Stacking of hexagonal nanocrystal layers during Langmuir-Blodgett deposition

Hexagonally ordered close-packed monolayers of sterically stabilized FePt nanocrystals were deposited on substrates using the Langmuir-Blodgett technique. Monolayers of nanocrystals were also stacked by sequential Langmuir-Blodgett transfer. The structures of the nanocrystal monolayers and multilayer stacks were examined with scanning electron microscopy (SEM) and grazing-incidence small-angle scattering (GISAXS). An analytical model derived from the quasikinematic approximation provides a convenient description of the GISAXS data of the stacked layers. The transferred monolayers showed good in-plane hexagonal order, even for trilayers. Bilayers exhibited spatial registry with the top layer positioned above the 3-fold coordinated sites of the bottom layer. Trilayers, on the other hand, exhibited significant disorder.