Investigating Zinc Ketoiminates as a New Class of Precursors for Solution Deposition of ZnO Thin Films

Zinc oxide (ZnO) has been recognized as one of the most promising metal oxide semiconductor material for processing low-cost thin film transistors (TFTs). Within the scope of this work, we demonstrate a simple, stabilizer free and very efficient chemical solution deposition (CSD) route to grow high quality ZnO layers. The identification of a highly soluble zinc ketoiminate precursor that undergoes hydrolysis under ambient conditions with the facile cleavage of the ligands was the key to develop a simple and straightforward process for ZnO thin films under mild process conditions. Upon heat treatment at moderate temperatures, the precursor decomposes cleanly yielding polycrystalline ZnO thin films, which was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The composition was investigated employing complementary techniques such as X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS) which revealed high purity ZnO layers. The functional properties in terms of transparency and optical band gap were determined by ultraviolet-visible (UV-Vis) spectroscopy. The transparent ZnO semiconductor thin films serve as active channel layer of thin film transistors (TFT) which was demonstrated by spin coating of the precursor. Subsequent curing in ambient air, yields a 10 nm film that is sufficient to fabricate working TFTs test structures.