Enhancement of the piezoelectric properties of (100) BiFeO3 films on Si by all-sputtered epitaxial growth

The epitaxial growth of perovskite-type ferroelectric thin films on Si substrates is expected to be a method that dramatically improves the electrical properties, including the piezoelectricity. Here, we report the epitaxial growth of all films from the buffer layer to the ferroelectric layer in a single sputtering chamber. This achievement was driven by the use of the TiN buffer layer and the search for adhesion layers to improve the low adhesion between Pt and TiN. As a demonstration of the epitaxial growth of ferroelectric films, (100) BiFeO3 films were fabricated using the biaxial combinatorial method. The films exhibited a crystal structure and electrical properties different from epitaxial films grown on oxide single crystals and oriented films. Under optimized conditions, the films showed well-developed polarization electric-field properties and a transverse piezoelectric constant e(31,f) similar to -6.0 C m(-2).