CoFe₂O₄-TiO₂ and CoFe₂O ₄-ZnO Thin film nanostructures elaborated from colloidal chemistry and atomic layer deposition

CoFe₂O₄-TiO₂ and CoFe₂O ₄-ZnO nanoparticles/film composites were prepared from directed assembly of colloidal CoFe₂O₄ in a Langmuir-Blodgett monolayer and atomic layer deposition (ALD) of an oxide (TiO₂ or ZnO). The combination of these two methods permits the use of well-defined nanoparticles from colloidal chemistry, their assembly on a large scale, and the control over the interface between a ferrimagnetic material (CoFe ₂O₄) and a semiconductor (TiO₂ or ZnO). Using this approach, architectures can be assembled with a precise control from the Angstrom scale (ALD) to the micrometer scale (Langmuir-Blodgett film). The resulting heterostructures present well-calibrated thicknesses. Electron microscopy and magnetic measurement studies give evidence that the size of the nanoparticles and their intrinsic magnetic properties are not altered by the various steps involved in the synthesis process. Therefore, the approach is suitable to obtain a layered composite with a quasi-monodisperse layer of ferrimagnetic nanoparticles embedded in an ultrathin film of semiconducting material.