Microstructure development of BiFeO3–PbTiO3 films deposited by pulsed laser deposition on platinum substrates

Abstract

BiFeO 3 -PbTiO 3 films around the morphotropic phase boundary were deposited by pulsed laser deposition on polycrystalline Pt/TiO x /SiO 2 /Si substrates. X-ray analysis confirms that 0.6BiFeO 3 -0.4PbTiO 3 films are (001) tetragonal preferentially orientated due to lattice matching with the underlying substrate.The misfit strain at the substrate -film interface is relieved by a ~19% orientation transformation from (001) to (100) due to the difference in lattice mismatch at the substrate-film interface and thermal expansion coefficients of the substrate and deposited film. 0.7BiFeO 3 -0.3PbTiO 3 films are mixed phase rhombohedral-tetragonal with (001) / (111) preferential orientated due to the lattice match to the (111) and (100) of the underlying platinum as well as being close to the morphotropic phase boundary. Inconsistent structural and electrical properties in reported BiFeO 3 -PbTiO 3 films are explained in terms of film morphology and diffusion of bismuth into platinum. Films below ~220 nm thickness produce short circuits due to a Volmer-Weber growth mechanism which results in physical defects within the films. Films above this critical thickness also produce variable electrical properties due to diffusion of bismuth into the underlying platinum electrode which has been confirmed by energy dispersive X-ray spectroscopy.

Brief Theoretical Overview of Bi-Fe-O Based Thin Films

“…Depending on the kinetic energy [63,64] of evaporated material, the increase of interaction will require a cooler temperature range to compensate for the collusion of evaporated particles, which would lead to an increase of the deposition rate. The main parameters, which effect the evaporation rate [61] of the targeted material, are energy intensity, pulse duration (period), laser wavelength and angle of incidence between laser beam [65] and target material. The evaporated material comes into contact with cooler substrate, where films will be deposited, and condensates on substate surface, creating the required films.…”