Low-temperature spray-deposited indium oxide for flexible thin-film transistors and integrated circuits

Indium oxide (In₂O₃) films were deposited by ultrasonic spray pyrolysis in ambient air and incorporated into bottom-gate coplanar and staggered thin-film transistors. As-fabricated devices exhibited electron-transporting characteristics with mobility values of 1 cm²V⁻¹s⁻¹ and 16 cm²V⁻¹s⁻¹ for coplanar and staggered architectures, respectively. Integration of In₂O₃ transistors enabled realization of unipolar inverters with high gain (5.3 V/V) and low-voltage operation. The low temperature deposition (≤250 °C) of In₂O₃ also allowed transistor fabrication on free-standing 50 μm-thick polyimide foils. The resulting flexible In₂O₃ transistors exhibit good characteristics and remain fully functional even when bent to tensile radii of 4 mm.