Characteristics of gravure printed InGaZnO thin films as an active channel layer in thin film transistors

Characteristics of oxide semiconductor thin film transistor prepared by gravure printing technique were studied. This device had inverted staggered structure of glass substrate/MoW/SiNx/ printed active layer. The active layer was printed with precursor of indium gallium zinc oxide solution and then annealed at 550 °C for 2 h. Influences of printing parameters (i.e. speed and force) were studied. As the gravure printing force was increased, the thickness of printed film was decreased and the refractive index of printed active layer was increased. The best printed result in our study was obtained with printing speed of 0.4 m/s, printing force of 400 N and the thickness of printed active layer was 45 nm. According to AFM image, surface of printed active layer was quite smooth and the root-mean square roughness was approximately 0.5 nm. Gravure printed active layer had a field-effect mobility of 0.81 cm2/Vs and an on–off current ratio was 1.36 × 106.