Photonic Cured Metal Oxides for Low-Cost, High-Performance, Low-Voltage, Flexible, and Transparent Thin-Film Transistors

Flash light-based photonic curing has recently emerged as a promising technique for low-cost and ultrafast production of flexible electronics. In this work, we demonstrate photonic curing-based low-cost fabrication of ZrO₂based high-k dielectric and ZnO-based semiconducting layers for low-voltage, high-performance, flexible, and transparent thin-film transistors (TFTs). Such metal oxide-based devices are extremely important to realize next-generation technologies with high power efficiency, optical transparency, mecahnical flexibility, high reliability, and environmental stability. In the current work, photonic cured ZrO₂ and ZnO layers were obtained by exposing their spin-coated precursor solutions to the high-energy pulsed light of a xenon flash lamp. The numbers of applied pulses were varied for optimization. Hence, the optimally cured ZrO₂ film exhibited excellent dielectric property with high areal capacitance of ∼485 nFcm^-2, low leakage current density of 10^-4 A cm^-2, and high breakdown strength of ∼2.3 MV cm^-1 which further enabled the low-voltage operation (< 3 V) for the fabricated TFTs. On the other hand, the optimally cured ZnO layer resulted in the high performance for the TFTs with field-effect mobility of 3.4 ± 0.1 cm² V^-1 s^-1, on-off ratio of 3.3 ± 0.8 × 10⁵, and threshold voltage of 0.8 ± 0.03 V. The mechanical flexibility of these devices was demonstrated by showing their operational stability under mechancial bending and after continuous bending cycles. These devices also exhibited optical transparency up to 80% in the visible wavelength range. To explain the behavior of these photonic cured layers and devices under different process conditions, several microscopic and spectroscopic studies were performed. Finally, the ultraviolet-visible absorption spectroscopy and a finite element simulation study also showed the viability of photonic curing to successfully fabricate solution-derived ZnO and ZrO₂ layers on a flexible substrate.