The influence of pH value and annealing temperature on the characteristics of ZnO–Ru composite films and their application in thin film transistors

• ZnO–Ru thin films are prepared using a sol–gel and spin coating method.
• The surface morphology of the ZnO–Ru films that are prepared from acid precursors is smooth and continuous.
• The surface morphology of the ZnO–Ru films that are prepared from basic precursors is rugged.
• The optical energy band gap is a function of the Ru-doping concentration and the annealing temperature.
• An acidic or alkaline pH for the precursors of ZnO–Ru films affects the TFT performance.

ZnO–Ru thin films were prepared using a sol–gel spin coating method. We investigated the effects of the Ru-doping concentration, the pH value of precursor and the annealing temperature on the characteristics of the ZnO–Ru thin films. The crystallinity of ZnO–Ru films decreases as the Ru-concentration increases. The surface morphology of the ZnO–Ru films is also related to the pH of the precursors. The optical energy band gap is a function of Ru-doping concentration and the annealing temperature. The correlations among the Zn/Ru ratio, the pH value of the pre-solutions, the annealing temperature and the characteristics of ZnO–Ru films are derived. In addition to the material properties, the application of ZnO–Ru films as a channel layer in thin film transistors is also discussed.

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