We developed a new method to realize enhancement-mode zinc oxide (ZnO) thin-film transistors (TFT) by metalorganic chemical vapor deposition (MOCVD). We used growth interruptions during MOCVD to encourage complete oxidation of deposited ZnO film, where diethylzinc and oxygen were used as sources. With this method, turn-off characteristics were significantly improved, and threshold voltage was shifted to positive voltages. ZnOTFTs grown at 450 degrees C showed 10(7) on/off ratio with 18 cm(2)/Vs mobility, and +5V threshold voltage. Our data support that the surface layer is also important in determining ZnO TFT characteristics. (C) 2009 Elsevier B.V. All rights reserved.