Additively Manufactured Zinc Oxide Thin-Film Transistors Using Directed Assembly
Zhimin Chai, Salman A. Abbasi, Ahmed Busnaina
Abstract
Zinc oxide (ZnO) has been extensively investigated for application in thin-film transistors (TFTs) due to its excellent electrical and optical properties. Although some ZnO-based TFTs have been successfully commercialized, the commercially available ZnO TFTs are mainly fabricated by physical vapor deposition methods, such as sputtering, which are costly and require state-of-the-art fabrication facilities. Here, we report the fabrication of ZnO TFTs using additive-directed assembly of ZnO particles into micropatterned films. By controlling the concentration of the ZnO nanoparticle suspension, void-free ZnO micropatterns can be assembled on silicon/silicon dioxide (Si/SiO 2 ) substrates over a 4 in. wafer. The assembled ZnO micropatterns are thermally sintered prior to the deposition of the source/drain electrodes. The results demonstrate that the TFTs fabricated using ZnO micropatterns sintered at or below 800 °C possess high on-currents because of the removal of the stabilizers. However, the TFTs are normally on with I on / I off current ratios below 10 due to the intrinsic high carrier concentration of ZnO. Whereas when the patterns are sintered at 1000 °C, a gate-voltage-modulated field effect appears. The TFTs work in an accumulation mode with I on / I off ratios above 10 6 . The emergent field effect is attributed to high-temperature sintering-induced interdiffusion of Si and Zn elements at the ZnO/SiO 2 interface, which causes the formation of the zinc silicate (Zn 2 SiO 4 ) phase and suppresses the carrier concentration.