Ultra-thin ZnO thin-film transistors with a channel thickness of <10 nm have disadvantages of a high threshold voltage and a low carrier mobility due to a low carrier concentration. Although these issues can be addressed by utilizing the strong reducing power of tri-methyl-aluminum, a method is required to control parameters such as the threshold voltage. Therefore, we fabricated a ZnO/Al₂O₃ thin-film transistor with a thickness of 6 nm and adjusted the threshold voltage and carrier mobility through the modulation of carrier generation by varying the growth temperature of Al₂O₃. As the growth temperature of Al₂O₃ increased, oxygen vacancies generated at the hetero–oxide interface increased, supplying a free carrier into the channel and causing the threshold voltage to shift in the negative direction. The optimized device, a ZnO/Al₂O₃ thin-film transistor with a growth temperature of 140 °C, exhibited a μ_sat of 12.26 cm²/V∙s, V_th of 8.16 V, SS of 0.65 V/decade, and I_ON/OFF of 3.98 × 10⁶. X-ray photoelectron spectroscopy was performed to analyze the properties of ZnO/Al₂O₃ thin films.

This study developed a transparent NO₂ gas sensor with enhanced sensing performance and high optical transmittance. Al-doped ZnO thin films were deposited by atomic layer deposition, which was chosen for its capability to precisely control surface chemistry at the atomic scale. Oxygen vacancies were effectively introduced by utilizing trimethylaluminum, a strongly reducing Al₂O₃ precursor, thereby increasing carrier concentration and enhancing gas-sensing performance. By adjusting the Al doping level, the optimized device achieved a 50 °C reduction in operating temperature, a 66.2-fold increase in sensitivity at 150 °C, and shortened response and recovery times. The morphology, crystallinity, and elemental distribution were analyzed using transmission electron microscopy, selected area electron diffraction, and energy-dispersive X-ray spectroscopy, while chemical bonding states were investigated via X-ray photoelectron spectroscopy. Optical properties were characterized using UV–visible spectroscopy, confirming an average transmittance of approximately 80% in the visible range. These results demonstrate the promise of transparent oxide gas sensors for integration into next-generation electronics and Internet of Things-based environmental monitoring systems.

We present a ZnSnO (ZTO) thin-film transistor (TFT) with enhanced mobility, achieved through the incorporation of a metal-capping layer. The fabrication of the ZTO active layer involves the deposition of a ZnO incubation layer, followed by super cycles of depositing ZnO and SnO2 layers through atomic layer deposition (ALD). An additional 60-nm-thick Al layer between the source and drain serves as a metal-capping layer and forms a conductive region. Rich in free electrons and located in the back channel away from the gate insulator, the conductive region leads to a primary ON-current path, thereby improving electrical characteristics and stability. Thus, the Al-capped ZTO TFT with a capping length of $200~\mu $ m exhibits decent performance with a saturation mobility of 16.89 cm2/V $\cdot $ s, a threshold voltage of 0.81 V, a subthreshold swing (SS) of 0.59 V/dec, and an ON/OFF current ratio over 107. Moreover, it exhibits a minimal threshold voltage shift of 0.9 V in the positive bias test and −0.14 V in the negative bias stress test. On ALD-based ZTO TFTs, these results demonstrate the applicability of the Al-capping method, which successfully overcomes the tradeoff between mobility improvement and bias stability.