Mechanical properties of ferro-electric composite thin films

Ferro-electric (BSTO) films of 1 mu m nominal thickness were deposited on single crystals of sapphire at substrate temperatures varying from 30 degrees C to 700 degrees C. Optical analysis showed that the thin films were amorphous up to 500 degrees C, while at 700 degrees C they were polycrystalline. The microstructure of the thin films was columnar at all substrate temperatures. The film microhardness increased with increasing substrate temperature. While the cohesion failure load of the films remained fairly constant, the adhesion failure load increased with increasing substrate temperature.