Local three-dimensional visualization of nanoparticle assemblies

High-angle annular dark-field (HAADF) imaging technique in the scanning transmission electron microscope has been exploited to study self-assembled multilayer structures of Au/Ag nanoparticles. The HAADF image intensity depends monotonically on the mass and thickness of the sample. Various film thickness between one to four monolayers can be easily distinguished by evaluating the contrast (see Figure).