Study of thin film adhesion properties of multilayer flexible electronics composites

The deformation between interface and adhesion mechanism of multi-layer flexible electronics composite were discussed. First, ITO (Indium tin oxide), Al (Aluminum) and ZnO (Zinc oxide) were directly deposited on a PET (Polyethylene terephthalate) substrate by RF (Radiofrequency) magnetron sputtering in room temperature to form the flexible multi-layer structures (ZnO/ITO/PET and ZnO/Al/PET) for piezoelectric transducers. ZnO thin film reveals a high (002) c-axis preferred orientation at 2θ=34.45° with an excellent piezoelectric property. To analyze adhesion following a periodic mechanical stress by vibrating flexible composite plates, nano-scratching test (Nanoindenter XP system) was used for scratch process to learn the relationship between normal force and penetration depth. The results show that the plastic deformation can be observed from SEM and OM observation between Al film and PET substrate. This behavior means that the deposited ZnO film has excellent adhesion with Al/PET conductive substrate compared with ITO/PET. Through nano-indentation test, ZnO film deposited on Al/PET substrate decreased the elastic modulus and hardness compared with ITO/PET substrate.