Stable and High Performance Flexible ZnO Thin Film Transistors by Atomic Layer Deposition.
Passivation is a challenging issue for the oxide thin film transistor (TFT) technologies because it requires prolonged high temperature annealing treatments to remedy defects produced in the process, which greatly limits its manufacturability as well as its compatibility with temperature sensitive materials such as flexible plastic substrates. This study investigates the defect formation mechanisms incurred by atomic layer deposition (ALD) passivation processes on ZnO TFTs, based on which we demonstrate for the first time degradation free passivation of ZnO TFTs by a TiO2/Al2O3 nanolaminated (TAO) film deposited by a low temperature (110 degC) ALD process. By combining the TAO passivation film with ALD dielectric and channel layers into an integrated low temperature ALD process, we successfully fabricate flexible ZnO TFTs on plastics. Thanks to the exceptional gas barrier property of the TAO film (water vapor transmission rate (WVTR)<10( 6) g m( 2) day( 1) as well as the defect free nature of the ALD dielectric and ZnO channel layers, the TFTs exhibit excellent device performance with high stability and flexibility: field effect mobility>20 cm2 V( 1) s( 1) subthreshold swing<0.4 V decade( 1) after extended bias stressing >10,000 s) air storage >1200 h) and bending (1.3 cm radius for 1000 times)
ACS applied materials interfaces