Effect of Monoethanolamine Stabilizer on the Solution-Processed InGaZnO Thin-film Transistors

In this work, monoethanolamine (MEA) is used as stabilizer in the precursor for solution processed indium gallium zinc oxide thin-film-transistor (a-IGZO TFT). IGZO precursor solution was prepared by mixing indium nitrate, gallium nitrate and zinc nitrate in 2-methoxyethanol by atomic ratio of 6:1:3, and with different MEA concentration. It is shown that the MEA has positive but non-linear influence on TFT's turn-on voltage, sample with 6 mg/mL of MEA shows the highest turn-on voltage of -0.8 V while sample without MEA shows turn-on voltage of -11.6 V. AFM images shows MEA stabilizer helps improve a-IGZO surface morphology. According to XPS analysis, different MEA concentration shows different adjustment on components of M-O-M (metal oxide), M-OH (oxygen defect) and M-O-R (organic residue). 6 mg/mL of MEA would significantly decrease M-OH component. A-IGZO with 6 mg/mL MEA doping owes less carrier concentration which leads to the more positive turn-on voltage. Based on the findings,a solution-processd IGZO TFT with mobility of 4.07 cm2V-1s-1 is achieved from precursors with higher In composition and 6 mg/mL MEA..