Performance improvement for printed indium gallium zinc oxide thin-film transistors with a preheating process

© 2016 The Royal Society of Chemistry. High performance indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) were fabricated by printing and spin-coating IGZO inks as a semiconductor layer at low temperature annealing. A preheating strategy was developed, which significantly enhanced the performance of IGZO TFTs while the post-annealing temperature was kept constant at 300 °C. It was found that when the temperature of preheating on a hotplate increased from 40 °C to 275 °C, the field effect mobility improved from 0.31 cm2 V-1 s-1 to 4.93 cm2 V-1 s-1 for printed IGZO TFTs and from 1.44 cm2 V-1 s-1 to 7.9 cm2 V-1 s-1 for spin-coated IGZO TFTs. The surface roughness of the IGZO films significantly decreased by increasing the preheating temperature from 40 °C to 95 °C. In addition, the analysis of IGZO film composition revealed that an additional nitrate bidentate configuration appeared in the films with preheating at 275 °C, though the substitution of a N atom for O sub-lattice (N)O was found in the film regardless of the preheating temperature. It was suggested that the performance enhancement was primarily attributed to the improvement in film texture brought about by the preheating strategy. Furthermore, the mobility enhancement at high preheating temperature was also related to the appearance of a bidentate configuration (M-O2-N).