A multiscale structural study of nanoparticle films prepared by the Langmuir–Blodgett technique

Abstract

Arrays of magnetic nanoparticles (NPs) represent a very interesting challenge toward the development of new devices for magnetic applications such as data storage and spintronic. The final properties of such assemblies depending essentially on the spatial arrangement of NPs, it is of first importance to investigate precisely their structure. Here, the structure of monolayer and multilayer films of magnetic iron oxide NPs assembled by the Langmuir–Blodgett (LB) technique has been studied by usual techniques such as SEM, AFM and ellipsometry and by a new and an easy to process enhanced optical technique: the Surface Enhancement Ellipsometry Contrast (SEEC) microscopy. This technique is based on the use of a new generation of microscope slides used as substrates which allow the strong enhancement of the sample contrast to a point where it becomes possible to visualize the structure of monolayer and multilayer films at the nanoscale with a conventional optical microscope. The SEEC microscopy is demonstrated to be complementary to usual characterization techniques to study the structure of NPs films, especially for films containing very small nanosized NPs which are more difficult to analyze by usual techniques. While the film structure is investigated with lateral resolution of microns, the layer thickness is analyzed at the nanoscale (with a precision of 0.3 nm) with a close fit to the experimental measurements on local (AFM) and on larger (ellipsometry) areas. This technique presents the advantage to visualize directly the topography of NPs assemblies on very large areas by extracting information such as the height profile, the film roughness and generating 3D images.