Universal Way to Enhance Solution-Processed High-κ Oxide Dielectrics Performance by Sulfate Incorporation

Vacuum-free, solution-processable high-κ-oxide dielectrics are considered to be a key element for emerging low-cost flexible electronics. However, they usually suffer from low breakdown strength and frequency-dependent capacitance, which limit their broader applications. Here, we report a universal way to improve solution-based high-κ oxide dielectric properties (e.g., Al 2 O 3, ZrO 2, Ga 2 O 3, Sc 2 O 3, Ho 2 O 3, and Sm 2 O 3 ) by sulfate incorporation. In-depth characterization shows that sulfate incorporation could reduce hydrogen and oxygen vacancy-related defects in high-κ oxides, thereby improving the dielectric performance. The optimized S-doped high-κ oxides show smooth surface (rms < 0.20 nm), low leakage current (∼10 –7 A/cm 2 @4 MV/cm), excellent dielectric breakdown strength (>10 MV/cm), and stable capacitance–frequency characteristics. Besides, oxide thin-film transistors based on these high-κ dielectrics exhibit excellent performance (e.g., mobility >20 cm 2 V –1 s –1, on/off ratio of ∼10 7, threshold swing of ∼0.14 V dec –1, threshold voltage of ∼0 V, and hysteresis of ∼0.02 V). Thus, this work provides a general approach for the development of high-quality solution-based high-κ oxides for transistor circuitry.