Electrically and environmentally stable nitric acid-assisted SnO2 films for the active channel layer of thin-film transistors

Electrically and environmentally stable SnO2 thin-film transistors (TFTs) were fabricated with nitric acid (HNO3)-added liquid precursors using a low-temperature sol–gel process. The structural, chemical, optical, and electrical properties were investigated. The HNO3-added precursors resulted in the formation of high-density and amorphous-phase SnO2 films at 300 °C. The added HNO3 boosted the oxidation and sol–gel processes, successfully producing SnO2 films with SnON, fewer defects, and higher quality than pure SnO2 films. The formation of the high-density, fewer defect and high quality SnO2 with SnON resulted in significantly enhanced field-effect mobility. The HNO3 precursor-based TFTs exhibited robustness to external continuous positive and negative biases while maintaining environmental stability by inhibiting the chemical reaction of H2O absorption on the SnO2 surface. Compared to the pure SnO2-based TFTs, the SnO2 TFTs fabricated with HNO3-added liquid-phase precursors exhibited a twenty-fold higher field-effect mobility in the saturation regime of about 6.64 cm2/Vs, as well as good stability with negligible parameter variations and good environmental stability for up to two months. These findings are useful for forming electrically and environmentally stable metal oxide layers at relatively low temperatures for many metal oxide-based applications, such as TFTs, resistive random access memory and transparent electrodes for devices and solar cells.