Proton Conducting Perhydropolysilazane-Derived Gate Dielectric for Solution-Processed Metal Oxide-Based Thin-Film Transistors

Perhydropolysilazane (PHPS), an inorganic polymer composed of Si–N and Si–H, has attracted much attention as a precursor for gate dielectrics of thin-film transistors (TFTs) due to its facile processing even at a relatively low temperature. However, an in-depth understanding of the tunable dielectric behavior of PHPS-derived dielectrics and their effects on TFT device performance is still lacking. In this study, the PHPS-derived dielectric films formed at different annealing temperatures have been used as the gate dielectric layer for solution-processed indium zinc oxide (IZO) TFTs. Notably, the IZO TFTs fabricated on PHPS annealed at 350 °C exhibit mobility as high as 118 cm2 V–1 s–1, which is about 50 times the IZO TFTs made on typical SiO2 dielectrics. The outstanding electrical performance is possible because of the exceptional capacitance of PHPS-derived dielectric caused by the limited hydrolysis reaction of PHPS at a low processing temperature (<400 °C). According to our analysis, the exceptional dielectric behavior is originated from the electric double layer formed by mobile of protons in the low temperature-annealed PHPS dielectrics. Furthermore, proton conduction through the PHPS dielectric occurs through a three-dimensional pathway by a hopping mechanism, which allows uniform polarization of the dielectric even at room temperature, leading to amplified performance of the IZO TFTs.