Transparent and Flexible Thin-Film Transistors with High Performance Prepared at Ultralow Temperatures by Atomic Layer Deposition

High-performance, transparent, and flexible thin-film transistors (TFTs) with polycrystalline channels in a bottom-gate structure are successfully fabricated at extremely low temperatures of 80, 90, and 100 degrees C by atomic layer deposition (ALD) in which ZnO and Al2O3 are used as channels and dielectric layers, respectively. The transistors are superior to silicon-based TFTs in which high temperatures are necessarily involved in both preparation and postgrowth annealing. Among all devices, TFTs grown at 100 degrees C exhibit the best performance which can be attributed to the lowest grain boundary trap density. Additionally, the TFTs are successfully transferred to plastic substrates without any performance degradation, which shows a high mobility of 37.1 cm(2) V-1 s(-1), a high on/off-state current ratio of 10(7) at V-DS = 0.1 V, a small subthreshold swing of 0.38 V dec(-1), and a proper threshold voltage of 1.34 V as well as an excellent bias stability.