 30sccm:25sccm, sputtering power of 300W,400℃annealing 10min.Second, we use the method of magnetron sputtering, get 45nm,60nm,75nm,95nm four different thickness of ZnO thin film layer by controlling the sputtering time at the sputtering time of 600s,800s,1000s,1200s. we found that in the 600s sputtering time, zinc oxide thin film transistors has best migration rate:0.789cm2/V·s, with the sputtering time increases from 800s to 1200s, migration rate of devices are: 0.271cm2/V·s,0.271 cm2/V·s,0.285cm2/V·s. Characterized by XRD and AFM found that in 45nm thickness film grows at the direction of both perpendicular and parallel to the substrate. grain boundary density is low along the direction of carrier transport. The film has best surface roughness and best film quality, So the devices has best performance at this film thickness.Third, the use of lithium fluoride modified the interface between the aluminum electrode and the active layer. Through the modified of the interface, migration rate of all devices are on the rise. When the active layer thickness is 45nm, the device The migration rate reached 0.920cm2/V·s, the device from the 800s to the 1200s the migration rate was 0.278cm2/V·s,0.319cm2/V·s,0.304cm2/V·s. Subsequently, the use of molybdenum oxide modified the interface between the aluminum electrode and the active layer. Through the modified of the interface, migration rate of all devices are decreased. When the active layer thickness is 45nm, the device The migration rate is 0.531cm2/V·s, the thickness of 95nm devices migration rate is 0.263cm2/V·s.Fourth, research the quality of pentacene thin films with different thickness, which is prepared by thermal evaporation, thickness of pentacene film is 5,10,15,20,30,40,50,60nm, obtained Preparation of thin film thickness of 10nm to 40nm film has better quality testd by XRD.Fifth, use the two different active layer-zinc oxide and pentacene composite made of zinc oxide/pentacene thin-film transistor(ZnO/Pentacene-TFT). Using the thermal evaporation prepared pentacene thin films. Then made the ZnO/Pentacene-TFT. The experiment found that migration of device without adding interface PhTMs cases, higher than the migration of the device has PhTMs, migration rate 0.552cm2/V·s.Finally, we fabricated ZnO/Pentacene-TFT with the thickness of pentacene range from 10nm to 40nm, and the thickness of ZnO of 45nm.then measuring the electrical properties. The result suggest that when the zinc oxide film thickness in the 45nm, and lOnm thick pentacene film, The device migration rate was the highest 0.552cm2/V·s.