Abstract:

In this paper, we describe multilayer ZnOthin films prepared by spin-coating precursor solutions of different concentrations. The multilayer ZnO thin films were employed as active layers in thin film transistors (TFTs). A TFT device based on a three-layer ZnO film prepared using precursor concentrations of 0.25, 0.10, and 0.05 mol·L-1 showed a higher mobility of 0.02 cm2 ·V-1·s-1 compared with a TFT device (mobility of 0.013 cm2 ·V-1·s-1) prepared using precursor concentrations of 0.05, 0.10, and 0.25 mol·L-1. Atomic force microscopy (AFM) showed that the former film with a root mean square (rms) of 3.95 nm for the roughness was smoother than the latter with a rms of 4.52 nm. We demonstrate that the roughness of the ZnO film plays an important role in the properties of the semiconductor film. A smoother film allows better contact between the source/drain and the active layer. In TFTs, charge carriers transport in the ZnO grains only near the ZnO/SiO2 insulator layer interface and the crystallinity of the initially formed layer of the filminfluences the performance of the TFT. X-ray diffraction (XRD) patterns showed that the initial layer formed was polycrystalline for the former film and amorphous for the latter. Our work demonstrates that the roughness of the semiconducting film and the crystallinity of the initially formed layer influence the properties of the multilayer semiconducting film.

Key words: Solution process, ZnO, Multilayer film, Field-effect, Thin filmtransistor