The electrical, optical, and structural properties of amorphous indium gallium zinc oxide (a-IGZO) films deposited at room temperature (RI) examined before and after annealing using a radio frequency (RF) magnetron sputtering system with different hydrogen and oxygen gas flow ratios. The carrier concentration and resistivity of the a-IGZO films fabricated under O-2/Ar + O-2 and O-2/Ar-4%H-2 + O-2 atmospheres were greatly dependent on the addition of hydrogen and heat treatment. Thin-film transistors (TFTs) with an a-IGZO channel layer deposited under O-2/Ar-4%H-2 + O-2 = 1.6% exhibited good subthreshold gate voltage swing (S), on/off ratio, threshold voltage and mu(FE) of 0.4 V decade(-1), 10(8), 0.3 V and 4.8 cm(2) V-1 s(-1), respectively. From analysis of the interfacial structure in TFTs before and after annealing, the electrical conductivity of the a-IGZO channel layer was greatly affected in regard to TFT performance due to the amorphous a-IGZO channel layer and SiO2 gate insulator. (C) 2012 Elsevier Ltd. All rights reserved.