Inkjet-Printed Ternary Oxide Dielectric and Doped Interface Layer for Metal-Oxide Thin-Film Transistors with Low Voltage Operation

Additive solution process patterning, such as inkjet printing, is desirable for high-throughput roll-to-roll and sheet fabrication environments of electronics manufacturing because it can help to reduce cost by conserving active materials and circumventing multistep processing. This paper reports inkjet printing of Y_xAl_2−xO₃ gate dielectric, In₂O₃ semiconductor, and a polyethyleneimine-doped In₂O₃ interfacial charge injection layer to achieve a thin-film transistor (TFT) mobility (μ_sat) of ≈1 cm² V⁻¹ s⁻¹ at a low 3 V operating voltage. When the dielectric material is annealed at 350 °C, plasma treatment induces low-frequency capacitance instability, leading to overestimation of mobility. On the contrary, films annealed at 500 °C show stable capacitance from 1 MHz down to 0.1 Hz. This result highlights the importance of low-frequency capacitance characterization of solution-processed dielectrics, especially if plasma treatment is applied before subsequent processing steps. This study progresses metal-oxide TFT fabrication toward fully inkjet-printed thin-film electronics.