The role of the sequence of plasma treatment and high temperature annealing on solution-processed a-IMZO thin film transistor

In this paper, we reported the effects of the order of plasma treatment and high temperature annealing on solution-processed amorphous indium magnesium zinc oxide (a-IMZO, In:Ga:Zn = 3:1:1) thin film transistors (TFTs). Specifically, we utilized two different processes to fabricate TFTs. In one process, the active layers were plasma-treated (PT, 10 W, 10min) before high temperature thermal annealing (TA, 400 °C), and in another process, the active layers were plasma-treated after high temperature annealing. The former achieves lower off-current (5.83 × 10⁻¹² A) and larger on/off current ratio (2.2 × 10⁷), because the oxygen-related ions in the N₂O plasma treatment can passivate the surface of the active layer and reduce the residual organic groups. However, introducing of O²⁺ and O²⁻ ions leads to an increase in interface defects. The latter sample reaches a mobility 1.97 cm²/V·s, as the generated nanopores during high temperature annealing provide path for more atomic oxygen to infiltrate the film during PT and the oxygen vacancies are reduced. However, the on-current drops sharply with plasma treatment power for the increase of oxidation depth. In addition, all the PT samples show small hysteresis and improved stabilities. Our study suggests that moderate plasma treatment can be adopted to improve the a-IMZO TFT device performances.