Interdiffusion at the substrate-film interface of BiFeO3-PbTiO3 thin films on Pt/Si substrates

BiFeO₃-PbTiO₃ films around the morphotropic phase boundary were deposited by pulsed laser deposition on polycrystalline Pt/TiO_x/SiO₂/Si substrates. X-ray analysis confirms that 0.6BiFeO₃-0.4PbTiO₃ films are (001) preferentially orientated upto 1 μm, due to lattice matching with the underlying silicon. The misfit strain at the substrate - film interface is relieved by an orientation transformation from (001) to (100). Above ~220 nm the films become resistive and a piezoelectric response is demonstrated through PFM. A piezoeolectric response is not detected below ~220 nm due to the presence of intermetallic phases present at the film - substrate interface. TEM EDX analysis confirms the destruction of the Pt bottom electrode with interdiffusion between the Bi and Pt. This paper discusses the structure of the films with changing film thickness, as well as interdiffusion between the Pt and Bi.