Solution-processed rare-earth thulium oxide with high permittivity for low-voltage transistor and inverters applications

The use of high-permittivity (high-k) thin films as gate dielectrics is essential in the development of low-power electronics. In this work, rare-earth thulium oxide (Tm₂O₃) thin films were prepared by a facile solution process and annealed at various temperatures from 400 to 700 °C. The evolution of the physical and dielectric properties of Tm₂O₃ thin film with annealing temperature was investigated. It is demonstrated that the Tm₂O₃ thin film annealed at 600 °C exhibits the optimal performance, including a low leakage current of 3 × 10⁻¹⁰ A/cm², a large areal capacitance of 250 nF/cm² at 100 Hz, and a high permittivity value of 14.2. The Tm₂O₃ thin film as a gate insulator was integrated into the thin film transistor (TFT) employing In₂O₃-based semiconducting channels. The In₂O₃ TFT with 600 °C-annealed Tm₂O₃ dielectric exhibits the superior performance, with a high I_on/I_off of 1.65 × 10⁷, a small subthreshold swing (SS) value of 0.2 V/dec, a V_TH of +1.8 V, and a mobility of 1.68 cm²/(V·s). Furthermore, an inverter constructed by connecting the TFT with a resistor exhibits full-swing characteristics. This work provides a facile and appealing method for preparing the high-k Tm₂O₃ thin films as alternative gate dielectrics with the potential for use in low-power electronics and logic circuit applications.