Densification Control as a Method of Improving the Ambient Stability of Sol-Gel-Processed SnO2 Thin-Film Transistors

We use sol-gel-processed SnO to fabricate thin-film transistors (TFTs) with good ambient stability, showing that SnO film densification can be effectively controlled by a choice of proper drying temperatures. In particular, TFTs comprising SnO2 films dried at 150 °C show conventional n-type semiconductor properties, high-saturation-regime field-effect mobility (7.3 cm Vs), good on/off current ratio, excellent sub-threshold swing values, and good electrical stability after 30-day exposure to ambient air, which alleviates the need for additional passivation layers to protect the active channel layer. Conversely, TFTs comprising SnO2 films dried at 50 or 100 °C show poor environmental stability due to low densification. Specifically, less dense films are characterized by the presence of loosely packed structures and small contact areas between crystallites, which promote the adsorption of gas molecules from the surroundings and result in significant TFT performance deterioration.