Interfacial interaction between ZnO thin film and polyimide substrate investigated by XPS and DFT calculation

The interfacial interaction between the ZnO film and the polyimide substrate was investigated by XPS and density functional theory (DFT) calculation, for the ZnO thin films deposited on polyimide (PI) substrates using cathodic vacuum arc deposition technique. The XPS results showed that a shoulder peak was present for the ZnO film with the thickness of about 15 nm, used for depth profiling, at the binding energy 1 eV higher than that of the Zn2p3 core level for bulk ZnO. Such a shoulder peak is attributed to the interaction between the ZnO and the polyimide. This agrees with the results of DFT calculation. Furthermore, the difference in adsorption energy between the polyimide monomer and the ZnO molecule at different adsorption sites showed that the carbonyl (C=O) plays an important role in the interfacial strength. Copyright (C) 2011 John Wiley & Sons, Ltd.