Integration of Self-Assembled Epitaxial BiFeO3–CoFe2O4 Multiferroic Nanocomposites on Silicon Substrates



Perovskite-spinel epitaxial nanocomposite thin films are commonly grown on single crystal perovskite substrates, but integration onto a Si substrate can greatly increase their usefulness in devices. Epitaxial BiFeO3–CoFe2O4 nanocomposites consisting of CoFe2O4 pillars in a BiFeO3 matrix are grown on (001) Si with two types of buffer layers: molecular beam epitaxy (MBE)-grown SrTiO3-coated Si and pulsed-laser-deposited (PLD) Sr(Ti0.65Fe0.35)O3/CeO2/yttria-stabilized ZrO2/Si. The nanocomposite grows with the same crystallographic orientation and morphology as that observed on single crystal SrTiO3 when the buffered Si substrates are smooth, but roughness of the Sr(Ti0.65Fe0.35)O3 promoted additional CoFe2O4 pillar orientations with 45° rotation. The nanocomposites on MBE-buffered Si show very high magnetic anisotropy resulting from magnetoelastic effects, whereas the hysteresis of nanocomposites on PLD-buffered Si can be understood as a combination of the hysteresis of the Sr(Ti0.65Fe0.35)O3 film and the CoFe2O4 pillars.