Low-temperature-annealed alumina/polyimide gate insulators for solution-processed ZnO thin-film transistors

•The surface property of the polyimide gate insulator was successfully modified by the introduction of a low-temperature-annealed amorphous alumina interlayer.•The alumina/polyimide gate insulator showed excellent electrical insulating properties.•The solution-processed ZnO TFT with the alumina/polyimide gate insulator exhibited reasonable TFT performance. We report here a low-temperature-annealed alumina/polyimide gate insulator with excellent electrical insulating properties for solution-processed ZnO TFTs. In this study, 150nm-thick polyimide and 20nm-thick alumina thin films were deposited by a simple spin-coating followed by a 200°C-annealing process. With the deposition of the alumina interlayer, the surface of the polyimide film was successfully modified. We prepared ZnO TFTs annealed at 230°C to investigate the potential of the prepared gate insulator. The field-effect mobility and the on/off current ratio of solution-processed ZnO TFTs with an alumina/polyimide gate insulator were 0.11cm2/Vs and 1.8×105, respectively, whereas a ZnO TFT with a polyimide gate insulator was inactive. The alumina interlayer introduced here might provide a compatible interface for the ZnO semiconductor.