Presented in this study are the results of an experiment that was performed regarding the effects of plasma post-treatment on the material properties of amorphous indium zinc oxide (a-IZO) films, and on the device characteristics of the thin film transistor when an a-IZO film is used as the channel layer. Prior to the source/drain deposition, post-treatment was performed on the area that was not covered by photoresist (PR), using Ar and H(2) plasma. The electrical resistivity of a-IZO films was dramatically reduced when they were plasma-treated. The creation of an oxygen vacancy and the formation of hydroxyls in the a-IZO film due to plasma treatment were identified via X-ray photoelectron spectroscopy (XPS) analysis. The change in the field effect mobility (mu(FE)) due to the plasma post-treatment was inversely proportional to the change in the contact resistance (R(C)) of the plasma-treated a-IZO layer. The prolonged (>1 min) treatment using H(2) plasma caused deep electron traps and surface damages, resulting in the increased R(C) (or decreased mu(FE)) of the a-IZO TFT. In addition, for the a-IZO TFT that underwent H(2) plasma treatment, the V(T) monotonically decreased whereas the V(T) of the a-IZO TFT that was Ar-plasma-treated remained almost the same as that of the untreated a-IZO TFT. (C) 2010 Elsevier B.V. All rights reserved.