High-Gain CMOS-Like Inverters Based on F-Plasma-Treated Ambipolar SnO Thin-Film Transistors

Although CMOS-like inverters based on ambipolar thin-film transistors (TFTs) have garnered significant interest due to their simplified fabrication and high integration density, achieving high-performance ambipolar TFTs remains challenging. In this work, we systematically investigate the effects of different annealing and passivation schemes—including annealing without passivation (AWP), annealing before passivation (ABP), and annealing after passivation (AAP)—using SiO2, Al2O3, and HfO2 passivation layers (PVLs) on the performance of SnO TFTs. Among them, the AAP-Al2O3 device exhibits the most balanced p-type and n-type conduction and superior negative bias stress (NBS) stability. Furthermore, the ambipolar characteristics, including the on/off current ratio, subthreshold swing (SS), and bias stress stability, were significantly enhanced by fluorine (F) plasma treatment on the SnO channel. Finally, a CMOS-like inverter composed of two identical F-plasma-treated ambipolar SnO TFTs achieved an exceptionally high voltage gain of 289 at a low supply voltage of 8 V. This work offers a simple and effective strategy for developing thin-film CMOS-like circuits suitable for the next-generation cost-effective electronics.