Enhancement Mode Flexible SnO₂Thin Film Transistors Via a UV/Ozone-Assisted Sol-Gel Approach

The effect of ultraviolet/Ozone (UV/O3)-assisted annealing process on the structural, chemical, and electrical properties of sol-gel-processed SnO2 films is investigated in this study. Via the UV/O3-assisted annealing processes, mixed-phase SnO2 films composed of amorphous SnO2 and polycrystalline SnO were obtained. Furthermore, the XPS spectra indicate an increase in the SnO2/SnO ratio and a substantial decrease in the number of -OH groups (serving as trap sites). This results in an increase in the conductivity and field-effect mobility of the films. The field-effect mobility of the UV/Ozone-assisted 300 °C-annealed SnO2 thin film transistor (TFT) increases considerably (by ∼ 500×), yielding a device with a field-effect mobility of 3.09 cm2/Vs. In addition, flexible SnO2 TFTs with Al2O3 insulator and Au gate on Polyimide substrate fabricated via gate electrode engineering shows a decreased conduction bandgap offset, compared to the SnO2 TFTs on SiO2, and enhancement mode operation properties (normally off at zero gate voltage) with a field-effect mobility of 1.87 cm2/Vs.