In this study, we investigated the electrical properties of DC sputtered amorphous In-Sn-Zn-O (a-ITZO) thin-film transistors (TFTs) fabricated under various process conditions. Fabricated a-ITZO TFTs achieved a threshold voltage (V-T) of 1.0 V, subthreshold swing (SS) of 0.38 V/dec and field-effect mobility (mu(eff)) of around 30 cm(2)/V s. An analytical field-effect mobility model is proposed for a-ITZO TFTs with key parameters extracted using different methods. The impacts of a-ITZO channel thickness and oxygen gas flow ratio on device performance were evaluated. Finally, the a-ITZO TFT bias-temperature stress (BTS) induced electrical instability was studied. In comparison to amorphous In-Ga-Zn-O (a-IGZO) TFTs, improved electrical stability was observed for a-ITZO TFTs using exactly the same BTS conditions. (C) 2015 Elsevier Ltd. All rights reserved.