Far-UV Annealed Inkjet-Printed In2O3 Semiconductor Layers for Thin Film Transistors on a Flexible Polyethylene Naphthalate Substrate

The inkjet-printing process of precursor solutions containing In nitrate dissolved in 2-methoxyethanol is optimized using ethylene glycol as a cosolvent that allows the stabilization of the droplet formation, leading to a robust, repeatable printing process. The inkjet-printed precursor films are then converted to In2O3 semiconductors at flexible-substrate-compatible low temperatures (150-200 degrees C) using combined far-ultraviolet (FUV) exposure at similar to 160 nm and thermal treatment. The compositional nature of the precursor-to-metal oxide conversion is studied using grazing incidence X-ray diffraction (GDCRD), X-ray reflectivity (XRR), and Fourier transform infrared (FTIR) spectroscopy that indicate that amorphous, high density (up to 5.87 g/cm(3)), and low impurity In2O3 films can be obtained using the combined annealing technique. Prolonged annealing (180 min) at 150 degrees C yields enhancement-mode TFTs with saturation mobility of 4.3 cm(2)/(Vs) and similar to 1cm(2)/(Vs) on rigid Si/SiO2 and flexible plastic PEN substrates, respectively. This paves the way for manufacturing relatively high-performance, printed metal-oxide TFT arrays on cheap, flexible substrate for commercial applications.