Influence of the thickness on structural, magnetic and electrical properties of BiFeO3-PbTiO3 thin film prepared by pulsed laser deposition

Single phase BiFeO₃-PbTiO₃ films around the morphotropic phase boundary were deposited by pulsed laser deposition on polycrystalline and (111) orientated Pt/TiO_x/SiO₂/Si substrates. X-ray and pole figure analysis confirms that 0.6BiFeO₃-0.4PbTiO₃ films are 100 preferentially orientated up to ~1.3 μm, whilst 0.7BiFeO₃-0.3PbTiO₃ films are preferentially 111 orientated up to ~290nm and become polycrystalline above ~460 nm. For all films the rms roughness decreases with increasing thickness up to the critical thickness of ~290 nm. Below ~290 nm all films appear to be conductive, however above ~290 nm the films appear resistive with the piezoelectric and magnetic nature being demonstrated through PFM and MFM. TEM EDX analysis confirms the destruction of the Pt bottom electrode with interdiffusion between the Bi and Pt. 0.7BiFeO₃-0.3PbTiO₃ films above the critical thickness were deposited on to an SRO buffer layre-Pt/TiO_x/SiO₂/Si. TEM EDX analysis confirm that the SRO buffer layer prevents interdiffusion at the interface, producing resistive films with a piezoelectric response. This paper discusses how the growth of the films up to the critical thickness, as well as interdiffusion between the Pt and Bi, has an impact on the films properties.